WATER QUALITY: Technical Information--"Aquatic biology: Some thoughts on its history, principles, and future needs" 




In Reply Refer To:                                April 15, 1980
EGS-Mail Stop 412


QUALITY OF WATER BRANCH TECHNICAL MEMORANDUM NO. 80.13

Subject: WATER QUALITY: Technical Information--"Aquatic biology: 
         Some thoughts on its history, principles, and future 
         needs" by Robert C. Averett, WRD, Lakewood, Colorado.

Enclosed for your information is the subject paper, which was 
prepared by Bob Averett for use at the 1979 California District 
Conference. Bob's thoughts about the past, present, and future of 
aquatic biology should be useful in putting that area of hydrology 
into perspective as we continue to expand our water-quality 
programs. Please circulate the paper as widely as possible in all 
district and project offices. Thank you.



                                R. J. Pickering 7

Enclosure

WRD Distribution: A, B, FO-L, PO

Key words: water quality, information, aquatic biology

Superseded memoranda: none




AQUATIC BIOLOGY:

SOME THOUGHTS ON ITS HISTORY, PRINCIPLES, AND FUTURE NEEDS
by
Robert C. Averett

INTRODUCTION

The title of this paper would indicate that it is a position paper 
on research needs in aquatic biology. In part that indication is 
correct; in part it is in error. An individual has no license to 
prepare a position paper on such a broad important subject as 
aquatic biology. What is intended in the pages that follow is to 
elaborate a bit upon the history of aquatic biology, at least the 
recent history. Following the historical part is a discussion on 
the modern view of process biology in streams and lakes. 
Obviously, we only will be able to touch upon the highlights. Next 
is a discussion of advances in the field in the past several 
decades, an era of significant importance in aquatic biology. It 
relates how these advances are tied to the past and the future. 
Finally, I will give my viewpoints on some of the items that need 
further exploratory work; items that I believe will make aquatic 
biology a more useful science to mankind.

I hope that this type of paper will be more useful as an 
instrument to stimulate thought and future research than as a 
guide to an understanding of how we do things. I ask the reader to 
keep in mind that the statements in this paper are, in most 
instances, my own interpretations. Another author might well see 
the past somewhat differently, and the future quite differently. I 
believe, however, that I have covered enough material to insure a 
strong enough link between the past and the future to put some 
reliability into both.

Anyone with the simplest knowledge of the history of science will 
know that these are fast-changing times. We often attribute this 
fast pace to the 1960's. Not so; they were the "much studied 
times", when research money and those who used it were easily 
obtainable. The 1960's were a peak period for data gathering, as 
well as a period for some excellent interpretation of those data. 
For example, biochemistry is a field of science that flourished in 
the 1960's, and continues so today, primarily I believe, because 
of the momentum that began in the 1960's.

Without question, most fields of science have moved ahead in 
recent years; some more rapidly than others, and some with a more 
scientific steadiness than others. I put aquatic chemistry in the 
latter category. Progress in aquatic chemistry has followed many 
of the best laid plans of experimental design--test, revise, test, 
revise, conclude, hypothesize, continue to disprove the 
hypothesis. Even so, while aquatic chemistry has made some 
excellent strides in recent years, its greatest thrust has been in 
analytical techniques. We are able to analyze for a great number 
of elements and compounds in water. Our understanding of what 
these analyses mean has not moved forward at anywhere near the 
same rate.

In most disciplines of science, we have attempted in very recent 
years to model the processes involved. Modeling, to mathematically 
mimic the elements of a natural process, would of course provide 
the best of both worlds. We could have it both ways in that we 
could not only understand the processes involved, but we also 
could describe them mathematically. The computer spawned the era 
of modeling and it has added much to our understanding of the 
several branches of science. The manipulation of computer-spawned 
mathematical models often has made us reevaluate our thinking and 
learn much more about the processes involved in nature. Such is 
science in its simplest but most productive form.

Where does aquatic biology fall within all of this fast-changing, 
much-studied, process-understanding, modeling myriad of things? 
Rather than give a positional answer--beginning, middle, or end, I 
prefer to discuss the past, followed by a brief essay on our 
understanding of aquatic ecosystems today, and then discuss the 
present, followed by some thoughts on the direction aquatic 
ecology should take to be a more useful science to mankind in the 
future. The future is the most fun to predict and, after all, it 
is the only place we are going with any assurance. But predicting 
the future always depends upon the progress and the direction of 
the past. Let us begin there.

WHERE HAVE WE BEEN?

I do not know where aquatic biology began. Man has always been 
interested in the aquatic flora and fauna about him, and early man 
certainly was aware of life in streams and lakes, for such life 
provided a source of food. In fact, many tribes of early man were 
welded to the stream bank or lake shore because of the source of 
food it supplies. We credit Carlos Linnaeus for first describing, 
in a logical manner, the numerous types of plants and animals on 
earth in his three books published in 1753, 1754 and 1758. 
Linnaeus was a classifier, a taxonomist, and as such was a 
descriptive scientist. His classification schemes and descriptions 
were more along the line of the naturalist of some 10-20 years 
ago, who knew certain things happened in a somewhat repeating 
manner, but never really understood why. This was scientific 
evidence without an experimental design.

Immediately after the work of Linnaeus, aquatic biology, and 
biology in general, underwent some significant discoveries and 
changes. Anatomy (form and structure) was still the keystone of 
the science; it was easy to study. Physiology (function), however, 
was becoming a branch of the biological sciences in its own right. 
Biochemistry, which united physiology and chemistry, was a century 
or more away from the time of Linnaeus. It was almost two 
centuries away if you consider only the modern concepts and 
discoveries of biochemistry.

I believe it was physiology that truly moved biology ahead as a 
science. While not appreciated nor understood as functional 
processes, many biological discoveries made at the change of the 
present century were physiologically orientated. It was, in fact, 
in the late 1800's and early l900's when aquatic biology came into 
its own. Agriculture, industry, and urbanization with the flush 
toilet altered the aquatic environment in many parts of the world. 
The environmental changes were stream bottom alterations, areas of 
depressed dissolved oxygen, the introduction of toxic materials, 
and combinations of the above. Aquatic life either disappeared or 
the species composition was altered greatly. The presence of some 
forms of aquatic life and the disappearance of others in streams 
receiving organic waste material were noticed and recorded by a 
number of investigators. The presence or absence of fish was 
particularly noticed, because fish were easy to observe and were 
of economic value. But effects on other aquatic organisms were 
recognized and studied as well, and we owe much of our present-day 
understanding of aquatic biology to these early-in-the-century 
investigators, especially Kolkwitz and Marrson 1908, 1909), who 
introduced the concept of classifying organisms based upon their 
location on organically polluted streams.

While lake studies were somewhat common place in Europe, they were 
relatively new in the United States until about 1910. Birge and 
Juday, two lake limnologists from the University of Wisconsin, 
pioneered lake studies in the United States. Their work on heat 
budgets and photoplankton distribution in lakes remains as a 
monumental work of science to this day. While Birge and Juday are 
credited as the "fathers" of lake limnology, the work on 
recognizing lakes as ecosystems truly belongs to Forbes, who in 
1887 wrote his classical paper "The Lake as a Microcosm" (see 
Forbes, 1925).

Studies of aquatic biology at the turn of the century and shortly 
thereafter set the stage for what was to come. Two things seemed 
reasonable then as they do today: (l) that the presence of 
particular organisms should indicate particular environmental 
conditions (indicator organisms); and (2) it should be possible to 
determine the concentrations of particular chemical constituents 
that are lethal to aquatic organisms (toxic levels, and thus be 
able to use streams for the production of aquatic crops as well as 
for waste disposal. Our success in these two endeavors, even 
today, has not been outstanding. We simply have underestimated the 
complexity of the aquatic environment. More on this will be 
discussed later.

In the late 1920's, 1930's, and 1940's, there was a somewhat 
sporadic research effort to view and measure the energy and 
material utilization by plants and animals. This research effort 
was not continuous throughout the three decades, and took place in 
institutions somewhat distant from one another. There seemed to be 
no pattern of concentrated effort. While research was pioneering 
in almost every detail, it also was, for the most part, very sound 
research based upon well-thought-out experimental designs. The 
works of Brody (1927) and Lindeman (1942) remain classics.

This energy and material utilization or "pathway" research paved 
the way for the concepts and principles of biological production, 
a study phase that began in earnest in the 1960's and is still 
going strong today. More will be said later on energy, material, 
and production. First, let us look at streams and lakes as 
environments, and at some new knowledge on stream ecology.

FRESHWATER ECOSYSTEMS

When compared to the oceans, freshwaters are dilute with regard to 
dissolved materials. All, however, support some type of aquatic 
life. The type of life varies greatly and the amount of living 
tissue that is produced per unit time also varies greatly and 
depends upon a number of factors, some of which are poorly 
understood.

Consider a stream that begins in the mountains, receives water 
from other streams as it moves downgradient, eventually enters a 
lowland river which eventually flows into another larger river, or 
flows into the sea. The uppermost reaches of the stream (first 
order) have steep gradients which result in a rather rapid 
movement of the water. The stream bottom is often bedrock, and 
usually the stream bank is crowded with terrestrial plants 
(grasses, shrubs, and trees). Some vegetation, often aquatic 
mosses (although there are few "typical" plants), will be found in 
the stream growing on the banks or bottom. Some attached algae 
(periphyton) also will be found, but that probably will be the 
extent of the aquatic plant life. If the stream bottom is 
examined, a distinct invertebrate fauna will be found. The fauna 
often will be of a type having strong holdfast organs and a 
streamlined body that assists them from being swept downgradient 
by the current.

From a descriptive standpoint, we could stop our discussion here 
for we have described the stream reach with such terms as steep 
gradient, terrestrial shoreline vegetation, bedrock bottom or 
substrate, some aquatic plants (mosses and periphyton), and 
aquatic invertebrates with strong holdfast organs.

The descriptive part is easy. The processes which make it possible 
for our stream to support this life, or for the life to live in 
the stream, is exceedingly complex. We might ask the questions, 
"Where do these invertebrates obtain their energy and material, 
why are there not more aquatic plants in the stream system, what 
role does the terrestrial vegetation play in the scheme of things, 
and how does this headwaters stream section affect life and 
chemical quality in downstream stream sections?" When we ask these 
questions we are beyond simple descriptive biology. We enter the 
field of process biology and we weld it to hydrology. We are 
relating stream processes to one another and making an effort to 
understand the entire ecosystem. Asking the above questions has 
been an active part of recent research in aquatic biology, and 
because of this research, we can now answer some of the questions.

A primary reason that there are few aquatic plants, including 
algae in the headwater stream, is that the stream section is 
shaded and only a very low light level reaches the stream bottom. 
The light energy is captured by the higher terrestrial vegetation. 
Another reason for few plants is the lower water temperature which 
in turn lowers the rate of plant production. A third reason is the 
lower concentration of dissolved or available nutrients in the 
stream reach. If, however, we measure the animal component of our 
stream, we find more biomass than we can seemingly account for on 
a material and energy budget. How can this be? The answer is 
relatively simple in that animal production in the stream depends 
upon the terrestrial input of material and energy. Leaves, twigs, 
needles, and of course, dissolved materials leached from the soil 
supply the material and energy necessary to drive the stream 
ecosystem. We term inputs of Such "outside" material as 
allochthonous. Simply, the material is transported from one 
ecosystem to another.

As the stream moves downgradient, it receives water from other 
streams and becomes a second, third, and so-on order stream. As 
the gradient lessens, the stream bottom changes, often resulting 
in a more diverse array of microhabitats for aquatic organisms. 
Alternating pools and riffles describe its profile. No longer is 
the stream bottom only bedrock. Now there is clay, sand, gravel, 
and boulders present, and each provides d habitat for various
plants and animals. Water movement may still be rather rapid but 
there are numerous places where an organism can avoid the direct 
effects of the current. While there is still streamside 
vegetation, the stream is often wide enough to permit direct 
sunlight to pass through the water. As a result, primary 
production in the form of algae and even some rooted aquatic 
plants are found. In much of the year, in-place primary production 
by plants supplies the material and energy to drive the stream 
ecosystem. We call this in-place primary production of organic 
matter autochthonous material; that is, material synthesized in 
the stream.

Because of the more varied habitat and increased organic 
production, this downgradient stream section will have a more 
varied fauna and higher rates of production. Remember too, that 
this stream reach obtains terrestrial material input 
(allochthonous material) from the headwater reach. In addition, 
this downgradient stream reach also receives allochthonous 
material from its surrounding basin.

Further downstream we reach a lowland river, a sort of catch basin 
for all upstream material. Slower velocities and deep pools 
characterize the river. Primary production by algae and higher 
aquatic plans insures that the stream is autochthonous with regard 
to material production. In many instances (in the absence of man's 
influence), the stream section would be self-supporting. Man's 
influence usually has been to add more organic matter from outside 
sources, especially domestic wastewater. The fauna of this 
downstream reach often will be a mixture of flowing and standing 
water types. Many of the fauna types in the deeper stream 
stretches are found in lakes as well. Because this river reach 
acts as a depository for sediments, the bottom material is often 
unconsolidated, and burrowing organisms are commonplace.

I have not mentioned fish in the above discussion, but they are 
important inhabitants of each reach described. They are extremely 
temperature dependent, but temperature alone does not completely 
influence their distribution or species composition. Fish 
production and biomass, however, in the absence of toxins, does 
increase in a downstream direction. The problem is that from an 
economic standpoint, the highest production rates may be of a 
species undesirable for man's use. I

Lakes are standing bodies of water which may have multi-
directional currents depending upon the wind direction and speed. 
As mentioned, lakes and large rivers have many habitants in 
common. Some areas of lakes that receive the Influence of winds 
may have micro-habitats similar to riffles in streams, and the 
fauna may be similar. Lakes act as depositories for earth and 
stream-borne materials and the bulk of their bottom material is 
unconsolidated. Thus, burrowing organisms are often most common in 
lakes. Many lakes undergo distinct spring and autumn circulation 
and summer stratification patterns. When stratified, the warmer 
surface water does not readily mix with the cooler bottom water. 
In lakes with high amounts of organic matter, bacterial 
respiration in the cooler bottom water may remove most, if not 
all, of the dissolved oxygen. When this occurs, a large part of 
the lake may be uninhabitable by higher organisms. Some burrowing 
organisms can survive under low dissolved-oxygen concentrations, 
but not under anoxic or depleted dissolved-oxygen conditions. Only 
anaerobic bacteria can remain alive under anoxic conditions.

Most lake problems today revolve around enrichment by phosphorus 
and other nutrients and the attendant problem of excessive 
production of algae--algal blooms. Not too long ago, we considered 
both nitrogen and phosphorus as the culprit nutrients. We argued 
among ourselves as to which was the most important and why, and we 
made studies that often showed that the nitrogen concentration in 
a lake was proportionately lower than was the phosphorus 
concentration on the basis of expected cellular concentrations. 
Our calculations may have been correct, but our knowledge of blue-
green algae physiology was primitive. We now know that blue-green 
algae, the group that causes most nuisance algal blooms, can fix 
nitrogen, much like legumes. Thus, phosphorus generally remains 
the main culprit nutrient for triggering excessive algal 
production. There are other nutrients that are required by algae, 
but phosphorus remains the most important for arresting algal 
production.

The study of freshwater ecosystems is not as simple as any of the 
descriptions given above. I have only touched upon some of the 
more simple concepts that will aid, I hope, in viewing where we 
are now, and how we have come to be where we are. For further 
reading see Cummins (1974), Likens and Bormann (1974), and Vannote 
and others (1980).

Let me add a thought here. In my opinion, the field of aquatic 
chemistry is in the position where analytical techniques far 
outstrip our ability to understand what the analyses mean. In 
aquatic biology, we have, I believe, better concepts of what is 
taking place than we have data to support the concepts. In some 
ways, aquatic chemistry and aquatic biology face opposite 
problems. It will be interesting to see where both sciences are in 
regard to this dilemma some 20-years hence. Whatever the results, 
let us hope that hard data replaces dogma.

THE PRESENT--WHERE ARE WE?

These are exciting and frustrating times in aquatic ecology. We 
have broken many of the old barriers that for so long dominated 
our thoughts. The past barriers to our thoughts, however, linger 
with us in too many instances, and they influence our present-day 
thinking. This is a part of life, progress, and science. Another 
problem that always must be faced in viewing science, especially 
the history of science, is determining where something began and 
where it ended. I stated earlier that I did not know when aquatic 
biology began. I do not even know where the present thrusts began, 
but many were post World War II. In the 1950's, we were confused 
and wondering if what we were doing then would have long-lasting 
usefulness, or if it was simply needs-of-the moment. We suspected 
the latter, but we were not strong enough in our knowledge or 
convictions to know if we had any reason to be correct. As it 
turns out, we were half correct and half wrong--a comfortable 
position even if you do not realize it. For example, the era of 
the 1950's was the era of the effects of organic waste on streams 
and stream ecosystems. Strange it would be at that time when we 
could not directly measure organic carbon. Today, we are able to 
make rather accurate measurements of organic carbon, but still do 
not have a clear idea of what the measurements mean.

It was the era of the 1950's tied to the era of the 1900-1910 that 
truly tied together our knowledge of untreated domestic sewage on 
stream. We had "pinned down" the culprit, the flush toilet. In 
fact, that was our goal--the federal water pollution control goal-
-to insist on secondary and tertiary treatment of domestic sewage. 
We won that one, because today most municipalities in the United 
States release a sewage effluent with a low biochemical oxygen 
demand; BOD, the household word of the 1950's.

In the 1950's, we studied and mastered the operation of sewage 
oxidation ponds for small municipalities. The problem in all of 
this was biological, the cure in all of this was biological, and 
the end result in all of this--cleaner streams and enhanced 
biological production--was obviously biological.

It would be foolish to end this phase of the present era with a 
positive statement that the problem of domestic wastewater is 
completely solved. It is not; but we can all hold our heads high 
in that truly significant progress was made in the late 1950's, 
1960's, and 1970's. Most domestic sewage-problem areas that remain 
could be solved easily with todays technology.

Problems related to aquatic biology did not end with the solution 
to the domestic wastewater problem. Other problems soon took their 
place. For one thing, we realized (again) that there were other 
sources of organic matter in streams that resulted in a high BOD. 
These were leaves, forest litter, and, in many parts of the 
northwest and north-central and southeastern parts of the country, 
pulp-mill wastes. With the latter we had a color, BOD, and a 
suspended organic solids problem on our hands, as well as a 
toxicity problem.

I cannot prove it and it would not be worth the effort if I could, 
but I firmly believe the domestic waste and pulp-mill waste 
problems directed us into the exciting aquatic biological research 
that began in the middle 1960's, and is continuing today. This 
research consists of a mixture of laboratory and field research 
(nothing new here), a bit of verification between laboratory and 
field research (much new here), and an appreciation of the 
progress from other fields of science and how they impinge upon 
aquatic biology (again much new here). After all, there had been 
great advances in biochemistry. The Krebs or citric acid cycle was 
well known and verified, and modern bomb calorimeters were 
providing methods not only for understanding, but for measuring 
energy and material utilization. Methods for the measurement of 
toxicity were more refined; this again was a result of input from 
other sciences, especially trace-element chemistry.

I should quickly add that biology is a synthetic science; that is, 
it depends heavily upon physics and chemistry for its 
understanding. Thus, advances in physics and chemistry usually 
have led to advances in biology. But, the sciences are very often 
complimentary; for example, the solubility product of cyanide was 
corrected as a result of biological toxicity tests, rather than 
chemical determinations. Even those concerned with the production 
of fish began to realize there was more to measure and understand 
than length and weight relations. Indeed, fish again became 
organisms of research concern, because they encompass the highest 
forms of life in aquatic systems. But fish and the organisms they 
feed upon have quite different nervous and circulatory systems. 
Parallel study emphasis was, therefore, placed on aquatic 
invertebrates. This was a good decision by many scientists, and 
placed study emphasis on a larger segment of the inhabitants of 
the aquatic ecosystem. Bacteria still were ignored somewhat, but 
their role in aquatic ecosystems was gaining attention.

Studies of aquatic ecosystems using artificial or laboratory 
streams gained prominence in the 1960's and into the 1970's as 
well. Streams were constructed to mimic natural conditions as much 
as possible, but also to provide controls on flow volume, rate of 
flow speed, light, temperature, and so forth. Such "stream" 
studies provided a great amount of insight into the role of algae 
and periphyton production and distribution in ecosystems. A great 
deal was learned about plant-animal relations and interactions as 
well. Studies in animal behavior (effects of crowding, competition 
for food, and so forth), secondary production, predation, and 
population dynamics were enhanced by the use of artificial 
streams.

Even so, artificial streams and the activities or events we 
attempted to measure by their use were quite simple compared to 
natural ecosystems. We simply do not know how to measure 
everything. But the impact on our understanding of stream 
ecosystems through the use of artificial streams has been 
tremendous and will be with us for decades to come.

It would be untrue to leave the implication that modern research 
in aquatic biology has been only the result of artificial streams. 
A great deal of other types of research has been carried out as 
well. Some are concerned with natural systems and others are 
concerned with physiological studies under laboratory conditions. 
Most of this research, at least that which has significantly 
advanced our understanding of aquatic ecosystems, has been tied to 
the modern concepts of biochemistry and our ability to understand 
chemical speciation and determine ultra-low concentrations in 
natural waters. Essentially, this is where we are now. There are a 
number of excellent well-designed studies underway using natural 
streams and making measurements under natural conditions. These 
studies, coupled with past laboratory studies, have increased 
greatly our knowledge of energy and material needs and utilization 
by aquatic animals, and nutrient requirements and uptake by 
aquatic plants. Coupled to these studies is a much better 
knowledge and understanding of animal toxicity; but, still too 
little is known or appreciated concerning sub-lethal or stress 
effects. More on this will be discussed later.

Lake studies have taken a quantum jump in recent years in the form 
of understanding nutrient requirements of algae, algal physiology, 
and in estimating water budgets. Much of our understanding of 
natural lake conditions is a result of the Canadian experimental 
lakes programs, headquartered in Winnipeg, Manitoba. Lake studies 
by United States scientists also have been imaginative and have 
provided much insight to lake ecosystems that was not available a 
decade ago. In spite of our progress in understanding lake 
ecosystems and nutrient requirements of algae, we have only few 
options for reversing enrichment. The most feasible way to control 
enrichment is to prevent it in the first place, an option that has 
been closed in many lakes.

That is probably enough on where we are. Without question, the 
past 20 or so years has provided some excellent insight and 
progress in aquatic ecology. Much of the research was tied to 
principles of physics and chemistry, which has broadened the field 
of aquatic biology. Moreover, agencies which at one time were 
concerned only with a single product (fish, for example) have 
broadened their scope in looking at the ecosystem instead of their 
product of interest. Thus, much improved studies in fish 
physiology, toxicology, and behavior have occurred in recent 
years. The simple recognition that fish are but a part of the 
ecosystem was, itself, somewhat of a breakthrough in aquatic 
research.

THE FUTURE--WHERE ARE WE GOING?

I cannot predict the future any better than anyone else, and there 
is always the chance I cannot do as well as others. But, I think I 
have some feeling as to what needs to be done and what can be done 
with our present understanding of aquatic ecosystems. I am going 
to discuss each item separately, even though there are pitfalls in 
using this approach.

1. Energy and material utilization by aquatic animals is an area 
for future endeavors. This is not a new concept. It was first 
derived by Ivlev (1945). We can now measure most components of the 
energy and material equation for animals as:

Qc = QW + Qs + Qd + Qa + Qg

Where

Qc ~ total energy and material consumed

QW - total waste

Qs ~ basal or standard energy and material utilization

Qd ~ energy cost of food transport

Qa = energy and material used in activity

Qg = energy and material used for growth

We know that on the right hand side of the equation, the first 
four components of energy and material must be satisfied before Qg 
(growth) can take place. The equation is, of course, incomplete, 
for it neglects energy and material utilization and losses related 
to reproduction, a vital component of population well being. 
Nevertheless, it points out how energy and material must be used 
to satisfy life processes before growth, a population requirement, 
can be met.

Much more direct research needs to be done on animal energy and 
material utilization under different environmental conditions. If 
we are to predict stress, we must base our predictions and 
findings on quantative values and these must be related to some 
vital factor needed by the organisms in order to survive. The 
above equation offers some promise in this direction.

2. The relation between organic matter and aquatic plants and 
animals will be a continuing and vital aspect of future research. 
This was touched upon earlier, and has been an area of active 
research in recent years. We now have a great deal of useful 
information on the role of benthic invertebrates in reducing 
coarse organic matter to fine organic matter. We know too that
many aquatic invertebrates are quite efficient at removing 
particulate organic matter and transforming it into living tissue. 
Aquatic biology is somewhat ahead of organic chemistry in defining 
sources and sinks of organic matter in aquatic systems. The two 
sciences should and must come closer together in the future. 
Organic chemistry and aquatic biology are working on the same 
ground at the present time, a fact that has never before been 
true.

3. The toxicity of substances to organisms, because of various 
man-caused inputs to stream and lake ecosystems, will continue to 
be an active area of study. Hopefully, however, new approaches 
will be undertaken to put more emphasis on the sublethal effects 
of introduced materials. We need to know much more about stress 
and sublethal concentrations of material; that is, those 
concentrations and conditions that do not cause death, but stress 
the components given earlier in the energy and material equation.

More also needs to be done on the activity and form that 
particular constituents take under natural conditions and the 
relative toxicity these constituents will have while in a 
particular form or activity.

4. More work on population ecology from the standpoint of 
processes carried out by populations is needed. We need less 
emphasis on population taxonomy and more on processes; a sort of 
population physiological approach. I quickly add that my comments 
are not anti-taxonomy. Certainly, we must be able to give a name 
to the organisms we work with. But taxonomy without an 
understanding of the role of the organism in the aquatic ecosystem 
is of little value to understanding the processes involved.

5. Modeling of the distribution of organisms also is important. We 
are, I believe, at the point where we can model particular aspects 
of the aquatic ecosystem. One such aspect is the distribution and 
movement of some organisms, especially phytoplankton in lakes. 
Modeling should not overtake our understanding of processes. But 
if used carefully, modeling can well point the way towards needed 
process research.

6. Lake restoration is a research activity that certainly is in 
need of a much more imaginative approach. A great deal of money 
and time has been spent reworking old tried-and-failed techniques 
for lake restoration. I do not have an answer, nor even a good 
approach for lake restoration success. But, we need to collate 
under a single cover those techniques that do not work-and get on 
with the job of looking at those environmental components that can 
be controlled and hence will control algal production.

These then are six areas where I think future aquatic biological 
research should be directed. Doubtless six more could be added 
and, in a few years hence, some removed. We have come a long way 
since Linneaus, and the future is brighter than ever.

References Cited

Brody, S. B., 1943, Bioenergetics and growth: New York, Hafner 
Publishing Co., 1023 p.

Cummins, K. W., 1974, Structure and function of stream ecosystems: 
Bioscience, v. 24, p. 631-641.

Forbes, S. A., 1925, The lake as a microcasm: Bulletin of Illinois 
Natural History Survey, p. 537-550.

Ivlev, V. S., 1945, The biological productivity of waters 
(translated from the Russian): Journal Fisheries Research Board of 
Canada, v. 23, p. 17271729, 1966.

Kolkwitz, R., and Marrson, M., 1908, Okologie der pflanzlichen 
Saprobien: Bericht der Deutchland Botanisch Gesellschaft, v. 26, 
p. 505-519.

Kolwitz, R., and Marrson, M., 1909, Ecology of animal saprobia: 
International Review of Hydrobiology and Hydrogeography, v. 2, 
p. 126-152.

Likens, G. E., and Bormann, F. H., 1974, Linkages between 
terrestrial and aquatic ecosystems: Bioscience, v. 24, p. 447-456.

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