EPA-600/3-76-027
April 1976
ENVIRONMENTAL
PROTECTION
AGENCY
DALIES. TEXAS
Ecological ReseartW|(ilft
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RESEARCH REPORTING SERIES
Research reports of the Off ice of Research and Development, U.S. Environmental
Protection Agency, have been grouped into five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ECOLOGICAL RESEARCH series. This series
describes research on the effects of pollution on humans, plant and animal
species, and materials. Problems are assessed for their long- and short-term
influences. Investigations include formation, transport, and pathway studies to
determine the fate of pollutants and their effects. This work provides the technical
basis for setting standards to minimize undesirable changes in living organisms
in the aquatic, terrestrial, and atmospheric environments.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/3-76-027
April 1976
BIOLOGICAL IMPACT CAUSED BY
CHANGES ON A TROPICAL REEF
by
Robert S. Jones
Richard H. Randal 1
Michael J. Wilder
The Marine Laboratory
University of Guam
Agana, Guam 96910
Grant No. R802&33
Project Officer
Kenneth T. Perez
Environmental Research Laboratory
Narragansett, Rhode Island 02882
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
ENVIRONMENTAL RESEARCH LABORATORY
NARRAGANSETT, RHODE ISLAND 02882
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DISCLAIMER
This report has been reviewed by the Environmental Research Laboratory,
U.S. Environmental Protection Agency, and approved for publication.
Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor
does mention of trade names or commercial products constitute endorse-
ment or recommendation for use.
11
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ABSTRACT
A biological study is conducted on a fringing coral reef adjacent to a
thermoelectric power plant on Guam, before and after release of plant
effluent. The before study shows corals of the reef front, submarine
terrace, and seaward slope to be devastated because of a recent infesta-
tion by the crown-of-thorns starfish, Acanthaster planci (L.). The reef
margin is found to comprise a rich and diverse coral reef community, pre-
sumably spared from Acanthaster attack by strong wave surge. The reef
flat is naturally depauperate due to frequent exposure at low tide.
Release of plant effluent results in an elevation of water temperature
on the adjacent reef flat and reef margin, and wave action exposes even
the deeper parts of the reef margin to temperatures above ambient as well
as other potentially detrimental effluent parameters such as chlorine and
heavy metals. Introduction of the effluent is shown to be responsible
for recent destruction of reef margin corals. Effluent is found to stra-
tify beyond the surf zone and is no longer a threat to benthic organisms.
Coral transect studies show an increase in recent coral re-colonization
on the reef front, terrace and slope since the Acanthaster infestation.
No such recovery is evident in benthic habitats of the reef margin, ex-
posed to effluent.
Thermal simulation experiments, performed on a series of reef corals in
the laboratory, suggest mean upper tolerance limits for the corals be-
tween 30 and 33°C. These temperatures are common on the reef margin ad-
jacent to the power plant. Sublethal elevation of temperature is shown
to reduce growth rate in some of the coral species.
Recommendations are made to release the effluent in deeper water in order
to provide a greater mixing zone and to relieve present stress on reef
margin organisms.
This report was submitted in fulfillment of Grant Number R802633-03 by
the University of Guam Marine Laboratory, under the sponsorship of the
Environmental Protection Agency. Work was completed as of November 197**.
111
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CONTENTS
Page
Abstract i j i
List of Figures vi
List of Tables ix
Acknowledgments xii
Sections
I Conclusions 1
II Recommendations 8
III Introduction 10
IV The Study Area 14
V Current Patterns 22
VI Temperature Regimes 42
VII Chemical Parameters 55
VIII Biological Impact of Effluent 61
IX Thermal Simulation Experiments 89
X Effects of Acanthaster Predation on
Tanguisson Corals 127
XI References 179
XII Appendices 181
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FIGURES
No. Page
1 Location map of Guam showing study areas 11
2 Aerial photograph of the Tanguisson Power Plant site 16
3 Detailed map of the Tanguisson Point study area
showing transect locations 19
k Reef profile at Transect B 20
5 Current patterns on the reef flat prior to
release of effluent 26
6 Current patterns on the reef flat after release
of effluent 26
7 Mean frequency diagram for current direction at
5m 29
8 Mean frequency diagram for current direction at
10 to 14 m 30
9 Mean frequency diagram for current direction at
23 m 31
10 Mean frequency diagram for current direction at
30 m 32
11 Mean frequency diagram for current direction, all
stations combined 33
12 Sample segment from one current meter tape indicating
a close fit between tide cycle and current direction 3**
VI
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FIGURES (Continued)
No. '_ Page
13 Sample segment from one current meter tape showing
a predominance of southerly components 35
]k Sample segment from one current meter tape showing
a predominance of northern components 36
15 One meter drift cross casts 38
16 Five meter drift cross casts 39
17 Ten meter drift cross casts kO
18 Plot of mean monthly sea surface temperatures for
a 10 year period at Tanguisson Point A3
19 Power plant operating temperatures k6
20 Surface and 1 m isotherms 50
21 Diagrammatic presentation of the influence of the
thermal plume on the reef margin 5**
22 Algal community after thermal discharge 65
23 Limits of coral kill as of December, 1972 76
2k Coral kill on upper surface of a reef margin
buttress 81
25 Pale and bleached corals on the walls and floor of
a reef margin surge channel 81
26 Dead coral and coralline algae surface being
recolonized by blue green algae 82
27 Vertical profile through the reef margin and
reef front zones 83
28 Limits of coral kill as of January, 1973 8A
29 Limits of coral kill as of October, 197*» 86
VII
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FIGURES (Continued)
No. Pa
30 Thermal simulation device 91
31 Acclimation tank 92
32 Fungi a scutar?a 97
33 Psammocora contigua 98
34 Pocillopora dam!corn is 100
35 Pocillipora setchelli 102
36 Pavona obtusata 103
37 Pavona varians 104
38 Pavona frond i fera 105
39 Pavona decussata 106
40 Pori<-c.3 lutea 108
41 Favia stell igera "1
42 Galaxea hexagonal is 112
43 Acropora as per a ^^
44 Acropora nasuta 115
45 Acropora palifera 116
46 Leptoria phrygia 117
47 Millepora platyphylla 118
48 Stylophora mordax 119
49 Platygyra rustica 120
50 Bleached polyps of Galaxea hexagonal is 122
51 Transect B station showing anchor links and station
number suspended by a float 123
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FIGURES (Continued)
No. Page
52 Diagram of the station quadrat transect method 129
53 Number of genera and species per transect station at
Tanguisson Point, 1970
5^ Percentage of reef surface covered by living corals
at Tanguisson Point, 1970
55 Rich coral growth on the upper surface and side of
a reef front buttress
56 Dense growth of Pocillopora colonies on the floor
of a reef margin surge channel
57 A view looking down the steep seaward slope zone 150
58 Number of coral genera and species per transect
station for 1970 165
59 Number of coral genera and species per transect
station for 1971 166
60 Number of coral genera and species per transect
station for 197A 167
61 Percentage of reef surface covered by living
corals from 1970 to 197^ for Transect A 168
62 Percentage of reef surface covered by living
corals from 1970 to 1971* for Transect B 169
i
63 Percentage of reef surface covered by living
corals from 1970 to 197^ for Transect C 170
IX
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TABLES
No. Page
1 Predicted and actual temperature changes of
plant effluent *»5
2 Reef flat salinities 56
3 Salinity data for influent and effluent 57
A Heavy metal analyses 59
5 Species listing of marine benthic algae 63
6 Visual fish counts 69
7 Relative resistance of corals to the effluent 78
8 A comparison of the percentage of living coral
covering the reef surface and the number of coral
genera and species present 80
9 Order of resistance and thermal tolerance limits
of coral species tested in thermal simulator 96
10 Growth of corals at experimental temperatures ^2t^
11 Checklist of corals 130
12 Relative frequency of occurrence and zonal
distribution of corals 139
13 Distribution of coral growth forms by reef zones
in 1970 1^3
lA Distribution of coral colony diameter by reef
zones in 1970 148
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TABLES (Continued)
No. - Page
15 Total number of genera and species by reef zones 153
16 Average percent of coral cover by reef zones 153
17 Checklist of corals and their relative frequency of
occurrence 157
18 Number of genera and species for the major groups of
corals found at Tumon Bay and Tanguisson Point 163
19 Changes in the number of coral genera and species by
reef zones from 1970 to \37k 171
20 Changes in the percentage of reef surface covered by
living coral by reef zones from 1970 to 1974 171
21 Distribution of corals by diameter from 1970 to 197^ 173
22 Distribution of corals by growth forms from 1970 to 197*» 171*
XI
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ACKNOWLEDGMENTS
The authors are grateful for financial support received from the Environ-
mental Protection Agency. Dr. Roy Irwin, the Project Officer (later
replaced by Dr. Perez) and Dr. Donald Phelps were particularly helpful
in administrative matters. EPA Regional Director, Paul De Falco was
instrumental in providing initial guidance in our first grant proposal
and has been a great help throughout the project, especially in pursuing
continued financial support.
Without the technical skills of Allan Beck and Ray Highland of the Na-
tional Marine Water Quality Laboratory in Rhode Island, we would still
be struggling with problems of building a large thermal simulator in our
remote locality. We are also indebted to personnel of the EPA Water
Quality Laboratory in Alameda, California for analyses of heavy metals.
We owe our appreciation to Mr. Paul Jokiel and our other counterparts at
the University of Hawaii for sharing their data on a related project.
Plant operations personnel at Tanguisson Point were always open and will-
ing to aid in our work. Cooperation from Guam Power Authority employees
Frank Melder, Bill Masters and Donald McCullum is especially appreciated.
Our thanks are also due to Mr. P. E. Cavote and Mr. George Pomeroy of
GPA management.
We are grateful to the U. S. Navy for providing helicopter support for
aerial photography, and NAVOCEANO for current data taken on Guam.
An extremely valuable record of temperature and salinity for the
Tanguisson study area was provided by our colleagues at the Guam Division
of Fish and Wildlife, in particular Mr. Harry T. Kami.
Marine Technicians Ted Tansy, Rodney Struck, Frank Gushing, Patrick
Beeman and Modesto Salas were helpful and efficient as always in field
operations, maintenance of gear, and construction of the thermal simula-
tor.
We appreciate the staff contributions of our colleagues Drs. R. T. Tsuda,
XII
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M. Yamaguchi, J. A. Marsh, Jr., and L. 6. Eldredge. Graduate students
John Rupp, Helen Larson, Tom Hohman, Ron Strong and Greg Gordon were
particularly strong contributors and hard workers. Other student
assistants were Dan Wooster, Chris Grimes, Mary Belk, and Jeanne
Holloman.
We are also grateful to the Harbor Branch Foundation, Inc. of Fort
Pierce, Florida for allowing use of their facilities and the time given
to one of the authors (Jones) to work on the manuscript. Manuscript
typists Mrs. June Jones and Mrs. Rose Neville labored long and hard
over the final manuscript and we very much appreciate their excellent
work. The Foundation's photographer, W.L. Davenport, is responsible
for the fine photocopy work of our original drawings.
Finally, we could never have put it all together without our Marine
Laboratory administrative staff, Mrs. Teresita Balajadia and Augusto
Terlaje. These fine people kept our scientists going through the
blizzard of paper work over the five years of our study period.
This paper represents Technical Report Number 17, the Marine Laboratory,
University of Guam, and Contribution Number 39, Harbor Branch Foundation,
I nc.
Xlll
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SECTION I
CONCLUSIONS
GENERAL BIOLOGICAL CONDITIONS OF THE TANGUISSON STUDY AREA PRIOR TO
RELEASE OF PLANT EFFLUENT
The first two generating units of the Tanguisson Power Plant are located
on an elevated terrace covered with bioclastic material. The plant site
is on an old coconut plantation. Attempts were made by the contractor
to save most of these trees, but a considerable portion of the previous
we11-developed strand vegetation was removed well outside the immediate
construction site to provide a mobilization area. On the landward side
of the plant is a steep limestone cliff with a talus slope at its base.
The cliff is about 100 m high and has a good growth of limestone forest
vegetation on its sides and slopes. This vegetation has been left basi-
cally undisturbed except where power transmission lines and a pipeline
pass up the cliff.
Seaward of the power plant is the first of the series of reef zones stu-
died. The intertidal is the first zone encountered and, in the immediate
vicinity of the plant, consists of the remnants of an elevated fossil
reef. There are sand beaches along the intertidal to the north and south
of the plant.
The reef zone seaward of the intertidal is the reef flat. This is a
limestone platform that is mostly flat and pavement-like except for a few
scattered holes and channels. The reef flat has a characteristic biota
that is mostly dominated by fishes, crustaceans, echinoderms, and benthic
algae. Corals are rare on the reef flat and in general, it is a biologi-
cally depauperate area due to frequent exposure of much of its surface
at low tide. Temperatures on the reef flat are often 2 to 3°C higher
than oceanic temperatures when low tides occur in midafternoon.
The next zone is the reef margin and is that portion of the reef where
waves break against the reef platform. The area is dissected by numerous
surge channels and is the site of a rich and diverse coral fauna. Unlike
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the remaining zones, this one has not been subjected to intense predation
by the coral-feeding starfish, Acanthaster planci (L.).
We suspect that heavy wave attack in this area prevents the animal from
attaching to corals in order to feed. Temperatures in this zone and
those that follow had a range of between 26 and 29°C, a mean annual tem-
perature of 27.6°C, and an annual fluctuation of only about 3°C.
The reef front is the next zone and In most respects closely resembles
the reef margin. The primary exception is that it is a deeper, more
steeply sloping zone and not subjected to breaking waves. The lower por-
tion of this zone has been completely devastated by Acanthaster.
At the 6 m contour, the reef front flattens out and grades into the first
submarine terrace. This area was, until recently, covered by a rich
coral community but has now been wiped out by Acanthaster. Nearly 100
percent of the former coral community was destroyed.
At about 15 ni, the submarine terrace ends and the bottom slopes steeply
down to the next submarine terrace at about 32 m. This drop-off is
known as the seaward slope and, as in the case of the first submarine
terrace, once supported a luxuriant growth of reef corals. Again the
area was found to be devastated by the starfish.
The second submarine terrace is basically a flattened shelf covered with
sand derived from the nearby seaward slope. Some scattered coral knolls
are found here but these too are now mostly devoid of live corals.
THE EFFLUENT AND ITS DISTRIBUTION
Circulating water is pumped through the power plant for once through
condenser cooling. The source of this water is the Philippine Sea. Each
generating unit uses about 17,000 gpm with one pump on the line, and
about 28,000 with two. (One pump per unit is now being used almost exclu-
sively since the time the original manuscript was prepared, personal commu-
cation with P. E. Cavote.)
At least four things happen to cooling waters and entrained planktonic
organisms as they pass through the plant.
1. Physical agitation at the circulating pumps.
2. Leaching of heavy metal ions, particularly copper, from the
piping.
3. Addition of chlorine to control sliming.
(Chlorination has been stopped completely since the preparation
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of the original manuscript, personal communication with P. E.
Cavote.)
A. Elevation of temperature.
The outfall site for this effluent is at the intertidal zone. Water
enters a stilling well and rises up to the level of the reef flat. Ef-
fluent then flows seaward, directly across the reef flat, in a relatively
narrow band (10 to 15 m wide). At the reef margin, the effluent encount-
ers breaking waves and is mixed with incoming seawater. This mixing
effectively carries effluent to the bottom of the surge channels. The
mixing water tends to be carried parallel to the reef margin and front
in a series of zig-zag patterns. The lateral movement is due to pre-
vailing offshore currents, and the zig-zag to wave action. Currents may
either run northeast or southwest at Tanguisson. When the effluent is
carried to the north, it immediately encounters a rip current that emer-
ges from the intake channel surface. The rip diverts the effluent sea-
ward out over the terrace and away from the reef margin and front. When
the plume is carried to the southwest a considerable portion of the reef
margin and front is washed by effluent. The effluent gradually shifts
seaward as it moves south toward Transect C. A second rip current occurs
in surge channels near Transect C that serves to divert the remainder of
the effluent seaward.
Once the effluent reaches the submarine terrace, it comes under the in-
fluence of the offshore water mass. Except for wave transport during
times of heavy seas, effluent entering this water mass is carried either
northeast or southwest and away from the study area. Its direction de-
pends upon tide and local climatic and related oceanographic conditions.
Effluent moving northerly was not tracked beyond Tanguisson Point.
Effluent moving south is usually deflected seaward off of Amantes Point
and moves in a westerly direction away from the island. This may be due
to a weak convergence zone that would be expected to form opposite the
Amantes headland. A recent drift cross study showed a drift that rounded
Amantes Point and continued south opposite Tumon Bay. The drift crosses
ultimately swung seaward as they approached Ypao Point. Except in the
areas immediately adjacent to the plant, we expect all effluent to be
carried gradually seaward primarily because of the influence of the pre-
vailing east and northeasterly winds on the surface water.
GENERAL BIOLOGICAL IMPACT OF THE EFFLUENT AND PLANT CONSTRUCTION
As the effluent passes clear of the mixing action of the surf zone, ther-
mal stratification occurs. The heated portion of the effluent is con-
fined to the upper 1 to 2 m of the water mass and is no longer a threat
to the benthic biota and most of the other organisms in the water column.
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Concern for potential environmental damage is, therefore, limited to the
reef flat and reef margin opposite the plant and usually between Transects
A and C. All other zones were found to be outside the vertical and hori-
zontal limits of the effluent plume.
On the reef flat we found that the few scattered corals that occurred
prior to plant operation died in the effluent plume. Fishes that are
characteristic of the reef flat (many are territorial species) abandoned
the plume area. The same was true for crustaceans and echinoderms.
Benthic algae normally present in this area, for the most part, dis-
appeared and was replaced by a predominately blue green algae community.
This implies that, with regard to the algal community, the area has re-
verted to an early stage of ecological succession that features the
pioneering blue greens. The reef flat is not considered particularly
rich in terms of diversity or biomass, and the area affected is confined
to the immediate area of the effluent plume. A "normal" reef flat com-
munity is found immediately adjacent to the plume.
The most striking effect on the reef that we can attribute to plant ef-
fluent, is on the reef margin. A massive die-off of the reef coral
community has occurred here. There is a central core of about 10,300 rrr
spread along along a linear front of about AOO m, where most of the corals
have been killed. A peripheral zone lies outside of this area that shows
dead, dying, and bleached corals (corals that have extruded their pig-
mented symbionts). This zone has shown a constant and gradual die off.
The coral kill began in December, 1971, when the plant (Unit No. 1) be-
gan full scale operation and is still going on today in the peripheral
zones after addition of Unit No. 2 in May, 1973- The total area affec-
ted to date is 20,000 m2 and spreads along 600 m of the reef margin.
The obvious question at this point is, what factor or factors in the
effluent are affecting the corals? The first factor mentioned above,
agitation, would not be involved with the coral kill but might affect
entrained planktonic organisms through mechanical damage. This was not
a part of the study and was not pursued except for one significant phe-
nomenon. In this case large numbers of the juvenile rabbitfish, Siganus
spinus, were entrained by the circulating water and killed, possibly by
mechanical damage from the pumps. We suspect that many thousands of
these animals are killed when they make their seasonal migrations from
the pelagic to the inshore environment. Enormous numbers of the juveniles
are found in the intake channels of both the Tanguisson and Piti power
plants during their migrations in April, May, June, and October.
Copper is known to be toxic to marine organisms. Total copper values in
the outfall were at times nearly three times (2.9 ug/1) higher than the
values in the intake channel (1.0 ug/l), and nearly 30 times higher than
control samples taken one half mile'to sea (O.I ug/l). The values were
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quite variable and are still below those reported as normal in oceanic
water (about 3 to 10 ug/1 total copper). We are uncertain at this point
as to what role copper might play in the death of the corals. We are,
however, of the opinion that the effect is minimal at this time. This
factor could be multiplied as the plant ages.
Chlorine is another toxic material that might have caused the death of
some of the first reef corals that were effected. There are no bioassay
data available as to the level of chlorine that is toxic to coral species
and we had no way of measuring either free or residual chlorine during
the project. We did note on one occasion, when the power plant ran out
of chlorine from November 2 to November 20, 1972, that reef flat fish
species began recolonizing the reef flat and the stilling well. These
species seemed unaffected by the turbulence of effluent or the heat.
However, when chlorination was started again, the species disappeared
immediately. Subsequent investigations by Guam Power Authority has
shown that biological fouling of the condenser tubes is minimal and
chlorination has ceased altogether.
Waste heat in the effluent is considered to be a very likely source of
most, if not all, of the coral damage. We found a mean delta T of 7.0°C
during the first 28 months of plant operation. The range of intake tem-
perature was 26.5 to 29.5 and mean was 27-7°C. Outfall temperature
ranges were 32.5 to 37.0 with a mean of 3A.7°C. Sampling showed that,
except during higher high water tides and heavy seas, there is little
reduction in temperature from the stilling well to the reef margin.
Wave attack immediately begins to mix the water, and the temperature
drops as mixing proceeds. Seawater temperatures fluctuate between 29 and
35°C along the reef margin adjacent to the plant. Data on the elevation
of temperatures at the reef margin are incomplete due to the inaccessa-
bility of this wave washed zone. We found that we were unable to work
in the area except during rare periods of extreme calm. At these times
the effluent was stratified and we were not able to measure its effect
below about 1 m. Attempts to place in situ temperature recording instru-
ments in this zone usually resulted in damage to the instruments.
In addition to effluent damage, there was some initial physical damage
to the reef from construction activities. A channel was excavated from
the reef margin and reef flat zones to provide access for cooling water
to plant condensers. The rich coral community at the immediate entrance
to the intake channel was obliterated by dynamiting and excavation. This
constitutes an area of only about 250 m2. There was little damage done
to the reef margin corals either to the left or right of this channel.
The remainder of the channel has physically replaced about 1835 m2 of
reef flat environment. In terms of biomass and diversity, the loss is
probably less than the smaller area disturbed along the reef margin.
THERMAL SIMULATION EXPERIMENTS WITH REEF CORALS
It was certain that plant effluent had caused a massive coral kill along
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the reef front, but it was not so obvious as to what plume parameter or
parameters might be involved. Synergistic effects or other factors which
we are as yet unaware of might be responsible for some of the damage.
A laboratory experiment was designed to eliminate all the potential power
plant stress parameters on reef corals except temperature. The system was
set. up at the Marine Laboratory and used fresh, uncontaminated seawater
from the reef margin at Pago Bay. Reef corals were subjected to tempera-
ture elevations of +2, +4, and +6°C above summer ambient (28.5°C). The
experimental tanks were heated with immersion heaters and had electronic
control devices. This, in effect, simulate the thermal influence of
plant effluent while eliminating the other parameters.
Eighteen species of reef corals have been tested in the thermal simulator
thus far. There was no significant difference in survival between most
coral species in the ambient control tanks and those at +2°C above sum-
mer ambient. At +4°C above ambient, most of the corals were usually
dead within 6 to 14 days. The coral la went through the same stages of
death as those at Tanguisson Point. The symbionts were expelled first,
leaving the coral polyps bleached white. This stage was usually reached
within a few days and was followed by death within the period described
above. Coral species in the +6 tanks were usually all dead within six
days or less. It would appear that the mean upper thermal tolerance limit
for the majority of the species is between 30 and 33°C. These tempera-
tures are not uncommon at the reef margin near the plant. The apparent
slow die off of the corals may be correlated with the mixing of plant
effluent with oceanic water. Corals would not receive constant exposure
in the peripheral zone of the coral kill due to variability of wave at-
tack in direction and magnitude, tide cycle, and current direction.
Corals tested at sublethal temperature elevations showed a general reduc-
tion in growth when compared with controls.
Effects of thermal stress on other marine organisms are considered in
separate reports in Appendices A to D.
SUMMARY
We feel that there is no doubt that effluent from the Tanguisson Power
Plant is responsible for the death of the corals along the reef margin
as well as their continued dying. Laboratory data indicate that eleva-
ted temperature is the primary but not necessarily the only causal fac-
tor.
Evidence gathered from the Acanthaster killed reef front, submarine ter-
race, and seaward slope zones indicates that corals are now resettling
and recolonizing these areas. There is no evidence of coral resettle-
ment in the reef margin area within the influence of effluent. Further-
more, it is apparent that the coralline algae are also being killed by
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the effluent (Appendix D). These organisms normally cover corals killed
by Acanthaster and result in a stabilization of the reef structure that
prevents erosion. There is the possibility that the absence of both cal-
cium carbonate secreting corals and coralline algae will result in bio-
geochemical and physical erosion of the reef platform opposite the power
plant.
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SECTION II
RECOMMENDATIONS
Jokiel and Coles (unpublished manuscript) recently completed a study of
the Kahe Point power generating facilities in Hawaii. Their results are
similar to ours and we feel that they summed up the problem quite well.
"The use of the marine environment for the disposal
of waste heat is an attractive concept in a land-
scarce island community. Cooling tower and cooling
pond schemes are expensive in terms of terrestrial
space. The Pacific Ocean represents a heat sink of
incomprehensible proportion. The major problem in
using the ocean as a receiving body for the heat
lies in getting the waste heat far enough away
from the shoreline so that shallow inshore marine
communities are not disrupted. Intial dilution
with the receiving water mass must be high so as
to avoid excessive temperature increases over am-
bient conditions."
We are in agreement with the logic expressed above and would recommend
the following:
1. Abandon the present outfall structure.
2. Build a new outfall line from the plant to the edge of
the submarine slope (a distance of about 250 m and
depth of about 10 m).
3. Place a diffuser structure at the end of the line.
k. Use the existing intake channel for the pipe run through
the reef flat and reef margin, thus eliminating the need
for additional channeling. If channeling is necessary on
the submarine terrace, now is the time to do it. Coral
recovery following Acanthaster damage is at an early
stage and would not be significantly affected if con-
struction is completed soon.
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The above action would result in relief of stress on thedamaged reef mar-
gin zone and we suspect that corals and coralline algae would recolonize
the area. Effluent released offshore would rise rapidly to the surface
due to the low density of hot water. This would provide a 10 m deep mix-
ing zone and the resultant surface plume would be stratified and well
clear of the benthic reef biota.
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SECTION Ml
INTRODUCTION
BACKGROUND
The island of Guam lies at the southern end of the Mariana chain. This
far-flung territory of the United States is experiencing the pressures
of boomtown growth. Both civilian and military components are contribu-
ting to this phenomenon. The island population in I960 was 67,000 --
it now stands at nearly 100,000 and the rate of growth shows no sign of
decreasing in the near future. There has been a frantic expansion of
construction activities on the island to create more homes for the growing
population and to provide more industrial, business, military, and tourist
facilities which support the expanding economy.
The explosive growth of so many power-consuming entities has, predictably,
caught the island woefully short of power-generat ing facilities. This
has led to short term and often shortsighted planning for new generating
plants. The net result is that locations for these new facilities are
frequently chosen for convenience of the power industry and with little
regard for the environment.
In order to meet the expanding power needs of Guam, plans were made to
construct generating facilities at Tanguisson Point (Fig. 1). A series
of four units were to be constructed on an incremental basis over a per-
iod of years to try to keep abreast of the growing power curve. Unit
No. 1 was scheduled for completion in early summer 1971 but did not be-
come operational until December 1971. (Two units were operational by
May 1973.)
Each unit was to have a generating capacity of about 26 megawatts. The
units were to be oil-fired, steam electric facilities, utilizing sea wat-
er for condenser cooling. Cooling water for all units was to be taken
from the adjacent waters of the Philippine Sea through an intake channel,
14 m wide and 2 rn below mean low water, cut through the reef margin and
reef flat. Plans for Unit No. 1 called for two circulating pumps with
capacities of about 17,000 gpm each, to carry water to the condensers.
10
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N
A
RITIDIAN PT
PHILIPPINE
SEA
ARfcOR
GUAM
PACIFIC
OCEAN
COCOS IS
0246
j i i _ «
MILES
Figure 1 Location map of Guam showing study areas
11
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Heated effluent was to be released in a stilling well at the intertidal.
With one pump on the line a delta T of 12-lA°F was predicted and with two
(about 28,000 gpm) 9~11°F (personal communication, Frank Melder). Opera-
tional plans called for use of both pumps about 50 percent of the time
during peak power times. (At the writing of this report, the Tanguisson
system was using only one pump per unit most of the time, personal com-
munication, P. E. Cavote).
At the suggestion of EPA Regional officials, the University of Guam sub-
mitted a research proposal to study the effects of Unit No. 1 on the
adjacent marine environment. This initial proposal was accepted and the
grant awarded on September 13, 1969-
SCOPE OF STUDY
The primary objective of the research was to evaluate (Phase I) the bio-
logical condition of a section of coral reef at Tanguisson Point prior to
the completion of Unit No. 1 and then to reevaluate the reef (Phase II)
after the plant became operational. The second phase would provide a
catalog of the induced environmental changes, if any. This objective
was deemed valuable because it was to be the first such study of thermal
impact on a wel1-developed fringing coral reef.
As a secondary objective, the survey included a study of the effect of
the coral feeding crown-of-thornsstarfish, Acanthaster planci (L.), which
had recently invaded Guam. The significance of this study was twofold.
First it was necessary to document (Phase I) any existing damage attri-
buted to the starfish and thus avoid possible confusion with effects of
thermal effluent that might be "discovered" later (Phase II). Second,
existing starfish damage provided a unique opportunity to study reef
recovery following severe damage. The starfish, in a sense, simulated
an environmental catastrophe that might have occurred through some form
of pollution.
By a fortuitous circumstance, one of the authors (Randall) had been study-
ing the distribution of reef corals prior to the starfish infestation
in Guam. This study was concentrated on the fringing reef opposite Tumon
Bay, an area contiguous with the Tanguisson Point study area (Fig. 1).
These valuable collections and transect information form a cornerstone
for this report because they provide us with a control area comparable
with the Tanguisson study area and allow us to make some reasonable ap-
proximations of what the Tanguisson reef was like in an undisturbed con-
dition.
Near the end of Phase I, the first of our two continuation proposals was
submitted to begin Phase II. The continuation proposal was accepted,
however, in addition to the original Phase II objectives, the Agency
asked that heavy metals be monitored and that thermal stress experiments
12
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be done in the laboratory. These additional objectives were added with-
out increase to the project budget. The net result of the additional
work load and cost was deemphasis of some of the original proposal objec-
tives and increased emphasis on the coral succession work and the new
thermal simulation experiments.
The availability of the necessary equipment for thermal simulation allowed
for some additional work on other organisms. This work was done by seve-
ral of our colleagues at the laboratory and the resultant papers are
found in Appendicies A-D. One such paper investigates the effect of ele-
vated temperature on the metabolism of Acanthaster planci. This work
was done by Dr. Masashi Yamaguchi and is found in Appendix A. Graduate
student John Rupp was a valuable research assistant during our work and
at the same time concluded a Master's thesis on the effects of elevated
temperature on the embryology of several tropical echinoderms (Appendix
B). The third contribution,by graduate student Tom Hohman and Dr. Roy
T. Tsuda, is a preliminary study dealing with the effect of temperature
on photosynthesis and respiration in the green alga,Caulerpa racemosa
(Appendix C). Graduate student Greg Gordon was provided with grant sup-
port for a preliminary study of the effects of heated effluent on two
species of coralline algae. This study was submitted as a student re-
port (Appendix D).
The data added by our colleagues is above and beyond the objectives of
our grant proposal and we are indebted to them for the additional results
regarding the effects of thermal effluent on tropical organisms.
13
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SECTION IV
THE STUDY AREA
GENERAL DESCRIPTION OF GUAM
Guam is the largest and most southerly of the fifteen small islands that
make up the Mariana group in the western Pacific Ocean. It is 48.3 kilo-
meters in length, and ranges in width from 6.5 kilometers at the narrow
central waist to 18.5 kilometers at its widest part. The island has a
land area of 5^9 square kilometers.
The northern half of Guam, that includes the study area, is a limestone
plateau bordered on the coasts by steep cliffs that range in elevation
from more than 180 m at the north end to less than 60 m at the centrally
located, narrow waist. The limestone is porous and no streams are found
on the northern plateau. The western and northern coasts are bordered
by fringing reefs.
CLIMATE
The following summary of climate and rainfall data is condensed from a
report found in Tracey et all. Guam has a warm, humid climate that is
mainly determined by its oceanographic setting. The island lies within
the belt of westward-moving, warm humid air of the tropics, which is
produced between the subtropical anticyclones of the northern and south-
ern hemispheres. Variations in the weather are caused by cyclonic
eddies or whorls that form continuously, sweep westward, and dissipate.
These disturbances may grow in size to become tropical storms or typhoons.
The period from July to November includes the rainy months, January to
May is considered the dry season, and June and December are transitional
months. The mean annual rainfall on Guam ranges from less than 228.6 cm
in the lee of the mountains to more than 279.4 cm in the higher mountain
areas. About two thirds of the annual rainfall occurs during the rainy
season. Tradewinds predominate during the dry season. Winds usually
become light and variable during the wet season, except during storm
conditions.
14
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PHYSIOGRAPHIC DESCRIPTIONS
General Comments
The northern limestone plateau, which borders the study area, is very
porous, resulting in a wel1-developed Ghyben-Herzberg fresh water lens
system. Water escapes continually along most sections of the intertidal
zone. This fresh water seepage onto the reef flat is particularly notice-
able along sandy beaches at low tide, where it forms small rills. Emery2
measured the fresh water seepage along a kj m section of Gogna Beach at
Tumon Bay and found it to be 42.5 liters per second. Analysis of beach
samples from Tanguisson Point by Emery2 shows that the sediments of this
region are nearly 100 percent bioclastic. This is due to the absence of
rivers and streams emptying onto the reef flats of the study areas.
The Tanguisson Power Plant is located on an elevated terrace that is
covered with beach deposits (Fig. 2). Vegetation around the plant is
composed of an old coconut plantation and a wel1-developed strand vege-
tation along the beaches. This terrace is backed by steep limestone
slopes and a cliff on the landward side. The cliff reaches heights of
about 100 m. Both the slopes and cliff support dense limestone forest
vegetation. To the south, the terrace narrows down and eventually dis-
appears near Amantes Point (Fig. 3). To the north, the terrace includes
the Naval Communications Station (NCS) swimming beach and then continues
along the coast up to Tanguisson Point where it narrows to a thin strip.
Immediately to the west is the first of the reef zones described below.
The reef platform and slopes are divided into several reef divisions
after Tracey et al. These divisions are based on various physical para-
meters such as degree of reef surface exposure at high tides, degree of
reef surface submergence at low tides, amount of reef slope, and reef
growth and erosional structures.
The biologic parameters have been deliberately omitted from the fringing
reef descriptions. This was done because later parts of this report
(Section X) describe reef coral distribution by zones in detail, and be-
cause future workers investigating reef recovery would experience diffi-
culty in comparing structures and descriptions of former living coral
reefs with those that have since been killed by Acanthaster plane!.
A series of transects were established and are shown on Figure 3. Reef
profile and zones for the Tanguisson study area are shown on Figure k.
Tanguisson Point Fringing Reef
Tanguisson Point study area (Figs. 1-3) is located between Amantes Point
and Tanguisson Point. The fringing reef platform along this section of
coastline is relatively narrow. It ranges in width from 70 m at Transect
15
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Figure 2 Aerial photograph of the Tanguisson Power Plant site
16
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A to 110 m at Transect C. The fringing reef has a westerly exposure to
the sea.
Intertidal — This zone is the portion of the beach or shore covered by
water at high tide and exposed at low tide. The intertidal zone bordering
the transect locations at Tanguisson Point is composed of bare limestone,
with the exception of a sandy section at Naval Communication Station
(NCS) swimming beach, and several other small sandy sections between
Transects B and C (Figs. 2-3). At Transect B this zone is kO m wide and
consists of limestone ridges, knobs, and pinnacles, separated by numer-
ous interconnecting channels (Fig. 2). These channels are relatively
flat-floored and about the same general level as the reef flat. The
upper half of the emergent structures is exposed during high tide and
deeply solution-pitted. Relief of these structures ranges from about a
meter at the shoreward side to 20 cm on the seaward side. Unconsolidated
sediments are scarce along the bare rocky regions, except for local pat-
ches of course gravel and boulders. Sediments at the two beach areas are
mostly sand, largely composed of worn foraminiferan tests. At low tide
fresh water can be seen escaping from the intertidal zone and at sandy
locations it forms small rills similar to those described by Emery^ at
Gognga Beach.
Reef Flat -- This is the flat limestone platform that extends from the
intertidal zone to the wave-washed reef margin (Figs. 2-k). The outer
seaward part of the reef flat is slightly elevated in respect to the
inner shoreward section and, at low tide, is often exposed while the
inner part retains water. On this basis, the reef flat is divided into
two subzones—an outer reef flat subzone that is exposed during low
tide, and an inner reef flat subzone that is covered by water at low
tide. The inner water mass is here called the "moat".
The inner reef flat subzone at Tanguisson Point, is poorly developed at
Transects A and C and is absent altogether at Transect B. During low
tide at Transects A and C, a few shallow, irregular-shaped pools and a
depressed zone north of Transect C retain water and constitute the moat
of the inner reef flat. The floors of these pools contain coarse gravel,
boulders, and scattered emergent limestone patches. At NCS Beach, water
is retained at low tide, but this is partly due to dredging and blasting
and does not represent natural conditions.
The outer reef flat subzone is more extensive than the inner reef flat
and represents most of the reef platform. At Transect B, where no inner
reef flat occurs, the outer reef flat extends from the reef margin to
the intertidal zones and is 60 m wide. At Transects A and C, the subzone
width is 50 m and 90 m respectively. At low tide, the exposed platform
is a flat pavement with very little relief. A few small shallow pools
(10 to 50 cm deep) are widely scattered over the surface. Sediments are
scarce and accumulate only in the small pools. An algal turf covers most
of the surface and contains many foraminifers.
17
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Reef Margin -- This zone is represented by that part of the seaward edge
of the reef flat platform that is constantly awash even at low tide
(Figs. 2-4). The reef margin at Tanguisson Point is slightly elevated,
about 20 cm above the outer reef flat level, and forms a low, poorly-de-
veloped algal ridge. The algal ridge development is greatest at Transect
B. Observations immediately seaward of Transect B show that the degree
of reef front slope is less than at Transects A or C, causing greater
surf action and thereby enhancing algal ridge development. The reef
margin width is fairly uniform and, at the transect locations, ranges
from 20 to 30 m. The seaward edge is very irregular and is cut at right
angles by short surge channels 1 to 3 m wide, 2 to k m deep, and up to
20 m in length. Some surge channels coalesce and fuse at their upper
margin, forming cavernous channels beneath the reef margin platform.
Most of the cavernous channels open at intervals along the fusion zone,
forming pools and open cracks. In cross section, most surge channels
are wider at the bottom than at the upper margin, which may be due partly
to growth at the upper regions and abrasion at the base or floor which
contains large, rounded boulders. Most boulders, however, do not show
evidence of constant movement because most are encrusted with red algae
and small coral growths. These boulders are probably moved about only
during typhoons and other storms. Surge channels are separated by lo-
bate elevations called buttresses that slope seaward toward the reef
front zone. The upper surface of a buttress is very irregular, with
knobs, pinnacles, and in many places is honeycombed with numerous inter-
connecting holes.
Reef Front — The reef front represents the extreme seaward edge of the
reef flat platform, where the reef margin abruptly increases in depth
and degree of slope (Fig. k). This zone is constantly covered with
water. The reef front is composed of the seaward sloping extensions of
the reef margin buttresses and surge channels. The point where the sub-
marine buttresses and channels terminate marks the seaward boundary of
the reef front. Generally, the 6 m submarine contour coincides with
the seaward limit of the reef front. Width of the reef front zone is
variable and ranges from 70 m at Transect A to 60 m at Transect C. Sub-
marine channels near the reef margin are 2 to 6 m in depth and commonly
branch into several secondary channels. These channels are similar in
cross section to those described above. Some submarine channels widen
into holes 5 to 15 m in diameter, with large boulders covering their
floors. Submarine buttresses slope seaward at 10° to 15° and are ex-
tremely irregular on the upper surface due to the presence of coral-algal
knobs, bosses, and pinnacles. At the seaward half of this zone, these
various prominences may have a relief of as great as 2 to 3 m.
Submarine Terrace— The first submarine terrace represents a noticeably
flattened region when compared to the reef front and seaward slope zones
(Fig. M. This zone ranges in width from MO m at Transect C, to 110 m at
Transect B. The shoreward margin of this zone begins at the 6 meter
18
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M
Reef margin
Transec
Trans^c
Tanguisson
Point
Dredged swimming
zone
Tanguisson Power
Plent
Transent 0
»Iriner reef flat
moat
j|lllll|l Limestone headlands
Amantes Point
600 Meters
Figure 3 Detailed map of the Tanguisson Point study area
showing transect locations
19
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pq
-i->
o
t-l
H
-4->
rt
0)
-------
contour but its seaward margin, where the steep seaward slope begins, is
located at the 10 to 15 m contour. Relief of the surface features ranges
from 1 to 2 m. Occasional coral mounds or pinnacles attain a relief of
3 m. Shallow channels up to a meter in width and depth cut across the
surface at some locations. Sediments are found in localized patches in
holes, cracks, and in shallow channels. These sediments consist mostly
of rounded boulders, coarse sand, and gravel.
Seaward Slope -- At the seaward edge of the Tanguisson Point submarine
terrace, the degree of slope abruptly increases and sharply differen-
tiates the seaward slope from the terrace. Width of this zone at the
three transect locations averages 70 m. The steep seaward slope flat-
tens into a second submarine terrace at about the 30 to 35 m depth. This
second terrace probably corresponds to the 32 m submarine terrace found
by Emery at Tumon Bay.
Distinct linear sediment tracks can be traced from the upper part of the
slope to the second submarine terrace below. Although depth of sedi-
ments was not measured at the second terrace, visual observations made
with SCUBA indicate a considerable accumulation at the base of the slope.
A conspicuous feature of the second submarine terrace is the presence of
scattered coral knolls. These knolls arise from the sandy terrace floor
at a AO to kS m depth and have a relief of up to 10 m.
21
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SECTION V
CURRENT PATTERNS
GENERAL COMMENT
Transport of water masses around the island of Guam Is similar to that
for most islands in the Central Pacific (i.e. Avery et al ). The pre-
valent northeast tradewinds of the area play a major role in generating
the enormous North Equatorial Current that sweeps by the island from
east to west. This great current is responsible for much of the energy
that transports water along the coasts. According to Emery the north
equatorial current splits on the northeast corner of the island and
streams around the south end of Cocos Island and around the north at
Ritidian Point (Fig. I). These two streams then sweep along the west
coast where they supposedly rejoin west of Apra Harbor. As they move
along the western coast, the near shore portions of the streams are dis-
torted and forced into complicated eddy systems by prominant headlands
and local submarine topography. These currents may also alter their
flow because of seasonal changes in strength and direction of the North
Equatorial Current. They are further complicated in some areas by tidal
currents superimposed on them, often resulting in a temporary reversal
of direction with changes in tide (Jones and Randall^).
Inshore water movement is generated primarily by tide changes and wave
action. These two forces combine to transport water over the reef margin
onto fringing reef platforms around the island. This water often forms
long shore currents on reef flats for some distance and then returns to
sea as rip currents via natural low spots and surge channels through the
reef margin.
It was apparent at the beginning of this study that the Tanguisson water
mass could be divided into three parts. First there is the shallow water
portion bathing the reef flat and a portion of the reef margin. Second,
there is that portion which encompasses the reef front and remainder of
the reef margin. The third component includes the submarine terrace
and seaward slope. Overlap of the first two parts may occur because
22
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of surge activity in the shoaling water that mixes them.
Effluent released on the reef flat is influenced first by current pat-
terns generated there and then passes into the influence of reef margin
and reef front water transport systems. After some mixing because of
wave attack in these zones, the remaining effluent is carried offshore
where it joins the currents that dominate the water mass over the terrace
and slope.
REEF FLAT AND UPPER MARGIN
Prior to plant startup, a series of reef flat stations were established
at the proposed outfall site near Transect B and along the coastline to-
wards both Transects A and C (Fig. 3). Current patterns were investiga-
ted by releasing fluorescein dye at these stations. The dye powder was
sewn into cloth bags and buoyed. Movement of the dye was timed and
plotted on scaled area charts and in some cases recorded with time lapse
photography. Wind, wave, and tidal data were recorded. The dye study
schedule was set to include both high and low tide stands and to cover
ebb and flow.
The same methods were used to study changes in current pattern induced
by the release of plant effluent after startup of Tanguisson No. 1. Dye
releases were then concentrated at the stilling well of the plant outfall
and around the intake channel. Construction of Tanguisson No. 1 was
under the jurisdiction of U. S. Navy Public Works and requests were made
to the Officer-in-Charge of Construction for current studies that might
have been made in the area during the planning stages. Although some
offshore and inshore dye studies had been made, little data could be found
to indicate the results of the study. One unidentified site plan was loca-
ted that showed a series of arrows drawn on the reef flat that indicate
current direction. These arrows show water flowing from the NCS (Naval
Communication Station) swimming lagoon across the proposed intake chan-
nel and thence seaward at a point directly adjacent to the power plant.
By the time our project began, the contractor had constructed an earth
fill causeway parallel to the proposed intake channel. The causeway was
used to excavate material blasted loose from the reef margin and reef
flat. When the intake channel was completed the causeway was removed.
Presence of the causeway and then the completed channel made it impossible
for us to determine current patterns over the Tanguisson reef flat prior
to construction. However, we have reason to believe that they were as
the Navy chart shows in part and in part as discussed below.
Because the Tanguisson reef flat has a slightly raised seaward margin,
there are two natural ways in which seawater may encroach on it. Rising
tides periodically cover and uncover it, and water transported by wave
23
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action may pour over the margin and spread out over the reef flat. The
predominant swell direction on Guam is northeasterly. This swell becomes
more northerly as it wraps around Ritidian Point. Swells approach the
study area consistently from the north and north northwest. As the
swells begin to "feel bottom" on the submarine terrace they wrap until
they basically approach the shore at right angles. Most break along the
margin from the northwest. Currents on the reef flat are generated by
water on the platform returning seaward. In the study area, there are
six major points where this seaward flow occurs (Fig. 5, l-Vl). These
are usually natural low spots on the reef margin and have one or more
large surge channels associated with them. The recently excavated in-
take channel provides an artificial escape point through the reef margin
(ill). Immediately southwest of the intake channel there is an area of
deep caverniculous surge channels that covers a broad front opposite the
outfall structure and Transect B (IV), This is one of the dominant
points for the seaward escape of water from the platform. The natural
depression in the margin is 50 m wide and has five to seven major surge
channels through it.
The following discussion considers the various currents generated on the
reef flat prior to plant startup (Fig. 5). During the somewhat rare
times of calm seas (little or no swell), flood tides gradually cover
the reef flat and there is a net movement of water shoreward with little
or no movement seaward. Dye placed in the intertidal in the vicinity of
Transect B tended to form an even stain and spread out from the shore
by diffusion of the dye particles. It usually took 30 minutes or more
for the cloud to reach the reef margin. Ebb tides under similar condi-
tions (calm sea) show a net movement seaward through the six points
(Fig. 5> I-VI). This continues until the Tanguisson reef flat is com-
pletely uncovered except for a few depressions that retain water at low
tide. Dye introduced at Transect B and opposite the outfall showed a
positive movement seaward, on ebb tides, through the cavernous surge
channels along the adjacent reef margin (IV). It took a dye cloud an
average of 20 minutes to reach the reef margin surge channels.
The situation described above changes somewhat if there is a surf breaking
on the margin. On a flood tide, wave transport adds to the net shore-
ward movement. Dye placed in the intertidal opposite Transect B and the
outfall, again showed a net movement seaward due primarily to diffusion.
This movement was very slow due to resistance caused by translated waves
on the reef flat. The dye patterns tended to oscillate back and forth
with each wave surge, just maintaining a net seaward movement. The direc-
tion of movement is still toward the surge channel sector opposite the
plant (Fig. 5, IV). During high surf conditions (2 + m) it often took the
dye cloud up to 60 minutes to reach the reef margin. A combination of
ebb tide and wave transport resulted in the same oscillatory movements of
dye clouds but the net movement to the surge channels at the reef margin
was somewhat faster, about 20 to 25 minutes,depend ing upon the magnitude
24
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of the surf. There are times, during strong west winds, when some of the
dye spreads northeast and enters the intake channel of the plant.
Figure 6 shows conditions that now exist since startup of the Tanguisson
Power Plant. Water that formerly entered the intake channel from the
adjacent reef flats still does so but the" strong rip current that moved
seaward before plant startup has been reduced somewhat because of cur-
rents generated in the channel by the power plant's circulating pumps.
Except at the surface on the seaward end, there is now a net movement
of water in the intake channel toward the plant.
Current-patterns opposite the outfall structure have been modified in
speed but not direction by plant effluent (Fig. 6). Circulating water
is released in a stilling well at the intertidal. The effluent wells
up onto the reef flat and moves seaward. During low tides and periods
of low surf, there is a well-defined stream of water that flows in a
direct line seaward. It takes 10 minutes or less for dye released at
the stilling well to reach the margin. Effluent enters the reef margin
and pours seaward through surge channels. During low spring tides, the
effluent forms cascades off of the reef margin into surge channels. At
high tides and periods of high surf, the effluent stream is interrupted
at the reef margin by wave transport. At this time, part of the stream
occasionally turns south and may exit at the second set of surge chan-
nels near Transect C (Fig. 5, V & VI). The larger portion of the efflu-
ent merges with part of the incoming wave transported water and escapes
seaward through surge channels opposite the plant in a series of pulses
between wave crests.
LOWER REEF MARGIN AND FRONT
The lower reef margin and front are essentially transition zones between
the reef flat and upper margin water masses and those of the terrace and
seaward slope. Dye studies were also used in this area but were concen-
trated where the reef flat current studies indicated exit of water from
the reef flat.
Except in the natural low areas north of Transect C (Fig. 5, V & VI),
where there is a strong seaward rip current during high tides and surf,
dye releases on the lower reef margin and upper reef front result in
slowly spreading stains that move parallel to the surf1ine and in the
direction of the prevailing current over the submarine terrace. A sus-
pended particle would tend to be swept back and forth over the margin
and upper front by wave surge and at the same time be carried slowly
along shore because of the influence of offshore water movements. Such
a particle describes a zigzag pattern. This type of movement results
in considerable mixing due to wave attack. No changes in this pattern
were observed after plant startup.
25
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IV
Figure 5 Current patterns on the reef flat prior to release of effluent
Figure 6 Current patterns on the reef flat after release of effluent
26
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The most consistent direction of movement along the reef margin is to the
southwest. West winds and strong tidal shift may set this water to the
northeast on occasion.
SUBMARINE TERRACE AND SEAWARD SLOPE
These areas tend to be dominated by the northwestern branch of the North
Equatorial current that swings around Ritidian Point, and by tidal cur-
rents.
A Hydroproducts Model 502 and three TSK Model 101 current meters were
anchored at various depths and along selected transect stations to deter-
mine set and drift of currents over the terrace and slope. These data
were to provide information on the movement of the effluent plume once
it passed over the reef margin and front. Over 1600 hours of current
meter data was recorded from Transects A and B at depths of 5, 10-1 A,
23 and 30 m. All months of the year (1969-1971) were monitored except
March, May, September, and November.
Single current meters are anchored devices, that provide only data for a
single stationary point. Drift crosses were used to track offshore water
masses. These devices provide a better idea of potential plume transport.
The drift crosses were set for one, five, and ten meter depths and re-
leased along Transect B. The casts were made from small boats and their
tracks plotted with hand bearing compass lines of position on known shore
points. Fifty drift cross casts were made from October 1970 to July 1971-
Casts were made during all months of the year except August, September
and November.
Analysis of the current meter tapes showed considerable variation between
the TSK meters and the Hydroproducts meter. Basically the TSK meters
showed a bidirectional flow at Tanguisson while the Hydroproducts instru-
ment indicated a unidirectional flow. We feel confident that the bidirec-
tional flow is a truer picture. Because there was some question about
data gained from in situ meters, we elected to use more drift cross data
than originally planned. These data tend to bear out the bidirectional
f low.
Mean current direction obtained from current meters is plotted in Figures
7 to 11. Data on the upper submarine terrace (5m) nearest to the efflu-
ent release point are shown in Figure 7- The basic directions are on a
northeast and southwest axis. The numerous small easterly components are
the result of wave surge operating very nearly at right angles to the
current axis. Figure 8 shows the current directions in the transition
zone between the lower terrace (10m) and upper slope (lAm). This region
shows a dominant southerly component with considerable representation in
southeast quadrants. These data were taken with the Hydroproducts meter
27
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and the north to northeasterly components are less well represented here
than in the upper terrace (Fig. 7). Again, the easterly components re-
flect wave surge against the current meter vanes which are normally set
either northerly or southerly with the prevailing currents. Figure 9
shows the resultant directions of current for meters set on the mid to
lower slope regions (23m). All measurements at this depth were taken
with the TSK meters and the data show equally numerous northwest-north-
east to southwest-southeast components. The Hydroproducts meter was set
several times at the bottom of the slope (30m) and again showed the odd
truncated pattern with very little northerly current evident (Fig. 10).
We are uncertain at this point why the Hydroproducts meter is unrespon-
sive to northerly components, but suspect a calibration problem. When
the data from all stations are combined and mean directions calculated,
the pattern shown on Figure 11 emerges. Here the basic current direction
lies from northwest-northeast to southeast-southwest. The most common
direction is southerly but may be somewhat biased due to the inclusion
of data from the Hydroproducts meter.
The current speed data also showed considerable variation between the
two types of meters. The TSK meters showed generally lower velocities
than the Hydroproducts meter. TSK readings rarely exceeded 0.3kt-> the
majority were less than 0.15kt. and included numerous zero readings.
The Hydroproducts meter showed a range from 0.1 to O.Skt. with no zero
readings. The majority of the readings were grouped around 0.4kt •
We feel that current direction and possibly velocity is correlated with
Guam's semidiurnal tides. There are numerous local meterological and
hydrographic phenomena that influence the degree of fit of this corre-
lation. Figure 12 shows a relatively close fit of current direction
with tide shift. In general, we found that on ebb tides, the current
ran to the north or northeast. On flood tides, we encountered a higher
frequency of southerly drifts. Some lags or shifts may be seen around
the tide turns on Figure 12. Figure 13 shows that on occasion, current
direction did not shift with tide for several successive cycles. In the
case of Figure 13 the tide ran continuously in a southerly direction.
Figure 14 demonstrates the same over-riding of tidal shift but with
northerly components dominating. Similar data are reported by Jones and
Randal P.
Drift cross data also suggest that currents in the Tanguisson area move
along a basic northeast to southwest axis. Figures 15-17 show direction
of drift indicated by 1m, 5m and 10m drift crosses. The occasional strong
westerly sets are resultant vectors between the northeast wind and tidal
shifts to the north. Due east or west vectors also occur temporarily
during times of tide change.
Again there is frequent apparent correlation between tide changes and
changes in current direction. But as in the case of current meter data,
28
-------
PERCENT FREQUENCY
I 1 1 1 1 1
0 5 1O 15 20 25
Figure 7 Mean frequency diagram for current direction at 5 m
29
-------
HILAAN PT.
ANGUISSON PT.
PERCENT FREQUENCY
I 1 1 1 1 1
0 5 10 15 2O 25
Figure 8 Mean frequency diagram for current direction at 10 to 14 m
30
-------
PERCENT FREQUENCY
I 1 1 —I 1 '
0 5 10 15 20 25
Figure 9 Mean frequency diagram for current direction at 23 m
31
-------
PERCENT FREQUENCY
H 1 1 1 1
5 10 15 20 25
Figure 10 Mean frequency diagram for current direction at 30 m
32
-------
PERCENT FREQUENCY
10 15 25 25
TANGUISSON PT.
. .POWER
L-J PLANT
AMANTES PT.
Figure 11 Mean frequency diagram for current direction, all
stations combined
33
-------
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current shifts may precede or lag behind tidal shifts or fail to change
at all.
In general, the drift cross patterns roughly approximate a northerly
drift on ebb tides and a southerly one during floods. Drift numbers 16
and 18 (Figs. 15-16) failed to follow the pattern. Both drifts showed
definite northerly directions during floods. The two casts were made in
July when the rainy season starts on Guam. At this time tradewinds often
break down and the strength of the North Equatorial Current may be re-
duced. The tide change during the drifts was from a higher low water to
a lower high water thus producing a weak flood. Both tide changes were
preceded by relatively strong ebbs from a higher high water to a high
low. Therefore the northerly flowing currents from the previous ebb may
have persisted through the next weak flood.
Drift cross observations indicated a range of current speed from 0.1 to
0.6 kt, with very few zero readings. The mean of the combined drift
cross speeds was 0.2 kt.
In 1971, the U. S. Navy Oceanographic Office sponsored a series of current
measuring stations at Tanguisson Point and nearby Hilaan Point to the
north. This study was conducted in two parts, one survey in the "winter"
and one in the "summer". The winter measurements were taken in February
1971 (Anon.5). The current meter set off Tanguisson Point showed:
"....pronounced movement to the northeast and southwest, and
observations are evenly distributed in these two
directions. Tidal movement shows as a factor when plotted
against monitored current, but ocean currents generated
by storms at long or short distances from Guam are of
greater impact than the tide and generally mask tidal
fluctuations."
Dye studies conducted at the same time showed general northwest-north-
east and southwest currents that agreed with current meter data.
The Navy's summer survey was conducted from August to September 1971
Huddel1 et al . The report summarized the previous winter data as
follows:
"Current speeds from the Tanguisson Point meter ranged up to
0.75 knot but they were most frequent between 0.05 and 0.25
knot. Most of the currents flowed northeast and southwest,
with northeasterly flow being predominant. Progressive
vector diagrams do not reveal any correlation between direc-
tion of flow and tidal phase."
This summary contradicts somewhat the discussion in the winter report.
37
-------
to
500
Figure 15 One meter drift cross casts
38
-------
50O
Figure 16 Five meter drift cross casts
39
-------
15
^
&
17
POWER
^•V^/STATION
METERS
I—I 1-
50O
Figure 17 Ten meter drift cross casts
40
-------
The summer report went on to describe the August to September current
meter sets at Tanguisson and Hilaan Points. The Tanguisson meter suffered
a mechanical failure but the first hours of operation were in basic agree-
ment with the winter readings at Tanguisson and the summer readings at
Hilaan Point. The Hilaan Point meter showed speeds of up to O.^kts. but
usually less than 0.2kt, A progressive vector based on 66 hours of
observations showed direction shifts between southwest and north-north-
east resulting in a net westerly drift.
Thirty-eight dye casts were also made during the above summer period along
with four drogue casts in the Tanguisson area. Flow was almost equally
divided between northeast and southwest. They reported the direction of
movement as being unrelated to the tide. Dye releases were observed oppo-
site the power plant over four ebb and four flood periods and one tidal
shift from flood to ebb. Of these, we feel that six show a correct tid-
al related pattern, three were incorrect, and one was inconclusive based
on our assumption that current flows southerly on floods and northerly on
ebbs. It is interesting that the tidal shift from flood to ebb resulted
in a directional change from south to north. All four drogues showed a
southerly set with a speed of
Neither the Navy survey nor our study seems to have satisfactorily answer-
ed the question of tidal influence on currents. However, both studies
are in agreement about the bidirectional current shifts that occur off
Tanguisson Point from northerly to southerly directions.
41
-------
SECTION VI
TEMPERATURE REGIMES
GENERAL COMMENT
Emery2 reported seawater temperatures for Apra Harbor, Guam between 27.2
and 29.*f°C (2.2°C range). Months with average water temperatures above
28.9°C were July through October. These data are in reasonable agree-
ment with data collected by the Guam Division of Fish and Wildlife from
Tanguisson Point. Division personnel take thermometer readings an aver-
age of three mornings per month from the reef margin near Transect A.
The data are presented in Figure 18 and are a good approximation of the
seasonal temperature regime for oceanic water around Guam. For a 10
year period, from 1963 through 1972, the mean water temperature was
27-6°C. Range maxima were 25.6°C, which occurred only once and 29.^°C,
which occurred on two occasions (3.8°C max. range). The extremes of
mean monthly temperatures were 25.9°C, which occurred once, and 29.0°C
which occurred twice (3.1°C range). The range of annual means for 10
years was 27.k to 27.9°C (0.5°C range). These data suggest that the
oceanic temperatures around Guam commonly fluctuate between 26.0 and
29,0°C and rarely fall below or climb above this 3°C range.
As pointed out in the Introduction, seawater at ambient temperature was
to be circulated through the Tanguisson Power units at a rate of 17,000
to 28,000 gpm depending upon the number of circulating pumps on the line.
According to engineering criteria the temperature of this water was ex-
pected to be increased by 12 to }k° F per unit with one pump in opera-
tion and about 9 to 11° F with two. Two pumps were to be used about 50
percent of the time, during peak power periods. The policy has changed
since the writing of this report, one pump per unit is now used most of
the time. If we assume that cooling water in the intake channel is pri-
marily oceanic (mean=27.6°C) and the maximum delta T would be \k° F,
then we can predict a mean outfall temperature of 35.^°C (delta T=7.8°C).
The range of oceanic circulating water temperatures (approximately 26-
29°C) would be increased to 33-8°C at the low end 36.8°C at the high end.
42
-------
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43
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After Tangulsson No. 1 began generating power, plant personnel provided
valuable temperature readings from Control Room thermocouples. These
data included intake and outfall temperatures for January 1972 through
April 197^ (Fig. 19). Thermometer and thermograph readings were obtained
several times from the intake channel and stilling well to verify these
data. Tanguisson No. 1 began regular power production in January 1972
and was the only plant in operation during the first 16 months. Unit
No. 2 was completed and began operations in May 1973. Both units opera-
ted together during most of the last 12 months of the field study (Fig.
19).
Table 1 shows that the actual mean outfall temperature was lower than
the predicted mean with one unit on the line. With both units operating,
the actual mean was higher than predicted. The range of monthly means
was also lower than predicted with one unit in operation but was near or
slightly above the predicted range with both units operating. The higher
temperatures were due in part to increase in intake water temperature dur-
ing the last 12 months (from a mean of 27.1°C for the first 16 months to
28.it°C for the last 12). The increase in ambient may be due to an infre-
quent warming trend in oceanic water near Guam, warm water pouring off
the shallow reef flats into the intake channel, recirculation of heated
water from both units back into the intake or a combination of all three.
Moreover, one might suspect some change when both plants began simultan-
eous operation. Note on Figure 19 that while ambient and outfall tem-
peratures did increase together for the last 12 months, the delta T did
not remain constant but instead increased from a mean of 6.5°C to 7-7°C.
REEF FLAT
Both before and after plant startup, recording thermographs were placed
along Transect B at stations B-2 and B-8 (plume axis). These stations
are on the reef flat, 20 and 80 m from the shoreline, and adjacent to
the outfall structure. Thermometer recordings were also made along the
plume axis at 10 m intervals from the stilling well to the reef margin.
These data were compared with thermocouple readings from the Control
Room of the plant and found to be consistent with them.
Prior to plant startup, mean monthly reef flat temperatures for the
months of May to September 1970 (warm months) and February to March 1971
(cool months) ranged from 28 to 30.9°C. The mean for the entire seven
month period was 29-3°C. Periodic fluctuations of considerable magnitude
were noted on several occasions duping low tide periods. The maximum
range of these fluctuations was 27.2 to 33«9°C but these times were rare.
The former occurred three times and the latter four during the seven
month sampling period. The high end of the scale is explained by the
coincidence of low tides and high mid-day temperatures. The low end is
correlated with low tides and encroachment of ground water escaping
44
-------
Table 1. PREDICTED AND ACTUAL TEMPERATURE CHANGES OF PLANT EFFLUENT
For Oceanic Water
10 year mean 27.6°C
10 year range of monthly
means 26 (25.9) - 29°C
Assume maximum predicted delta T of lA°F for Tanguisson power units
Predicted mean 35.4°C (delta T = 7.8°C)
Predicted range of monthly
means 33.8 - 36.8°C
Actual intake mean for first
16 mos. (1 unit) 27.1°C
Actual outfall mean for first
16 mos. (1 unit) 33-7°C (delta T = 6.6°C)
Actual intake mean for last
12 mos. (2 units) 28.A°C
Actual outfall mean for last
12 mos. (2 units) 36.0°C (delta T« 7.6°C)
Actual range of monthly outfall
means 16 mos. (1 unit) 32.5 - 3M°C
Actual range of monthly outfall
means 12 mos. (2 units) 3^.9 - 37°C
45
-------
CO
IO
-------
along the Intertidal from the Ghyben-Herzberg lens. This flow Is
heaviest after recent rains. Both situations are moderated, as expected,
with the next flood tide. These data are in agreement with temperature
data from the Agana Bay reef flat in 1969 and 1970 (Jones and Randall^).
The Agana data show a mean temperature of 29.1°C and a range of 28.0 to
30.5°C for the months of January, February, April, May, September, Novem-
ber and December. The differences between the high ends of the ranges
at the two study areas is because of the greater water depth, at low
tide, in Agana Bay.
It is apparent then that even in normal (before plant operations) times,
temperatures several degrees above oceanic surface temperatures may occur
naturally on the reef flat. The normal mean reef flat temperature (29.3°C)
tends to run nearly 2°C higher than oceanic (27-6°C), but these conditions
are temporary and are relieved during the next flood tide. The power
plant, on the other hand, pours a constant volume of heated water across
the reef flat adjacent to the plant. Data in Table 1 and Figures 19 and
20 show that reef flat temperatures in the plume were considerably higher
than normal reef flat temperatures taken prior to plant operations. The
plant effluent mean (both units = 36.0°C) is 8.*f°C higher than the ocean-
ic mean and 6.7°C higher than the normal reef flat mean (29.3°C).
Although the high temperatures tend to be moderated somewhat during times
of high tide and high surf, these same oceanographic conditions also tend
to spread the plume front as it approaches the reef margin and thus ex-
poses a broader and deeper portion of the reef margin biota to water tem-
peratures above normal.
REEF MARGIN AND UPPER FRONT
Recording thermographs were placed at station B-]k (140 m from shore),
directly in the surge channels opposite the power plant. Recordings
were made both before and after plant startup. This area is subject to
violent wave attack and attempts to use in situ instruments has met with
only moderate success. Thermographs were lost or damaged on several
occasions and we eventually had to abandon our efforts. Attempts to
sample the region with hand held thermometers has rewarded the authors
with assorted cuts, bruises and broken thermometers. The subsurface
waters of the reef margin can only be sampled during times of calm
weather when wave mixing is at a minimum and surface stratification
maximum. Our inability to place in situ temperature recording devices
in this area is particularly unfortunate because it is a critical inter-
face between the coral reef community and the effluent.
Surface water temperatures taken by the Division of Fish and Wildlife
are from this zone (Fig. 18). These data were taken along an elevated
47
-------
reef section opposite Transect A (Fig. 3) and therefore are a measure
of incoming wave transported water. Temperature measurements taken by
project personnel at and around Transect station B-]k reflect both in-
coming wave transported water and reef flat water escaping through the
reef margin surge channels at this point (Fig. 5 IV).
Prior to plant startup, a series of thermograph sets showed a mean tem-
perature of 29.0°C at Station B-H. This is 1.4°C above the oceanic
mean recorded at the reef margin near Transect A. The difference, as
noted above, is due to reef flat water escaping along Transect B. The
range of monthly means was 28 to 30.2°C. Thermograph readings (instru-
ments in 1-2 m depths) in September and October 1972 showed higher temp-
eratures after plant startup. The mean for this period was 30.9°C and
the range 29-9°C to 32.1°C. On October 19, 1972 a series of thermometer
readings were taken along Transect B. This particular field trip was
part of an investigation of a recent coral kill along the margin. Water
temperature in the intake channel was 28.6°C. Water in the stilling
well and at mid reef flat was 33.^°C. These measurements were taken
when the sea was relatively calm (0.5 m swells) and during a low tide
that exposed most of the reef flat. Water was cascading off the reef
flat and into reef margin surge channels. The temperature of the cas-
cading water was 33-2°C. One meter seaward of this point the tempera-
ture was 33.1°C. Effluent was stratified in the upper 0.5 to 1 m of
water between wave sets. During times of breaking swells, alternate
flashes of hot and cold water could be felt at the bottom of the surge
channels. At the midpoint of the reef margin width (Fig. A), surface
water temperatures were 32 to 32.8°C. Thus, although there is a ten-
dency for the low density hot water to stratify as it crosses the reef
margin on calm days, a strong swell normally predominates on the reef
and results in mixing water into the deepest parts of the surge channels.
LOWER FRONT AND TERRACE
Water temperatures in these areas, prior to plant operations, were con-
sistent with those shown in Figure 18. The sheer size of this water mass
effectively damps out major diurnal fluctuations of ambient temperature.
After plant startup, it soon became obvious that the effluent behaves in
a relatively consistent manner. Once the effluent passes through the
wave-mixed reef margin and enters the quieter waters of the reef front
and terrace, the warm water tends to restratify in the upper 1 m of the
offshore water mass (Fig. 27). When strong currents are in motion, this
plume drifts with the prevailing current either to the northeast or
southwest. The preceeding current study shows the net movements to be
southerly. At these times the plume is diverted seaward as it meets the
seaward flowing rip currents at the surge channels north of Transect C
48
-------
(Figs. 6, III and 21).
A somewhat different condition prevails when current flow and wave trans-
port is reduced or absent. Four studies were made at such times between
August and September 197^ (both units operating). The limits of the
thermal plume were studied by establishing stations at 10 m intervals
along temporary transect lines running at right angles to the reef margin.
Transect B served as the control transect. Temperature profiles were
made at the surface and 1 m depths (Figs. 20A-H). From the isotherms
it is evident that the effluent spreads out in a seaward direction as
expected. In most cases there is a difference in the distance out to
ambient water reached by the surface and the 1 m profiles. This would
seem to indicate rapid stratification of the effluent as it proceeds
seaward. The seaward bulge that occurs in Figures 20E-G occurred during
a flat calm sea with zero current offshore.
49
-------
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SECTION VII
CHEMICAL PARAMETERS
SALINITY
Salinity measurements were taken in the intake channel and stilling well
and along Transect B. Samples were collected in bottles and analyzed in
the Laboratory with a Hytech Salinometer.
A nine month (March to November 1969) sample period, conducted by the
Division of Fish and Wildlife, showed that average monthly oceanic sur-
face salinities in the area range from 33-83 to 3^.63 with a mean of
3A.28°/oo. The only major variations in salinity expected were those
of the reef flat environment where ground water escapes from the Ghyben-
Herzberg fresh water lens system. The primary intrusion of this water
is along the intertidal zone of the reef flat. Salinity is considerably
lowered at this point (Table 2). At times, the eggs and larvae of the
toad Bufo marinus are found in brackish pools along the intertidal.
Natural freshwater springs are also found beyond the reef flat platform.
Several of these springs are evident in reef margin surge channels.
Similar springs have also been encountered at various points on the sub-
marine terrace. Sudden changes of temperature are easily distinguished
by divers passing through the rising freshwater. During times of heavy
flow, shimmering clouds of low density spring water can be seen rising
in the water column. Construction of the intake channel has broken
through the limestone cap of the reef flat and freshwater also escapes
along the channel margin.
The data in Table 2 show a salinity gradient along Transect B from the
intertidal to the reef margin. Salinities as low as 1.84°/oo were re-
corded near shore. The rate of mixing is dependent upon wind, sea and
surf conditions and to a certain extent upon the tidal phase. Periods
of calm associated with low tides result in low salinities on the inner
reef flat. High tides during calm weather often result in a visible
lens of fresh water that is carried seaward over the reef margin and
onto the surface above the submarine terrace. Table 3 shows that seawater
55
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oo
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03
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56
-------
is diluted somewhat in the intake channel. A gradient occurs from the
channel surface to the bottom at the intake structure. Salinity changes
between the intake and the stilling well are minimal and less than the
natural changes that occur on the reef flat.
Table 3. SALINITY DATA FOR INFLUENT AND EFFLUENT (o/oo).
STATIONS
Channel Channel Mid-
Entrance Entrance Intake Intake Intake Stilling Reef Reef
Date Surface Bottom Surface Midwater Bottom Well Flat Margin
18 Oct. 72 — — 33-68 — 33.92 33.92 33.74 33-76
2 Nov. 72 - 33-32 — --- 33.76 33.76 33.75
8 Nov. 72 33-84 33.90 33.93 33.65 33.62 33-63
14 Nov. 72 34.09 34.17 32.73 34.09 34.12 34.76 33.98 34.14
22 Nov. 72 34.06 34.09 30.24 34.12 34.12 33.98 33.99 34.20
Mean 34.08 34.13 32.76 34.04 34.06 34.01 34.00 33.90
OXYGEN
There was no evidence to show that dissolved oxygen values varied signi-
ficantly from intake to outfall. A sample of data taken in November
1972 Is given below.
Date Intake (mg/1) Outfall (mg/l)
2 Nov. 1972 6.45 6.50
8 Nov. 1972 7.63 7-77
14 Nov. 1972 6.97 6.98
22 Nov. 1972 7.07 7-00
A reduction of percent saturation of 15 to 20% may be expected at higher
outfall temperatures but this change in itself would probably not be of great
57
-------
environmental significance. Dissolved oxygen values of over
7.0 mg/1 were higher than expected for oceanic water but were found
both in intake and outfall channels.
CHLORINE
Chlorine was used during the first year of operation as a desliming and
anti-foul ing agent in the circulating water system. The project did not
include an investigation of either free or residual chlorine in plant
effluent. However the known toxicity of chlorine makes at least a dis-
cussion of its use worthwhile.
The consulting engineers for Tanguisson No. 1 recommended from "past
experience" a chlorfnation dosage of 5 ppm chlorine rate for 20 minutes,
three times per day. Actual usage was about 70 Ibs per day or a little
over one ton per month. In this case 23.3 Ibs of chlorine was used over
a 20 minute treatment period on each of the three working shifts (per-
sonal communication, Frank Melder). This produced a theoretical 5 ppm
rate ahead of the circulation pumps.
On November 2, 1972, the plant chlorine supply ran out and none was
available on the island. It was nearly a month before chlorine was
available again. Examination of the water boxes and condenser tubes at
this time showed very little sliming or other fouling. We were invited
to observe the operation, and strongly urged the plant operations per-
sonnel to discontinue use entirely. Plant management decided to reduce
the chlorine treatment to one shot per day using about 23 Ibs in 20 min-
utes or about 700 Ibs per month. When no loss in plant efficiency was
noted, this was further reduced to 12.5 Ibs in 10 minutes or about AOO
Ibs per month. Finally plant management decided to discontinue use al-
together. This condition still existed at the writing of this report
and no plans are evident for restarting treatment.
The halt in use of chlorine served not only to reduce potential environ-
mental damage but also cut operational costs.
HEAVY METALS
A special request was made by a Project Officer to monitor copper, cad-
mium, and nickel in the plant effluent. Water samples were taken on
three occasions and shipped to the EPA Water Quality Laboratory at
Alameda, California for analyses. The data are presented in Table k.
There is very little evidence to indicate that large quantities of these
metals are escaping from the power plant. Copper is obviously higher
in the stilling well than in either the intake or offshore water. However,
58
-------
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this amount does not exceed that shown by Goldberg' for open ocean water
(3.0 ug/1) and by Alexander and Corcoran for water in the Florida Straits
(10 ug/1. total Cu).
Cadmium was present in amounts usually less than 0.1 ug/1. However, cad-
mium values increased to 0.4 at the mid-terrace station on Transect A
on one occasion and went as high as 0.3 and 0.8 ug/1 in the open ocean
station. This is higher than normal seawater values (Table k).
Contamination is suspected in the taking of these three samples.
Nickel values seemed variable, however, the values near the power plant
were often higher than oceanic water.
It is apparent that considerably more sampling would be called for, in-
cluding replicate sampling from each station, if we are to obtain an
accurate picture of heavy metal distribution. The three samples taken
were from within the first four months of plant operation and the con-
tent of these metals in the effluent might be low and expected to increase.
It should also be noted that the red clay soils of the northern plateau
contain all three of these metals. It is not inconceivable that they are
introduced by way of the freshwater lens.
60
-------
SECTION VIM
BIOLOGICAL IMPACT OF EFFLUENT
GENERAL COMMENT
It became obvious In the early stages of this work that the thermal plume
would have little Influence on the benthos after it passed through the
surge zone along the reef margin. Once over the reef front and terrace,
the effluent was stratified in the upper one to two meters and offered
no threat to organisms below these depths. Consequently, biological
surveys along the reef front, terrace, and slope concentrated on the
effects of the Acanthaster damage and the subsequent recolonization by
corals.
The reef flat and reef margin environments were, however, directly impinged
upon by the effluent plume and the studies there were concentrated on de-
lineating the effects of the effluent. Biologically, the reef flat was
found to be naturally depauperate, while the reef margin was a diverse,
rich ecosystem that had remained unaffected by the Acanthaster infesta-
tion.
ALGAE
A series of quantitative algal transects were made by Dr. R. T. Tsuda
from March to July, 1970. Dr. Tsuda found the algal community in all
reef zones to be "typical" for these habitats. The only differences
were in the Acanthaster damaged reef front, terrace,and slope. In these
areas, algal species composition was virtually identical to undamaged
areas but the standing crop of algae was higher, presumably due to the
reduction in live coral cover. No changes were noted in qualitative
transects run by Dr. Tsuda in the same areas from May through July 1972,
over one year after the power plant began to operate.
Considerable change was noted, at this time however, in the reef flat
and reef margin zones where there was obvious influence from the thermal
plume.
61
-------
Table 5 lists the change in species composition encountered over the reef
flat and upper reef margin in the immediate vicinity of thermal discharge.
Thirty-nine species were encountered before plant operation (Unit No. l)
and only 12 afterward, a 69% reduction in the number of species. The blue
green algae became the dominant group present. Species of this group are
well known for their role as pioneering species. They are among the first
algae to appear and often dominate early successional stages on coral reefs.
They are, for example, among the first colonizers of coral coral la after
the polyps are removed by Acanthaster. As succession proceeds, the spe-
cies are normally replaced by species from other algal divisions. The
blue green species are rarely replaced entirely but are merely reduced in
their role as the dominant algal species.
Thus, introduction of effluent from Tanguisson No. 1 effectively reduced
the reef flat and upper reef margin algal community to an earlier stage
of succession. However, unlike natural perturbations, the effects of
thermal effluent are persistent as long as the plant remains operational.
Hence, normal algal succession following the initial kill and recoloni-
zation does not advance but rather holds at the level of the early pio-
neering species, the blue greens. Exceptions to this were Halimeda
opun t ia, and Cladophoropsis membranacea, green alqae; Dictyota divaricata
and Padina tenuis, brown algae; and Amphi roa fVagi 1issima and Polysiphonia
scopulorum, of the red algae. These species all seemed somewhat resistant
to plume effluent but, Cladophoropsis membranacea seemed to thrive there.
This species produced a thick mat within the limits of the plume and
showed an obviously lower biomass and patchy distribution outside of the
plume during its growing season. Prior to plant operation, Gel id ium pusi1 -
lum was the dominant alga from the intertidal to the reef margin, this
species has disappeared in the vicinity of the plume. Figure 22A & B show
the general distribution of the dominant algal mats opposite the outfall in
December 1972 and October 1971*.
The October survey was conducted after Tanguisson No. 2 went on the line.
Eight more of the species including four of the original blue green have
disappeared. Only four of the 39 species observed prior to release of
plant affluent now remain (a 90% reduction in the algal mat). Microcoleus
lyngbyaceus now completely dominates the plume area, even in the spur and
groove system of the reef margin. Of the above species that were consi-
dered somewhat resistant to effluent, only Cladophoropsis membranacea re-
mains since Tanguisson No. 2 startup and it is restricted to the plume
marg ins.
Due to heavy sedimentation from continued construction up through November
1972, very few algal species settled in the intake channel. The dominant
species were Jania capillacea, Gelidiella acerosa, Amph i roa fragilfssima,
and Galaxaura marginata of the red algae and Sargassum cristaefolium o"T~
62
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the brown (Fig. 22A). Blue green algae were still present in the channel
but were no longer dominant as they had been after the initial channel
construction. Figure 22B shows that three of the intake channel species
have disappeared and seven new species added since startup of Tanguisson
No. 2. £. marginatus remains the domant alga in the channel.
FISHES
The effect of thermal effluent on fishes was examined primarily in the
reef flat, reef margin and reef front zones. The submarine terrace and
other seaward zone fish communities were not influenced significantly by
effluent because of thermal stratification.
Timed random counts were made in each zone. These counts enumerate only
the number of species and not the individuals of each species. Several
trial counts were made and plotted as number of species versus time (60
minutes). These species/time curves showed that 30% of the ubiquitous
species present were accounted for in the first 20 minutes of counting.
Therefore this time was selected for the random counts. No attempt was
made to observe the cryptic species. Our objective was only to show
obvious differences in species richness before and after the injection of
plant effluent.
Twenty minute random counts were made in 1971 prior to the beginning of
plant operations and were repeated in 1972 after plant operation started.
These data are shown in Table 6 for each of the pertinent zones.
The reef flat zone has a characteristic but somewhat depauperate fish
community (Table 6). When Tanguisson No. 1 began operating, all members
(32 species) of this reef flat community, including territorial species,
disappeared from within the limits of the thermal plume. Other workers
(Clarke et al° and Chesher'^) have reported aggregations of fish species
around thermal outfalls. This is not the case at Tanguisson. Here, the
stilling well was devoid of fishes as was the adjacent reef flat from inter-
tidal to reef margin. Large numbers of fishes do appear along the margin
but in less than normal concentrations for this habitat. Typical reef
flat species begin to reappear in a southerly direction along the reef
flat. The reef flat community north of the intake channel is a part of
the NCS swimming lagoon and has a past history of disturbance from dredg-
ing activies. The area is not influenced by effluent discharge and is
not considered further here.
During the period from November 2 to November 20, 1972, the power plant
personnel ran out of chlorine which forced a halt in treatment for con-
densor fouling organisms. (Personal Communication, F. Melder). During
this period, common reef flat species began to immediately recolonize
the reef flat, even within the "thermal effluent". Eleven species were
67
-------
recorded in the area (Table 6). The stilling well also became populated
with fishes in spite of hot water and considerable turbulence. A total
of nine species were observed including large schools of Siganus spinus
and Mulloidichthys samoensis (Table 6). These species and those of the
adjacent reef flat remained and even increased in numbers until November
20 when a new shipment of chlorine was received by the plant. Chlorine
treatments were started again on this date. By the afternoon of the next
day, all species of fishes had disappeared from the stilling well and the
area under the effluent plume over the reef flat was devoid of fishes.
No change was noted at the reef margin.
The reef margin and upper front zones have a diverse fish community asso-
ciated with the live corals that normally occur along the reef margin and
front. A twenty minute random count was made in the upper reef front and
margin in November 1971 just prior to the first injection of hot water
from Tanguisson No. 1 (Table 6). At this time 63 species were observed.
Another count was made in February 1972 after injection of effluent began
and corals began dying. This count yielded a kk% reduction from 63 to
35 species (Table 6). Three subsequent counts made in the summer of 1971*
showed a mean count of 37 species. Hence, there was no significant increase
in the number of species some two and one half years later. The last
counts were made with both generating units in operation but unlike the
coral (see below) and algal observations, there were no additional reduc-
tions in the fish population. The same basic species composition also
rema i ned.
Three 20 minute counts were also made in 197^ adjacent to the power plant
and over the lower reef front where the effluent is normally stratified.
The mean of these three counts was 69 species or some k(>% increase just
seaward of the surf zone where mixing of the hot water occurs. Another
count made north of the outfall site outside of the influence of thermal
discharge, showed 77 species. There seems to be little question that
many of the species normally found in the reef margin and upper front are
avoiding the area, most likely because of the hot water. No chlorine was
being used when the 197^ counts were made. Even those species that are
found within hot water dominated areas tend to wander continuously in and
out of the surge channels. A few territorial species are found in cooler
water layers at the bottom of the deepest surge channels.
Although an increase in number of species was noted in the lower reef
front under the stratified effluent, the fish community still did not
appear normal. We suspected that the combination of Acanthaster destruc-
tion of corals in the lower reef front and the effluent in the margin and
upper front might adversely influence the fish community. Four additional
20 minute random counts were conducted in a similar reef environment near
Cocos Island (Fig. l) where neither Acanthaster damage nor thermal effluent
existed. The mean of the four counts yielded 81 species which does suggest
68
-------
Table 6. VISUAL FISH COUNTS (1971-1972). Contrast is shown in each zone,
before and after the release of plant effluent. In addition, a
comparison is made during and after the November 2 to November
20, 1972 period when the power plant was not using chlorine.
SPECIES
Acanthuridae
Acanthurus lineatus
A. nigroris
A. nigrofuscus
A. triostegus
A. xanthopterus
A. glaucoparieus
A. olivaceus
A. guttatus
Ctenochaetus striatus
Naso lituratus
N. unicorn is
Apogon i dae
Apogon sp.
Ba list 5 dae
Rhinecanthus rectangularis
Balistapus undulatus
Blenni idae
Entomacrodus sp.
Istiblennius coronatus
1. cyanostigma
Cirripectes variolosus
en
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Table 6 (Continued)
SPECIES
Runula tapeinosoma
Rhabdoblennius snowi
Praealticus natal is
Salarias fasciatus
Canthigasteridae
Canthigaster janthinopterus
C. amboinensis
C. solandri
C. bennettt
Carangidae
Caranx sp. 1 (juveniles)
Caranx sp. 2
Chaetodontidae
Chaetodon auriga
C. citrinellus
C. lunula
C. ornatissimus
C. ephippium
C. punctato-fasciatus
C. fa leu la
C. unimaculatus
C. quadrimaculatus
Heniochus permutatus
Forcipiger flavissimus
Pomacanthus imperator (juv.)
Intake Channel (1970
0
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REEF
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Table 6 (Continued)
REEF STILLING REEF
FLAT WELL MARGIN
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Table 6 (Continued)
SPECIES
M. pardalis
Stethojul is axi 1 laris
S. 1 i near is
Hemigymnus melapterus
Thalassoma umbrostigma
T. quinguevi ttata
T. purpureum
T. fuscum
Lab ro ides dimidiatus
Lutjani dae
Scolopsis cancel latus
Lutjanus monostigmus
Channel (1971)
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0
0
0
0
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STILLING
WELL
CM (TV
crv -3-
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MARGIN
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Monacanthidae
Amanses sandwich?ens is 0000 000 +0
Mugi1idae
Chelon vaigiensis 0+00 000 0+
Mullidae
Parupeneus trifasciatus 0000 000 ++
P_. bifasciatus 0000 000 +0
Mulloidichthys samoensis +000 0+0 00
Ostraciontidae
Ostracion meleagris 0000 000 +0
72
-------
Table 6 (Continued)
REEF STILLING REEF
FLAT WELL MARGIN
P** C*\ P"*- O"\
o*\ •—
OQ
0
0
0
0
0
0
0
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4->
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Serranidae
Cephalopholis urode1 us 0000 000 +0
Teuthididae
Siganus spin us +00+ 0 + 0 + +
Zancli dae
Zanclus cornutus _P__P__P_0. _P__°__P_ + +
Totals 12 32 0 11 090 63 35
73
-------
that a combination of factors may be operating.
Fishes common in the intake channel before Tanguisson No. 1 began opera-
ting in 1971 are shown in Table 6. Except for transients, most of the
species listed are common in channel structures such as this. The intake
channel fish community had not yet reached its full potential in terms of
succession. This process was considerably delayed by the fact that intake
construction for Tanguisson No. 2 had kept the channel turbid until Novem-
ber 1972. One twenty minute random count made in the intake channel in
the summer of 197^ yielded 57 species, a clear sign that succession was
far more advanced (a 79% increase from 12 species).
Although entrained organisms were not a specific objective of this study,
one observation was made that warrants mention. From April to June and
again in October, huge schools of larval ma'Kahac, Siganus spinus, move
from the pelagic environment into the inshore waters of Guam. These lar-
vae metamorphose into juveniles and enormous schools are found concentrated
on reef flats. The people of the island traditionally harvest the juvenile
fishes in great quantity for consumption. During the 1972 manahac run,
large schools of the species were found in the intake channel of Tanguisson
No. 1. Near the end of the period when plant personnel had suspended
chlorination treatments, the water boxes of the plant were opened and
condenser tubes inspected for possible fouling. Hundreds of specimens of
ma'Kahac were found plastered to the interspaces between the condenser
tubes and on the floor of the water boxes. It is quite likely that many
thousands, of the animals are entrained in the circulating water and killed
by either mechanical damage or temperature increase. This high mortality
is probably a seasonal phenomenon involving this species primarily. It
is doubtful that normal channel inhabitants are drawn into the circulating
system. No attempt was made to study the possible destruction of larvae
or juveniles of other fish species passing through the plant.
CORALS
The fringing reefs located along the northwest coast of Guam (Fig. 1)
supported a rich and diverse coral community prior to the Acanthaster
plane? infestation of this region (Tracey et al' and Randal 1'^). Randall
describes the reef complex at Tumon Bay in detail. The rich coral zones at
Tumon Bay and nearby Tanguisson Point (Fig. 1) became infested with /\.
plane? in 1967 and 1968 (Randall12. '*» l8 and Chesher]5). Intensive pre-
dation left the seaward slope, submarine terrace, and the outer part of
the reef front zones with less than 10 percent of the reef surface covered
with living corals. The reef margin and inner part of the reef front were
not heavily infested by starfish, because of wave agitation in these zones,
and much of the coral community survived. Section X of this report des-
cribes the reef complex at Tanguisson Point in detail after the starfish
predation of 1967 and 1968.
74
-------
Prior to plant operations, it was predicted that effluent from Tanguisson
No. 1 might kill part of the surviving coral reef community existing on
the reef margin and reef front zones (Jones et al^3). The prediction
was based on the fact that the coral reef community, in the above reef
zones, has developed in and 5s adjusted to the small annual temperature
changes that occur in this part of the Pacific Ocean. Moreover, thermal
stress on reef corals is probably greater when applied continuously, as
is the case with power plant effluent, than when applied diurnally from
insolation or seasonal changes.
Final testing of Tanguisson No. 1 began in December, 1971 and the plant
became fully operational in January, 1972. Effluent was discharged at
the outfall site onto the inner part of the reef flat platform (Fig. 23).
The movement, and factors affecting the movement of this effluent
toward the reef margin are discussed in the previous section on currents
and is shown in Figures 6 and 21.
During the testing period, the first observation of a "coral-kill" in the
outfall region was made (on December 27, 1971). At that time a two-man
team was recovering ^thermographs from the reef margin on Transect B and
noticed that numerous corals were of a pale or bleached-white color (Fig.
24-26). The results of a survey showed that the zone in which freshly
killed corals were found was roughly limited to the region outlined in
Figure 23. The boundaries of the coral-kill zone were not sharply de-
fined except for a shoreward section located along the inner reef margin
where the effluent first makes contact with living corals (Fig. 23d). In
a peripheral zone (Fig. 23f) the corals killed were usually limited to
the upper surfaces of submarine buttresses and the upper margins of the
surge channels (Fig. 24 and 27). The coral species killed in the peri-
pheral zone were presumably those with less thermal tolerance (Table 7).
As the warmer area of the coral-kill zone (Fig. 23e, core zone) was
approached, the density of bleached and freshly killed corals increased
along with the number of species affected. In the core area itself the
coral-kill was not limited to the upper regions of reef topographic fea-
tures. It extended downward as well, along the walls of surge channels,
submarine channels, and the floors of these two features (Figs. 25 and 27)
Although heated outfall water has a tendency to float on the surface of
the cooler ambient temperature seawater, data presented in the previous
section on temperature indicates that wave and surf action mixes the
effluent at the reef margin and inner part of the reef front zones (Fig.
27). This mixing action extends the vertical range in which corals are
killed. Seaward of the surf zone the warmer water becomes stratified and
is generally restricted to the upper one meter layer of water. It has
little effect on living corals, since the water depth there is usually
greater than one meter, except where the upper parts of corals knobs and
knolls extend up into this one meter layer (Fig. 27).
75
-------
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76
-------
Table 7 was based on observations of the number of bleached corals, and
surviving corals from the central core of the coral -kill zone outward to
the peripheral region. Corals of the genera Acropora, Mont ipora, and
Poci 1 lopora were found to be the least tolerant to effluent. The only
coral species consistently surviving in the central core zone were
Goniastrea ret iformis, Psammocora (P.) haimeana, Favites abdita, Cyphas-
trea chalcidicum and a small, cryptic, encrusting Porftes species.
Close observation revealed that not all the pale colored or bleached
corals were dead. Some were still living, with polyps and tentacles ex-
tended. Others were partly killed with the uppermost, bleached part of
the coral lum dead and the basal-lateral parts bleached and living. Nu-
merous authors have shown that corals under stress begin to expel their
zooxanthel lae. The loss of this brown colored algal symbiont leaves the
coral either a bleached white color, or more commonly, reveals the pre-
sence of other pale colored pigments normally masked by the zooexanthel lae
(Fig. 25). Under continued stress the corals lose more zooexanthel lae
and pigments, becoming white and colorless (Fig. 25). If stress is unin-
terrupted, death of polyps and disintegration of the coenosarc follows.
This is in basic agreement with observations made at the Kahe Pt. genera-
ting facility in Hawaii by Jokiel and Coles . Usually, the first orga-
nisms to recolonize this new surface are various species of blue-green
algae (Fig. 26).
The reef margin and reef front zones have been monitored continuously
since the initiation of field work and the establishment of permanent
Transects A, B, and C in 1970 (Fig. 3). Transect B bisects the main part
of the outfall plume, where it crosses the reef flat zone and enters the
reef margin and reef front zones (Fig. 23g) . Quadrat stations on Transect
B (reef flat, reef margin, and reef front zones) were analyzed for per-
cent of living coral covering the reef surface and species composition
before the coral-kill during April 1970, after the coral-kill in May 1972
and again in January 1973. Table 8 summarizes the results of these tran-
sect studies by quadrat stations in the region of the coral -kill
Small seasonal changes in seawater temperatures, changes in wind and swell
direction, and continued stress from the effluent plume have subsequently
changed the boundaries of the original coral-kill zone of December 1971
(Fig. 23) to that shown in Figure 28 for January 1973. The initial region
affected (peripheral zone) in Figure 23 was 118 m by 32 m. The core zone
was 80 m in length and 26 m in width. The total area affected was 3,776
m^ and the core zone was 2,080 m2. The affected region shown in Figure 28
was drawn from field data collected one year later. The damaged area in-
creased to a total of 186 m by 55 m, and the core zone increased to 108 by
*»0 m. The area affected increased to about 10,000 m^ overall and k, 320 m^
for the core region.
77
-------
Table 7- RELATIVE RESISTANCE OF CORALS TO THE EFFLUENT AT TANGUISSON
POINT. Loss of pigment is used as an index.
Name of Coral
Stylocoeniella armata
Psammocora nierstraszi
Psammocora (P.) haimeana
Stylophora mordax
Pocillopora eydouxi
Pocillopora meandrina
Pocillopora setchelli
Pocillopora verrucosa
Acropora abrotanoides
Acropora studeri
Acropora hum! 1 is
Acropora hystix
Acropora murrayensis
Acropora nana
Acropora nasuta
Acropora ocellata
Acropora palmerae
Acropora smith i
Acropora surculosa
Acropora syringodes
Ac ropo ra va 1 i da
Acropora ward! i
Montipora concicula
Montipora elschneri
Montipora foveolata
Montipora hoffrneisteri
Montipora verri 1 1 i
Montipora verrucosa
Montipora sp. 1
Montipora sp. 2
Pavona clavus
Pavona varians
Coscinaraea columns
Porites austral iensis
Porites lobata
Porites 1 utea
Porites sp. 1
Favia favus
Favia pal 1 i da
Favia speciosa
Normal Pale Bleached
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Dead
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
78
-------
Table 7- (Continued)
Name of Coral
No rma1
Pale Bleached
Dead
Favia stel 1 igera
Favia rotumana
Favites abdita
Favites complanata
Favites favosa
Favites flexuosa
Plesiastrea versipora
Goniastrea retiformis
Goniastrea parvistella
Platygyra rustica
Platygyra sinensis
Leptoria cyaci 1 is
Leptoria |>hrygia
Hydnophora microconos
Leptastrea purpurea
Leptastrea transversa
Cyphastrea chalcidicum
Galaxea hexagonal is
Lobophyllia costata
Acanthastrea echinata
He 1 i opo ra coe ru } ea
Millepora dichotoma
Mi 1 lepora exaesa
Millepora platyphylla
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
TOTAL SPECIES
10
19
18
17
79
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Figure 24 Coral kill on upper surface of a reef margin
buttress
Figure 25 Pale and bleached corals on the walls and floor of
a reef margin surge channel
81
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Figure 26 Dead coral and coralline algae surface being
recolonized by blue green algae
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The damage reported above was caused primarily by the discharge of efflu-
ent from Tanguisson Unit No, 1. Now that Tanguisson Unit No. 2 is in
operation, along with Unit No. 1, the volume discharge has doubled over
the adjacent fringing reef community. This increased discharge was ex-
pected to affect a greater area of the reef community than that which was
previously affected with only one generating unit in operation. The ex-
tent of the coral-kill area (core and peripheral zones) was again assessed
in October, 1974, with both power plant units in operation.
Preliminary investigations revealed the presence of a peripheral zone of
pale or bleached-colored and recently killed corals along the fringing
reef from the intake channel southward to Transect C (Fig. 29). The
width of the affected reef area was again determined by measuring the
seaward extent of the core and peripheral zones from the inner reef mar-
gin zone along a series of transect lines. The outer boundaries of the
core and peripheral zones are roughly outlined in Figure 29. In general»
the core zone has its maximum width at Transect B. From there, it extends
laterally along the reef margin northward about halfway to the intake
channel and southward to the cavernous surge channels shown in Figure 5
(VI). Maximum width and length of the core zone was found to be ^0 m by
kQQ m with an affected area in which over 90 percent of the corals have
been killed. Maximum width and length of the peripheral zone is about
55 m by 600 m. Since the last measurements of the coral-kill zones were
made in January, 1973 (Fig. 28), the core zone area has increased from
k,320m2 to 10,300m2 and the peripheral zone from 10,000 m2 to 20,000 m2
(Fig. 29).
The area of the core and peripheral zones has at least doubled since the
number of power plant units doubled. This increase has been due mainly
to a lateral extension of the affected area both north and south of the
outfall at Transect B. There was no increase in maximum width because the
warm water becomes stratified seaward of the surf zone (Fig. 27). Lateral
extension of the affected area has been due to the greater volume of the
thermal effluent present, which is transported more or less parallel to
the reef margin and upper reef front zones in the manner described for
this region in Section V (Currents). Jokiel and Coles^ report a doubling
of affected reef areas at Kahe Pt. with a one-third increase in generating
capacity and waste heat discharge rate.
Transect studies conducted during 197^ show a further reduction in the
percentage of substrate covered by living corals at Stations B-13 and 14
(130 m and 1^0 m from shoreline), but normal values for this parameter
were found in the deeper water from Station B-15 (150 m) seaward (Table 8).
The relative resistance of various coral species to thermal effluent is,
85
-------
o
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to
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o
o
Oi
-------
for the most part,the same as that described during the earlier observa-
tions (Table 7). Regardless of when observations were made in the peri-
pheral zone, one could always find living pale or bleached corals in
which there had been a loss, to some degree, of zooxanthellae and other
pigments. Many of the corals in this zone are intermittently exposed to
elevated temperatures, depending upon the temperature and volume discharge
of the plant effluent, local weather and tidal conditions, as well as
seasonal induced variations. Corals in the peripheral zone are thus sub-
jected to sublethal thermal stress because of the constantly changing
thermal plume dimensions. If the corals are exposed for a short period
to elevated temperatures, they may react by expelling pigmented symbionts,
but then resume normal coloration during periods of time when no longer
subjected to thermal stress. Many of the less tolerant coral species
have already been killed in the peripheral zone (Table 7) and it is sus-
pected that many of the more tolerant species will also be killed as
they are subjected to the sublethal thermal stress conditions over a
longer period of time. Jokiel and Coles'" reported basically the same
conditions in their Kahe Pt. study.
There is little evidence of new coral recruitment by planulae settling in
the peripheral zone, so with time, the central core zone will probably
encroach somewhat into the peripheral zone. It is doubtful though that
the overall dimensions of the affected area will increase appreciably
in size at the present discharge rate and temperature of power plant
effluent. As pointed out in Section V, the intake channel seems to pre-
sent a northern barrier to the movement of the plume along the nearshore
environment. The attenuation of plume temperature to a tolerable level
places the extreme southern boundary near Transect C (Fig. 29).
CORALLINE ALGAE
In terms of reef building and maintenance, another group of important
organisms affected by the effluent were the crustose coralline algae
(Appendix D). In the reef margin and reef front zones Porolithon onkodes,
an encrusting coralline, covers more reef surface area, when considering
the numerous holes, cracks, and cavernous regions of these zones, than
any other organisms. Porolithon gardineri forms rounded clumps of close-
ly set branches, and in the reef margin zones is often more abundant than
corals. Porolithon gardineri has about the same degree of tolerance to
the effluent as the corals. Porolithon onkodes shows slightly greater
resistance than P_. gardIneri. The reef surface covered by these two en-
crusting and ramose corallines in the core zone has been greatly reduced.
In the peripheral zone, the Porolithon kill is patchy and more or less
restricted to the upper parts of surge channels, submarine buttresses
and knobs. Porolithon onkodes seems to be surviving in the small cracks,
holes, and on the basal branches of dead ramose coral colonies. In these
cryptic locations the encrusting coralline has a normal pink to red col-
87
-------
oration. Under the influence of the effluent, this red pigmentation
turns pale and finally, at death, becomes a chalky white color. Blue-
green algae are usually the first organisms to recolonize the freshly
killed surface (Fig. 26).
Unless another carbonate secreting organism recolonizes this important
niche, erosion of the reef margin and inner part of the reef front zone
will probably take place. Recent investigations at Tumon Bay revealed
that Acanthaster plane? has killed nearly all the corals in these two
reef zones (both zones endure less wave exposure than Tanguisson reefs).
This coral kill by the starfish at Tumon Bay is not as serious as that
at the Tanguisson outfall site because the dead corals in Tumon were
rapidly encrusted with coralline algae, thereby maintaining the struc-
tural integrity of the reef framework. In time, the reef margin corals
at Tumon Bay will become re-established, but at the outfall site at
Tanguisson, there are no such corals or coralline algae recolonizing the
region where the effluent has killed them.
88
-------
SECTION IX
THERMAL SIMULATION EXPERIMENTS
Jokiel and Coles recently reviewed the literature on the effects of
short-term exposure of reef corals to lethal temperatures. The above
authors were part of a team of University of Hawaii scientists working,
with support from another EPA grant, to provide information on upper
thermal tolerance limits and growth rate of adult Hawaiian corals and
settlement of their planulae. Unpublished laboratory data (Jokiel, per-
sonal communication) as well as field data (Jokiel and Coles^') indi-
cates that lethal temperatures, for the common species of Hawaiian corals,
are approximately 31-32°C; and that prolonged exposure to temperatures
of 30 to 31°C may lead to sublethal effects such as loss of pigment or
eventual death. They suggested that absolute temperature levels rather
than the degree of thermal enrichment over seasonal temperature was the
most critical factor. It was evident that temperatures above summer am-
bient (27°C for Hawaii) were more likely to be damaging than equal tem-
perature increases over winter ambient. In fact, corals showing sub-
lethal damage (pigment loss) in summer, often recovered in winter months.
The Hawaii group has suggested (unpublished work) that Hawaiian corals
were probably adapted to temperatures at or below 27°C, which is the
highest (summer) oceanic temperature in the Hawaii study area. They
postulated that physiological races of the same coral species found in
Hawaii exist in the warmer waters of the Indo-Pacific and these races may
well have tolerance ranges set higher than those found in Hawaii. The
Hawaii group also found (unpublished data) that the coral growth optimum
fell within the normal ambient range (22-27°C) for the study area,
Kaneohe Bay, Oahu.
In the Fall of 1971, the EPA requested that the Guam team aid in testing
the above hypothesis and catalog the upper thermal tolerance limits for
additional coral species. Guam lies within the Indo-Pacific region
(Wells'") referred to by Jokiel and his colleagues and the island has a
mean annual temperature (27-6°C) slightly greater than the maximum for
Kaneohe Bay (27°C). In Guam the seawater temperature regime follows the
89
-------
wet and dry seasons. For example, the coolest water temperatures are
found from January to April, which approximates the dry season. The
warmest months are June through November, the wet season. Transitional
months are usually May (sometimes June) and December. The cool months
have an oceanic water temperature range of approximately 25-5 to 28.3°C
with a mean of 26.8°C, for a 10 year period (Fig. 18). Warm months
range from 27.3 to 29-0°C with a mean near 28.5°C. According to the
above hypothesis, reef corals on Guam should be adapted to higher tem-
peratures than Hawaiian corals.
The thermal simulation apparatus used by the University of Hawaii group
utilized a heat pump and a titanium tube heat exchanger. Temperature
of seawater was controlled by mixing heated with ambient temperature
seawater. This system worked well but was beyond the budget and support
facilities of our project. With the aid of personnel from the EPA
National Water Quality Laboratory in Rhode Island, we were able to de-
sign a system that utilized commercial immersion heaters and electronic
controllers (Fig. 30). The first model of our system included a delta T
tracking feature. This device tracked ambient temperature and maintained
experimental temperatures at 2°C increments (+2, +A, +6) above ambient.
The delta T system is vital in temperate environments where diurnal tem-
peratures ranges may fluctuate considerably. However, in Guam's tropical
environment, oceanic water temperature rarely fluctuates more than 0.5
to 1°C diurnally and only 3°C annually. It is also clear from work by
Jokiel and Coles'' and others that temperature maxima to which corals
are most logically adapted are near summer ambient. Therefore it would
be of little value to test corals at temperatures based on ambient values
below summer ambient. We therefore, modified our control system to hold
the desired 2°C increments above a summer mean ambient of 28.5°C. This
resulted in experimental temperatures of 30.5°C (+2), 32.5°C (+k), and
34.5°C (+6).
Our experimental temperatures fluctuated somewhat due to controller
variability and numerous power failures that were common in Guam during the
research period. We exerted every effort to hold our experimental temper-
atures within +_ 0.5°C of the desired values. No attempt was made to hold
the ambient (control) tanks to 28.5°C. They were allowed to fluctuate
normally.
Corals were acclimated for one to two weeks prior to introduction to the
simulator (Fig. 31). The corals were placed in pans of fresh seawater
and floated in the experimental tanks until they reached the experimental
temperature (two to three hours). They were then arranged in rows within
the tanks. The tanks were set up in replicates of three for each experi-
mental temperature (Fig. 30). The rows of coral specimens were alterna-
ted between tanks to avoid bias in placement. Coralla were placed on
inverted specimen jars to prevent bacterial contamination that often
90
-------
Figure 30 Thermal simulation device
91
-------
Figure 31 Acclimation tank
92
-------
occurs when the coral la are in contact with the bottom. It was also
necessary to place one layer of plastic screen over each tank to cut
down (by about 30%) on the intense sunlight of our Latitude (13°N).
Unless this was done, the corals tended to lose their- pigments and often
died in the shallow tanks even in the absence of thermal stress. The
12 experimental tanks were 79 to 59 by 50 cm and rigged with stand-pipes
to hold the water level at 39 cm (182 liters). Uncontaminated seawater
flowed constantly through the system at four liters/minute. A scanning
telethermometer with recorder was set to minotor all tanks as well as
the ambient control tanks, continuously.
The first experiments were conducted over 30 day periods to ensure ade-
quate time for measurable growth, at least in the control corals. This
period was later reduced to 14 days to allow a greater number of species
to be tested for thermal tolerance. In most cases, percent gain of the
coral skeleton was still detectable.
Eighteen species of hermatypic corals belonging to 12 different genera
were tested (Table 9 and Figs. 32 to 49). Some of the species were
tested more than once and the total number of experimental runs was 24.
In all, 1,218 individual coral specimens were tested over a total of 544
test days.
Mean ambient (control) temperatures fluctuated between 27-5 and 29.5°C
(2°C span). They rarely were more than +_ 1°C from summer ambient (28.5°C)
and usually were within j^ 0.5°C. Three hundred two control specimens
were tested over the 18 species. Only three specimens died (]%). The
dead corals were restricted to three of the species (Figs. 32, 43, and
48). These losses were considered as chance occurences, which reduces
the percent dead to zero.
In the 30.5 (+2) tanks the temperatures fluctuated between 29.5 and 31.5
(2°C) span). One of the 2k test runs was eliminated because of a tempera-
ture control failure. Of the other 23, seven fell to a mean of 29-5°C,
one rose to a mean of 31-5°C and the remainder were at or within +_ 0.5°C
of 30.5°C.
Two hundred ninety-six specimens were tested over the 18 species. Of
these, 28 died (9%)- The dead corals were restricted to eleven species.
(Figs. 32, 33A, 35, 37, 38, 40B, 41, 43, 45, 46 and 49). Nine species
lost one to three individuals each, one species lost seven and one lost
nine. Among the losses, 12 were considered likely due to chance. This
would reduce the number of corals killed by heat to 16 (5%). The
apparently legitimate losses were seven by Fungia scutaria, and nine
by Leptoria phrygja. The loss of _F. scutaria is thought to be reason-
able because this is a deep water species in Guam and not normally
subjected to fluctuating temperatures. We suspect that the loss of
nine out of nine j^. phrygla is possibly due to some form of
93
-------
contamination in that experimental run but cannot say this with assurance.
All the specimens were "healthy" until the 10th day of the 14 day experi-
ment. Although the few losses at +2 above summer ambient might well be
indicative of the beginning of heat damage, we prefer to be conservative
and assume most of the deaths were chance occurrences.
The 32.5°C (+k) experimental temperature fluctuated between means of
31.5 and 33-5°C (2°C span). Of the 2k experiments, only one mean tem-
perature rose to 33-5 and three fell to 3l«5°C. The remainder were at
or within +_ 0.5°C of the desired temperature (32.5°C).
Three hundred five specimens were tested over the 18 species. Of these,
210 specimens died (63%). Significant numbers of specimens died among
15 of the 18 species. Six of the deaths are considered as possibly
due to chance (three out of nine for Payona obtusata and three out of
35 for Acropora aspe ra, Figs. 36 and 43). No deaths were recorded in the
single experiment with Platygyra rustica (Fig. 49). Moreover, in one of
two experiments with Psammocora contigua (Fig. 33B), one of three experi-
ments with Porites lutea (Fig.40C)and one of two experiments with
Galaxea hexagonal is (Fig. 42A), no specimens were killed. The surviving
_P_. contigua and P_. lutea were at temperatures of 32.0°C which is within
the +_ 0.5°C tolerance. Both failed to survive when temperatures were
raised in duplicate experiments from 32 to 33 and 32.5°C respectively.
—• hexagonal is and _P_. rustica were at 31.5°C, a full degree below the
desired experimental temperature of 32.5°C and their survival might well
have been favored. 6_. hexagonal is failed to survive when temperatures
were raised in duplicate experiments from 31-5 to 32°C (Fig. 42B) . It
is therefore evident from duplicate experiments run with _P_. contigua,
P. lutea and G_. hexagonal is, that if the experimental temperatures had
Feen held at the desired mean of 32.5°C there might well have been no
survivors. It is apparent that all three species were favored, where
they survived, by lower than desired temperatures. No duplicate experi-
ments were conducted with P_. rustica but it is quite likely that it may
also have failed to survive if held at the correct experimental tempera-
ture.
The data suggest that, of the 18 coral species tested, the majority, if
not all, should not survive mean temperatures between 32 and 33°C over
periods of usually less than 14 days (Table 9 and Figs. 32 to 49).
Stylophora mordax (Fig. 48) and Acropora pal ifera (Fig. 45) failed to
survive even at 31.5°C, and Leptoria phrygia(Fig. 46) all died at
30.5°C (possibly contamination).
The 34.5°C (+6) temperatures fluctuated between 33 and 35°C (2°C). Of
the 2k experiments only one rose to 35-5 and two fell to 33.0 and 33-5
respectively. The remainder were held within +_ 0.5°C of the desired
34.5°C.
94
-------
Three hundred fifteen specimens were tested and three hundred fifteen
died (100%). None of the 18 species survived the +6 regime (Figs. 32
to
Our bioassay attempted to locate thermal death point for each coral by
bracketing with +2°C increments held at +_ 0.5°C of the desired experi-
mental temperatures. This is a rather broad bracket and makes precise
location of thermal death point difficult. We know the lowest test
temperature at which all specimens survived and the highest test tempera-
ture at which all were dead. Therefore, we can only provide a range of
minimum and maximum test temperatures between which the thermal death
points can be expected to lie.
Of the 18 species of Guam corals tested, Table 9 shows that all were
killed at some point between 29.0 and 3/».5°C (delta T's +0.5 to +6.0°C
above summer ambient, 28.5°C). This is a rather wide span of 5.5°C.
Even if the _L_. phrygia experiment is omitted because of potential con-
tamination of the +2 group, the 29.5°C level found in five species (Table
9) is considered low and resulted from failure to control, in several
cases, the desired lower experimental temperature $0.5°C, +2°C) . This is
unfortunate because of the gap it leaves between the normally sublethal
+2 and the lethal +k regimes. It is doubtful that few, if any, of the
corals tested would die at 29.5°C, only 1°C over summer ambient. The
remaining 12 species had examples of survivors at test temperatures of
30-32°C (Table 9, Figs. 32 to
While our data are by no means conclusive, we would expect that the
majority of the species tested have a mean death point between 30 and
33°C (3°C span). We suspect that the lower range is nearer 31.0. Sub-
lethal effects might well be expected to occur at or below 30°C.
Next we must view these data in a perspective that includes the power
plant. While we do not doubt that coral species may endure temperatures,
for short periods of time above the range shown herein, the power plant
represents continual discharge of effluent and constant exposure of
corals to thermal stress. Figure 19 shows the mean outfall temperature
for a 28 month generating period to be 3k.7°C. The highest test tempera-
ture where death occurred was 3**.5°C. In other words, all corals tested
died at temperatures 0.2°C or more below the 28 month mean (Table 9).
During the last 12 months of plant operation observed, both Units 1 and
2 were on the line and the mean outfall temperature was 36°C (+7«5°C
over summer ambient), 1.5°C or more over the highest test temperature.
It is therefore evident that coral species that die in a range between
30 and 33°C are not likely to survive exposure to prevailing plant tem-
peratures.
The data in Section VI show that lethal temperatures can occur along the
95
-------
Table 9- ORDER OF RESISTANCE AND TOLERANCE LIMITS OF CORAL SPECIES
TESTED IN THERMAL SIMULATOR.
SPECIES
Pavona obtusata
Psammocora contiqua
Acropora aspera
Porites lutea
Platygyra rustica
Pavona frondifera
Galaxea hexagonal is
Fung 5 a Scutari a
Pocillopora dam i corn Is
Pavona varians
Favia stel 1 igera
Pocillopora satchel li
Pavona decussata
Acropora nasuta
Millepora platygyra
Ac ropo r a pa 1 i f e r a
Stylophora mordax
Leptoria phrygia
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reef margin opposite the power plant. MoreoverT the field data presen-
ted in Section VIII verify the death of corals in situ.
Death of the corals was always proceeded by a loss in pigment that re-
sulted in a bleaching of the polyps (Fig. 50). This response is identi-
cal to that reported in the field. Jokiel and Coles^ have reported the
same phenomenon in Hawaiian corals. Corals that survived in the control
tanks and the +2°C tanks did not lose a significant amount of pigment.
Our data are too inconclusive to adequately support the hypothesis of
Jokiel (personal communication) and his colleagues, which would suggest
that Guam corals are adapted to higher temperatures than Hawaiian corals.
However there is some evidence for a trend in this direction at least at
the upper end (32°C Hawaii vs 33°C Guam).
Growth experiments were interesting but usually less striking than the
preceeding. Corals (survivors) were weighed underwater, before and
after the \k to 30 day experimental periods. The weights were taken to
the nearest O.lg and corrected to dry weight using the following formula:
DcF
m =
Dc-Dw
Where: m = dry weight of the coral
DC = coral density (aragonite = 2.9*0
Dw = density of seawater
F = underwater weight of the coral
The formula is thus based on the specific gravity of CaCO^ (aragonite).
When checked empirically, the results were found to be variable. Coral
specimens were allowed to dry and were weighed in air. Next, the speci-
mens were submersed for one to two weeks and then weighed underwater.
When the formula was applied, deviations were evident. Kornicker and
Squires'7 report that it may take up to eight months for porous coral
skeletons to become completely saturated with water. It is the resul-
ting difference between specific gravity of pure aragonite (2.9*0 and
that forming complex coral skeletons that introduces the variability.
Therefore the dry weight values given should be considered less than
perfect.
Data for all specimens of each species had to be pooled and differences
between weight in and weight out converted to percent gain in skeletal
weight. These data are shown in Table 10. Pooling the data was unfor-
tunate but necessary because coral growth was quite variable within
experimental sample groups. This occurred because of differences in
specimen sizes. Smaller specimens had faster growth rates than larger
ones because of differences in ratio of total living tissue (coenosarc)
121
-------
Figure 50 Bleached polyps of Galaxea hexagonal is
122
-------
Figure 51 Transect B station showing anchor links and station
number suspended by a float
123
-------
Table 10. GROWTH OF CORALS AT EXPERIMENTAL TEMPERATURES.
X=corals failed <->
c
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12
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Desired Ex|
28.5(Amb.)
Actual %wt.
Temp Gain
28.0 22.0
28.0 20.0
29-5 16.0
28.5 14.0
29.5 12.0
28.0 11.0
29.5 10.0
29.0 9-0
28.5 8.5
29.0 7-0
29.0 7-0
27.5 6.5
28.0 3-3
29.5 3.2
27.5 3.2
29.5 3.0
29.0 2.8
29.0 2.7
28.0 2.6
28.0 2.2
28.0 2.0
28.5 1.8
28.0 1.0
29.0 0.4
se ri mental Ten
30.5 (+2)
Actual %wt.
Temp Gain
30.0 17.0
30.0 16.0
29-5 2.0
29-5 15.0
29.5 18.2
30.0 9-0
30.5
29.5 0.2
31.0 6.0
31.0 5.0
29-5 2.5
30.5 2.2
31.5 2.4
30.0 2.4
30.0 1.5
30.5
31.0 2.9
30.5 2.7
30.5 0.2
30.5 2.6
29-5 0.3
29.5 i.o
31.0 1.0
tips. °C
32.5 (+4)
Actual %wt.
Temp Ga i n
32.0 (-)l.O
32.0 (-)2.0
32.0 X
32.0 X
31.5 6.5
32.0 6.0
32.0 X
32.0
32.0 X
33.0 X
33.0 X
32.0 X
32.5 x
33-5 X
31-5 1.3
32.0 X
32.0 X
33.0 X
32.5 X
32.5 X
32.0 1.6
32.0 X
31.5 X
33.0 X
124
-------
areas to total weight of the corallum (cube/square ratio). These rela-
tionships and resultant growth rate differences are difficult to measure
and control intraspecifically and virtually impossible interspecifically
because of growth form and size differences in the coral la of the 18 spe-
cies and 12 genera examined.
In spite of the inherent variability, there are some obvious trends of
interest. No growth was recorded for specimens in the +6 (3^-5°C) re-
gime because all specimens normally died within three to ten days and
before they had an adequate growth period.
Growth was observed in the +A (32.5°C) tanks in only four cases, Platygira
rustica, Ga1axea hexagona1is, Pavona obtusata and Acropora pal ifera. In
every case, there was a reduction in growth from both ambient and +2°C
corals. In general, most of the specimens tested at +4°C failed to sur-
vive long enough to show measurable weight gains. Table 10 shows that
corals that survived gained skeletal weight at the +2 (30.5°C) regime
in every case where data are available. In H out of 21 tests, where
data are available, weight gained was less than that recorded for ambient
corals. In six of the tests, the weight gain in the +2 regime was greater
than ambient. They were equal in only one case. For eight of the test
samples, the differences in weight gained between ambient and +2 was 1.0%
or less. In four of these eight, ambient gain was greater than +2 gains
and in four, +2 gains were greater. Because of the considerable varia-
bility inherent in the measurement of weight, little significance should
be attached to these eight tests.
Significant skeletal weight gain occurred in the ambient held specimens
at temperatures between 27.5 and 29-5°C. This range includes growth at
temperatures l.O°C above summer ambient (28.5°C). Measurable ske-
letal weight gain also occurred between 29-5 and 31.5°C, 1.0 and 3-0°C
above summer ambient. Growth was virtually eliminated above these
ranges.
The general reduction in skeletal weight gain between ambient and +2°C
clearly points out one of the elements of sublethal effects on hermaty-
pic corals. Jokiel and Coles (personal communication) found the same
sublethal effect as well as reduction in planula settlement in at least
one species (Pocillopera damicornis).
125
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SECTION X
EFFECTS OF ACANTHASTER PREDATION ON TANGUISSON CORALS
In February 1967, the coral eating "Crown-of-Thorns" starfish, Acanthaster
planci (Linnaeus), was noted (Randall'2» 18) |n above normal population
densities along local portions of the relatively sheltered northern half
of Tumon Bay (Fig. 1). The infestation spread to Tanguisson Point loca-
ted 2.k kilometers north of Tumon Bay, sometime between June 1968, and
September 1968. By April 1969, nearly all the starfish had migrated out
of the Tanguisson area, leaving over 95 percent of the reef building
(hermatypic) corals dead in the area seaward of the reef front zone.
OBJECTIVES
One of the grant objectives was a study of the damage to Tanguisson reefs,
attributable to Acanthaster. This was to be completed prior to release
of plant effluent in order to avoid confusion between environmental damage
that might ultimately result from plant operations and that caused by
Acanthaster. Unfortunately, the Tanguisson reef was destroyed prior to
the start of the research and it was necessary to extrapolate about its
pre-Acanthaster conditions from research on the nearby Tumon reef. A
thorough study of coral distribution on the Tumon Bay fringing reef was
conducted by Randall12* '° prior to the infestation of Guam by Acanthaster
planci and before the grant research began. The Tumon reef is contiguous
with the Tanguisson fringing reef and the two, except for the reef flat
zones, were very similar in terms of coral species composition and distri-
bution. Collections and observations were also made at Tanguisson by
Randall12' 18 during his 1966 to 1969 study of Tumon.
The second objective, regarding the Acanthaster damaged zones of the
Tanguisson reef, was a study of potential coral recovery following intense
predation. This natural catastrophe simulated a possible pollution-induc-
ed one and basic research on coral recovery and recolonization was done.
126
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INITIAL ACANTHASTER DAMAGE (1968-1970)
Previous Work
Little previous work has been done on the fringing reefs of Guam with
respect to coral distribution. Most studies are of a geological nature,
dealing mainly with various physical parameters of the reef complex.
Some coral collections were made on Guam and Saipan by Cloud'9» 20,
during U. S. geological surveys of these two islands. A list of coral
genera was compiled from these collections by Wells''. Tracey et al ,
conducted several reef traverses in the study area. As far as could
be determined, no systematic coral collections were made by them but
several coral genera are listed by reef zones from "Reef Traverse 2, at
Tumon Bay." The following genera were reported: from the reef margin-
Ac ropora, Poc?1lopora, Favia, and Mi 1lepora; from the reef flat-Porites
in the outer part, Acropora, Pavona, and Poci1lopora in the inner part.
Other work on the reefs of Guam was done by Stearns^l, Cloud^^ and
Tayama^3. Coral distribution was not included in these studies. A
study of the marine geology of Guam by Emery2 includes investigations
of submarine slopes, lagoon floors, channels through fringing reefs,
beaches, and rocky shores.
Observations on Acanthaster were first reported by Chesher'5. Chesher
describes A_. plane! population movements, densities, feeding behaviour,
relative coral predation rates, control measures, and possible causa-
tive factors related to the sudden increase in numbers of starfish in
various Indo-Pacific regions. Tsuda^ describes the current status
°^ —• plane! on Guam with regard to population densities, location of
infested reefs, and the extent of the coral damage.
Methods
Three permanent Transects (A, B, and C), were established at Tanguisson
Point. Figure 3 shows the location of these transects. Stations were
established at 10 m intervals along the transects from the upper inter-
tidal zone to a depth of 30 m on the seaward slope. These station
locations were permanently marked by placing three to five links of
ship anchor chain (^.7 kg per link) at each. Stations were identified
by attaching numbered fiberglass cards to the anchor chain links. For
ease in locating the transect stations, the numbered cards were
suspended approximately 0.5 m above the anchor links by a plastic float
(Fig. 51). At each station a reference point was established at the
point where the numbered card was attached to the anchor links.
127
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Two wire grid quadrats, each one meter square, were positioned at the
station reference point (Fig. 52). After positioning of the quadrat
grids, the following data were recorded from each: (1) the transect
station number; (2) the quadrat number; and (3) the specific name, size,
and growth form of each living coral found within the confines of the
grid. The various coral growth forms differentiated follow those des-
cribed by Wells^S. A columnar form was added which differentiates an
intermediate mode of development between the massive and ramose forms.
A subdivision of ramose forms into corymbose, cespitose, and arborescent
modes of branching was made.
The diameter of individual coral colonies was measured with a meter
stick with moveable trammel points. If circular, the colony diameter
measurement was made at the widest point across the corallum. If the
colony shape was not circular, its outline was sketched and several
measurements of length and width were recorded.
Distribution of Corals
Coral distribution at Tanguisson Point is based upon data from the three
transects, general field observations, and specimen collections. Exten-
sive systematic coral collections were not made at the Tanguisson study
region because a similar species composition was collected at Tumon Bay
(Randall 12). jne only corals collected at Tanguisson Point were those
that could not be identified in the field, those that represented new
growth forms, or those that were not previously collected at Tumon Bay.
Field work for the study was started at Tanguisson during September
1969, and was continued until July 1970. Table 11 lists the coral spe-
cies known from the study area.
Table 12 lists the frequency distribution of coral species observed on
the transects by reef zones. This table shows that 86 species repre-
senting 30 genera occurred on the three transects. Combining this with
the number of species shown on Table 11 that did not occur on the tran-
sects, the total number of species is raised to 96 representing 33
genera. From the total number of species and genera occurring at
Tanguisson Point, 91 species represented by 30 genera are hermatypic,
scleractinians and the remaining five species representing three genera
are nonscleractinians. No ahermatypic corals were observed or collected
at Tanguisson Point, even though investigations were made to depths of
35 m.
Intertidal (5 to [0 m wide)-- In most places the intertidal zone is
either bare reef-rock, sand, or an irregular raised strip of solution-
pitted limestone (Fig. 2).
128
-------
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129
-------
Table 11. CHECKLIST OF CORALS THAT WERE OBSERVED ON THE TRANSECTS AND
COLLECTED FROM TANGUISSON POINT.
[* Indicates that the specimen was collected, # indicates
a species observed on the transects, + indicates a species
observed in the study area, ++ indicates a species which
was identified from dead corals at Tanguisson Point. The
locality and reef zone in which the coral was observed
or collected (University of Guam catalog number is in-
cluded if specimen was collected) follows the symbol.
The following-reef zone abbreviations are used: IRF,
inner reef flat; ORF, outer reef flat; RM, reef margin;
RF, reef front; ST, submarine terrace; and SS, seaward
slope.]
Class ANTHOZOA
Subclass Zoantharia
Order SCLERACTINIA
Suborder ASTROCOENIINA
Family ASTROCOENII DAE
Subfamily ASTROCOENIINAE
Genus Stylocoeniella
Stylocoeniella armata (Ehrenberg,
*Tanguisson Point - 1555, RF
#Tanguisson Point - RF, ST, SS
183*0
Family THAMNASTERII DAE
Genus Psammocora
Psammocora exesa Dana,
1846
RF
#Tanguisson Point -
++Tanguisson Point - SS
Psammocora nierstrasz? van der Horst, 1921
#Tanguisson Point - RM, RF, ST
Sugbenus Stephanaria
Psammocora (S.) togianensis Umbgrove, 19^0
•H-Tanguisson Point - SS
Subgenus Plesioseris
Psammocora (P.) haimeana Milne Edwards and Haime, 1851
#Tanguisson Point - SS
130
-------
Table 11. (continued).
Family POCILLOPORIDAE
Genus Stylophora
Stylophora mordax (Dana, 1846)
#Tanguisson Point - RF, ST
Genus Poci1lopora
Pocillopora eydouxi Milne Edwards and Ha5me, I960
#Tanguisson Point - RF
+Tangu!sson Point - ST
Pocillopora ligulata Dana, 1846
*Tanguisson Point - 1599, 1600, RF
Pocillopora meandrina Dana, 1846
#Tanguisson Point - ORF, RM, RF
Pocillopora setchelli Hoffmeister, 1929
#Tanguisson Point - RM
Pocillopora verrucosa (Ellis and Solander, 1786)
#Tanguisson Point - RM, RF, ST, SS
Poci1lopora sp. 1
#Tanguisson Point - ORF, RF, ST
Family ACROPORIDAE
Genus Acropora
Acropora abrotanoides (Lammarck, 1816)
#Tanguisson Point - RF
Acropora humi1 is (Dana, 1846)
#Tanguisson Point - RF, SS
Acropora hystrix (Dana, 1846)
-Tanguisson Point - 1550, RF
#Tanguisson Point - RM, RF
Acropora kenti (Brook, 1892)
+Tanguisson Point - ST, SS
Acropora murrayensis Vaughan, 1918
#Tanguisson Point - RM, RF
Acropora nana (Studer, 1879)
"Tanguisson Point - 1549, RF
#Tanguisson Point - RM, RF
Acropora nasuta (Dana, 1846)
#Tanguisson Point - RM, RF
131
-------
Table 11. (continued).
Acropora ocellata (Klunzinger, 18/9)
*Tanguisson Point - 1559, 1560, 1561, 1562, RF
Acropo ra pa 1 if era (Lanmarck, 1816)
++Tanguisson Point - SS
Acropora palmerae Wells, 1954
#Tanguisson Point - RM, RF
Ac ropo ra ramb1e r i (Bassett Smith, 1890)
++Tanguisson Point - SS
Acropora rayner? (Brook, 1892)
++Tanguisson Point - RF
Acropora smith! (Brook, 1893)
#Tanguisson Point - RM, RF
Acropora squarrosa (Ehrenberg, 183*0
*Tanguisson Point - 1553, 1557, RF
Acropora studer? (Brook, 1893)
#Tanguisson Point - RF, ST
Acropora surculosa (Dana, 1846)
#Tanguisson Point RF, ST
Acropora syringodes (Brook, 1892)
*Tanguisson Point - 1551, 1552, 1563, 1564, RF
Acropora valida (Dana, 1846)
#Tanguisson Point - RF
Acropora sp. 1
#Tanguisson Point - RF
Genus Astreopora
Astreopora gracilis Bernard, 1896
#Tanguisson Point - RF, ST
Astreopora myriophthalma (Lammarck, 1816)
#Tanguisson Point - ST
Genus Montipora
Montipora conicula Wells, 1954
#Tanguisson Point - RF
Montipora elschneri Vaughan, 1918
#Tanguisson Point - RF
Montipora foveolata (Dana, 1846)
#Tanguisson Point - RF, ST
Montipora granulosa Bernard, 1897
#Tanguisson Point - RF
Montipora hoffmeister?^ Wells, 1954
#Tanguisson Point - RF
Montipora monasteriata (Forskaal, 1775)
#Tanguisson Point - RF
132
-------
Table 11. (continued)
Montipora tuberculosa (Lammarck, 1816)
#Tanguisson Point - ST
Montipora verri HLVaughan, 1907
fTanguisson Point - RM, RF, ST, SS
Montipora sp. 1
fTanguisson Point - RF, ST, SS
Montipora sp. 2
#Tanguisson Point - ST
Montipora sp. 3
#Tanguisson Point - RF, ST
Montipora sp. 4
#Tanguisson Point - RF
Montipora sp. 5
ifTanguisson Point - RF, ST
Suborder FUNG UNA
Superfamily AGARCIICAE
Family AGARICCIIDAE
Genus Pavona
Pavona clavus (Dana, 1846)
#Tanguisson Point - RF, ST
Pavona varians Verrill, 1864
#Tanguisson Point - RF, ST
Subgenus PseudocoTumnastraea
Pavona (P.) pol1icataTWelIs, 1954
ffanguisson Point - RF
Subgenus Polyastra
Pavona (P.) sp. 3
#Tanguisson Point - RF, SS
Genus Leptoseris
Leptoseris Hawaii ens is Vaughan, 1907
#Tanguisson Point - SS
Genus Pachyseris
Pachyseris speciosa (Dana, 1846)
+Tanguisson Point - SS
•H-Tanguisson Point - SS
133
-------
Table 11. (continued).
Family SIDERASTREIDAE
Genus Coscinaraea
Coscinaraea columna (Dana, 1846)
#Tanguisson Point - RM
-H-Tanguisson Point - SS
Superfamily FUNGIICAE
Family FUNG I I DAE
Genus Cycloseris
Cycloseris cyclolites (Lammarck, 1816)
-Tanguisson Point - 1568, ST
#Tanguisson Point - SS
Cycloseris sp. 1
#Tanguisson Point - ST
Superfamily PORITICAE
Family PORITIDAE
Genus Gonioppra
Gonioppra columna Dana,
#Tanguisson Point - ST, SS
Goniopora sp. 1
++Tanguisson Point - SS
Genus j^orites
Porites australiensis Vaughan, 1918
#Tanguisson Point - RF, ST
Porites lobata Dana, 1846
#Tanguisson Point, 1846
Porites lutea MiIne Edwards and Haime, 1851
#Tanguisson Point - RM, RF, ST, SS
Porites sp. 1
*Tanguisson Point - 1648, RF
#Tanguisson Point - RM, RF, SS
Porites sp. 2
*Tanguisson Point - 1490, 1491, SS
134
-------
Table 11. (continued)
Subgenus Synaraea
Porites (S.) convexa Verri11, 1864
+Tangu!sson Point - SS
Porites (_S_.) hawaiiensis Vaughan, 190?
#Tanguisson Point - SS
Porites (S.) horizontalata Hoffmeister, 1925
#Tanguisson Point - SS
Porites (S_.) iwayamaensis Eguchi, 1938
#Tanguisson Point - ST, SS
Genus Alveopora
Alveopora verrilliana Dana, 1872
*Tanguisson Point - 1570, ST
Suborder FAVIINA
Superfamily FAVIICAE
Family FAVIIDAE
Subfamily FAVMNAE
Genus Favia
Favia favus (Forskaal, 1775)
fTanguisson Point - RF, ST
Favia pall Ida (Dana, 1846)
fTanguisson Point - RM, RF, ST, SS
Favia stelligera (Dana, 1846)
#Tanguisson Point - RM, RF, ST
Favia rotumana (Gardiner, 1889)
#Tanguisson Point - ST
Genus Favites
Favites complanata (Ehrenberg, 1834)
*Tanguisson Point - 1601, ST
#Tanguisson Point - RF, ST, SS
Favites favosa (Ellis and Solander, 1786)
#Tanguisson Point - ST
Favites flexuosa (Dana, 1846)
#Tanguisson Point - SS
Genus Plesiastrea
Plesiastrea versipora (Lammarck, 1816)
*Tanguisson Point - 1639, RM
#Tanguisson Point - RM, RF
++Tanguisson Point - SS
135
-------
Table 11. (continued)
Genus Goniastrea
Goniastrea parvistella (Dana, 1846)
#Tanguisson Point - RF, ST
Goniastrea pectinate (Ehrenberg, 1831)
#Tanguisson Point - ST, SS
Goniastrea retiformis (Lammarck, 1816)
#Tanguisson Point - RM, RF, ST
Genus Platygyra
Platygyra rustica (Dana, 1846)
#Tanguisson Point - RF, ST
Platygyra sinensis (Milne Edwards and Haime, 1849)
«Tanguisson Point - 1568, RF
#Tanguisson Point - RF, ST
Genus Leptoria
Leptoria gracil is (Dana, 1846)
*Tanguisson Point - 1603, 1647, RF
#Tanguisson Point - RM, RF, ST
Leptoria phrygia (Ellis and Solander, 1786)
+Tanguisson Point - RM, RF, ST
#Tanguisson Point - RM, RF, ST
Genus Hydnophora
Hydnopnora microconos (Lammarck, 1816)
#Tanguisson Point - RF
++Tanguisson Point - SS
Subfamily MONTASTREINAE
Genus Leptastrea
Leptastrea purpurea (Dana, 1846)
#Tanguisson Point - RF, ST, SS
Leptastrea transversa (Klunzinger, 1879)
*Tanguisson Point - 1571-1, RF
#Tanguisson Point - ST, SS
Leptastrea sp. 1
#Tanguisson Point - RF, SS
136
-------
Table 11. (continued)
Genus Cyphastrea
Cyphastrea chalcfdicum (Forskaal, 1775)
#Tanguisson Point - RF, SS
Chyphastrea sera Mia (Forskaal, 1775)
#Tanguisson Point - RF
•H-Tanguisson Point - SS
Genus Echinopora
Echinopora lamellosa (Esper, 1787)
#Tanguisson Point - RF, SS
Genus Diploastrea
Diploastrea heliopora (Lammarck, 1816)
+Tanguisson Point - ST, SS
Family OCULINIDAE
Subfamily GALAXEINAE
Genus Galaxea
Galaxea fascicularis (Linnaeus, 1758)
#Tanguisson Point - RF, ST, SS
Ga1axea hexagona1is MiIne,Edwards and Haime, 1857
#Tanguisson Point - RF, ST, SS
Family MUSS I DAE
Genus Lobophyl1ia
Lobophyl1ia corymbosa (Forskaal, 1775)
#Tanguisson Point - SS
Lobophyl1ia costata (Dana, 1846)
#Tanguisson Point - RF, ST
Genus Acanthastrea
Acanthastrea echinata (Dana, 18^6)
-Tanguisson Point - 16^5, RF
fTanguisson Point - RF, ST
137
-------
Table 11. (continued)
Family PECTIN I I DAE
Genus Echinophyi1ia
Echlnophyllia asper Ellis and Solander, 1786
#Tanguisson Point - SS
Subclass OCTOCORALLIA
Order COENOTHECALIA
Family HELIOPORIDAE
Genus Heliopora
Heliopora coerulea (Pallas, 1766)
#Tanguisson Point - ST
Class HYDROZOA
Order MILLEPORINA
Family MILLEPORIDAE
Genus Mi 1lepora
Milleppra dichotoma Forskaal, 1775
#Tanguisson Point - RF
+Tanguisson Point - ST
Millepora exaesa Fors kaa1, 1775
#Tanguisson Point - RF, ST
Millepora platyphylla Hemprich and Ehrenberg, 183^
#Tanguisson Point - RM, RF
+Tanguisson Point - ST
Order STYLASTERINA
Family STYLASTERIDAE
Subfamily DISTICHOPORINAE
Genus Distochopora
Distochopora violacea (Pallas, 1776)
#Tanguisson Point - RM
138
-------
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Reef Flat (70 to 100 m wide)-- The fringing reef platform along Tanguisson
Point is divided into inner and outer reef flat subzones, but the inner
reef flat is very poorly developed. At low tide the impounded water or
moat, which delineates the inner reef flat subzone, represents a very
small percentage of the reef platform and is not contiguous along the
entire study region (Fig. 3). The inner reef flat subzone is represented
by several small pools (Fig. 3) at Transects A and C. No corals occurred
on the transects, but several small colonies of Porites lutea were observ-
ed in a small pool near Transect C. The outer reef flat subzone is, in
most places, a flat limestone pavement with very little relief. Only
eight colonies of corals were encountered on the transects. One each of
Poci1lopora meandrina and Porites lutea and six of Acropora nana. These
colonies were found occupying shallow pools near the reef margin zone.
Coral observations along other parts of the outer reef flat are similar
to those found near the transect regions.
Reef Margin (20 m wide)— This zone is awash constantly and represents
conditions favorable for coral development. Figures 53 and $k reflect
this change in habitat by abrupt increases in the percentage of reef
surface covered by living corals and number of species and genera per
transect station.
The reef margin environment can be divided into three separate habitats:
the well-lighted, strongly-agitated water region found on the upper sur-
face of buttresses that separate surge channels; the open surge channels
and pools; and the poorly-lighted, cavernous regions of surge channels
and pools. On the upper surface of the buttresses (Fig. 55), the most
common corals were: Ac ropoj-a pa I merae; Goniastrea retiformis1, Mi I lepora
platyphyl la; Poci 1 lopora meandrina, P_. setchel I i, and P_. verrucosa. Tn~
the surge channels and open pools habitats the more common corals encount-
ered were: Acanthastrea echinata; Acropora hystrix, A. murrayensis, A.
nana, A_. nasuta-, Favia pal 1 ida, F. stelligera; Favites abdita; GoniaTtrea
ret?:formis; Leptoria gj-aci 1 ?s, JL_. phrygia; Montipora verri 11 i', Mi I lepora
platyphylla; Plesiastrea versipora; Pocil lopora verrucosa, P_. setchel I i,
—' roeandrina; and Porites lutea. Growth forms in the surge channels are
mostly encrusting, low flattened massive growths, or cespitose with
closely set branches (Fig. 56). In open pools the growth forms are more
like the forms encountered on the shoreward half of the submarine terrace.
Corals encountered in cavernous regions of surge channels and pools were
mostly encrusting forms of Psammocora nierstraszi, Chyphastrea chalcidicum
Porites sp. 1, and an encrusting growth form of Coscinaraea columna.
Cespitose growth forms are predominant when considering the entire reef
margin zone (Table 13).
Corals not encountered on the reef margin quadrat stations, but commonly
observed there were: Acropora abrotanoides, A_. smithi, A_. surculosa;
Hydnophqra microconos; Pavona clavus, P. (Pseudocolumnastraea) pollicata;
and Stylocoeniella armata. Porites sp. 1 and Sty 1ocoenie11 a armata were
found in all three reef margin habitats in small holes, cracks, and on
142
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Figure 55 Rich coral growth on the upper surface and side of
a reef front buttress
Figure 56 Dense growth of Pocillopora colonies on the floor
of a reef margin surge channel
146
-------
the underside of large spreading coral la.
Eighty-seven percent of the colonies measured in this zone were less than
15 cm in diameter (Table 1A). The great number of small coral colonies
could have been the result of coral recovery following a limited amount
of Acanthaster predation in this zone during the summer of 1968. Surf
conditions are much reduced during Summer months, thus, allowing the
starfish to successfully feed in this zone. Observations of corals in
the 0-5 cm range reveal that some were newly settled juvenile colonies,
whereas many others were small surviving patches of larger colonies.
Reef Front Zone (50 to 70 m wide)-- Major differences in coral distri-
bution began to emerge at the reef front zone because of prior A_. plane?
activity. The percentage of reef surface covered by living corals was
high only for the first one to three quadrat stations immediately sea-
ward of the reef margin zone (Fig. $k). This high percentage of cover
at first indicates that starfish predation was absent or at least nearly
so along this narrow one to three quadrat band and quite high for the
remainder of the zone (Fig. 5*0- Observations and collections at
Tanguisson Point reveal that ramose, cespitose, and corymbose growth
forms were previously more abundant. This was indicated by the many dead
coral la of these growth forms which had been overgrown by coralline algae
and various encrusting Mi 1lepora and Montipora species. Breaking waves
and accompanying surge seemed to result in selective feeding by A_. planci
on corymbose and cespitose Acropora growth forms in this section of the
reef front. During the earlier /\. planci infestation and predation per-
iod some starfish were observed feeding in this part of the front zone.
Chesher'5 also reported some starfish activity in this zone, but noted
that they had difficulty in attaching their tube feet to smooth, rounded
coral la. From the above data and observations, it would seem that se-
lective feeding behavior by A_. p 1 anci has changed the distribution of
corals in this narrow band of surge and wave-assaulted reef front, but,
because of coral resettlement by different species and growth forms,
the percentage of corals covering the surface remained nearly the same.
Common corals observed in inner part of the reef front zone were:
Acanthastrea echinata, Acropora abrotanoides, A_. studeri, A_. hystrix,
A_. murrayensis, /\. nasuta, A_. surculosa; Fa via stel 1 igera; Galaxea
hexagonal is; Goniastrea retiform!s; Leptorla grac?1 is; Mi 1lepora platy-
phylla; Montipora verrM Montipora sp. 1, Montipora sp. 2; Pavona
varians; Platygyra s 1 nensis*, Poci 1 lopora verrucosa; Porites lutea; and
Stylophora mordax.
Seaward of the narrow wave and surge agitated section of the reef front,
the percentage of living corals covering the reef surface (Fig. 5*0
dropped rapidly to less than one percent for some quadrats near the sub-
marine terrace. The reef front zone at Transect B is shallower than that
147
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at Transects A and C. This extends the wave-assaulted section of Trans-
ect B farther, thus lessening the degree of starfish infestation seaward
and explains the presence of a fairly high percentage of living coral
found covering the reef surface over the outer part of the zone (Fig. 5*0 .
Observations of dead coral la (Fig. 51) indicated that species composition,
colony diameter, and growth forms were very similar to those found living
at Tumon Bay (Randall'2). Even though slightly less relief of topo-
phic growth structures such as coral-algal knobs, bosses, and pinnacles,
was noted at Tanguisson Point, it is still obvious that reef development
was taking place like that at Tumon Bay.
Most living colonies encountered were either small, regenerated parts of
larger, older, dead coral la, or small encrusting coral la from new planu-
la settlement. Prior A_. plane! predation did not, in many cases, kill
the entire corallum. Some small, inacessible sections of the corallum,
especially if of irreguler lobate or cuneate growth form, survived the
predation. These surviving sections resume growth by growing upward and
spreading outward over dead parts of the parent corallum and appear as
small encrusting patches. Most young colonies established from newly
settled planulae also appear as small encrustations, even though later
growth development may be of ramose or massive form. Corallum diameter
was therefore, small (Table 1A) and the number of encrusting growth
forms was high (Table 13) because of patchy regeneration and the pre-
sence of newly settled corals. Some corals observed to be regenerating
from surviving parts of older colonies were: Cyphastrea sera ilia; Favia
stel1igera; Goniastrea parvistella, £. retiformis; Leptoria gracilis;
Lobophyl 1 ia corymbosa, L_. costata; Pavona clavus; Plesiastrea versipora;
Porites austral iens is and _P_. lutea. Corals that were developing from
newly settled planulae were: Acropora studer?, A_. hum? lis, A_. surculosa,
Astreopora sp. 1; Favia favus, JF. pa 11ida; Favites complanata; Leptas-
trea purpurea, Leptastrea sp. 1; Mi 1lepora platyphylla; Montipora
foveolata, ML granulosa, M_. verri11i, Montipora sp. 1, Montipora sp. 3,
M^. conicula; Pavona varians; Poci 1 lopora sp. 1 and Porites lutea.
Table 12 lists 65 species representing 2k genera for the reef front zone.
Adding to this list those species collected but not observed at the
transect stations (Table II), increased the total species for the zone
to 69 species representing 2k genera.
Submarine Terrace Zone (kO to 110 m wide) and Seaward Slope
Zone (50 to 70 m wide) -- The submarine terrace and seaward slope zones
were the most heavily infested with A_. plane? during the initial invasion,
and as a result nearly all the original coral populations were killed
(Figs. 51 and 57). Regeneration of small sections of larger colonies
and resettlement of some corals had taken place as described for the
reef front, but to a lesser degree, especially on the seaward slope.
149
-------
Figure 57 A view looking down the steep seaward slope zone
150
-------
Eighty-six to 84 percent of the corals were less than 5 cm in diameter
(Table 14) and 78 to 81 percent were of encrusting growth form (Table
13). The average percentage of living coral covering the reef surface
in these zones (Fig. 5*0 was less than one. At Transect A, station 25,
the highest percentage of coral coverage (4%) was found, caused by a
single patchy, living colony of Porites (Synarea) horizontalata. Figure
53 shows a drop in the number of genera and species per transect station
from that found in the reef front zones.
For the submarine terrace zone, 45 species represented by 22 genera
(Table 12) occurred within the quadrat stations. Specimen collections
made in this zone increased the number of species and genera to 47 and
2k respectively. The most common corals encountered on the submarine
terrace were: Favia favus, F_. pal 1 ida, F_. stel 1jgera; Goniastrea parvis-
tella, G_. pectinata; Leptastrea purpurea; Leptoria phrygia; Millepora
exaesa; Montipora verrilli, Montipora sp. 1, Montipora sp. 3; Pavona
varians; Porites lobata and P_. lutea.
The total number of species occurring on the seaward slope transects was
28 species representing 19 genera (Table 12). If the corals observed
off the transects in this zone are added to the above, the number is
raised to 32 species and 21 genera. This was a considerable reduction
when compared to the submarine terrace and was related to less regenera-
tion from older colonies and a reduction in the number of new corals
developing from planulae settlement. A considerable number of dead coral la
of some species was encountered on the seaward slope that were not ob-
served as living species (Table 11). This indicated that not all the
original species were regenerating in this zone, nor had resettlement of
these species taken place. Some of the dead coral la that could be iden-
tified in the field and that were not observed as living on the seaward
slope transect stations were: Acropora rayneri, /\. rambler?, A_. pal if era;
Coscinaraea columna; Cyphastrea serail ia; Goniopora sp.; Hydnophora
microconos; Pachyseris speciosa; Psammocora exesa, P_. (Stephanaria) togia-
nensis; Plesiastrea versipora, plus some tuberculate Montipora species.
Common living corals observed on the seaward slope were: Favia pal 1ida;
Ga 1 axea fascicularis; Leptastrea purpurea, L_. transversa, Leptastrea sp.
1; Montipora sp. 1; Porites lutea; and Stylocoeniella armata.
Observations of the submarine terrace and seaward slope zones at Tanguisson
Point and from other reefs of Guam indicate that some coral species are
not usually preyed upon by /\. planc| (Fig. 57)• Some of these corals
observed at Tanguisson Point were: Acanthastrea echniata; Diploastrea
he!iopora; Ga1axea fascicularis, £. hexagonal is; Goniopora columna;
Hel iopora coerulea; Mi 1 lepora dichtoma, M^ exeasa, M_. platyphyl la; and
and Poci1Iopora eydoux?.
151
-------
Comparison of Coral Reefs at Tumon Bay and Tangulsson Point
Comparisons of physical reef characteristics and coral distribution indi-
cate that the reef margin, reef front, submarine terrace, and seaward
slope zones at Tumon Bay and Tanguisson Point were similar (except for
slightly less topographic relief at the latter) in reef development be-
fore starfish predation took place (Randall '2). The only zones not com-
parable at the two locations are the subzones of the reef flat, which
were not initially infested with starfish during the population explosion
stage. Based on the above assumptions, a comparison can be made of the
coral communities between the two study locations.
The following data summarize the number of genera and species, for the
major divisions of corals, at Tumon Bay before the Acanthaster infesta-
tion and Tanguisson Point after the infestation.
Tumon Bay Tanguisson Point
(From Randall12' l8)
Genera Species Genera Species
Hermatypic Scleract inians 31 139 30 91
Ahermatypic Scleractinians 2 200
Non-Scleractinians 3 535
Total 36 H6 33 96
The data above show that the total number of living coral genera surviving
the A., plane? predation is nearly the same as that found before predation.
The only genera not found at Tanguisson Point, after the starfish preda-
tion, but that were earlier found at Tumon Bay before the starfish pre-
dation were Euphyl 1 la, Paracyathus, and Polycyathus. Of these three
genera, two (Euphyl 1 ia and Polycyathus) were more or less restricted to
the reef flat and Paracyathus is an ahermatypic coral of little impor-
tance in terms of reef building. The high number of genera surving A_.
planci predation, even though of low density, may be essential in the
recovery of devastated reefs if diversity of seed populations is an im-
portant prerequisite.
The number of species found on the Tanguisson reefs after /L plane?
predation is 3^ percent less than at Tumon Bay. The number is reduced
to 27 percent if those species that are specific for the reef flat moat,
which is well developed only at Tumon Bay, are discounted.
Comparisons of Coral Distribution by Reef Zones -- The number of coral
152
-------
genera and species that were observed or collected from the various reef
zones at Turnon Bay and Tanguisson Point are shown in Tgble 15.
Table 15. TOTAL NUMBER OF GENERA AND SPECIES BY REEF ZONES.
Reef Zone
Reef margin
Reef front
Submarine terrace
Seaward slope
Tumon Bay
(From Randall12),
before Acanthaster
Genera
Tanguisson Point
after Acanthaster
32
28
26
Species
26
98
73
Genera
12
2k
2k
Species
21
69
1,7
57
21
32
Some /\. planci predation occurred in the reef margin zone at Tanguisson,
but not to the extent that coral distribution was greatly changed there.
/\. planci predation has caused extensive damage in the reef front zone.
A 30 percent reduction in the number of species and a 25 percent reduc-
tion in the number of genera has occurred in this zone. Coral damage to
the reef front zone is not uniformly distributed across it. A comparison
of Figure 5k with Table 16 shows that the inner (shoreward) sections of
the reef front zones at Tanguisson Point have a near pre-starfish per-
centage of reef surface covered by living corals, while the outer (sea-
ward) sections show a great reduction.
Table 16. AVERAGE PERCENT OF CORAL COVER BY REEF ZONES.
Reef margin
Reef front
Submarine terrace
Seaward slope
Tumon Bay Transects
(From Randall12), before
Acanthaster
26. k
59.1
50.1
Tanguisson Point
Transects, after
Acanthaster
22.6
20.9
0.9
0.5
However, a comparison of Figure 53 with Table 15 shows that the inner
(shoreward) part of the reef front has changed in the number of coral
species even though the percentage of living coral coverage (Fig.
153
-------
has not greatly changed. Upon close inspection of this zone, It was
found that A,, plane! predation had selectively killed many of the ramose
growth forms of corals, especially the acroporoid species. This selec-
tive predation resulted in lowering the percentage of reef surface cover-
age, but subsequent resettlement and regeneration of encrusting coral
growth forms has restored the normal percentage of coral cover found there.
This section of the reef front is located in a zone of wave agitation
where starfish have difficulty in remaining attached to coral la other
than ramose forms and, as a result, selective predation occurs. Future
assessment of coral damage caused by /\. plane? on the wave-assaulted
regions of the reef front zones, and possibly the reef margin as well,
must therefore be made with care. It is within this section of the reef
front where near optimum coral reef development takes place and probably
optimum coral growth rates as well. Many regions in Guam and other parts
of the Indo-Pacific possess reefs that have undergone _A. plane! preda-
tion in the past several years. Resettlement and regeneration of speci-
fic fast growing corals may, by now, have obscured much of the coral da-
mage in the wave assaulted reef zones.
Quantitative transect data for the submarine terrace and seaward slope
zones at Tumon Bay were not recorded before A_. planci predation there,
but species diversity and percent of coral coverage studies of these
zones were made (Randall^). jne number of of major coral species and
genera observed in these zones at Tanguisson Point indicate a similar
degree of development to that which was previously found at Tumon Bay
(Randall'2). The number of species found on the submarine terrace and
seaward slope at Tanguisson Point is much lower than at Tumon Bay because
of the extensive starfish damage. Table 16 shows that the total reef
surface occupied by living corals on the submarine terrace and seaward
slope averages less than one percent of surface coverage at Tanguisson,
whereas at Tumon Bay the mean percent of coverage for six sample quadrats
at each zone was 59-5 and 50.1 respectively. It was in these two zones
that A_. planci predation was most intense. It was astonishing to see
such large areas of previously living coral killed in less than a year's
time by A_. planci.
Comparison of Corallum Size Distribution — There has been a shift in
corallum size in all reef zones where corals were killed by Acanthaster.
This shift was less intensive on the reef margin and inner part of the
reef front zones. At Tanguisson Point 99 percent of the coral la found
in zones of previous starfish predation were less than 10 cm in diameter,
whereas at Tumon Bay less than 50 percent were in this size range for the
same zones. Reduction in corallum size in regions of starfish predation
is due to the small size of newly established coral la and the small size
of regenerating parts of older, larger coral la that survived the initial
A. planci predation.
154
-------
CORAL RECOVERY (1970 to 197*0
The purpose of this part of the study is to assess, over a period of
four-and-a-half years, the changes that have occurred in the distribution
of reef corals in the Tanguisson area. The first distributional analysis
of the reef corals was made during the first six months of 1970 and dis-
cussed above. A second analysis was made during the same period in 1971
(Randall^) and a third was made in October, 197^. Living corals were
found at 59 stations in 1970, at 65 stations in 1971, and at 62 stations
in 197^- In regard to stations with living corals present from 1970 to
1971, there was a gain and a loss of one station each on the outer reef
flat zone, a loss of one station on the reef margin zone, and a gain of
seven stations on the seaward slope zone. From 1971 to 197^, there was
a loss of three stations at Transect B where the corals were killed by
the thermal plume from the Tanguisson Power Plant.
The number of living coral colonies found within the confines of the
quadrat stations was 1302 in 1970, 2116 in 1971, and 2816 in 197^. The
following data summarize the changes in the number of colonies found in
the quadrat stations from 1970 to 197^ by reef zones.
Reef Margin 181 166 AO
Reef Front 632 789 918
Submarine Terrace 320 632 1035
Seaward Slope 161 521 817
TOTALS 1302 2116 2816
The above data show that the greatest rate of new colony recruitment was
during the one year period from 1970 to 1971> when there was a 62.5% in-
crease compared to a 33.1% increase for the three-and-one-half year
period from 1971 to 1974. Highest coral recruitment is found in those
zones which previously sustained the greatest degree of coral damage from
Acanthaster plane? predation. Although the reef front zone shows rela-
tively less coral recruitment, than the submarine terrace or seaward
slope zones, the inner part of this zone was not greatly damaged by A_.
planci infestation, which tends to mask the rather vigorous recruitment
which is actually taking place in the outer part of the zone where da-
mage to corals was much greater. There has been a steady decline in the
number of colonies in the reef margin zone because of the corals that have
been killed there by hot water effluent from the Tanguisson Power Plant
at Transect B and to some extent at Transect C.
155
-------
Species Comparison
Table 17 lists the coral species composition along with their relative
frequency of occurrence on the fringing reef at Tanguisson Point during
the 1970, 1971 and 197*» study periods and for the Tumon Bay control reef
studied in 1968. At the control reef, 15 species are more or less re-
stricted to the reef flat zones (Table 17)- These restricted species
would not be expected to occur at Tanguisson Point because the reef flat
zones are poorly developed there and a well defined inner reef flat "moat"
is absent.
Table 17 shows, that from a total of 96 species and 33 genera found at
Tanguisson Point during the 1970 study, all but eight species and one
genus were again found during the 1971 study and by 197^ all but two of
the species were again found. Twenty-two species and six genera were
found in the 1971 study which were new to the Tanguisson Point area and
k2 new species and six new genera were found in 197^. Of the 22 new spe-
cies records found in 1971, 12 were new to the Tumon Bay control reef
and of the k2 new species found in 197^, 13 were also new to the control
reef area. At Tanguisson Point from 1970 to 197'> the relative frequency
of occurrence for 88 common species increased for 41, decreased for 44,
and remained unchanged for three species. From 1970 to 1974, 94 common
species showed frequency of occurrence increased for 30, decreased for 60
and was unchanged for five. This decreasing frequency of occurrence
trend indicates a reduction in the new colony recruitment rate which may
be related to the greater percentage of reef substrate surface which is
now colonized by living corals (Table 20).
For the reef as a whole, Table 18 shows that the total number of genera
has increased by five at Tanguisson Point from 1970 to 1971 and by six
from 1970 to 197**. This increases the total number of genera found at
Tanguisson Point in 197** to 39, which is greater than the total of 36
found at the Tumon Bay control reef prior to the A_. plane? infestation
period. The same table, shows an increase of 14 species from 1970 to
1971 and 40 species from 1970 to 1974, but unlike the number of genera
which now surpasses that found at the Tumon Bay control reef, the number
of species is still considerably below that found prior to the starfish
infestation period.
A zonal analysis (Table 19) shows very little change in the number of
genera and species on the inner reef flat, reef margin, and reef front
zones. Only small changes should be expected in these zones since there
has been comparatively little Acanthaster damage to the corals on this
part of the reef. Greatest changes have occurred in the submarine ter-
race and seaward slope zones where Acanthaster predation on corals was
more intense, although there has been a slight reduction in the number
of genera and species in the reef front zone quadrat stations because of
156
-------
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thermal discharge at Transect B.
Figures 58-60 show the number of genera and species for each transect by
stations and reflects more exactly where changes have occurred. Two
artifacts are present in Figures 59 and 60. The first is at Transect A
In the reef margin zone and the second at Transect B in the reef margin
and inner (shoreward) part of the reef front zones. At both of these
transect locations a reduction in the number of genera and species has
occurred. At Transect A this reduction was caused by a bloom of a blue-
green alga, Anacystis dimidiata which, in a small localized region,
covered nearly 100 percent of the reef surface. Many corals were killed
as a result of their living tissues being covered by gelatinous shards
of this alga. At Transect B the reduction was caused by the presence of
heated effluent from the power plant outfall. Transect B bisects a por-
tion of the outfall plume. Nearly all the corals have been killed on
the reef margin and inner (shoreward) part of the reef front zones.
Figures 58, 59, and 60 otherwise show that greatest changes in the num-
ber of genera and species has taken place on transect stations located
on the submarine terrace and seaward slope zones.
It appears then, that species diversity is increasing fairly rapidly at
Tanguisson Point, which is due in part to the recolonization of not only
the former species which commonly occurred there, but also to species
that do not normally occur in the area. Possibly the corals new to the
area represent a pioneer group which recolonize the reef surface recently
killed by Acanthaster predation. Porter reported a similar phenomenon
on the west coast of Panama where corals were killed by Acanthaster.
As more reef surface becomes covered with living corals, especially by
those species which formerly occupied the region, interspecific compe-
tion may well become an important factor which could again restore the
pre-Acanthaster species composition to the reef. Until competition be-
comes a limiting factor at Tanguisson Point, species richness could go
beyond the 146 species level found previously at the Tumon Bay control
reef.
Reef Surface Coverage by Living Corals
The percentage of living coral covering the reef surface (Table 20) in-
creased on all transects and reef zones except for the reef margin on
Transects A and C and the inner reef flat, reef margin, and reef front
on Transect B. Reduction of reef surface coverage in these zones is
due again to the Anacystis dimidiata^ bloom on Transect A and the pre-
sence of the outfall plume at Transects B and C. Figures 61-63 show
the percent of coral coverage for each station on the three transects
and indicates that the highest relative gains have taken place in the
submarine terrace and seaward slope zones where A. plane? damage to the
164
-------
GENERA
-SPECIES
20-
10-
TRANSECT C 197O
REEF
FLAT
-20
-10
p. , , ,//', ,',,, . ,,',,, ,l, iTiV i i i i ii i -0
u i ' i i i i i i • i i i i i • i i i i i i i i i • i • i i i i i 11 11
O 5 1O 15 20 25 30 35
TRANSECT B 1970
20-
-2O
0- i i i i i i i i fill i—i i i i i i i i i i i i i i I'T i iA i -0
u I • • • • i i i »l i i i i i i i i i i i ' • i i i i i i I i M i l_w
15 20 25 30 35
10-
-10
TRANSECT A 1970
20-
REEF ! R I R F
FLAT
1 ' ' ' | I I i I TV* il|lllljl|ll|ll'l|«'l|
O 5 ID 15 2O 2^ 30 35
TRANSECT STATIONS
Figure 58 Number of coral genera and species per transect
station for 1970
165
-------
--GENERA
—SPECIES
TRANSECT C 1971
i i I i I i
3b 35
2.O-
1O
REEF
FLAT
TRANSECT B 1971
•20
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' 'W " 35
TRANSECT A 1971
1O
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i i i I i i ' i i i i i
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1'0 15 2'0 25 3'0 35
TRANSECT STATIONS
Figure 59 Number of coral genera and species per transect
station for 1971
166
-------
GENERA
SPECIES
20
10'
TRANSECT C 1974
REEF
FLAT
-20
-10
I I i ii i i « i i i i • i i i | i i i • i i « ' > I i ' i
5 10 15 20 25 30 35
TRANSECT B 1974
20-
1O-
REEF
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M
RF
i i i i i i i i i i i i i * i i i i i i i
0 4 10 1% 20
L2O
-10
30 35
TRANSECT A 1974
20-
10-
REEF
FLAT
SS
1 • L .' *. • \
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•„ • :^-v
-20
-1O
\l T I I «l | I I I I |
25 3O 35
TRANSECT STATIONS
Figure 60 Number of coral genera and species per transect
station for 1974
167
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3OO
Figure 61 Percentage of reef surface covered by living
corals from 1970 to 1974 for Transect A
168
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Figure 62 Percentage of reef surface covered by living
corals from 1970 to 1974 for Transect B
169
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10 15 20
TRANSECT STATIONS
25
30
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1OO 15O 2OO
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25O
3OO
Figure 63 Percentage of reef surface covered by living
corals from 1970 to 1974 for Transect C
170
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171
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reef corals was greatest.
Corallum Size Distribution
Table 21 lists the frequency distribution of corals by diameter for each
reef zone from 1970 to 1974. The greatest number of corals are distri-
buted in the 0-5 cm range, where 58 to 62 percent of the total number
of colonies are found. These large percentages are due mainly to the
new settlement and growth of coral planulae on the algal encrusted sur-
face of corals previously killed by A_. pianci. Even though large num-
bers of corals were distributed in the 0-5 range in 1971 and 1974, sixty-
two percent of the corals were also found in that range in 1970. Most
of these colonies were represented, at that time,by small patches of
coral la, surviving from larger colonies, that were not completely killed
by /\. plane!. The second largest size distribution is in the 6-10 cm
range which mostly represents an increase in growth of the surviving
coral patches described above, plus some early recolonization from plan-
ula settlement. Most of the increase that took place in the 0-5 and
6-10 cm size ranges occurred in the submarine terrace and seaward slope
zones where /\. plane! activity was greatest. There has been a decrease
in the number of colonies in reef margin zones because of the coral kill
due the algal bloom at Transect A and the outfall plume at Transect B.
Most of the larger coral la are found in reef zones which were not sub-
jected to intensive damage from /\. plane!.
Cora Hum Growth Form Distribution
If the observed increase in the total number of new colonies found at
the station quadrats are due to recent coral planula settlement, then
a marked increase in the number of encrusting growth forms should be
expected, since most newly settled corals go through an encrusting stage
early in their development. Table 22 shows such an increase in the num-
ber of encrusting growth forms, from 788 in 1970, to 1468 in 1971. An
overall reduction of these forms from 1971 to 1974 probably represents
the transition of some of the encrusting colonies into other growth
forms, particularly those of the massive form. There has been a decrease
in the number of all growth forms in the reef margin zone, and for the
encrusting forms in the reef front zone from 1971 to 1974. In the reef
margin zone this reduction is a result of the corals being killed by the
algal bloom at Transect A from 1970 to 1971, and from the outfall plume
at Transects B and C from 1971 to 1974. The reduction in the number of
encrusting forms has been highest in the reef front zone which probably
represents a transition of many of these into massive and cespitose growth
forms.
172
-------
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Summary
1. During 1968 and 1969, at Tanguisson Point, over 95 percent of
the living reef corals were killed by A_. plane? in the submarine
terrace and seaward slope zones. A considerable number of corals
were also killed in the outer part of the reef front zone.
2. the number of living coral colonies recorded on the Tanguisson
Point transects has increased from 1302 in 1970, to 2116 in 1971,
and to 2816 in 197^. Most of these new colonies have developed
in the submarine terrace, seaward slope, and outer part of the
reef front zones.
3. From 1970 to 197** the total number of coral genera has increased
from 30 to 32 on the Tanguisson Point transects aid from 33 to
39 when additional genera observed between Transects A and C are
included.
k. During the 1970 to 197^ study period, the total number of species
has increased from 86 to 111 on the Tanguisson Point transects
and from 96 to 136 when additional species observed between
Transects A and C are included.
From 1970 to 197^ there were A2 species and six genera of corals
recorded that were new to the Tanguisson Point transects. Of
these new species 13 were also new to the Tumon Bay control reef.
Of all the species recorded in 1970, only two were not recorded
again in 197^.
5. When increases in the number of genera and species are compared
by reef zones at Tanguisson Point from 1970 to 197^» there has
been little change in the zones where /\. planci damage was mini-
mal (except for damage caused by the alga bloom at Transect A
and the power plant effluent at Transects B and C). The most
significant increases have occurred on the submarine terrace and
seaward slope zones where /\. planci infestation and damage to
reef corals was greatest.
6. From 1970 to 197^ the percentage of reef surface covered by
living corals has increased in all reef zones at Tanguisson
Point except the reef margin at Transect A (reduction caused by
algal bloom) and the inner reef flat, reef margin, and reef
front zones at Transects B and C (reduction caused by power plant
outfall). The greatest relative increase in the percentage of
reef surface covered by living corals has occurred on the subma-
rine terrace and seaward slope zones.
175
-------
7. During the 1970 to 197^ study period, increases in coral size
has been greatest in the 0-5 cm range and in the 6-10 cm range.
Most of these increases have occurred in the submarine terrace
and seaward slope zones.
8. During the study period, greatest changes in the distribution of
coral growth forms has been an increase of the encrusting types
from 1970 to 1971 and an increase in the massive cespitose forms
from 1971 to 197^. Most of these changes have occurred in the
submarine terrace, seaward slope, and outer part of the reef
front zones.
Conclusions
The increase in the total number of new coral colonies observed, the
increase in species diversity, and the increase in the percentage of
reef surface covered by living corals indicate that coral recovery is
taking place at Tanguisson. Most of the coral recovery is taking place in
those zones where /\. planci infestation and the resulting damage was
greatest. The increases observed for the percentage of reef surface co-
vered by living corals is due to recolonization by the settlement of pla-
nula and an increase in size of the few surviving patches or colonies
of coral that remained after the starfish infestation period.
Based on a pre-Acanthaster value of 59.1 percent living surface coverage
for the submarine terrace zone at the Tumon Bay control reef and an
average yearly gain of 2.76 percent coverage for the submarine terrace
zone at Tanguisson Point, from 1970 to 197**, it will then take this reef
zone about 21.k years to attain the same degree of coverage found before
A- planci predation. With 50.1 percent pre-Acanthaster value of living
coral coverage for the seaward slope zone at the control reef and an ave-
rage gain of l.M percent coverage for the seaward slope zone at Tanguisson
Point, from 1970 to 197/*, it will then take the reef zone, there, about
3^.7 years to attain the same degree of coverage as was found before /\.
planci predation.
The above recovery rates were determined from four years of data and a
simple linear extrapolation based on the control reef values taken in
1967 and 1968. Actually, the percentage of substrate coverage rates are
quite linear for the Tanguisson reef when plotted over the four year study
period. Moreover, at Tanguisson Point, the structural integrity of the
reef framework and accompanying structural relief features, including the
once living individual coralla, are still intact. There has been little
evidence observed which indicates a physical disintegration of the above
eatures. As the present reef surface is recolonized, the living corals
will inherit an intact substrate which possesses nearly all the structural
176
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relief features of a thriving and developing reef. An observer, unaware
of the previous destruction of the living coral reef surface, would be
hard pressed to detect the recent hiatus in reef development of a few
years duration which was caused by A_. plane? predation.
The above reef recovery hypothesis is, at best, tenuous and based only
on gains in reef "surface coverage" by living corals. For a reef to
attain a massive framework development, from a disintegrated reef sur-
face, it might take a much longer period of time, possibly as much as
the 700 years predicted by the late T. F. Goreau^7.
CORAL RECOLONIZATION IN THE INTAKE CHANNEL
An intake channel was excavated across the reef flat platform and reef
margin to provide access for cooling water to plant condensers. The
excavation comprises an area of about 1835 m in the reef flat zone and
an area of about 250 m2 at the reef margin zone. Since the part of the
channel once occupied by the intertidal reef flat platform is now per-
manently 1.5 to 2.5 m deep, it was expected that some coral colonization
and growth would appear on the channel walls and floor.
On October 16, 197^, a survey was made to determine the degree, if any,
to which corals had recolonized the new subtidal channel surfaces. The
channel sides consist of steeply-sloping, rather blocky irregular lime-
stone walls and the channel floor consists of poorly sorted limestone
boulders, gravel and sand.
The inner two-thirds of the channel floor and inner third of the channel
walls were devoid of corals. The outer two-thirds of the channel walls
possessed widely scattered corals, none of which were greater than 15 cm
in diameter. In order of their abundance, the corals observed were
Poci1lopora damicornis, Poci1lopora setchel1i, Acropora surculosa,
Acropora nasuta, Acropora abrotanoides, Acropora plamerae, and Poci1lo-
pora brevicornis. Overall the coral density along the channel wall was
less than one per square meter and the percentage of substrate covered
by living coral was less than one percent.
The outer third of the channel floor has even fewer corals than the
channel walls. It appears that the unstable boulders, gravel, and sand
in the channel floor prevents coral development except for an occasional
colony growing on a larger more stable limestone block or boulder. Corals
observed in their order of abundance were Pocillopora damicornis, Porites
jutea, Acropora nasuta and Acropora surculosa.
177
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SECTION XI
REFERENCES
1. Tracey, J. I., Jr., S. 0. Schlanger, J. T. Stark, D. B. Doan,
and H. D. May. General geology of Guam. U. S. Geol.
Sur. Prof. Pap. 403-A:1-104 (1964).
2. Emery, K. 0. Marine geology of Guam. U. S. Geol. Sur. Prof.
Pap. 403-B:l-76 (1962).
3- Avery, D. E., D. C. Cox, and T. Laevastu. Currents around
the Hawaiian Islands. [Interim Progress Report 1]
Hawaii Institute of Geophysics, Report No. 26, University
of Hawaii. 22 pp. (1963).
4. Jones, R. S. and R. H. Randall. An annual cycle study of
biological, chemical, and oceanographic phenomena
associated with the Agana ocean outfall. University of
Guam, Marine Laboratory, Technical Report No. 1. 67 pp.
(1971).
5. Anon. Interim report of the February 197' current and ecology
survey of Guam. U. S. Naval Oceanographic Office (1970-
6. Huddell, H. D., J. C. Willet and G. Marchand. Nearshore currents
and coral reef ecology of the west coast of Guam, Mariana
Islands. Special Publication 259. Naval Oceanographic
Office. 185 pp. (197^).
7. Goldberg, E. D. Biogeochemistry of trace metals. In
Hedgpeth (ed.) Treatise on Marine Ecology and Paleoecology.
Geol. Soc. America Mem. 67, 1:3^5-358 (1957).
8. Alexander. J. E. and E. F. Corcoran. The distribution of
copper in tropical seawater. Limnology and Oceanography.
12(2):236-2A2 (1967).
178
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9. Clarke, W. D., J. W. Joy, and R. J. Rosenthal. Biological
effects of effluent from a desalination plant at
Key West, Florida. Water Pollution Control Research
Series 18050 DAI 02/70. 73 pp. (1970).
10. Chesher, R. H. Biological impact of a large-scale desalination
plant at Key West. Water Pollution Control Research
Series I8o80 GBX 12/71. 1^8 pp. (1971).
11. Jokiel, P. L. and S. J. Coles. Effects of heated effluent
on hermatypic corals at Kahe Point, Oahu. Pacific
Science 28(l):l-l8 (1974).
12. Randall, R. H. Reef physiography and distribution of corals
at Tumon Bay, Guam, before Crown-of-Thorns starfish,
Acanthaster plane? (L.) predation. Micronesica 9(0
(1973).
13. Jones, R. S., R. T. Tsuda, and R. H. Randall. A study of
ecological succession following natural and man-induced
changes on a tropical reef. Second Quarterly Report to
Project Officer, Contract No. 18050 EUK. 15 pp. (1970).
]k. Randall, R. H. In Press. Coral reef recovery following
intensive damage by the "Crown-of-Thorns" starfish,
Acanthaster planci (L.). Publ. Seto Mar. Biol. Lab.
15. Chesher, R. H. Destruction of Pacific corals by the sea
star Acanthaster planci. Science 165=280-283 (1969).
16. Wells, J. W. Recent corals of the Marshall Islands. U. S.
Geol. Sur. Prof. Pap. 260-1:385-^86 (1951*).
17. Kornicker, L. S. and D. F. Squires. Floating corals; a
possible source of erroneous distribution data.
Limnology and Oceanography. 7(k):Wj-k52 (1962).
18. Randall, R. H. Tanguisson-Tumon, Guam, reef corals before,
during and after the Crown-of-Thorns starfish,
(Acanthaster planci) predation. Master of Science
Thesis, University of Guam. 119 pp. (1971).
19- Cloud, P. E. Superficial aspects of modern organic reefs.
Sci. Monthly 79(4) : 195-208 (195*0.
179
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20. . Submarine topography and shoal-water ecology,
Part k of Geology of Saipan, Mariana Islands. U. S. Geol
Surv. Prof. Pap. 280-K:36l-^5 (1959).
21. Stearns, H. T. Geologic history of Guam. Geol. Soc. Amer.
Bull. 52(12) :19l*8. [Abstract] (19^0).
22. Cloud, P. E., Jr. Reconnaissance geology of Guam and
problems of water supply and fuel storage. Military
Geology Branch, U. S. Geol. Sur., open file report.
50 p. (1951).
23. Tayama, R. Coral reefs of the South Seas. Japan Hydrogr.
Off. Bull. 11:1-292. [Japanese and English] (1952).
2A. Tsuda, R. T. (compiler). Status of Acanthaster planci and
coral reefs in the Mariana and Caroline Islands, June
1970 to May 1971. Technical Report No. 2, Marine
Laboratory, University of Guam. 127 pp. (1971).
25. Wells, J. W. Scleractinia, p. F328-FW. Jhi R. C. Moore
[ed.] Treatise on invertebrate paleontology. Chap.
F. Geol. Soc. Amer. and Univ. Kansas Press (1956).
26. Porter, W. P. Predation by Acanthaster and its effect on
coral species diversity. Amer. Natur. 106 (950):A87-
^92 (1972).
27. Goreau, T. F. Post pleistocene urban renewal in coral reefs.
Micronesica 5(2):323~326 (1969).
180
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SECTION XII
APPENDICES
Page
A. Effect of Temperature on the Metabolic Activity 182
of the Starfish, Acanthaster plane!
B. Effects of Temperature on Fertilization and 184
Early Cleavage of some Tropical Echinoderms
C. Thermal Stress in Caulerpa racemosa as Measured 186
by Oxygen Technique
D. Effect of Heated Water on two Species of Crustose 193
Coralline Algae, Porolithon onkodes and
Hydrolithon reinboldi
181
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APPENDIX A
EFFECT OF TEMPERATURE ON THE
METABOLIC ACTIVITY OF THE STARFISH
ACANTHASTER PLANCI (L.)
by
Masashi Yamaguchi
This Paper has been published in:
Pacific Science (197*0, Vol. 28, No. 2, p. 139-146
182
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ABSTRACT
Standard rate of oxygen uptake in the coral reef asteroid Acanthaster
planci (L.) was determined for the temperature range of 25° to 33°C and
a metabolic rate-temperature (M-T) curve was drawn. Acanthaster planci
is a metabolic conformer. The rate of oxygen uptake increased with
increase of temperature to 31°C. The rate decreased at 33°C, which is
slightly above the ambient temperature for the laboratory-reared Acan-
thaster planci tested. The decrease indicates a disturbance in the me-
tabolic activity due to the elevated temperature. The incipient thermal
death point for the asteroid was estimated to be near 33°C, at which
temperature the animals did not maintain a normal behavior in feeding
and resting cycles. Increasing modification in thermal conditions by
human activity would pose a hazard to the maintenance of coral reef
communities if Acanthaster planci represents metabolic conformer inver-
tebrates with narrow tolerance to elevated temperature.
183
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APPENDIX B
EFFECTS OF TEMPERATURE ON FERTILIZATION
AND EARLY CLEAVAGE OF SOME TROPICAL ECHINODERMS WITH
EMPHASIS ON ECHINOMETRA MATHAEI (DE BLAINVILLE)
by
John H. Rupp
This Paper has been published in:
Marine Biology 23, 1883-189 (1973)
184
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ABSTRACT
Select temperatures, above normal, are shown to reduce success of ferti-
lization and normal early cleavage in the laboratory for the echinoderms
Acanthaster plane? (L.), Culcita novaeguineae Muller and Troschel,
Linckia laevigata (L.)> Echinometra mathaei (de Blainville), and
Diadema savignyi Michel in. The data indicate that cleavage is more sen-
sitive to increased temperature than is fertilization. Upper tolerance
limits for early cleavage in most of the species examined is near 3^-0°C.
The early developmental stages of A. plancl were the most sensitive to
elevated temperature, and those of j[_. mathaei, the least sensitive.
Further experiments with E_. mathae? showed that unfertilized ova were
still viable, dividing normally when fertilized after 2 h exposure at
36.0°C. The ova were significantly less viable after 3 h. Early cleav-
age stages of JE_. mathaei were resistant to 36.0°C for exposure times of
up to kO min. but were inhibited beyond this period. It is suggested
that the ability of £. mathaei to develop normally at 3A.O°C (6 C°
above ambient temperature) and to withstand limited exposure to 36.0°C
may account for the wide distribution of this species in habitats which
are often subjected to broad temperature fluctuations, such as reef
flats.
185
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APPENDIX C
THERMAL STRESS IN CAULERPA RACEMOSA (FORSSK.) J. AG.
AS MEASURED BY THE OXYGEN TECHNIQUE
by
Thomas C. Hohman and Roy T. Tsuda
186
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INTRODUCTION
Numerous studies (see BieblM have been carried out on thermal tolerance
in marine algae. The majority of these studies have focused on temperate
algal species, and deal with tolerance limits and the optimum temperatures
at which these species can survive. While these reports indicate that the
majority of species studied are characteristically found growing within
a specific temperature range, and rarely survive temperatures outside of
this range, little quantitative data have been presented to demonstrate
the metabolic changes of algae within this range.
Recently, Yokohama2 reported on the photosynthesis-temperature relation-
ship in several marine algae from Shimoda, Japan, which has a seasonal
seawater temperature fluctuation between 13° and 2^°C. He provides
quantitative photosynthetic and respiration values for several algal spe-
cies at various temperature points within their thermal tolerance range.
However, the situation on coral reefs is considerably different since the
yearly temperature fluctuation is small and the marine algae are already
living very close to their upper temperature tolerance in the natural
environment (Mayer3).
The purpose of this paper is to determine the effects of temperatures
within the tolerance range on plant photosynthesis and respiration, and
to explore the method of quantifying thermal stress in marine algae by
using the net photosynthesis respiration ratio (P/R ratio) as an indica-
tor. At ambient temperature when the light intensity is above saturation
level, the P/R ratio is expected to be above 1. Any significant decrease
in the P/R ratio at temperatures higher than ambient during the light
hours may be interpreted as an indication of metabolic stress. If the
P/R ratio is 1, the algae are still capable of surviving. However, if
the P/R ratio is less than 1, the algae, although still alive, cannot
theoretically survive for any length of time unless heterotrophy is
taking place.
MATERIALS AND METHODS
Caulerpa racemosa (Forssk.) J. Ag., a green siphonaceous alga commonly
found on reef flats, was chosen as our experimental alga because consi-
derable information has been gathered on its photosynthetic periodicity
(Hohman^) and its ecological response to different light intensities
(Peterson-*). In addition, this alga is accustomed to periodic exposure
at low tides and seems better adapted to tolerate temperature extremes
than algae inhabiting the subtidal zone.
In this preliminary study, three experiments were run which differed
only in the duration at which the algae were held in their respective
temperature baths - experiment 1, 12 hours; experiment 2, 2 hours; and
187
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experiment 3, 0 hours.
Specimens of Caulerpa racemosa of comparable size and age were collected
from the same field population and taken to the laboratory where all
visible epiphytes were removed. Five specimens were held in each of the
four separate temperature baths which were supplied with fresh flowing
seawater and exposed to natural illumination (ca. 10,00 f.c.). The baths
differed only in the temperature of the water - bath 1 (ambient tempera-
tures of 28 to 29°C), bath 2 (ambient plus 2°C) , bath 3 (ambient plus
4°C), and bath k (ambient plus 6°C).
One hour before incubation, four light bottles and three dark bottles
(^35 ml capacity) were filled with previously vacuumed filtered sea-
water of known oxygen concentration and were placed in each bath to be
temperature equilibrated. Vacuum filtered seawater at a pressure of 8 mm
of mercury decreased oxygen concentration by 20%.
Algae were then placed into three of the light bottles and two of the
dark bottles. The remaining two bottles without algae were used as con-
trols. The algae were incubated for 30 minutes at the same time each
day, i.e., 1200 to 1230, to negate differences caused by photosynthetic
periodicity. Prior experiments (Hohman^) with incubation periods of
15, 30, 45, and 60 minutes showed that a 30-minute incubation was suffi-
cient to observe noticeable changes in oxygen concentration without
demonstrating a bottle effect.
At the end of the incubation period, the water was siphoned into 300 ml
BOD bottles for oxygen determination and measured using the azide modi-
fication of the Winkler technique APHA"). Replicate titrations were run
and differed by less than 0.5%. Rates of net photosynthesis, respira-
tion, and P/R ratios were calculated for the algae in each bath.
At the completion of the experiments, the algae were placed in pre-
weighed containers, stored in a drying oven at 105°C for 2k hours, and
weighed to the nearest .001 gram. These values were then used to correct
differences in the biomass of each alga; thus, final values for net
photosynthesis and respiration are expressed as mg 0_ per gram dry weight
per hour.
RESULTS AND DISCUSSION
The results of the three experiments (Fig. 1) agree closely. The highest
rate in net photosynthesis in each of the experiments occurs at 28° (am-
bient). At temperatures above 28°C, the photosynthetic rates decrease
continuously in each experiment.
The respiration rates of Caulerpa racemosa demonstrate a sharp increase
188
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189
-------
between 28° and 30°C. This increase was much higher than expected.
Most Investigators (Giese') report a two to fourfold increase in the
respiration rate (QJQ value of 2 to 4 ) with a 10°C rise in temperature.
In these experiments we obtained a doubling with only a 2°C rise in tem-
perature. This observation reinforces the idea that tropical organisms
do live closer to their upper temperature limits.
At higher temperatures, between 30° and 3^°C, the algae in each experi-
ment again demonstrate agreement by showing a continual decrease in
respiration rates with an increase in temperature. When the respiration
rate begins to decline, it can be assumed that the algae have been ex-
posed to temperatures higher than optimum in the biokinetic zone, thus
resulting in injury.
Figure 2 presents the P/R ratios for each of the three experiments at
the four temperatures. Regardless of the duration of the holding period,
the algae incubated at ambient temperature all demonstrated a P/R ratio
much greater than 1. When the temperature was increased to 30°C, again
regardless of the length of the holding period, the P/R ratio in each
of the experiments decreased to about I.00. This indicates that the
2°C rise in temperature - from 28° to 30°C - exerts a very large thermal
stress on the algae. These results are similar to that cited by Moore°
in a study by Montfort" in which the P/R ratio first rose and then fell
when Porphyra, a red alga, was exposed to various temperatures between
5° and 21°C.
In the experimental temperature bath at 32°C, only the algae incubated
for short duration were able to maintain a P/R ratio at about 1.00. The
algae which were exposed to this temperature for 12.5 hours had a P/R
ratio much lower than 1.00. Obviously, the algae cannot tolerate this
temperature extreme for prolonged lengths of time.
All of the algae maintained at 3k°C exhibited a net photosynthesis of
0.00; thus the P/R ratios are also 0.00. This observation indicates
that the algae cannot tolerate this temperature even for short periods
of time. The lighter green color and flaccid condition of these algae
at the completion of the experiments confirm the above observation.
These changes are considered (Biebl') as signs of death. Similar obser-
vations were made on algae stored at 32°C for periods greater than two
hours. The observations possibly show that a net photosynthesis of
0.00 or a P/R ratio of 0.00 is an indication of death.
This preliminary study on Caulerpa racemosa indicates that the P/R ratio
may be used to quantify thermal stress or even death in marine algae.
It is anticipated that these studies will be extended to include those
blue-green algae which inhabit thermal effluent areas near power plants.
190
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4.00
a:
a:
a.
3.00
2.00
1.00
0.00
12-Hr. Hold ( )
2-Hr. Hold ( )
0-Hr. Hold ( )
28
30 32
Temperature (°C)
Figure C-2. Net photosynthesis/respiration ratio
191
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LITERATURE CITED
1. Biebl, R. Temperature resistance of marine algae. Proc. Seventh
Intern, Seaweed Symp. (Sapporo, Japan). 23-28 (1972).
2. Yokohama, T. Photosynthesis-temperature relationship in several
benthic marine algae. Proc. Seventh Intern. Seaweed Symp.
(Sapporo, Japan). 286-291 (1972).
3. Mayer, A. G. The effects of temperature upon tropical marine
animals. Paps. Tortugas Lab. 6(l):l-24 (191*0 -
4. Hohman, T. C. Diurnal periodicity in the photosynthetic activity
of Caulerpa racemosa (Forskaal) J. Agardh. M.S. thesis,
Univ. Guam. Agana, Guam. 43 p. (1972).
5- Peterson, R. D. Effects of light intensity on the morphology and
productivity of Caulerpa racemosa (Forskaal) J. Agardh.
Micronesica 8(1):63-86 (1972).
6. American Public Health Association. Standard methods for the
examination of water, sewage, and industrial wastes.
Twelfth edition. New York. 769 p. (1965).
7. Giese, A. C. Cell physiology. Third edition. W. B. Saunders Co.
xx + 671 p. (1968).
8. Moore, H. B. Marine ecology. John Wiley and Sons, Inc., New York.
xi + 493 P. (1962).
9. Montfort, C. Zeitphasen der Temperatur-Einstellung and jahrzeitliche
Umstellung bei Meeresalgen. Ber. dent, botan. Ges.
53:651-674. [Not seen by authors] (1935).
192
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APPENDIX D
EFFECT OF HEATED WATER ON TWO SPECIES OF
CRUSTOSE CORALLINE ALGAE, POROLITHON ONKODES
AND HYDROLITHON REINBOLDI
by
Gregory Gordon
193
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INTRODUCTION
Reef corals are often credited entirely with formation of tropical reefs,
but the corals share their importance as reef builders with another
group of organisms, the crustose coralline algae (Corallinaceae). These
algae are important for their contribution in cementing the reef struc-
ture. One species, Porolithon onkodes, has long been noted for its key
role in this regard. This species is adapted to live on the reef margin
where the force of the waves is met and absorbed. Although other corals
coralline algae are found here, P_. onkodes is usually the dominant organ-
ism and imparts to the reef margin its characteristic pink color. Coral
reef biologists generally agree (Gardiner, 1903) that without this
living layer of calcium carbonate secreting organisms (primarily P_.
onkodes) on the reef margin, the force of wave attack and subsequent
run-off would erode away the reef margin. It is not known how quickly
this might occur, but the process would be hastened by the many burrow-
ing organisms that tend to weaken the reef structure. Forms of stress
that would remove both corals and coralline algae could lead to this
condi tion.
The heated sea water effluent from Guam's Tanguisson Power Plant Is re-
leased on the reef flat and flows across it to the reef margin where it
begins mixing with oceanic water. It has been noted in the field (Sec-
tion VIM) that scleractinean corals are killed by this effluent. The
purpose of this preliminary study was to observe, experimentally and in
the field, the tolerance of Porolithon onkodes and Hydrolithon reinboldi
to thermal stress. Hydrolithon reinboldi \s a reef flat crustose coral-
1ine algae commonly found on Guam reefs.
MATERIALS AND METHODS
The same thermal apparatus described by Jones and Randall (Section IX)
for testing corals was used. Temperature increments of +2°C were added
so that in each series of three tanks the temperature would be 28 (con-
trol), 30, 32, and 3k°C.
Specimens of Porolithon onkodes were collected by breaking off pieces
from the reef margin with hammer and chisel. Hydrolithon reinboldi
commonly encrusts entire rocks on the reef flat and these rocks were
gathered. Specimens tested were held in the Marine Laboratory running
seawater system for at least two weeks prior to being used in the ther-
194
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mal experiment. H_. reinboldi showed little obvious sign of stress as a
result of this, but nearly half of the P_. onkodes specimens died during
this acclimation period. Other P_. onkodes specimens experienced death
of some of the cells around the edges of the specimen. Perhaps this was
a result of the damage caused by collecting them, or it may reflect the
sensitivity of P_. onkodes to stresses inherent in the seawater system
itself. Survivors eventually stabilized.
To reduce the initial shock of the heated water, specimens were placed in
buckets of ambient temperature seawater. The buckets were placed in the
tanks and the specimens allowed to slowly acclimate to the tank tempera-
tures. When the water temperature of the buckets equaled that of the
tanks, the specimens were placed in the tanks (about three hours).
Determining the death point of an alga is difficult. The most accurate
methods measure changes in the plant's physiology such as their rate of
photosynthesis versus their rate of respiration and noting when this
P/R ratio drops (see Appendix C). Because of time limitations, the
method used here had to be a subjective visual observations. The thalli
of the specimens were observed for loss of color. White was considered
dead, although other color changes were noted and experience eventually
proved that these color changes were merely early indications of death.
A thallus becomes completely white only after cell pigments have diffused
out or decomposed. Death undoubtedly precedes this final step of decom-
position with at least 2k hours seeming to be a conservative minimum.
A complication in the study occurred because the specimens do not res-
pond as one organism. Death of the thallus often is by degrees, with
some cells turning white (dying) while others remain a healthy color
(alive). This slow destruction was followed and recorded as the percent
of the thallus appearing white versus the percent remaining healthy.
The percentages were determined visually and recorded in increments of
5%. I was confident that the observations were in error by no more than
+5%. In some cases it was necessary to use specimens that had already
experienced partial damage while in the holding tanks. Die off occurred
early and the thalli eventually stabilized. To simplify determination
of the amount of change occurring, the entire original thallus was given
a percent dead versus a percent alive ratio. To use the initial percent
alive values from these specimens, the values were multiplied by a con-
version factor determined from the original percent deadrpercent alive
ratio. This corrected the percent alive number to one that indicated
the percent that remained alive from the 100% that started out the ex-
periment alive. (For example, if 80% of the original thallus was alive,
then 80 divided into 100 gives a conversion factor of 1.25. The con-
version factor was multiplied by all subsequent percent alive values.
An experimental percent alive value of 60% would be corrected to 75%).
195
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It was then possible to sum the percent alive values of the six specimens
from each temperature series to obtain a mean number of the percent of
algae remaining alive after each day. The daily mean values have been
plotted on graphs showing the results from the four temperature series.
On days when the specimens were not checked, the days have been left
blank in the graphs, and dotted lines used to connect the plots for the
mean values of each series. HL reinboldi was tested for 14 days and
_P_. onkodes for 28 days.
Field observations were made in an effort to correlate the experimental
work with the situation as it now exists on the reef flat affected by
the Tanguisson Power Plant effluent water. Subjective observations were
made at low tide on the reef flat and reef margin in the area in front
of and south of the power plant where the hot water effluent impinges
on the reef. Observations were also made in the surge channels in front
of the effluent area to observe possible effects along the sides and
bottom of these channels.
RESULTS AND DISCUSSIONS
The results of the experiments are presented in Figures 1 and 2.
Figure 1 shows that Porolithon onkodes in the 32° and 34°C tanks exhibits
signs of stress after one day. At the end of six days, all the algae in
these two temperature series were dead. This is in marked contrast to
the results for Hydrolithon reinboldi, Figure 2. This reef flat algae
seems to tolerate for five days the stress of the 34°C water. It then
began to die slowly in the 34°C tanks, and all would have probably died
if the experiment had run for a longer period of time. In the 32°C tem-
perature series, 30% of the thalli of H^. reinboldi remained alive after
14 days.
In the 28°C (ambient) and 30°C tanks, the jP_. onkodes showed signs of
stress after 14 days that was not exhibited by j^. reinbold?. HL rein-
bo 1 d?, after 14 days, had mean values of 98 and 99 percent of its thalli
remaining alive in the 28° and 30°C tanks respectively. P_. onkodes had
mean values of 82 and 50 percent in the 28° and 30°C tanks respectively.
After 28 days P_. onkodes had mean values of 51 and 24 percent from the
28° and 30°C tanks respectively. This may indicate that with time, slow
attrition of _P_. onkodes occurs, even in ambient seawater. This makes it
more difficult to assess the effects of the 30°C seawater on P_. onkodes,
but does indicate the sensitivity of the species to stress. Since the
percent alive values are consistently lower in the 30°C tanks, it still
appears reasonable to assume that the temperatures of +2°C above ambient
stressed the P. onkodes enough to cause some death.
196
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197
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Figure D-2. Hydrolithon reinboldii.
198
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The experimental results indicate that the reef flat coralline algae
Jl' re!nbpldi is adapted to withstand the effects of higher than ambient
water temperatures better than _P_. onkodes. This would be expected since
reef flat algae are normally subjected to higher than ambient oceanic
water temperatures during the daytime low tides of summer. _P_. onkodes
grows on the reef margin where it is continually washed by seawater at
ambient temperature. Thus adaptation to water temperatures much higher
than ambient would not be expected.
The experimental design does not emulate the thermal stress normally ex-
perienced on the reef flat where the alternating high and low tides re-
sult in a cycle including periods of thermal stress followed by periods
of immersion in ambient seawater. This is in contrast to the continual
immersion in heated water that occurred in the experiment and opposite the
power plant.
Coralline algae usually grow outward from a central area, often overlap-
ping itself or other organisms. On the reef margin, individuals of P_.
onkodes are continually overlapping each other so that any specimen col-
lected is likely to be composed of more than one individual. A result
of these patterns of growth is that in any type of specimen collected,
cells of that specimen are likely to be of differing stages of growth
and development. This may partially explain why some of the thalli died
and the remainder stayed alive in a given specimen. The cells comprising
it were in varying stages of senescence, and as a result some were weaker
than others. Stresses that normally would have been tolerated, instead
led directly or indirectly to their death.
Section VI of the primary report reported temperatures in the effluent
at a low tide as follows: the stilling well was 33.^°C, mid-reef flat
was 33.^t°C, water cascading into the surge channels was 33«2°C, and at
the midpoint of the reef margin width was 32 to 32.8°C. The reef flat
temperatures approximate the temperatures in the 3^°C temperature series.
Along the reef margin the temperatures would roughly correspond to the
32°C temperature series.
Utilizing temperature data from the field and the experimental results,
it would be logical to predict that no H_. reinbold? would be found on
the reef flat in the stream of the heated effluent water, and that along
the reef margin in this area the £. onkodes would be dead. This is
essentially the situation that was found to exist when field observations
were made on the reef flat and reef margin at the Tanguisson Power Plant
site.
The reef flat in the area covered by the effluent contains a great deal
of rock and rubble of the type commonly found encrusted by H^. reinboldi
199
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on normal reef flats. The turbulence of this water would seemingly make
it an even more suitable habitat under conditions of ambient seawater
temperatures. Observations of this area revealed very little crustose
coralline algae of any type. Some H_. reinboldi was seen, but it was
always growing in small depressions, where perhaps the effluent would
tend to flow over the top and not impinge directly on the algae. Occa-
sional waves do wash into this area, bringing with them cooler water.
This cooler water, being denser, may settle into the depressions, thus
insulating the algae. In no case was there extensive growth of coralline
algae in this area. Both north and south of this intake channel, where
there is little or no impingement of hot water effluent, H. reinboldi
was again found.
In dealing with 1P_. onkodes along the reef margin,the following condition
was noted. Daytime low tides begin in May and impose a seasonal stress
on the reef flats of Guam. This is frequently noticable along the raised
algal ridge in back of the reef margin where the _P_. onkodes is often ex-
posed, and if it becomes dessicated, will die. Weak surf conditions are
common in the summer, and so this die off commonly happens. Littler
(1973) described this phenomenon in Hawaii and indicates that with the
resumption of heavy surf and daytime high tides, £_. onkodes quickly re-
colonizes the area. I inspected the Tanguisson reef platform in mid-
July and by this time one could see that these seasonal stresses had
resulted in some natural death along the reef margin. It was not possible
to separate this from death due to the hot water effluent. To deal with
the situation, I considered partial death along the reef margin as normal
and made what I consider to be conservative estimates of the effects of
the hot water effluent on the reef margin.
Damage to the reef margin has been heavy in front of the plant outfall
and south for a distance of approximately 100 m. No _P_. onkodes ?s found
growing on top of the reef spurs except at their extreme seaward point
where the spurs are below water at all times. Along the sides and bottom
of the spurs there was no P_. onkodes. The only algae seen were In holes
and crevices in the substrate where they would be protected from direct
impingment of the heated water. In this region, nearly all the P_. onko-
des has been killed, and filamentous blue-green algae now predominate in
the area.
In that area 100-200 m south of the Tanguisson Power Plant, the _P_. onko-
des along the reef margin has received at least moderate damage from the
heated water effluent. This is primarily evident on top of the spurs of
the reef margin. The surge channels and sides of the spurs were not
checked, but since the heated water does not run directly into the spurs
at this point, plant influence is probably confined to the surface layer
of water, and thus only the top of the reef margin is likely to be affec-
ted.
200
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Beyond 200 m the amount of damage gradually diminishes, but it was im-
possible for me to estimate at what point there was no further death
resulting from the power plant.
CONCLUSIONS
1. Poro1ithon onkodes growing along the reef margin is less tolerant of
the stresses resulting from hot water effluent than is the reef flat spe-
cies, Hydro!ithon reinboldi.
2. Almost all the H_. reinboldi formerly growing in the area where the
heated effluent water from Tanguisson Power Plant now flows across the
reef is now dead.
3. Significant damage has occurred to the groove and spur system of the
reef margin directly in front of the Tanguisson Power Plant where the
heated effluent water is discharged. This damage is caused by the heated
water killing the _P_. onkodes normal ly found living there. Reef margin
damage extends south of the power plant for at least 200 m, with the
amount of damage gradually diminishing the further south one goes.
4. Death of the F\ onkodes along the first 100 m of reef margin has
probably made that area more susceptible to erosional effects of break-
ing waves and water.
201
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BIBLIOGRAPHY
Gardiner, J. S. 1903- The Fauna and Geography of the Maldive and
Laccadive Archipelagoes, Vol. 1. Cambridge University Press,
Cambridge. 939 pp.
Littler, M. M. 1973- The population and community structure of
Hawaiian fringing reef crustose Coral 1inaceae (Rhodophyta,
Cryptonemiales). J. exp. mar. Biol. Ecol. vol. 11:103-120.
202
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List of Figures
Figure 1. Location map of Guam showing study areas.
Figure 2. Aerial photograph of Tanguisson No. 1 site. Tanguisson
No. 2 is under construction directly adjacent to No. 1.
Figure 3. Detailed map of the Tanguisson Point study area showing
transect locations.
Figure *». Reef profile at Transect B, Tanguisson Point; vertical
exaggeration X5. The flattened region seaward of the seaward
slope is the beginning of the second submarine terrace.
Figure 5- Current patterns on the reef flat prior to release of
effluent. The dashed lines show movement of wave transported
water onto the reef flat and the subsequent movements of that
water along shore. The stippled arrows, labeled with roman
numerals, show the major escape points of the reef flat water.
(a- power plant, b- shoreline, c- reef flat, d- Naval
Communications Station swimming lagoon, e- intake channel,
f- outfall site).
Figure 6. Current patterns on the reef flat after release of
effluent. The actual changes are shown at the intake (a),
and outfall (b) channels; otherwise, the patterns are the
same as Figure 5-
Figure 7- Mean frequency diagram for current direction at 5 m
(TSK meter).
Figure 8. Mean frequency diagram for current direction at 10 to
]k m (Hydroproducts meter).
Figure 9- Mean frequency diagram for current direction at 23 m
(TSK meter).
Figure 10. Mean frequency diagram for current direction at 30 m
(Hydroproducts meter).
Figure 11. Mean frequency diagram for current direction, all
stations combined. The data are biased by the inclusion of
the truncated pattern produced by the Hydroproducts meter.
203
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Figure 12. Sample segment from one current meter tape indicating a
close fit between tide cycle and current direction. Some early
shifts are evident but in general, there is a northerly set
during ebb tides and a southerly one during floods. (Arrows
are direction only).
Figure 13- Sample segment from one current meter tape showing a
predominance of southerly components with no correlation with
tide cycle.
Figure 14. Sample segment from one current meter tape showing a
predominance of northern components with no correlation with
tide cycle.
Figure 15- One meter drift cross casts. The drift cast numbers are
as follows:
1-
2-
3-
10/6/70
10/9/70
12/23/70
4- 23/23/71
5- 3A/71
6- 3/17/71
7- 3/24/71
8- 3/31/71
9- VI8/71
Flood to ebb
Flood
Flood to ebb
Ebb to flood
Flood to ebb
Ebb
Ebb to flood
Ebb
Flood to ebb
10- 4/29/71
11- 5/6/71
12- 5/11/71
13- 6/9/71
14- 6/17/71
15- 6/23/71
16- 7/1/71
17- 7/9/71
18- 7/15/71
Flood to ebb
Ebb
Ebb
Ebb
Flood (weak)
Ebb
Flood (weak)
Ebb
Flood (weak)
Figure 16. Five meter drift cross casts.
on Figure 15-
Figure 17- Ten meter drift cross casts.
on Figure 15-
Data for cast numbers
Data for cast numbers
Figure 18. Plot of mean monthly sea surface temperatures for a
10 year period at Tanguisson Point, Transect A. Vertical bar
represents monthly range of temperatures.
Figure 19- Power plant operating temperatures. Mean intake and
outfall temperatures and delta T's are shown for the first
16 months of operation (1 unit) and the last 12 months
(2 units). The numbers in parentheses represent mean
temperatures and delta T's for the 28 month period.
Figure 20 A,B. Surface and 1 m isotherms for August 2, 1974.
Figure 20 C,D. Surface and 1 m isotherms for August 20, 1974.
204
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Figure 20 E,F. Surface and 1 m isotherms for September 5, 197^-
Figure 20 G,H. Surface and 1 m isotherms for September 12,
Figure 21. Diagrammatic presentation of the influence of the
thermal plume on the reef margin. The rip currents at the
intake channel and near Transect C provide partial boundaries
to the effluent, diverting it seaward.
Figure 22 A. Algal community after thermal discharge, (a- outfall
channel and Microcoleus lyngbyaceus; b- Padina tenuis;
c- Dictyota divaricata and mats of Calothrix, Microcoleus, and
Schizothrix; d- Cladophorops is membranacea; e- Hal imeda
opuntia; f- Amph i roa f ragi 1 issima; g- Polysiphonia scopulorum;
h- intake channel; Jania cap! 1 lacea, Gelidiella acerosa,
Sargassum cristaefol ium, Amph i roa f ragil issima, and Galaxaura
marginatusT"!
Figure 22 B. Algal community after thermal discharge of Tanguisson
No. 1 and 2 (a- outfall channel and Microcoleus lyngbyaceus;
b- Cladophorops is membranacea; c- intake channel; Ga 1 axau ra
marginata, Neomeris annulata, Jania cap? 1 lacea, Boergesenia
forbesi i , Polysiphonia scopulorum, Chlorodesmis fastigiata,
Hal imeda opuntia, Caulerpa cupressoides, Schizothrix
calcicola, and Enteromorpha compressa"n
Figure 23. Limits of coral kill as of December, 1971 (a- intake
channel, b- outfall channel, c- reef flat zone influenced by
effluent, d- contact zone of effluent with living corals,
e- core zone of coral kill, f- peripheral zone, g- Transect B) .
Figure 24. Coral kill on upper surface of a reef margin buttress.
Figure 25. Pale and bleached corals on the walls and floor of a
reef margin surge channel.
Figure 26. Dead coral and coralline algae surface being recolonized
by blue green algae.
Figure 27. Vertical profile through the reef margin and reef front
zones showing mixing and then stratification of the effluent.
Figure 28. Limits of coral kill as of January, 1973. See Figure
23 for legend.
Figure 29. Limits of coral kill as of October, \31k. See Figure
23 for legend.
205
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Figure 30. Thermal simulation device. (A- oblique view, B- side
view). Figure 30 A shows the common seawater feeder trough
with valves to provide seawater to acclimation tanks on the
left and the experimental system on the right. Control tanks
are in the foreground with the +2, +4, and +6 tanks extending
into the background. There are three replicate tanks in each
temperature series. Tanks with white tops are heater tanks
with immersion heaters and control boxes.
Figure 31. Acclimation tank. Corals are placed on inverted jars
to avoid bacterial contamination that often occurs when they
are on the bottom.
Figure 32. Fungi a scutaria. This and all experimental results to
follow are based on delta T's above summer ambient of 28.5°C.
Actual mean ambient temperature during the experiments are
given in parenthesis. (Mean ambient = 29-0°C).
Figure 33 A. Psammocora contigua. (Mean ambient = 29.0°C).
Figure 33 B. Psammocora contigua. (Mean ambient = 28.0°C).
Figure 34 A. Pocillopora damicornis. (Mean ambient = 29«0°C).
Figure 34 B. Pocillopora damicornis. (Mean ambient = 27.5°C).
Figure 35. Pocillopora setchelli. (Mean ambient = 29.5°C).
Figure 36. Pavona obtusata. (Mean ambient = 28.0°C).
Frgure 37. Pavona varians. (Mean ambient = 28.0°C).
Figure 38. Pavona frond ifera. (Mean ambient = 29.5°C).
Figure 39 A. Pavona decussata. (Mean ambient = 29.5°C).
Figure 39 B. Pavona decussata. (Mean ambient = 28.5°C).
Figure 40 A. Porites lutea. (Mean ambient = 28.0°C).
Figure 40 B. Porites lutea. (Mean ambient = 29.0°C).
Figure 40 C. Porites lutea. (Mean ambient - 28.0°C).
Figure 41. Favia stel1igera. (Mean ambient = 28.0°C).
206
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Figure 42 A. Galaxea hexagonal is. (Mean ambient = 27.5°C).
Figure 42 B. Ga1axea hexagona1is. (Mean ambient = 29.5°C).
Figure 43. Acropora aspera. (Mean ambient = 29.0°C).
Figure 44. Acropora nasuta. (Mean ambient = 28.5°c).
Figure 45- Acropora pal ifera. (Mean ambient = 28,0°C).
Figure 46. Leptoria phrygia. (Mean ambient = 29.0°C).
Figure 47- Millepora platyphylla. (Mean ambient = 28.5°C).
Figure 48. Stylophora mordax. (Mean ambient = 28.0°C).
Figure 49. Platygyra rustica. (Mean ambient = 29-5°C).
Figure 50. Bleached polyps of Galaxea hexagonal is.
Figure 51. Transect B station showing anchor links and station
number suspended by a float. Station 23 is located on the
inner part of the submarine terrace. The outer part of the
reef front is visible in the background. Ninety percent or
more of coral colonies visible have been killed by Acanthaster
plane? and most are still intact and in position of growth.
Figure 52. Diagram of the station quadrat transect method used at
Tanguisson Point. Two one meter square quadrats are shown
positioned at the stations.
Figure 53- Number of genera and species per transect station at
Tanguisson Point, 1970. Cross-hatched area indicates genera
and non-hatched area species.
Figure 54. Percentage of reef surface covered by living corals
at Tanguisson Point, 1970. Each column represents a transect
stat ion.
Figure 55- Rich coral growth on the upper surface and side of a
reef front buttress at Tanguisson Point. The large colony
in the foreground consisting of upright plates is Millepora
platyphylla.
Figure 56. Dense growth of Pocillopora colonies on the floor of
a reef margin surge channel.
207
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Figure 57- A view looking down the steep seaward slope zone on
Transect A. In the foreground, at 2k m depth, a large colony
of Pocillopora eydouxi (1 m dia.) has survived the Acanthaster
predation. Note the presence of numerous dead coralla. In
1967 this slope was covered with a rich growth of living corals
to depths of more than 50 m.
Figure 58. Number of coral genera and species per transect station
for 1970.
Figure 59- Number of coral genera and species per transect station
for 1971.
Figure 60. Number of coral genera and species per transect station
for 197**.
Figure 61. Percentage of reef surface covered by living corals from
1970 to 197A for Transect A.
Figure 62. Percentage of reef surface covered by living corals from
1970 to 197*1 for Transect B.
Figure 63. Percentage of reef surface covered by living corals from
1970 to 1971* for Transect C.
Appendix C, Figure 1. Net photosynthesis ( ) and respiration
( ) values, +\ S.D. from the mean, at four temperatures.
Appendix C, Figure 2. Net photosynthesis/respiration ratio at four
different temperatures obtained in the three experiments.
Appendix D, Figure 1. Porolithon onkodes. Six specimens were run in
each of the four temperature series, and their daily mean
percent of thallus alive is plotted for 28 days or until death
occurred. Dotted line indicates days when specimens were not
checked.
Appendix D, Figure 2. Hydrolithon reinboldii. Six specimens were run
in each of the four temperature series, and their daily mean
percent of thallus alive is plotted for \k days. Two of the
specimens in the 32°C tanks developed combined bacterial and
fungus infection which killed them. These two specimens were
disregarded and the mean of four specimens was used in the
graph. Dotted line indicates days when specimens were not
checked.
208
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TECHNICAL REPORT DATA
(I'li'asc read luurucluim, on the rcvcnc before com/ilcling}
1. HI Pom NO
EPA-600/3-76-027
2.
4. n TLL AND SUBTITLE
BIOLOGICAL IMPACT CAUSED BY CHANGES ON A
TROPICAL REEF
7. AUTHOR(S)
Robert S. Jones, Richard H. Randall, and
Michael J. Wilder
). PERFORMING ORG MMIZATION NAME AI>
The Marine Laboratory
University of Guam
Box E.K.
Agana, Guam 96910
ID ADDRESS
1?. SPONSORING AGENCY NAME AND ADDRESS
Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Narragansett, Rhode Island 02882
3. RECIPIENT'S ACCESSION-NO.
5. REPORT DATE
April 1976 (Issuing
Date)
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NO.
1BA022
11.M«MXR*KKGRANTNO.
R802633
13. TYPE OF REPORT AND PERIOD
Final
COVERED
14. SPONSORING AGENCY CODE
EPA-ORD
16. SUPPLEMENTARY NOTES
16. ABSTRACT
A biological study is conducted on a fringing coral reef adjacent to a thermo-
electric power plant on Guam, before and after release of plant effluent. The
before study shows corals of the reef front, submarine terrace, and seaward slope
to be devastated because of a recent infestation by the crown-of-thorns starfish,
Acanthaster planci (L.).
Introduction of the effluent is shown to be responsible for recent destruction
of reef margin corals. Effluent is found to stratify beyond the surf zone and is
no longer a threat to benthic organisms.
Coral transect studies show an increase in recent coral re-colonization on the
reef front, terrace and slope since the Acanthaster infestation. No such recovery
is evident in benthie habitats of the reef margin, exposed to effluent.
Thermal simulation experiments, performed on a series of reef corals in the
laboratory, suggest mean upper tolerance limits for the corals between 30 and 33°C.
These temperatures are common on the reef margin adj acent to the power plant.
Sublethal elevation of temperature is shown to reduce growth rate in some of the
coral species.
I7. KEY WORDS AND DOCUMENT ANALYSIS
I. DESCRIPTORS
Bioassay
Temperature
Coral
Reefs
Chlorine
IM ur; i tuHunoN sr AT t ME NT
RELEASE TO PUBLIC
b.lDENTIFIERS/OPEN ENDED TERMS
19. SECURITY CLASS (This l(cport)
UNCLASSIFIED
20. SECURITY CLASS (Tills page j
UNCLASSIFIED
c. COSATI Field/Group
6F
21. NO. OF PAGES
223
22. PRICE
IPA Form 2220-1 (9-73)
209
«USGPO: 1976-657-695/5398 Region 5-11
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