Thanks to Rich Miller, Steve Wells, Chris Eckley, Sam Cimino, Jeff Brittain, Tim Elder, Meredith Holgerson, Gene Foster, Joe Maser, and David Walters for critical feedback; Jared Anderson, Jesse Klinger, Sean Dinsmore, Zachary Neumann, James Willacker, and John Pierce for field and lab assistance; Stewart Rounds, Chris Deutsch, Mark Chappelle, Kathryn Tackley, and Dan Turner for logistical support; and the US Army Corps of Engineers for site access. Funding support was provided by Portland State University (ALS, MPJ), Sigma Xi (MPJ), the Willamette Chapter of Sigma Xi (MPJ), USGS Environmental Health Mission Area, Contaminant Biology Program (CES), and USGS Water Mission Area - National Water Quality Program (ARS). Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Science of the Total Environment
Freshwater ecology, Freshwater zooplankton -- ecology
Methylmercury (MeHg) bioaccumulation in freshwater aquatic systems is impacted by anthropogenic stressors, including climate change and nutrient enrichment. The goal of this study was to determine how warmer water temperatures and excess nutrients would alter zooplankton communities and phytoplankton concentrations, and whether those changes would in turn increase or decrease MeHg concentrations in freshwater zooplankton. To test this, we employed a 2 × 2 factorialexperimental design with nutrient and temperature treatments. Mesocosms were filled with ambient water and plankton from Cottage Grove Reservoir, Oregon, U.S.A., a waterbody that has experienced decades of elevated MeHg concentrations and corresponding fish consumption advisories due to run-off from Black ButteMine tailings, located within the watershed. Treatment combinations of warmer temperature (increased by 0.7 °C), nutrient addition (a single pulse of 10× ambient concentrations of nitrogen and phosphorous), control, and a combination of temperature and nutrients were applied to mesocosms. The individual treatments altered phytoplankton densities and community structure, but alone the effects on MeHg concentrations were muted. Importantly, we found a significant interactive effect of nutrients and temperature: the nutrient addition appeared to buffer against increased MeHg concentrations associated with elevated temperature. However, there was variability in this response, which seems to be related to the abundance of Daphnia and edible phytoplankton. Nutrients at low temperature were associated with marginal increases (1.1×) in zooplankton MeHg. Our findings suggest that global change drivers that influence community composition and ecosystem energetics of both zooplankton and phytoplankton can alter MeHg pathways through food webs.
Locate the Document
Jordan, M. P., Stewart, A. R., Eagles-Smith, C. A., & Strecker, A. L. (2019). Nutrients mediate the effects of temperature on methylmercury concentrations in freshwater zooplankton. Science of The Total Environment, 667, 601-612.