Craig Williamson

Beyond the Holy Grail: Adding Browning to the Lake Management Paradigm

The holy grail of lake management can be found in the strong relationship between nutrient loading and chlorophyll concentrations. Increase nutrients enough, and you may get harmful algal blooms, cyanotoxins, and dead zones. These events plague western Lake Erie, coastal oceans, and many other inland waters. Yet a recent survey of 2,913 lakes in the USA shows that overall little has changed with either nutrients or chlorophyll in recent decades. In the meantime, lakes in many parts of the world are turning browner due to up to a doubling of terrestrially derived dissolved organic matter. Hot spots of this lake “browning” include northern Europe and northeastern North America. Lake browning is both a good news story involving recovery from anthropogenic acid deposition in response to the Clean Air Act Amendments of 1990, and a bad news story related to climate change and increases in precipitation and extreme storm events. What are the implications of browning for lake management? Reductions in water transparency can increase surface water temperatures, lead to stronger thermal stratification, and contribute to oxygen depletion. Anoxia can in turn stimulate regeneration of phosphorus from the sediments, and combined with warmer surface water temperatures, increase the potential for harmful algal blooms that further decrease water transparency. Both increases and decreases in dissolved organic matter also have important implications for fisheries management. Understanding the causes and consequences of change in water transparency is essential to effective management of water quality, fisheries, and disinfection of parasites and pathogens in lakes.


Craig Williamson is the Ohio Eminent Scholar of Ecosystem Ecology at Miami University in Ohio where he leads the Global Change Limnology Laboratory. His expertise is in the ecology of UV radiation and climate change, with a current focus on the effects of browning on lakes. His research is based at the Lacawac Sanctuary and Biological Field Station in the Poconos of Pennsylvania but extends worldwide. Research questions range from UV effects on the ecology of zooplankton, larval fish, and infectious diseases, to deploying advanced sensors to decipher the sentinel responses of lakes to climate change. He is the Chief Scientific Adviser of the Pocono Lake Ecological Observatory Network (PLEON), an outreach program on public education and monitoring of Pocono lakes. He is active in the Global Lake Ecological Observatory Network (GLEON) where he leads the Climate Sentinels Working Group, and serves on the United Nations Environment Programme Environmental Effects Assessment Panel (UNEP EEAP).

Amina Pollard

Potential Uses of Population-Scale Information from the US National Lakes Assessment

Scientific investigations conducted at different spatial and temporal scales can be complementary. To maximize this potential, we in the scientific community collectively have to work to find connections among approaches, data, and conclusions resulting from studies conducted at different scales. The effort to identify connections includes noting the strengths of different projects and recognizing how this information can be leveraged to develop a more complete understanding. In this presentation I discuss three examples that demonstrate how broad, population-scale information can be leveraged to better understand relative condition and change in lakes. I will provide an overview of the US National Lakes Assessment (NLA) project. The NLA is a collaborative, coordinated partnership project among States, Tribes, and the US Environmental Protection Agency designed to provide national and regional-scale statistics describing select biological, chemical, physical, human use, and watershed characteristics in lakes. Multiple researchers from state and federal agencies as well as universities have used NLA data from a few sites to the full national set to test hypotheses about lake ecology and management, but there are also opportunities to consider the perspective that population-level information can bring to aquatic sciences. The first example leverages national-scale data to examine temporal change in nutrient concentration. In conjunction with comparable national streams data, information from NLA has been used to show population-level changes in total phosphorus concentration across the US. A subsequent study builds on these findings to describes temporal changes in the context of a nutrient – color paradigm in lakes. A second example highlights how population information from different spatial scales can be leveraged to better understand relative condition of lake shoreline habitat. Finally, by connecting an individual lake to the NLA inferences, I highlight an approach for using population information to provide context for local data. These examples demonstrate how population-scale lake data generated by NLA can be leveraged to inform hypothesis generation, strengthen the case for management activity, and understand phenomenon occurring at local scales in the context of large-scale patterns. The views expressed in this abstract are those of the author and do not necessarily represent the views or policies of the US Environmental Protection Agency.


Amina Pollard is an ecologist working in the Office of Water at the US Environmental Protection Agency. She is a graduate from Lawrence University (BA, 1995), Wright State University (MS, 1997), and the University of Wisconsin Madison (Ph.D., 2002). Dr. Pollard leads the US National Lakes Assessment. At the broadest level this survey characterizes select measures of biological, chemical, physical and recreational status of lakes to determine whether conditions are changing over time. She collaborates with scientists and resource managers across the US to implement this survey and to communicate results to diverse audiences. Dr. Pollard’s research explores local and regional environmental controls on the biological assemblages in lakes, streams, and wetlands. The third component of Dr. Pollard’s career involves working at the interface of science and policy locally, nationally, and internationally.