Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder

CIRES’ William Lewis Lecture, “Lakes, Nutrients, and Water Sin” on April 30

William Lewis, Director of the CIRES Center for Limnology, University of Colorado Boulder, and Professor of Ecology and Evolutionary Biology, will deliver a Distinguished Research Lecture entitled “Lakes, Nutrients, and Water Sin” at 4 pm on Tuesday, April 30. The lecture will be held in the Glenn Miller Ballroom at the University Memorial Center; a reception will follow. Please RSVP here.

Dr. Lewis, who has studied aquatic ecosystems for five decades, will explain a commonly misunderstood aspect of human influence on aquatic ecosystems: enrichment with plant nutrients.

On April 30, find out what Lewis means by “water sin,” learn more about the effect of humans on Colorado waters, and consider the future of the world’s lakes, streams, and rivers as he answers the question: “Can anthropogenically enriched aquatic ecosystems be restored to a natural state?”

See below for a Q&A with Dr. Lewis.

Q: Why is it important to understand the effect of nutrients on a body of water?

A: Nutrients have a powerful effect on the nature of aquatic environments, especially lakes. The effects are most obvious through growth of algae, which is stimulated by nutrient enrichment. Stimulation of algal growth changes the appearance of lakes and their suitability for use as a water source for consumption or other domestic purposes. Nutrient enrichment also changes lake food webs, which are perturbed by an increase in algal abundance, usually in a way that is undesirable for humans. For example, in a lake that has provided a good fishery, nutrient enrichment often creates a much poorer fishery as the lake shifts from a natural condition to a human-influenced condition. Changes caused by nutrient pollution we typically find undesirable.


Dr. Lewis capturing zooplankton in Lake Lanao, Philippines in 1970.

Q: What first sparked your interest in limnology?

A: After I finished my undergraduate degree, I planned to do doctoral work on fish. My professor, who wanted me to study some unusual fish in a Philippine lake, had a grant for a two year study of the lake and its fish. I asked him if I could study the lake instead of the fish. He said that he was disappointed, but agreed to study the fish, and allowed me to study the lake, and that is how I came to study lakes as ecosystems.


Q: What is different about studying the fish in a lake versus the lake as a whole?

A: Often ecologists study species populations or communities of organisms, which could be fish, arthropods, or algae, for example. These studies can be exciting and important, but ecological science also requires study of entire ecosystems. The attraction for my work in the Philippines was that tropical lakes at that time were virtually unstudied except by scientists who had visited them briefly. I had the chance to study a large, unpolluted tropical lake for two years with grant support that allowed a broad range of data collection. It was an unusual opportunity to study an unfamiliar type of lake that likely would show some important differences from more familiar lakes of temperate latitudes.


Lake Dillon. Photo: K. Weeman

Q: You founded the Center for Limnology in 1980s—at that time, what void did it fill?

A: In the 1980s, the Center for Limnology had support for work on tropical lakes and rivers and also on Colorado lakes, streams, and rivers in a number of locations. We were doing extensive laboratory and field work with students and research staff; data collection was directed toward water quality and aquatic life. The complexity of the program called for formation of an organization that would coordinate the work and be responsible for helping use our resources in the best way possible. The Boulder Campus uses the term “Center” for an organization of this type. With approval of the appropriate CU administrators, the Center for Limnology was formed and has been functioning continuously since that time.


Q: Take us back to 1974 when you first came to CU Boulder. What was the state of Colorado’s lakes and rivers?

A: Many of the rivers and lakes in Colorado and in the United States generally were badly polluted by 1974. The Federal Clean Water Act was first passed in 1972 and finalized in 1974. When I arrived at CU, the Act was beginning to exert a new influence on U.S. water quality. The Clean Water Act carried strong federal legal authority, shared with the states, to control water pollution. It affected, through a mandatory permitting process, every entity that discharged waste from a point source into waters of the United States. There was a terrific concern among organizations that operated wastewater treatment plants, including cities and industries, as to how they would accommodate the new law.


Q: Did the Clean Water Act help Colorado’s lakes and rivers?

A: Water quality of Colorado’s lakes, streams, and rivers is much higher now than it was in 1974, as shown by impressive rebound of aquatic life and by the broad suitability of our waters for domestic use, recreation, and agriculture. The Clean Water Act was amazingly effective. It was badly needed, and it led to water quality improvement practices that have not been overly burdensome.


Q: Did the Clean Water Act regulate nutrients?

A: Because of the Clean Water Act, cities changed their treatment practices greatly and many problems that were present in 1974 are now resolved. However, there was one very important omission: nutrients. The Environmental Protection Agency, as well as the public, thought it was most important to focus first on pollutants that are toxic to aquatic life or to humans, and on pollution of water with excessive organic matter that decays in aquatic ecosystems. Also, the scientific basis for nutrient control was weak when the Act was first implemented. But now the EPA has notified the states that there will be national requirements for nutrient control. The regulations are being developed and Colorado is adjusting to nutrient limitation. Control of nutrients will require large investments because humans mobilize large amounts of nutrients.


Lake Dillon in the fall. Photo: Center for Limnology

Q: You and your team have been collecting information on of Lake Dillon (and other lakes and rivers) for over 35 years now. What is the value of these long, unbroken data records?

A: Lakes show much variability from year to year, which means that the functioning of a lake is best understood on the basis of extended study. Also, trends in lakes, such as those caused locally by humans or by broader forces such as climate change, can only be seen clearly through the lens of a long record.


Q: Why did you focus on Lake Dillon specifically?

A: I started a long term study of Lake Dillon in 1981 because the State and the EPA wanted the lake to be studied. It was in very good condition at that time, but the watershed, which lies in Summit County, was developing rapidly. The regulators wanted a forecast of future deterioration of water quality, especially with reference to nutrients. They also wanted to know what measures were needed to hold the lake in a stable state.


Q: In addition to Colorado, where else in the world have you studied aquatic ecosystems?

A: I have studied lakes, streams, and rivers in the Philippines, Laos, Puerto Rico, and the Orinoco Basin of Venezuela.


Orinoco River, Venezuela. Photo: Luis Alejandro Bernal Romero, Flickr

Q: Of those places, what is your favorite?

A: The Orinoco River of Venezuela and Columbia is the world’s third largest river by discharge, and is almost entirely pristine. It is a river that looks now the way it did 500 years ago. Its floodplain margins are occupied by hundreds of natural floodplain lakes.


Q: Coming back to our state: What is your favorite lake or river in Colorado?

A: Among lakes, I favor Lake Dillon, a reservoir in a spectacular setting, and Grand Lake, our largest natural lake, also in an extraordinary place. Flowing waters of great beauty in Colorado are so many that I cannot call out just a few, but I do like very much the Colorado River and the Roaring Fork.


Q: What are the most misunderstood or little-known facts about Colorado's aquatic ecosystems?

A: It is difficult to appreciate that nutrients, which stimulate the growth of plant life, can be very damaging to aquatic ecosystems. We think of nutrients in terms of human well being as seen in the benefits of nutrients for agriculture and landscaped properties. Algae that receive these same nutrients become abundant in nuisance proportions, and in doing so degrade aquatic ecosystems. Water managers and ecologists are aware of this problem, but the public is less aware of it.


Q: In today’s world—with many aquatic ecosystems altered by human influence—can we have optimism that these environments can recover from degradation?

A: In most of the developed world, improvements in water quality and conditions for aquatic life have been quite remarkable in the last 30 years, which is reason for optimism about our ability to reverse damage and prevent further damage. Past improvement of water quality is a great example of science, management, public money, and smart legislation applied successfully to problems whose resolution gives a net benefit to society.

CIRES is a partnership of NOAA and CU Boulder.

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