J.
RESULTS FROM GLNPO's BIOLOGICAL
OPEN WATER SURVEILLANCE PROGRAM
OF THE
LAURENTIAN GREAT LAKES
1999
Richard P. Barbiero1 and Marc L. Tuchman2
iDyncorp I&ET Inc.
6101 Stevenson Avenue
Alexandria VA 22304
2U.S. EPA
Great Lakes National Program Office
77 W Jackson Boulevard
Chicago IL 60604
January 2002
EPA-905-R-02-001
U.S. Environmental Protection Agency
Great Lakes National Program Office
77 W Jackson Boulevard Chicago IL 60604 USA.
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Introduction
The Great Lakes National Program Office
(GLNPO) of the United States Environmental
Protection Agency (USEPA) has been conduct-
ing regular surveillance monitoring of the Great
Lakes since 1983. This monitoring is intended
to fulfill the provisions of the Great Lakes Wa-
ter Quality Agreement (International Joint Com-
mission, 1978) calling for periodic monitoring of
the lakes to:
1) assess compliance with jurisdictional control
requirements;
2) provide information on non-achievement of
agreed upon water quality objectives;
3) evaluate water quality trends over time; and
4) identify emerging problems in the Great
Lakes Basin Ecosystem.
The monitoring effort is focused on whole lake
responses to changes in loadings of anthropo-
genic substances, so sampling is largely re-
stricted to the relatively homogeneous offshore
waters of each lake. Because of the daunting
logistical exigencies of sampling such a large
area, temporal resolution is currently limited to
two well-defined periods during the year: the
spring isothermal period and the stable, strati-
fied summer period.
GLNPO's monitoring of the Great Lakes was
initially limited to Lakes Michigan, Huron and
Erie. In 1986 samp ling was extended to include
Lake Ontario, and in 1992 sampling of Lake Su-
perior was added. In addition to a wide range of
physical and chemical parameters, the lakes have
been sampled for phytoplankton and zooplank-
ton, including crustaceans and rotifers, since the
inception of the program. In 1997, a benthic
invertebrate biomonitoring program was added
to complement the existing open water surveil-
lance sampling.
In this report we will present results of
GLNPO's biological surveillance sampling pro-
gram from all five Laurentian Great Lakes. Our
goal here is to provide a general description of
the offshore planktonic and the benthic com-
munities of all five Great Lakes from GLNPO's
1999 surveys. In addition, we will present infor-
mation detailing the use of benthos data for the
assessment of the ecological health of the Great
Lakes.
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Methods
Field Methods
In the spring of 1999, samples were taken from
Lake Erie aboard the Canadian vessel Risley be-
tween 10 and 13 March. The remaining four
lakes were sampled from the R/V Lake Guard-
ian between 17 April and 6 May. All five lakes
or three stations were designated master sta-
tions. These were located at the deepest point
in sub-regions of each lake determined to be ho-
mogeneous from previous studies.
At each station integrated samples for phyto-
plankton enumeration were created from a corn-
Figure 1. Stations sampled during GLNPO's 1999 survey.
Plankton & Benthos Sites
Plankton Only Sites
Benthos Only Sites
were sampled from the R/V Lake Guardian
during the summer survey, which ran from 3
August to 1 September. Between 13 and 23 sta-
tions were sampled on each lake for plankton,
benthos, or both (Figure 1). In each lake, two
posite of water samples taken at discrete depths
(spring: surface, 5M, 10M, and 20M; summer:
surface, 5M, 10M, and upper metalimnion) with
Niskin bottles mounted on a SeaBird Carousel
Water Sampler. Samples were preserved in the
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
field with Lugol's solution, and with formalin
upon return to the laboratory.
Two net tows were performed at each site for
zooplankton sample collection, using a 0.5 m
diameter conical net (D:L = 1:3). The first tow
was taken from 20 meters below the water sur-
face or 1 meter above the bottom, whichever
was less, using a 64 jam mesh net, and the sec-
ond tow from 2 meters above the bottom or
100 m, whichever was less, using a 153 jam mesh
net. If the station depth was less than 20 m,
both tows were taken from one meter above the
bottom. Triplicate tows of each depth were
taken at the master stations. After collection,
zooplankton were immediately narcotized with
soda water, and were preserved with sucrose
formalin solution (Haney and Hall, 1973) ap-
proximately twenty minutes later.
During the summer survey, quantitative samples
for benthic invertebrate analysis were collected
from selected sites using a Ponar grab sampler.
Samples were taken in triplicate, and material
sieved through a 500 |Im mesh net. Samples
were preserved with buffered formaldehyde
with Rose Bengal to a final concentration of 5-
10 % formaldehyde.
Laboratory Methods
Phytoplankton were identified and abundances
were estimated using the Utermohl technique
(Lund et al. 1958) at a magnification of 500x,
with diatoms other than Urosolenia
(—~Rbi%psolenia) identified as either centrics or
pennates. Diatoms were identified, and relative
abundances determined, from permanent slide
mounts at 1250x. Relative proportions of each
taxon of centrics and pennates were then multi-
plied by the appropriate Utermohl counts. At
least 10 individuals of each taxon were measured
per sample, and cell volumes computed using
appropriate geometrical formulae. Primary
taxonomic keys used were Prescott (1962),
Kramer and Lange-Bertalot (1986, 1991, 1997),
Patrick and Reimer (1966, 1975) and Germain
(1981).
Samples for zooplankton analysis were split in
the lab using a Folsom plankton splitter, and
four stratified aliquots examined per sample for
crustaceans using a stereoscopic microscope. In
addition, duplicate 1 ml aliquots were drawn
from an appropriate split of samples collected
with the 64 |lm mesh net, and were examined
for rotifers and nauplii under a compound mi-
croscope. Immature calanoids and cyclopoids
were identified to the lowest taxonomic level
possible, usually suborder or genus. The pri-
mary key used to identify crustaceans was Balcer
et al. (1984), with Hudson et al. (1998), Brooks
(1957), Edmundson (1959) and Rivier (1998)
also consulted. Rotifers were identified accord-
ing to Edmonson (1959) and Stemberger (1976).
Length measurements were made on the first
twenty individuals of each species encountered
per sample (crustaceans) or per lake (rotifers).
Crustacean biovolumes were computed using
length-weight relationships found in the litera-
ture, while rotifer biomass was calculated ac-
cording to A. Ruttner-Kolisko (in Bottrell et al.,
1976).
Organisms were picked out of benthos samples
under low magnification using a dissecting mi-
croscope. Oligochaetes and chironomids were
mounted on slides and identified under a com-
pound scope at 63x; other organisms were iden-
tified under a dissecting scope. Taxonomy fol-
lowed Kathman and Brinkhurst, 1998
(oligochaetes); Holsinger, 1972 (amphipods);
Wiederholm, 1983 (chironomids) and Merritt
and Cummins, 1996 (all else).
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Results
Phytoplankton
Spring
During spring, a total of 289 phytoplankton taxa
were found in the 72 samples examined. All
lakes supported well over one hundred taxa,
with slightly over 200 taxa found in Lake Erie
(Figure 2a). Our definition of phytoplankton
taxa here is somewhat more broad than that
reported in 1998, in that strictly benthic taxa,
excluded in 1998, are included here. This no
doubt would increase taxa numbers in Lake Erie
to a greater extent than in the other lakes due to
its shallowness. In spite of greater overall taxa
richness, the average number of taxa per site
was lowest in Lake Erie (55), while for the other
lakes this figure ranged from 65 to 74. Diatoms,
overwhelmingly the most diverse group across
all lakes, contributed between 40 and 55% of
the species found in each lake (Figure 2b).
Chlorophytes and chrysophytes each
contributed between 16 and 36 species per lake,
or about 15% to 23% of species, while between
11 and 14 species of cryptophyte were found in
each lake. Other groups, while occasionally
responsible for high numbers of individuals,
were considerably less diverse. The
contributions of these major taxonomic groups
to taxa richness were very similar to what was
found in 1998.
Total phytoplankton biovolumes across the
lakes ranged from 4.6 104|lm3ml-1 at a site in
Lake Superior to 3.8 106|lm3ml-1 at a site in the
western basin of Lake Erie (Figure 3).
Biovolumes were relatively uniform within each
lake, with the dramatic exception of Lake Erie,
where biovolumes spanned over 1.5 orders of
magnitude. This spatial heterogeneity was
apparent within as well as between basins.
Whole-lake median biovolumes were fairly
similar from lake to lake, ranging from 4.4 105
|Im3mH in Lake Huron to 8.7 105|Im3mH in
Lake Erie, with the exception of Lake Superior
where the median biovolume was only 6.5 104
|Im3mH.
Ml
HU
ER
ON
Diatoms Q Chrysophytes | | Cyanophytes
Chlorophytes FJ Cryptophytes Q Other
Figure 2. A.) Phytoplankton species richness, spring cruise,
1999. Boxes represent minimum, mean, and maximum
numbers of taxa per station at each lake; circles represent
total numbers of taxa found in each lake; B.) Contribution of
major taxonomic groups to species richness.
Diatoms were the dominant phytoplankters at
most sites, making up between 76 and 92% of
phytoplankton biovolume, on a lake-wide basis,
in all lakes except Superior, where on average
diatoms made up just under half of the
biovolume (Figure 4; Table 1). Either
chrysophytes or cryptophytes were second in
importance, although neither division
contributed more than 11% of the
phytoplankton biovolume in any lake except
Lake Superior. Cyanophytes contributed about
10% to Lake Superior phytoplankton
biovolume, but only made up minor amounts of
biovolume to the other lakes. Biovolumes of
chlorophytes were uniformly low throughout
the lakes in spring.
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Figure 3. Biovolume of the total phytoplankton community in the Great Lakes,
spring 1999. Inset shows box plots of phytoplankton biovolumes for each lake.
The dominant species in all five lakes was the
typical spring centric diatom Aulacoseira islandica
(Table 1). This species contributed between
22% (Superior) and 78% (Erie) of total
phytoplankton biomass, on a lake wide basis.
The congener Aulacoseira subarctica achieved
relatively high abundances in Lake Michigan, as
has been seen before, but not in any other lakes.
Dominance in Lake Huron was shared by the
pennate diatom Tabellaria flocculosa, a species
which also showed up in notable numbers,
along with the pennate A-Sterionella formosa, in
Lake Superior. In Lake Erie, Stephanodiscus
alpinus and Stephanodiscus hant^schii f. tenuis
accounted for much of the biovolume not
contributed by A., islandica.
Summer
A total of 305 phytoplankton taxa were
identified from epilimnetic samples taken during
the summer survey. Overall patterns of taxa
richness from lake to lake was similar to that in
spring (Lake Erie highest, Lake Ontario lowest,
upper lakes intermediate), as were average
numbers of taxa found at sites within lakes,
although Lake Erie had slightly greater species
richness in summer compared to spring (Figure
5a). The diversity of the diatom communities
was reduced in summer, compared to spring,
while the numbers of chrysophyte, and in the
lower lakes chlorophyte, taxa increased (Figure
5b). The contribution of cryptophytes and
cyanophytes to species richness was 12% or less.
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Figure 4. Relative biovolumes of major phytoplankton groups in the
Great Lakes, spring cruise, 1999. Inset shows whole-lake averages.
J Centric Diatoms
I Pennate Diatoms
j Chlorophytes
Chrysophytes
] Cryptophytes
Cyanophytes
I Dinoflagellates
I Other
Ml
HU
ER
ON
fj Diatoms Q Chrysophytes Q Cyanophytes
Q Chlorophytes Q Cryptophytes Q Other
Figure 5. A.) Phytoplankton species richness, summer cruise,
1999. Boxes represent minimum, mean, and maximum
numbers of taxa per station at each lake; circles represent
total numbers of taxa found in each lake; B.) Contribution of
major taxonomic groups to species richness.
Phytoplankton biovolumes were considerably
more similar across the lakes in summer,
compared to spring, due in large part to
increases in biovolume in Lake Superior and
the eastern basin of Lake Erie (Figure 6).
Consequently, median biovolumes were
confined to a smaller range than in spring,
varying only from 3.3 105|lm3mH in Lake
Huron to 5.9 105|Im3mH in Lakes Erie and
Ontario.
All lakes with the exception of Lake Superior
experienced substantial reductions in the
proportion of diatoms in the summer (Figure 7;
Table 2). The average proportion of diatoms in
Lake Superior, in contrast, increased from 48%
to 62%. The importance of dinoflagellates
increased in all lakes but Superior, with the
largest populations found in Lake Michigan,
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Figure 6. Biovolume of the total phytoplankton community in the Great Lakes,
summer 1999. Inset shows box plots of phytoplankton biovolumes for each lake.
1*106|im3/ml
5*105|im3/ml
where a majority of phytoplankton biovolume at
many sites was contributed by dinofiagellates.
While estimation of dinoflagellate biovolume is
problematic, in that individuals can be extremely
large and therefore the chance occurrence of a
single individual in a counting chamber can
constitute the majority of biovolume in that
sample, the high proportion of dinoflagellate
biovolume across many sites in Lake Michigan
suggests that this group did in fact maintain
large populations in the summer. Proportions
of chrysophytes increased in Lake Huron, while
chlorophytes increased substantially in Lakes
Erie and Ontario. There was some indication of
north/south differentiation in Lake Huron, with
communities in the north supporting a higher
percentage of diatoms. The difference in
community composition between Lakes
Michigan and Huron, and in particular the great
proportion of diatoms in the latter lake,
contrasts with what was found in 1998 (Barbiero
and Tuchman, 2001), and suggests that year may
have been anomalous.
Dominance during the summer cruise was for
the most part distributed amongst a larger
number of species (Table 2). Ceratium
hirundinella figured prominently in all lakes but
Superior; both Fragilaria crotonensis and various
species of the summer centric diatom Cyclotella
appeared in substantial numbers across all lakes,
although each lake, and in the case of Erie each
basin, supported fairly species assemblages of
this latter genus (Figure 8).
8
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Figure 7. Relative biovolumes of major phytoplankton groups in the
Great Lakes, summer cruise, 1999. Inset shows whole-lake averages.
j Centric Diatoms
I Pennate Diatoms
j Chlorophytes
Chrysophytes
j Cryptophytes
Cyanophytes
I Dinoflagellates
] Other
Figure 8. Relative abundance of Cyclotella species, summer cruise, 1999.
Inset shows whole-lake averages.
SU Ml HU W C E ON
C. ocellata
C. comensis v. 1
C. comensis
C. pseudostelligera
C. delicatula
C. com fa
OTHER
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Zooplankton
Spring
Crustacean community diversity was low across
the lakes, with almost all sites supporting less
than 10 taxa (Figure 9a). Species richness was
lowest in Lake Superior, where no more than 5
taxa were found at any site, while average
numbers of taxa per site ranged only between 6
and 8 for the other four lakes. Total numbers
of taxa found in each lake ranged from 9
(Superior) to 21 (Erie), which is very similar to
what was found in 1998.
30
25 -
20 -
15 -
SU
Ml
HU
ER
ON
Figure 9. Minimum, maximum and mean number
of taxa per site (boxes), and total number of taxa
per lake (circles), for A.) crustaceans; and
B.) rotifers, spring 1999.
Areal abundances of crustaceans (excluding
nauplii) varied from 1,727 animals nr2 at a site
in eastern Lake Erie to over 1.5 106 nr2 at a site
in southern Lake Michigan (Figure 10).
Abundances overall were lowest in Lake Erie
and highest in Lake Huron. It should be borne
in mind that, given the shallowness of most sites
in Lake Erie, abundances would be relatively
higher in that lake if considered volumetrically,
although they would still be low compared to
the other lakes (see Table 4). Within each lake
abundances were fairly uniform, with the
exceptions of Lake Michigan, where there
appeared to be strong north-south
differentiation in abundances, and Lake Erie,
where abundances varied substantially between
basins. Spatial heterogeneity is not apparent in
the case of the latter lake in Figure 10 due to
scaling of the figure.
During spring, crustacean communities across
all five lakes were dominated by copepods,
although the relative importance of calanoids
and cyclopoids varied from lake to lake.
Immature copepods made up a substantial
portion of the individuals found at all sites. In
the upper lakes and the western basin of Lake
Erie, calanoid and cyclopoid copepods were
present in approximately equal numbers. In
Lakes Michigan and Huron, Leptodiaptomus
ashlandi and Leptodiaptomus minutus, along with
the large, deep-water species Umnocalanus
macrurus, accounted for most of the calanoids
(Table 3). There was a slight tendency towards
an increase in the relative importance of
cyclopoid copepods at the northern stations in
Lake Michigan, though differences were slight.
In the shallow western basin of Lake Erie _L.
ashlandi and L. minutus were also the dominant
calanoids, with L. marcrurus largely absent, while
in Lake Superior L. macrurus, along with its
immatures, and another large, deep-water form
Leptodiaptomus sicilis, were the dominant
calanoids. In the central and eastern basins of
Lake Erie, as well as Lake Ontario, cyclopoid
copepods accounted for the great majority of
individuals; in all lakes Diacyclops thomasi was the
dominant cyclopoid. Only the central basin of
Lake Erie supported significant numbers of
cladocerans, mostly Eosmina and Eubosmina, in
10
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Figure 10. Areal abundances of major crustacean groups in the
Great Lakes, spring 1999. Inset shows whole lake averages.
Bosmina spp.
I Daphnia spp.
I Other Cladocerans
Calanoida
I Imm Calanoida
I Cyclopoida
I Imm Cyclopoida
SU
HU W C E ON
ER
1.0*106/m2
0.5*106/m2
0.15*106/m2
the spring. In all lakes (or in the case of Lake
Erie, basins), 95% of the crustacean community
was made up of 4 species or less.
Comparing the relative contribution of rotifers
and nauplii to zooplankton community biomass
is problematic, since the former are enumerated
only from shallow tows, which have been
shown to provide highly misleading estimates of
adult crustacean biomass, particularly if taken
during the day. Crustacean abundances are here
given on the basis of areal units, which assumes
that the entire community is captured at the
depth to which tows are taken. Judging from
the results of previous studies examining the
depth distribution of crustaceans in the Great
Lakes, this is probably a reasonably safe
assumption for all species except the deep-living
Leptodioptomus sidlis and Umnocalanus macrurus.
To compare rotifer and nauplii biomass on an
areal basis to crustacean biomass would similarly
assume that tows to a depth of 20 m capture the
majority of populations of the former, an
assumption which is difficult to assess due to a
lack of information. In lieu of more comparable
data, however, combining areal abundances for
the two groups (i.e. rotifers and nauplii and
crustaceans) based on estimates from the two
different tows probably provides the best
estimate of the relative contribution of nauplii
and rotifer biomass to the total zooplankton
community. It should be borne in mind,
however, that distribution of a substantial
portion of rotifer or nauplii biomass below 20 m
would result in underestimation of their relative
importance.
11
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Figure 11. Areal biomass of major zooplankton groups in the
Great Lakes, spring 1999. Inset shows whole lake averages.
I Cladocerans
I Calanoida
1 Imm Calanoida
I Cyclopoida
1 Imm Cyclopoida
1 Nauplii
1 Rotifers
Nauplii contributed between 3% and 16% of
zooplankton biomass across the lakes, with the
highest contribution in western and eastern
Lake Erie, and the lowest in Lake Ontario
(Figure 11). Rotifers made up a small portion of
zooplankton biomass, contributing at most only
6% in central and eastern Lake Erie. Species
richness of rotifers, however, was roughly
similar to that of crustaceans, averaging between
4 and 10 taxa per site for the five lakes. In all
between 17 and 20 taxa were found in each lake
(Figure 9b). Sjnchaeta was the most widely
distributed genus, while Notholca was particularly
abundant in the central and western basins of
Lake Erie and in Lake Huron. Kellicottia was
most abundant in Lake Superior, but was also
present at most sites except the western and
central basins of Lake Erie, while the eastern
basin of Lake Erie was unusual in its large
population of Kemtella (Figure 12).
Summer
Species richness of the crustacean community
was substantially higher during the summer,
compared to spring, with sites supporting
between 4-15 taxa (Figure 13a). Total numbers
of taxa found in each lake varied from 13 to 24.
Again, Lake Erie had the greatest number of
species overall, and Lake Superior the lowest.
Total crustacean abundances (excluding nauplii)
were substantially higher during the summer
than in spring across all lakes (Figure 14). The
greatest increase was seen in the eastern basin of
Lake Erie, where areal abundances increased by
several orders of magnitude. The upper lakes
12
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Figure 12. Relative abundance of rotifer genera, spring cruise, 1999.
Inset shows whole-lake averages.
Synchaefa
Notholca
KellicoWa
Polyarthra
Keratella
Gastropus
Collotheca
Asplanchna
Conochilus
Ploesoma
Other
exhibited more modest increases of 2-4 x spring
numbers. The prominent north/south
differences in abundances seen in Lake
Michigan in the spring were not apparent in the
summer, though substantial intersite differences
were still found in Lake Erie.
As in spring, copepods, particularly immatures,
contributed significant numbers to all sites.
Immature cyclopoids were abundant in all lakes,
while large numbers of immature calanoids were
found in all lakes except Lake Ontario and the
western basin of Lake Erie. As in spring,
calanoid copepods in Lakes Michigan and
Huron were primarily the diaptomids L. ashlandi
and L. minutus; Skistodiaptomus oregonensis was the
most common calanoid in Lake Erie, while _L.
macrurus and L. sicilis were again the
25 •
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£
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5 •
20 -
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5 -
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o
o
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Figure 1 3. Minimum,
of taxa per site,
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maximum
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A
B
ER ON
and mean number
and total number of taxa per lake,
for A.) crustaceans; and
B.) rotifers, summer 1999.
13
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Figure 14. Areal abundances of major crustacean groups in the
Great Lakes, summer 1999. Inset shows whole lake averages.
I Bosmina spp.
1 Daphnia spp.
1 Other Cladocerans
I Calanoida
1 Imm Calanoida
I Cyclopoida
1 Imm Cyclopoida
predominant calanoids in Lake Superior.
Diacydops thomasi was the dominant cyclopoid
species in all lakes except Erie, where Mesocyclops
edax was most numerous. There was some
indication of spatial heterogeneity in Lake
Michigan; calanoid copepods were relatively
more important in the south and cyclopoids
more important in the north, as was seen in the
spring. Cladocerans, largely absent in the
spring, made up a substantial portion of the
crustacean communities in the summer in all
lakes except Lake Superior. Species of Eosmina/
Eubosmina were the most prominent cladoceran
in all lakes except Lake Superior; Daphnia galeata
mendotae was the other dominant cladoceran in
Lakes Huron and Michigan, as was Daphnia
retrocurva in Lake Ontario. In Lake Michigan, D.
populations were notably higher in
the southern area of the lake, and
longiwstris populations higher in the northern
region. The abundance of the smaller bodied
Bosmina in both Lakes Michigan and Huron
contrasts with the Daphnia dominated
community seen in 1998 (Barbiero et al., 2001),
and suggests greater predation pressure on the
zooplankton community in 1999. As was seen
in 1998, Holopedium gibberum and Daphnia galeata
mendotae were present in approximately equal
numbers in Lake Superior, though neither
organism was particularly abundant in that lake.
Daphnia species weren't as numerous in Lake
Erie, compared to the other lakes. This genus
typically experiences its seasonal maximum in
late June or July in that lake, and it is likely that
our sampling occurred after populations had
already declined.
14
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Figure 15. Areal abundances of predatory cladocerans in the
Great Lakes, summer, 1999, as estimated from 100 m tows.
Note differences in scale.
The three major predatory cladocerans found in
the lakes are the native Leptodom kindtii, and the
two exotic cladocerans Bythotrephes cederstroemi
and Cercapagis pengoi (Figure 15). Of the three,
Bythotrephes was the most widely distributed,
showing up, albeit in small numbers, in all parts
of the lakes with the notable exceptions of
western Lake Erie and Lake Ontario. Leptodom
was almost entirely restricted to the lower lakes,
although small numbers were found at two sites
in southern Lake Michigan. While less widely
distributed than Bythotrephes, densities of
were substantially larger. Offshore
15
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Figure 16. Areal biomass of major zooplankton groups in the
Great Lakes, summer 1999. Inset shows whole lake averages.
Cladocerans
Calanoida
Imm Calanoida
Cyclopoida
Imm Cyclopoida
Nauplii
Rotifers
populations of Cermpagis in the Great Lakes
were still restricted to Lake Ontario, where this
recent invader was first recorded in 1998,
although in 1999 it had spread throughout the
lake (Ojaveer et al., 2001). Individuals had also
been found in nearshore waters of southern
Lake Michigan in August of 1999 (Charlebois et
al., 2001), but populations had apparently not
extended to offshore sites. Abundances of this
organism were markedly higher than for both
Bythotrephes and Leptodora; a maximum density of
37,000 rrr2 was recorded for Cermpagis at a site in
the eastern portion of Lake Ontario, compared
to maximum densities of 6,000 for 'Leptodora in
central Lake Erie, and 1,600 for ~Bythotrephes in
eastern Lake Erie.
Rotifer diversity, like that of crustaceans, was
higher in the summer compared to the spring
(Figure 13b). Numbers of taxa per site ranged
between 6 and 14, with each lake supporting
between 14 and 18 taxa overall. Rotifers made
up slightly larger percentage of total biomass
across the lakes in summer, compared to spring,
although in all but the western and central
basins of Lake Erie their contribution to
biomass was still 5% or less (Figure 16). The
contribution of nauplii to biomass increased in
the western and central basins of Lake Erie, but
remained unchanged elsewhere, ranging
between 3% and 5% in the other lakes. The
relative importance of rotifers and nauplii in
Lake Erie was related, no doubt, to the overall
low crustacean biomass seen in that lake, which.
16
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Figure 17. Relative abundance of rotifer genera, summer cruise, 1999.
Inset shows whole-lake averages.
Conochilus
Keratella
Polyarthra
Kellicottia
Collotheca
Ploesoma
Synchaeta
Ascomorpha
Asplanchna
Brachionus
Gastropus
Other
as noted, was probably due in part to seasonally
of the cladoceran community.
Dominant rotifer genera in the summer
included Conochilus, abundant in Lakes Huron,
Superior, and the central and eastern basin of
Lake Erie, Keratella, achieving notable
populations in Lake Ontario and Lake Michigan,
and Polyarthra, which was most prominent in the
western basin of Lake Erie and in Lake
Michigan (Figure 17). Populations of Keratella
were also found, notably in Lake Superior, Lake
Ontario, and parts of Lake Erie. A shift in the
rotifer community away from Notho/ca, Synchaeta
and Kellicottia to Polyarthra and Conochilus from
spring to summer was also seen in 1998.
17
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Benthos
Most sites supported a very limited number of
benthic taxa, with numbers of taxa found per
site ranging from 1 to 22 for the five lakes, and
all lakes but Erie averaging less than 10 taxa per
site (Figure 18). Lake Erie supported the great-
est number of taxa overall (40), while benthic
invertebrate communities in Lake Superior rela-
tively taxa poor, with a total of 12 taxa found in
the lake.
Depth appeared to be an important factor in de-
termining the number of taxa found at a site.
Regression analysis found a highly significant (p
< 0.001) inverse relationship between depth and
taxa number for sites shallower than 70 m
(Figure 19); beyond this depth sites supported
uniformly low numbers of taxa with little appar-
ent relationship to depth.
Areal abundances of benthic organisms varied
greatly within each lake, although lake-wide av-
erages were fairly similar amongst all lakes but
Superior (Figure 20). Abundances varied from
site to site within each lake by about an order of
magnitude, two orders of magnitude in the case
of Lake Superior. At least part of this variability
40 -
30 -
20 -
10 -
su
Ml
HU
ER
ON
Figure 18. Minimum, maximum and mean number
of benthic taxa per site, and total number of taxa
per lake, summer 1999.
was due to depth, which set a clear upper limit
to benthic abundances, although low abun-
dances were also seen at some shallow sites
(Figure 21).
1C
20 -
1 15-
E
13
Z
ro
» 10 -
H-
5 -
Q
Taxa#= -0.15Depth+ 17.5
° r2 = 0.50
O
JCOO O
$OO
00 0 •
• O
O
0 50 100 150 200 250 300
Depth (m)
Figure 19. Relationship between depth
and benthic taxa richness, summer 1999.
14000 -
12000 -
10000 -
g 8000 -
c
§ 6000 -
4000 -
2000 -
0 -
C
O
0
O °
^ £
d*
\ •
. |° °«po*
8 •* oo 0°o o? o •
50 100 150 200 250 300
Depth (m)
Figure 21. Relationship between depth
and benthic abundance, summer 1999.
The amphipod Diporeia is a glacial relict that has
historically been one of the most abundant and
widespread organisms in the Great Lakes, and
indeed in most large lakes in previously glaciated
regions of the Holarctic (Dermott and Corning,
1988). In 1999 it was by far the dominant ben-
thic invertebrate in the upper three lakes, al-
though it was absent from Lake Erie, nearshore
sites in Lake Ontario, Saginaw Bay in Lake
18
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Figure 20. Areal abundance of benthos in the Great Lakes, summer 1999.
Figure 22. Relative abundances of major benthic groups
in the Great Lakes, summer 1999. Inset shows whole lake averages.
Ohgocheata
Chironomidae
Diporeia spp.
Sphaeridae
Other
19
-------
GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Figure 23. Abundance of Diporeia spp. in the Great Lakes, summer 1999
6,000 m'2
3,000 rrr2
1,000 trr2
Huron and Green Bay in Lake Michigan
(Figures 22, 23).
Recently it appears that this organism has been
in decline in significant portions of its range in
the Great Lakes. Dramatic declines have been
reported at shallow stations in both southeast-
ern Lake Michigan (Nalepa et al. 1998) and east-
ern Lake Ontario (Dermott, 2001), and it is no
longer found in Lake Erie (GLNPO data).
In general, Diporeia populations have declined
between 1997 and 1999 at most of our Lake
Michigan stations. Significantly, these declines
have not been restricted to shallow southeastern
stations, but have occurred at both northern and
deep station where populations have dropped
from thousands of individuals/m2 to hundreds
during the past three years. Similar declines
have been seen at most stations in Lake Huron
between 1997 and 1999. While overall abun-
dances in Lake Huron were lower in 1999 than
in 1998, and in 1998 than in 1997, these abun-
dances have still tended to be substantially
higher than those reported historically (e.g.
Teter 1960, Henson 1970, Shnvastava 1974).
In Lake Ontario, Diporeia was absent from sta-
tions < 100 m in depth in our study, while in
1972 (Nalepa and Thomas 1976) this organism
accounted for 22% and 61% of the benthic
community at sites between 7 - 35 m and 40 - 90
m, respectively. No consistent trends have been
noted at our deeper stations in the years 1997-
1999, and abundances at these stations, generally
between 1,000 and 2,000/m2, have tended to be
substantially higher than most historical reports
(e.g. Kinney 1972, Nalepa and Thomas 1976,
20
-------
GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Figure 24. Relative abundances of oligochaete taxa
in the Great Lakes, summer 1999. Inset shows whole lake averages.
Stylodrilus heringianus
Imm. Lumbriculidae
| Enchytraeidae
] Naididae
j Aulodrilus americanus
Limnodrilus hoffmeisteri
Potamothrix vejdovskyi
] Quistadrilus multisetosus
| Spirosperma ferox
I Tubifex tubifex
] Other Tubificidae
] Imm. Tubificidae w/o hair
Imm. Tubificidae w/ hair
Golini, 1979). Our study does not include sub-
stantial coverage in the eastern and southeast-
ern areas of the lake where the most dramatic
declines have been seen (Dermott, 2000). Simi-
larly, we have seen no consistent trends in Lake
Superior between 1997 and 1999. While de-
clines had been seen at most stations in the lake
between 1997 and 1998, these were largely re-
versed in 1999. Abundances recorded during
those three years are generally in line with, or
slightly higher than, historical reports (e.g. Hil-
tunen 1969b, Schelske and Roth 1973, Cook
1975).
Oligochaetes were the second most dominant
group, and made up the greatest percentage of
individuals at those sites where Diporeia did not.
They were the most diverse group, with over
30 different species identified in 1999. Mem-
bers of the oligochaete family Lumbridulidae
increased in importance along the sequence
Erie- > Ontario- >Huron/Michigan- > Superior,
which is in keeping with their preference for
lower productivity environments, while mem-
bers of the Tubificidae were more common in
the lower lakes and at shallower sites in Lakes
Michigan and Huron (Figure 24).
21
-------
GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Figure 25. Relative abundances of chironomid taxa in the
Great Lakes, summer 1999. Inset shows whole lake averages.
| Chironomus
] Microtendipes
I Paracladopelma
I Hamischia
I Cryptochironomus
\ Micropsectra
\ Tanytarsus
| Procladius
\ Coelotanypus
\ Heterotrissocladius
} Other
Over 20 genera of Chironomidae were also
found in the lakes (Figure 25). The oligotrophic
genus Heterotrssocladius was the only chironomid
found in Lake Superior, and also dominated the
off-shore sites of Lakes Michigan and Huron.
Communities in the lower lakes were more di-
verse, supporting notable populations of Chi-
ronomus, Procladius and Micropsectra, among other
genera.
22
-------
GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Benthic Indices
Direct assessment of benthic communities has
long been considered an essential element in de-
termining the impacts of anthropogenic stress
on aquatic systems (Wilhm and Dorris, 1968).
Benthic invertebrates exhibit a number of char-
acteristics that make them particularly well
suited for use as biomonitoring tools: they have
differing sensitivities to stressors, thus commu-
nity make-up can be expected to vary in a pre-
dictable way with the level of anthropogenic
stress; they are longer lived than most plank-
tonic organisms, and thus can integrate the ef-
fects of environmental conditions over time;
and they are relatively sedentary, and are there-
fore easier to sample than nektonic organisms,
such as fish, and can serve as indicators of spe-
cific areas. In addition to serving as indicators
of general ecosystem condition, the health of
the benthic communities is of inherent interest
due to their pivotal ecological role. Many ben-
thic invertebrates are detritivores, feeding on or-
ganic material produced in the pelagic zone.
Since these organisms are often important com-
ponents of fish diets, they provide an important
link in the food chain.
Two common approaches to using benthic in-
vertebrates as indicators of aquatic systems in-
volve focusing on populations of particularly
sensitive indicator species, or examining associa-
tions of species with differing, and known, toler-
ances to environmental perturbations. Here we
combine both approaches, assessing the popula-
tion of the sensitive species Diporeia, and using
an index of oligochaete community makeup.
Diporeia
As seen, Diporeia is a widely occurring amphi-
pod in the deeper waters of the Great Lakes.
This surface-feeding detritivore is an important
Figure 26. Abundance of Diporeia abundance across
the Great Lakes in summer, 1999, in relation to SOLEC criteria.
O Better Than SOLEC Criteria
O Meets SOLEC Criteria
O Worse Than SOLEC Criteria
SOLEC Criteria:
Depth < 100m: 220-320/m2
Depth > 100m: 30-160/m2
23
-------
GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
fish food item (Scott and Grossman, 1973), and
is thought to obtain a large portion of its annual
energy directly from the spring diatom bloom
(Gardner et al., 1990), thus providing an impor-
tant direct link between pelagic production and
higher trophic levels. This glacial relic is sensi-
tive to low oxygen concentrations and to many
toxicants (Nalepa and Landrum, 1988), and due
to its high lipid content and absence of biotrans-
formation capability has a high bioaccumulation
potential for organic contaminants (Landrum
and Nalepa, 1998). These characteristics make it
an appropriate organism for biomonitoring,
both for its inherent ecological importance, and
for its potential usefulness as an indicator of
overall system health.
Provisional target abundances of Diporeia have
been established for different depth ranges in
the Great Lakes (SOLEC, 1998). When applied
to GLNPO's benthos data from 1997, all sta-
tions in the upper lakes either met or exceeded
these criteria. While historically present there,
Diporeia is not currently found in Lake Erie. Dz-
porezawzs absent from half the sites examined in
Lake Ontario in 1997, and met the criteria in
four of the remaining, mostly offshore, five
sites. In 1998, four sites in Lake Superior that
had exceeded abundance criteria in 1997 simply
met the criteria, while two sites in Lake Michi-
gan that had exceeded the criteria slipped below
criteria. Two sites were added in 1998, one in
northern Green Bay and one in Saginaw Bay;
both were below criteria. In contrast, abun-
dances of Diporeia at one site in Superior in-
creased sufficiently to exceed the criteria when
in 1997 it had merely met criteria. Results from
Lakes Erie and Ontario were identical to the
previous year. Results from 1999 were similar
to 1998; classifications of sites changed only in
Lake Superior, where one site fell below criteria,
while a second site went from exceeding to sim-
ply meeting criteria. In general, these results in-
dicate that Diporeia populations are at sub-
optimal levels, according to SOLEC criteria, in
shallower regions of all lakes except Lake Supe-
rior. This is most notable in Lake Erie, where
this genus appears to have disappeared. On the
other hand, offshore populations meet or ex-
ceed SOLEC criteria. In Lake Superior, popula-
tions have shown a greater tendency to fluctu-
ate, at least in comparison to the SOLEC crite-
ria. While it is possible that these changes might
reflect changes in water quality in the lakes, it is
also possible that they merely represent natural
annual fluctuations in recruitment or mortality.
It will be necessary to continue to monitor these
populations to establish ranges of natural varia-
tion.
Milbrink Oligochaete index
The association of oligochaetes with organic en-
richment of water was first noted by Aristotle
(Hynes, 1960). A number of classification sys-
tems have since been developed to try and
quantify that relationship, a great number of
these, significantly, developed by investigators
working on the Great Lakes. Initially, these sys-
tems used total oligochaete numbers to reflect
trophic conditions (Wright, 1955; Carr and Hil-
tunen, 1965; U.S. Department of the Interior,
1968). However, since different species within
the class have widely differing sensitivities to or-
ganic enrichment, much information is lost with
this approach. Further refinements have there-
fore focused on particular families (e.g. Tubifici-
dae: King and Ball, 1964; Goodnight and
Whitley, 1960) or species (e.g. Umnodrilus hoff-
meisteri: Brinkhurst, 1967). Using data from
Green Bay, Howmiller and Scott (1977) intro-
duced an index based on community structure
which incorporated information on the ecologi-
cal attributes of a number of the constituent
species. In this index, species were assigned to
categories depending on their preference for/
tolerance of oligotrophic, mesotrophic or eutro-
24
-------
GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
phic conditions. Milbrink (1983) pointed out
that this index did not take into account differ-
ences in absolute oligochaete abundance, nor
did it accommodate the flexible ecological affini-
ties of Tubifex tubifex, which can be extremely
abundant both in conditions of gross pollution,
and in situations of limited competition where
anthropogenic influences are slight, such as in
deep oligotrophic waters (Milbrink, 1973). He
therefore added a scaling factor based on total
oligochaete abundance, and gave T. tubifex a dual
ranking, depending on both the co-dominant
species and the total abundance of oligochaetes.
In addition, he added a fourth category to How-
miller and Scott's original three, with this limited
to the typical eutrophic indicator species Umno-
drilus hoffmeisteri, and T. tubifex in instances where
total numbers are high and L. hoffmeisteri is a co-
dominant. When T. tubifex occurs with Stylo-
drilus as a co-dominant, it is included in Group
0. We have adopted Milbrink's modifications of
Howmiller and Scott's original index, while re-
taining the latter's original classification of spe-
cies on the basis of these being more appropri-
ate to the Great Lakes. The index is calculated
where no, n\, ni and »3 are the total numbers of
individuals belonging to each of the three eco-
logical groups. Species characteristic of
oligotrophic waters are assigned to Group 0,
those of mesotrophic waters Group 1; those of
eutrophic waters Group 2; while L,. hoffmeisteri
and T. tubifex (under the conditions stated
above) comprise Group 3. The coefficient c de-
pends upon total oligochaete number as out-
lined in the following table:
c=l n>3600
c=3/4 1 200 < n < 3 600
c=l/2 400 < n < 1 200
c=l/4 130 < n < 400
c=0
-------
GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Figure 27. Milbrink's (1983) Modified Environmental Index,
applied to data from GLNPO's summer 1999 Survey
higher productivity (nearshore southern Lake
Michigan; Saginaw Bay, Lake Huron) exhibiting
higher index values. Sites in Lake Erie generally
fall in the eutrophic range, while in Lake On-
tario nearshore sites are classified as mesotro-
phic, and offshore sites are oligotrophic.
It should be noted that these two approaches
complement each other. While the primary
strength of Howmiller and Scott's Environ-
mental Index is in assessing organic enrichment,
Diporeia should provide a more sensitive indica-
tor of other environmental stressors, such as
toxics, and can presumably respond to changes
in pelagic productivity, particularly in environ-
ments that don't support substantial oligochaete
communities. It should be noted, however, that
no benthic index has been routinely applied to
the open waters of all the Great Lakes, and
therefore that refinements in interpretation
should be expected.
26
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Summary
Spring phytoplankton communities in the Great
Lakes were dominated by diatoms in all lakes.
Biomass was highest in the western basin of
Lake Erie and lowest in Lake Superior. Summer
communities shifted away from diatoms, except
in Lake Superior, where they remained co-
dominant with chrysophytes. Dinoflagellates
contributed a substantial amount of biovolume
in Lake Michigan, while in communities in Lake
Huron contained large populations of chryso-
phytes in the south and diatoms in the north.
Both Lakes Erie and Ontario supported mixed
communities with chlorophytes, cryptophytes
and dinoflagellates all prominent.
Crustacean zooplankton communities were
composed in most cases of less than a dozen
species. Communities in the upper lakes con-
tained about equal proportions of cyclopoid and
calanoid copepods, in contrast to the clear
dominance by calanoids in 1998. Lake Michigan
exhibited marked north south differentiation in
population sizes. Aside from the western basin
of Lake Erie, the lower lakes were dominated by
cyclopoid copepods. In summer, both Lakes
Michigan and Huron supported populations of
Bosmina relatively larger than were seen in 1998.
Benthos communities showed strong relation-
ships between depth and both species richness
and total abundance. The amphipod Diporeia
dominated most deeper communities in the up-
per lakes and in Lake Ontario, while oli-
gochaetes were most important at shallower
sites. Comparison of Diporeia abundances with
SOLEC criteria indicated that populations were
less than desired at shallow stations in Lake On-
tario and Michigan, Green Bay and Saginaw Bay.
This organisms has entirely disappeared from
Lake Erie. Use of an oligochaete community
index classified most sites in the upper lakes as
oligotrophic, all sites in Lake Erie as eutrophic,
and deep and shallow sites in Lake Ontario
oligotrophic and mesotrophic, respectively.
Acknowledgements
The data presented in this report was largely a
result of the efforts of the following individuals:
Jennifer Gronefeld, Larissa Granovski and Jo-
seph B. Volerman (phytoplankton), Linda A.
Kuhns, Lori L. Schacht and Ruth E. Little
(zooplankton), and Ken K. Klubek (benthos) of
Grace Analytical Lab. Their hard work and
dedication is highly appreciated. Excellent
graphical and analytical support was provided by
Mark A. DiMartino. We would also like to ex-
press our great appreciation to captain Dave
Moser and the entire crew of the R/V Lake
Guardian for their assistance throughout the
course of this work, and in particular the captain
and crew of the Canadian Coast Guard Ship
Samuel Risley for their extraordinary hospitality
during the spring Lake Erie survey.
27
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
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30
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Tables ^^^^^^^^^^^H
Table 1. Average lakewide biovolume (|Im3 mb1) of dominant (>5% biomass at any site) phytoplank-
ton taxa, spring, 1999.
Superior Michigan Huron Erie Ontario
BACILLARIOPHYTA
A-Sterionellaformosa Hass.
Aulacoseira subarctica (O. Mull.) Haworth
Cymatopleura solea (Breb. & Godey) W. Sm.
Diatoma tenue var. eloneatum Lyneb.
o J o
Fragilaria crotonensis Kitton
Aulacoseira islandica O. Mull.
Nit^schia gracilis Hantz.
Stephanodiscus alpinus Hust.
Stephanodiscus binderanus (Kutz.) Krieg.
Stephanodiscus hant^schii f. tennis Hak. & Stoerm.
Stephanodiscus niagarae Ehr.
Stephanodiscus subtransylvanicus Gasse
Synedra ftliformis Grun.
Synedra ulna var. chaseana Thomas
Tabellariaflocculosa (Roth) Knud.
CHRYSOPHYTA
Dinobryon cylindricum Imhof
Dinobryon divergent Imhof
Dinobryon sodale var. americanum (Brunnth.) Bachm.
Haptophyceae
Mallomonas spp.
Unidentified coccoid ovoid (Chrysophyta)
Unidentified flagellate #5
CRYPTOPHYTA
Cryptomonas curvata Ehr.
Cryptomonas erosa Ehr.
Cryptomonas erosa var. reflexa Marss.
Cryptomonas ovata Ehr.
Cryptomonas pyrenoidifera Geitl.
Rbodomonas minuta Skuja
Rbodomonas minuta var. nannoplanctica Skuja
CYANOPHYTA
Anacystis montana f. minor Dr. & Daily
Qscillatoria spp.
Qscillatoria tenuis C.A. Ag.
PYRROPHYTA
Glenodinium spp.
Gymnodinium helveticum Pen.
Gymnodinium helveticum f. achroum Skuja
Gymnodinium spp.
Veridinium spp.
6,018
408
0
6
2,368
13,060
263
1,129
0
32
1,806
1,911
418
291
3,897
0
0
355
3,500
1,408
911
8
364
4,359
1,758
1,256
1,503
2,475
904
3,282
2,067
0
1,536
0
0
2,506
0
2,834
64,780
1,746
8,172
13,231
266,857
14,532
10,345
131
352
2,679
8,897
14,141
15,521
6,484
0
0
80
2,736
4,215
1,107
128
2,899
9,339
2,480
3,431
3,516
4,174
2,136
3,631
0
0
2,841
9,085
6,249
3,912
598
8,620
15,070
2,087
1,065
25,017
132,554
800
1,716
0
7
1,769
3,902
1,806
4,018
121,219
4,489
2,147
1,814
3,586
1,970
844
10
1,114
6,631
3,111
3,575
2,635
2,948
1,134
4,122
0
3,632
2,816
0
4,131
2,499
1,066
6,106
0
0
1,169
31,488
789,661
767
50,645
14,434
66,996
5,831
1,748
273
1,657
4,637
0
288
0
6,903
837
3,164
0
2,242
260
318
732
3,773
4,229
3,514
0
0
104
514
0
12,244
951
19,222
0
7,113
310
2,984
326,446
6,431
12,170
70
709
0
66
193
0
14,272
0
0
0
8,471
2,761
892
1,309
0
17,625
7,569
2,900
2,712
8,570
3,942
2,435
0
0
2,924
0
25,648
4,126
0
31
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Table 2. Average lakewide biovolume (|Im3
phytoplankton taxa, summer, 1999.
BACILLARIOPHYTA
Cydostephanos tholiformis Stoerm. Hak. & Ther.
Cydotella comensis Grun.
Cydotella comensis var. 1
Cydotella comta (Ehr.) Kutz.
Cydotella delicatula
Cydotella ocellata Pant.
Diatoma tenue var. elongatum Lyngb.
Fragilaria crotonensis Kitton
A-ulacoseira islandica O. Mull.
A-ulacoseira italica (Ehr.) Kutz.
Stephanodiscus niagarae Ehr.
Synedra delicatissima var. angustissima Grun.
Tabellariaflocculosa (Roth) Knud.
CHLOROPHYTA
Cosmarium depressum (Nag.) Lund
Eudorina elegans Ehr.
Gloeocystis planktonica (W. & G.S. West) Lemm.
M-icractinium pusillum Fres.
Mougeotia sp.
Pediastrum duplex var. gradllimum W. & G.S. West
Pediastrum simplex (Meyen) Lemm.
Pediastrum simplex vx. duodenarium (Bail.) Rabh.
Scenedesmus bijuga (Turp.) Lag.
Tetraspora lacustris Lemm.
Ulothrix sp.
CHRYSOPHYTA
Chrysophycean coccoids
Chrysosphaerella longispina Laut. emend. Nich.
Dinobryon bavaricum Imhof
Dinobryon bavaricum var. vanhoeffenii (Bachm.) Krieg.
Dinobryon divergens Imhof
Dinobryon sertularia Ehr.
Dinobryon sertularia var. protuberans (Lemm.) Kreig.
Dinobryon sodale Ehr.
Dinobryon sodale var. americanum (Brunnth.) Bachm.
Mallomonas sp.
CRYPTOPHYTA
Cryptomonas curvata Ehr.
Cryptomonas erosa Ehr.
Cryptomonas erosa var. reflexa Marss.
Cryptomonas obovata Skuja
Cryptomonas ovata Ehr.
Cryptomonasphaseolus Skuja
ml"1) of dominant (>5% biomass at
Superior
0
13,189
1,075
147,021
21,541
5,880
75
10,676
0
0
0
1,144
18,369
1,307
0
356
0
0
0
0
0
134
0
306
480
26
9,190
4,432
6,567
7,230
4,389
14,459
6,276
857
0
8,248
4,771
153
0
0
Michigan
0
4,923
21,147
16,773
2,333
324
0
59,414
0
0
0
0
275
1,183
3,505
902
0
0
0
0
0
1,036
0
0
6,502
7,646
785
0
9,036
0
0
2,481
284
4,720
5,177
25,842
23,510
0
2,475
1,104
Huron
0
1,765
12,942
82,284
10,304
651
227
25,054
127
0
0
2,214
2,932
810
0
1,985
0
0
0
0
3,886
715
4,015
0
755
34,788
14,907
0
10,599
922
3,239
2,294
1,643
4,025
0
13,556
4,572
0
3,175
824
Erie
25,781
13,324
76
0
133
41,858
0
35,872
11,427
90,455
23,795
426
1,949
2,786
0
4,801
6,100
70,700
1,846
2,214
2,113
7,241
617
1,465
193
308
894
0
4,515
0
0
3,908
5,018
5,999
0
22,652
9,189
0
8,021
56,042
any site)
Ontario
179
3,190
3,717
7,060
618
787
17,180
89,675
0
0
0
0
15,762
5,826
0
1,637
0
0
0
0
0
1,870
0
51,713
1,371
0
0
0
15,029
0
0
674
626
564
0
48,437
29,126
4,797
9,800
4,387
32
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Table 2. (cont.)
Cryptotnonas pyrenoicKfera Geitl.
RAodomonas minuta Skuja
RAodomonas minuta var. nannoplanctica Skuja
CYANOPHYTA
A-gmenellum quadruplicatum (Menegh.) Breb.
A.gmeneUum thermale (Kutz.) Dr. & Daily
Anabaena drdnalis Rabh.
Aphanothece dathrata W. & G.S. West
Gomphosphaeria lacustris Chod.
Lyngbya sp. #1
Osdllatoria limnetica Lemm.
PYRROPHYTA
Ceratium hirundinella (O.F. Mull.) Schr.
'Pen.
Superior Michigan Huron Erie Ontario
Peridinium sp.
sp.
0
6,731
2,030
96
0
0
2,201
292
1,198
19
0
3,896
2,661
5,062
582
6,757
6,388
1,024
0
13,281
7,044
526
0
417
273,162
0
7,219
21,128
347
4,477
3,919
89
0
0
1,805
4,396
0
0
8,446
8,688
18,028
5,397
8,910
2,545
4,783
948
104
13,977
27,759 101,948
0 0
4,808 2,757
11,571 23,184
4,402
14,706
38,630
8,964
0
0
4,144
1,157
0
9,648
76,541
7,775
16,233
14,051
33
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GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Table 3. Average lake-wide densities (individuals nr2) of crustacean zooplankton taxa during spring
survey, 1999. Numbers in parenthesis indicate volumetric densities (# nr3). Densities for the three ba-
sins of Lake Erie (W=western, C=central, E=Eastern) are shown separately.
Cladoceera
Holopedium gibberum
Daphnia retrocurva
Eubosmina coregoni
Alona spp.
Chydorus sphaericus
Leydigia spp.
Bosmina longirostris
Total Cladocera
Copepoda
Calanoida
Senecella calanoides
Senecella copepodites
Umnocalanus macrurus
Umnocalanus copepodites
Epischura copepodites
Diaptomus ashlandi
Diaptomus minutus
Diaptomus sicilis
Diaptomus sidloides
tomus oregonensis
tomus cop
Total Calanoid
Cyclopoida
A.canthocyclaps vernalis
Cyclops bicuspidatus thomasi
Diacyclops nanus
Eucjclops agilis
Cyclops copepodites
Mesocjclops edax
Mesocjclops copepodites
Tropocyclops pmsinus mexicanus
Tropocjclops copepodites
Total Cyclopoid
MI
20
HU ERW
ERG ERE
ON
35
6
45
86
(1)
68
134
755
13,874
6
59,455
1,459
75.751
(765)
42,327
15,471
9
57.807
(583)
48
85
153
(2)
4
10,578
26,207
16,680
16,474
8,817
1,304
145,745
225.809
(2,329)
93,960
157,042
2,889
253.891
(2,674)
102
529
793
1.424
(19)
25
49
368
14,138
132,033
93,021
34,113
2,389
186,962
463.097
(5,866)
250,318
111,836
2,107
53
364.313
(4,795)
1
138
1
182
322
(43)
1
19
1,636
1,903
627
2
36
451
4.675
(602)
752
1
3,292
34
4.080
(539)
210
7
5
2,702
5
1,352
4.280
(228)
55
598
12
3,620
267
4.552
(231)
7,908
28,656
2,449
39.013
(1,996)
2
21
5
17
45
(1)
2
57
12
44
115
(3)
2
43
9
1,804
3
15
434
2.310
(52)
1,755
565
2.321
(25)
2,662
31,982
64
3,209
1,261
46,378
85.556
(890)
195,855
57,042
268
253.164
(2,673)
34
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GREAT LAKES BIOLOGICAL
OPEN WATER SURVEILLANCE PROGRAM
1999
Table 4. Average lake-wide densities (individuals nr2) of crustacean zooplankton taxa during summer
survey, 1999. Numbers in parenthesis indicate volumetric densities (# nr3). Densities for the three ba-
sins of Lake Erie (W=western, C=central, E=Eastern) are shown separately.
Cladocera
Eythotrephes cederstroemi
Cercopagis pengoi
Leptodora kindti
Polyphemus pediculus
Diaphanosoma birgei
Holopedium gibberum
Ceriodaphnia spp.
Daphniagaleata mendotae
Daphnia longiremis
Daphnia retrocurva
Eubosmina coregoni
Alona spp.
Eosmina longirostris
Eosmina spp.
Total Cladoceran
Copepoda
Calanoida
Senecella calanoides
Senecella copepodites
Umnocalanus macrurus
Umnocalanus copepodites
Epischura lacustris
Epischura copepodites
Eurytemora affinis
Diaptomus ashlandi
Diaptomus minutus
Diaptomus reighardi
Diaptomus sicilis
Diaptomus siciloides
Diaptomus oregonensis
Diaptomus copepodites
Total Calanoid
SU
56
19,268
14,434
13
2,113
126
36.011
(12,204)
666
35
23,919
156
228
35
48
23
17,903
264,254
307.269
(743)
MI
148
101
412
78
268,328
4,229
474,717
748.013
(24,642)
79
13,077
159
3,473
13,189
222
42,763
36,348
7,351
2,278
331,007
449.946
(14,989)
HU
314
110
275,148
112
15,639
109,030
238,176
638.529
(7,600)
158
12,518
263
4,009
6,144
77,862
67,193
6,605
3,172
695,792
873.716
(2,352)
ERW
2,294
9,463
37
1,916
10,223
5
22,284
46.222
(8,861)
59
204
57
1,477
200
2,588
85
11,180
15.852
(11,653)
ERG
229
1,297
42,323
1,239
28,372
7,134
6,126
22,432
395,268
504.420
(7,745)
47
4,113
16,773
1,351
36,537
309
64,069
186,626
309.827
(4,737)
ERE
937
2,904
51,479
1,921
979
177,036
235.255
(361)
15,063
38,858
1,154
49,515
445
68,000
416,460
589.494
(3,086)
ON
16,521
574
111
111
5,829
1,559
448,322
627,660
1.100.686
(4,888)
30,454
1,342
111
4,896
2,401
32,745
71.950
(12,736)
35
-------
GREAT LAKES BIOLOGICAL OPEN WATER SURVEILLANCE PROGRAM 1999
Table 4. (cont.)
Cyclopoida
Acanthocyclops vernalis
Cyclops bicuspidatus thomasi
Eucydops agilis
Cyclops copepodites
Meso/ydops edax
Mesocydops copepodites
Tropocydops prasinus mexicanus
Tropocydops copepodites
Total Cyclopoid
SU
MI
HU ERW
ERG
ERE
ON
33,970
57,302
91.272
359
156,189
576,338
41,661
18,178
792.725
23,379
422,900
284
112
1,069
172
447.916
1,157
5
51,748
40,079
65,945
494
72
159.500
16,680
149,083
60,983
70,673
2,241
264
299.925
743
28,779
354
397,994
34,214
13,814
21,109
1,977
498.984
794,900
862,980
1.657.880
(17,323) (14,768) (21,901) (5,755) (8,142)
(917) (11,057)
36
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