THERMAL EFFECTS ON ECOLOGICAL SYSTEMS

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                 THERMAL EFFECTS ON ECOLOGICAL SYSTEMS

                              A. F. Bartsch, Director
                 Pacific Northwest Water Laboratory, Federal
                 Water Pollution Control Administration, Dept.
                 of the Interior, Corvallis,   Oregon.
                                    and
                             D. I. Mount, Director
                 National Water Quality Laboratory, Federal
                 Water Pollution Control Administration, Dept.
                  of the Interior,  Duluth,  Minnesota.
         "Temperature,  a catalyst, a depressant, an activator, a restrictor,
a stimulator, a controller, a killer is one of the most Important and most
influential water quality characteristics to  life in water.  Temperature deter-
mines those species that may be present; it activates tho hatching of young,
regulates thair activitysand stimulates  or suppresses their growth and
development; it attracts, and kills when  the water becomes  too hot or becorr.es
chilled too suddenly. Colder water generally suppresses development; war.T.er
water generally accelerates activity and may be a primary cause of aquatic
plant nuisances when other environmental factors are suitable."

        What I have Just read is taken verbatim from the Introduction of a
Federal Water Pollution  Control Administration report titled "Temperature
and  Aquatic Life." ^  It points to many of the considerations that arise
when we think of thermal effects on ecological systems.

         So that all of us are thinking in the  same terms, let me define this
new  popular word "ecology" as the study of the interrelationships between
organisms and their environment.  We are concerned today with environments
that  are modified through augmented heat input.  There are three ecological
aspects I wish to explore:  (1) the broad implications for this planet,
(2]l effects on ecological .systems in the water environment,  and  (3) potential
uses of heat.
Implications for This Planet

        In the current issue of BioScience, (2) LaMont C^.Cole, currently-
Ptesldent of the American Institute of Biological Sciences,  examines the
earth's heat budget and man's effect on it.  Let me briefly paraphrase his
Analysis for you.

        Of all the earth's  sources of energy,-99.999% reaches us as radiation
from the sun.  Through photosynthesis over the ages, some energy from this
Source has been stored in organic fuels which, at some  future time, rr.ay
release heat into the environment.  Heat also emerges from the center o£
the earth, perhaps from natural radioactivity.  There are several other
minor heat sources.
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      If the surface of the earth is to maintain its present mean tempera:
which lies in the neighborhood  of 59°F, It must rid itself of a quantity 0«
heat equal to the input.  This is.important because a mean  temperature n
of only 5.4°F is believed likely to melt the icecaps of Greenland and
Antarctica, raise the sea level  by some 328 feet, put Florida under waicr
and drown most of the world's major cities.  For this to happen would
require only a 4.2% increase in the earth's heat  budget.

      So, let's look at what people do  to the heat budget.  The amount of
energy now being produced by man is exceedingly trivial—only about 25/
of i% of  the total radiated by the earth. It is thus obvious that this ac:Y,
now has  an absolutely insignificant direct effect on the average tempera:-.
of the earth's surface.  But the question is—Will this still be  true as we
go on increasing our demands for power?  What will happen, for example,
If power  production and non-electrical  uses of fuel Increase at  the .now
anticipated rate of 7% per year? The answer is that in 91 years there ecu
be a warming of  1.8°F, which could result in some shifts in plant cornniL;
distribution.  But to reach that  critical 5.4°F increase and  face all the du
consequences I mentioned would take about •gStf  years!  Well,  that's fine
and so let's relax, but let's also keep  this prospect in the  back of our mL
as we concentrate on the more urgent problemsj that are here today.

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Responses to Heat in the Water Environment

      So our planet seems secure;  let's go on then to examine the responi
to heat in the smaller sphere of the water environment.

      As temperature in water environments rises, the rates of various
chemical and biochemical reactions are accelerated.  Production of hydro
sulfide in bottom sludges doubles with a rise of  18°F.  The BOD reaction,
by,which organic matter is stabilized,  is most rapid at 86°F, so that a
Stream may be cleansed of its waste load more quickly as temperature goe
up.  But  this accomplishment is not without cost.  As dissolved oxygen  is
used up more rapidly to satisfy the needs of the  process, rising tempera-
ture impairs, reaeration.  As a  result,  the stream's oxygen  resources
diminish, and all the undesirable side  effects of oxygen depletion can
come into being.  Elevated temperature has been noted to substantially
reduce the assimilation capacity in some rivers.  &)  As a result, waste
treatment performance must beimproved or streamflow for dilution must be
increased.^)

      These and many other responses  help to create a new heat-modified
environment to which living organisms  must respond.  Through its ihfluenc
on molecular movement and speed of chemical reactions, temperature con'-
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  the rate of metabolism and activity of all organisms.  This applies to
  aquatic plants.  It Is  true of animals that can maintain a relatively
  constant temperature; It also affects those whose temperature approxi-
  mates that of the environment	the so-called cold-blooded animals. For
  this reason, temperature may be the most important single environmental
  factor affecting life and life processes.

      Aquatic algae are affected profoundly by temperature changes  (Fig. 1).
  From 68-75°F, diatoms dominate the algal population.  As temperatures
  rise to 86-95°F, green algae are most common. Above 95°F, blue-green
  algae predominate.  No one has a good word to say for blue-green algae.
  They are unattractive as food for aquatic life,  they cause blooms and
 drifting windrows of stinking scum,  they destroy recreation, and create
 difficult and costly water supply problems.  Sometimes, especially  in the
 Midwest, they even become toxic and cause catastrophic deaths of livestock,
 game animals, birds,  and fish.

      We are concerned on a national  scale with the exploding problem of
 eutrophication,  or lake aging.  The most distasteful symptom is the
 abundance of these same unwanted blue-green  algae.  The principal remedial
 attack now used  is to  limit the  input of stimulatory plant nutrients through
 tertiary treatment of municipal sewage. Apparently now we must keep an
 eye on the heat  budgets of susceptible waters as'well.

      It has been known since the turn of the century that the character-
 istics of bottom-dwelling organism populations are clues to the  quality
 of the environment.  When the habitat becomes more stringent, as it does
 from the addition of pollutants, the variety of surviving organisms becomes
 progressively less.  This commonly known principle is the basis for
 diagnostic schemes still used to detect and measure pollution.  Studies
 on a Pennsylvania stream (5) show this principle is valid for elevated tem-
 perature, also (Fig.  2).  The number of kinds of organisms decreased by
 55% as temperature went up  from 80 to 87°F. When temperature  increased
 further to 93°F,  there was a 24% additional loss.  Such population changes
 under the influence of  heat are an important reason for concern.  Because
 these organisms are  the food of sport and commercial fishes, they need
 to be preserved,  for without them the fisheries  also will disappear.

      The physiologist considers a number of vital mechanisms when he is
concerned with the direct impact of heat on fishes. Oxygen consumption
goes up as temperature rises because the fish begins to live at a faster
pace.  But unfortunately for  the fish, both water in the stream and heir.o-
globin in the  fish's  blood can hold less oxygen at elevated temperature.
The result—less efficient gill function, breathing rate goes  up,  and
greater energy output is required just to stay even.
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      Enzyme activity performs all the basic functions of the body.  But
 when temperature is high enough, heat-stimulated enzymes malfunction b
 exhausting their substrates, or by  producing toxic byproducts, or by heat
 denaturation which, in effect, destroys the enzyme molecule.  No one
 knows w,hy trout die from heat at temperatures that allow carp to thrive.
 We still ask —  Why do fish die from heat? Is it from enzyme failure?
 These are  crucial questions now  being examined by scientists in the
 Pacific Northwest Water Laboratory at Corvallis, Oregon.

    -  Nutrition and growth are intimately related to temperature so that
 a temperature rise within limits stimulates more activity, Increased food
 consumption, and accelerated growth.  Beyond  these limits, the fish's
 well-being deteriorates rapidly.

      The  physiologist looks also at reproduction, because this is vital
 to production of a harvestable fish crop.  This function is most  sensitive
 and vulnerable to temperature modification.  Similarly, it has been found
 that many  diseases are induced by high temperatures. -It appears that
 heat makes fish more  susceptible and the pathogens  more prolific and viru
 lent.  Faster breathing also brings pathogens moving over the gills at a
 greater frequency,

      Heat also influences toxicity.  Elevated temperatures  enhance the
'action of toxicants, so less is required to affect aquatic life.  In rivers
 that contain a variety  of potential toxicants, their synergistic inter-
 actions are usually intensified by increased temperature.  Such a case
 was reported recently  on the Miramichi River in New  Brunswick '°I where
 Zinc and copper weakened the fish and elevated temperature promoted
 a fish kill caused by disease.

      .As yet, we do not know the full impact of fluctuating  temperature on
 aquatic life.  This may be an important consideration where  thermally
 produced power forms  the basic electrical supply with peak power needs
 met by Intermittent use of hydroelectric facilities.  It is known  that
 fish acclimate faster to rising than to declining temperatures, so  that"
 slugs of cold water from the base of a dam could cause serious  harm in
 a warm river.

      With this as a brief background, I wish now to examine specific
 examples of some of these heat Impacts on  fishes.

      To illustrate the effect of a range of constant temperatures on the
 reproductive potential, one can use a minnow that is widely distributed
 In the United States.  The fathead  minnow (Fig. 3) is an important food
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 source for sport and commercial fishes.  Observations show that a
 constant temperature of 79°F, as compared to 72°F, resulted in a 25%
 loss In"reproductive capacity.  At 86°F, reproduction was almost nil.
 A temperature of 92°F would cause no mortality but would nonetheless
 eliminate the species because reproduction would be Inhibited.  This
 illustrates the great sensitivity of the reproductive stage.

      Scientists at the Pacific Northwest Water Laboratory currently are
 investigating the survival, fertility, and condition of adult salmon that
 were forced to-make a simulated spawning migration at elevated temperatures,
 Neither cohos nor sockeye survived 72°F for. two  weeks, and relatively few
 survived 68° for one month.'  The resulting influences on fertility among
 the survivors is unknown at this time.  Finally,  the  condition of fish
 held at 50°F was judged far superior to that of fish held at 62°F. For
 example,  both male and female sockeye in colder water lost about 8% of
 their body weight,  but at 62°F males lost about 10.5% and females  lost
 about 13.2%.

      The National Water Quality Laboratory at Duluth has examined the
 effect of temperature on the growth rate of the white sucker,  a commer-
 cially Important fish in  the Midwest.  As shown in Fig. 4, rising tem-
 perature has a beneficial effect up to a point. Beyond that point,
 adverse effects show up rapidly.  From 50°F to 81°F, there is pronounced
 increase in the growth of the suckers.  When the temperature  exceeds
 81°F, growth Is reduced.  At 86°F, it is only one-seventh of that occurring
 at 81°F.   Even worse, a temperature of 90°F will kill this fish in a  96-hour
 period! It is important  to note that the best  temperature for growth  is
 very close to the lethal temperature.  One, two,  or three degrees may
 determine the difference between high production and complete elimination
 of a fish population.

      All fishes  are not alike; species vary In the temperature at which
 they do best. Fig. 5 shows this characteristic for three species —
 largemouth bass, northern pike, and brook trout.   The temperature providing
 best growth increases from 59°F for the brook trout,  to 70°F for  the
 northern pike, to 81°F for the largemouth bass.   This emphasizes the
 principle that the best temperature and also the maximum permissible
 temperature depend on the species that are being considered.  If a brook
 trout stream is warmed to 81°F,  its temperature would be suitable as a
 largemouth bass stream. The trout would be killed,  pike would  be in an
 Undesirable temperature range, but largemouth bass  would be at their
 optimal temperature environment.  This emphasizes the significance of
 temperature  in determining whether a given river supports cold  water or
warm water species of fish.
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      I call your attention next to. a theoretical consideration of the way
 in which heat input can shorten the miles of stream suitable for habita-
 tion by salmonids (Fig. 5).  This chart was prepared by the National
 Water Qua-lity Laboratory at Duluth.  It shows  a situation in which the
 effect ofa'dded heat does not occur at the point of discharge but,  instead
 at some point many miles downstream.  The stream represented here is cc'
 considering the climate in which it exists, and usually it is fed by
 springs or snow melt. Many trout and salmon  streams are like this.  The-/
 naturally warm up progressively downstream without any artificial heat
 addition.   The  lower curve of the graph shows  the natural temperature
 pattern that would exist from headwaters to mouth if no heat were  added.
 At 100 miles downstream, the temperature naturally exceeds the limit for
 trout.  If heat is  added at a point 17 miles below the headwaters,  suffi-
 cient to raise the stream temperature 2°F, the  stream is not harmed at
 that point for the production of trout.  But downstream the temperature
 reaches the limit for trout sooner, at approximately 83 miles.  As  a
 result, the lower 17 miles of the stream are unfit for trout production
 even though the heat was added 60 miles upstream.  If'the heat input
 upstream raises the temperature 5°F rather than 2°F, destruction of trout
 habkat extends farther upstream.  The upper line in the graph shows that
 there has  now been a loss of 42 miles of trout waters as a result of
 upstream heat addition.

      Not cited specifically in th'is example is one of the most insidious
 problems of thermal pollution.  It is the fact that small increases  in
 temperature, while they may not kill the desirable cold water fishes, can •
 foster  the welfare and successful competition of warm water fish.  In
 most trout streams, warm water fishes do not reproduce because the numbs
 of degree days  is not sufficient for maturation of the gonads.  Relatively
 small changes can meet such needs and allow their reproductive prolifera-
 tion. There then  follows a population shift from desirable cold water
 fishes to less desirable warm  water ones.  The latter can also serve as
 a reservoir of diseases that can have devastating effects on trout and
 salmon.
PotentialUses of Heat

      After calling attention to these many ecological Implications of
thermal pollution,  it is only fitting that I terminate these remarks in
some more optimistic tone.  To do so,  I wish to simply enumerate some
of the possibilities now considered for beneficial uses of waste heat.

      In the United States  — in fact, right here In Oregon —  studies
supported by the Eugene Water and Electric Board are to demonstrate that
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 warm water can stimulate and enhance plant growth and protect fruit trees
 from killing frost.  The Pacific Power and Light Company also is supporting
 work at. Oregon State University to determine if growing seasons can be
 lengthened and crop yields increased by warming the soil.

      In Wisconsin, the Department of Natural Resources and the Wisconsin
 Electric  Power Company have joined in a program of intensive fish pro-
.ductlon in heated fish-rearing ponds.  This program, to be located at
 Two Creeks, should be in operation  by 1971.

      According to scientists at Massachusetts Institute of Technology, a
 cooling 'trend  in waters along the Maine coast has caused a decline in
 growth rate  of lobsters.  Researchers have a plan to use power plant cool-
 Ing water to warm the water in shoreline coves so lobsters will thrive
 again.  New York State is considering a similar proposal for a site on
 Long Island near Montauk Point.

      The Institute of Marine Science, at the University of Miami, has
 joined the Florida Power and  Light Company in a waste heat use project.
 The-objective is to learn if a heated effluent can be used to raise pink
 shrimp and pompaho.

     ,At Northport,  New York, a 10,000 square foot oyster hatchery is being
 built so that heated  water from the Long Island Lighting Company power
 plant can be used to maintain optimal temperature for oyster spawning and
 production.  Oysters in the heated water are expected to spawn ten months
 out of the year rather than the normal three or four.   As  the young
 oysters grow they will be placed on rafts and moved into Long Island
 Sound.

      In England, Scotland, and Russia there are  several additional programs
 to use waste heat in experimental or commercial production of fish and
 shellfish.

      Finally, at Tapiola, Finland, not far from Helsinki, cooling water
 from the  community power plant is routed through a  piping system to
 business and residential buildings.  It provides heating, as needed, 270
days per year.
Conclusion

      In conclusion, these are examples of the thermal effects on ecological
systems.  The planet as a whole is not much affected by man's  heat-
generating activities.  But in the aquatic environment, there is  a great
potential for destruction through thermal pollution.  This can be avoided
if we give proper attention to the ecological knowledge now at hand.

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                        LITERATURE CITED
1.    "Temperature and Aquatic Life.  Laboratory Investigations - Number
      Tech. Advy. & Investig. Br., Tech. Serv. Prog., FWPCA. U.  S. Dep».
      Int., Cincinnati, Ohio. Dec. 1967.

2.    Cole, L.C. "Thermal pollution," BioScience 19, 989-992.  Nov.  1969.

3.    Krenkel, P.A., E. L. Thackston, and F. L.  Parker.  "Impoundment and
      temperature effect on waste assimilation," J. San.  Engrg. Div.,
      Proc., Am. Soc. of Civil Engrs.,  Feb.  1969.

4.    "FWPCA Presentations  - ORSANCO Engineering Committee, "  17th
      Meeting, Ohio Basin Region, FWPCA, U. S. Dept.  Int., Cincinnati,
      Ohio, Sept. 10, 1969.

5.    Trembley,  F. J.  "Research Project on Effects of Condenser  Discharge
      Water on Aquatic Life," Prog. Report, 1969.  The Inst.  of Res.,
      LehighUniv., 1961.

6.    Pippyi J.H.C. and G.  M. Hare.  "Relationship of river pollution to
      bacterial infection in salmon (Salmo salar)  and suckers (Catastomns
      commersoni),"  Trans.  Am.  Fish. Soc. 98, 685-690.  1969.
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