The U.S. Environmental Protection Agency (EPA) released the 2012 National Lakes Assessment (NLA) data in December, which are now publicly available online.
Every five years, the EPA launches a comprehensive sampling campaign, where together with state and local governments, tribes, and many other agencies, they sample over 1000 lakes and reservoirs (hereafter, together referred to as waterbodies) across the United States. The final set of waterbodies that are sampled are selected randomly using a statistical survey design to appropriately sample waterbodies that are representative of the U.S. waterbody population across multiple size classes. The first comprehensive survey conducted by the EPA was in 2007, and so this represents the second survey. Approximately 400 waterbodies were resampled in 2012, and approximately 600 were newly sampled waterbodies.
For each sampled waterbody, there are a diverse suite of variables collected and analyzed such as: waterbody morphometric characteristics, lakeshore land use, profiles of e.g. temperature and dissolved oxygen, many water chemistry variables, and phytoplankton and zooplankton metrics such as density and biomass at the genus resolution. Field crews follow standardized protocols at each waterbody, and water samples for water chemistry and plankton counts are analyzed at central laboratories, subjected to multiple phases of quality control.
The EPA uses the data they collect in a variety of ways. One objective is to assess the water quality status of waterbodies in the U.S., and how the water quality may vary between ecoregions. Metrics are calculated to quantify the biological integrity, trophic state, recreational suitability, and any environmental stressors that may be affecting the water quality of each sampled waterbody. Moreover, by collecting data every five years, while resampling a portion of the previously sampled waterbodies, the EPA can determine how the water quality changes through time. After each survey the EPA publishes multiple status reports online for the general public.
Ultimately, the EPA’s NLA represents a unique, comprehensive, and rich dataset that is used by individuals across multiple fields. Researchers can use this dataset to ask novel and multiple-scale questions, as is now being done in the Global Lake Ecological Observatory Network (GLEON). “One of the new frontiers in limnology is asking questions about inland waters at the continental and global scale. Without large datasets, like the NLA, this line of inquiry would not be possible. It is only with the help of national scale endeavors that scientists can pursue this line of research,” highlighted Hilary Dugan, a GLEON member and postdoctoral researcher at the University of Wisconsin-Madison. Emily Read, a GLEON member and Research Scientist at USGS added, “The investment in the 2007 and 2012 NLA by EPA Office of Water far exceeded any sampling effort that would likely be possible by a single institution through traditional funding means. The role of Federal science and monitoring agencies is key to more basic and applied academic research and vice versa.”
Numerous reports, publications, and Master’s and Ph.D. theses have incorporated the EPA’s data. Many GLEONites have used NLA data extensively, including projects that Dugan and Read have been involved in. For example, both cohorts of the GLEON Graduate Student Fellowship Program have used NLA data to address specific research questions. The first cohort published a paper led by Read that used the NLA 2007 data to assess the relative importance of in-lake conditions versus land use and regional controls on water quality parameters across the U.S. One key finding from the study was that lake specific characteristics (e.g., waterbody morphology) were more important in explaining lake water quality than regional factors.
The second GLEON fellowship program cohort is currently analyzing NLA data to examine how changes in waterbody salt concentrations can alter plankton communities. “The data used for this project are entirely derived from the NLA. We leverage the NLA’s extensive spatial variation in lake chloride concentration and plankton community composition to effectively address our research aims,” noted Nicholas Skaff, a Ph.D. Candidate at Michigan State University and member of the second cohort.
In addition to working with the NLA dataset through the GLEON fellowship program, I have used the data on a variety of other projects. I use this rich dataset to ask multiple-scale questions regarding how multiple environmental variables affect plankton communities and water quality in and between natural lakes and reservoirs – projects not possible without the NLA.
The work the EPA has accomplished in championing these nationwide, comprehensive surveys is impressive and greatly appreciated by researchers across multiple fields. The data also are a huge benefit to policymakers and the public, and can be utilized to ask novel and large-scale water quality and ecological research questions, with policy implications. The EPA is set to conduct their third comprehensive sampling campaign this summer, and it will be exciting to have another round of data!
Jonathan Doubek is a Ph.D. Candidate in the Department of Biological Sciences and a fellow in the Interfaces of Global Change at Virginia Tech, and he is co-chair for the GSA.