A macrosystems study of global chloride trends, drivers, and ecological impacts in lakes

HILARY DUGAN; SARAH BARTLETT; SAMANTHA BURKE; JONATHAN DOUBEK; FLORA E. KRIVAK-TETLEY; NICHOLAS SKAFF; JAMIE SUMMERS; KAITLIN FARRELL; IAN MCCULLOUGH; ANA MORALES-WILLIAMS; DEREK ROBERTS; FACUNDO SCORDO; ZUTAO OUYANG; PAUL HANSON; GRACE HONG; KATHLEEN WEATHERS

Chuncheon

Workshop; GLEON 17 Chuncheon, South Korea; 2015

Global Lake Ecological Observatory Network - Korean Society of Limnology - Kangwon Nation University - National Institute of Ecology - National Institute of Environmental Reserch - Korean Environment Corporation - National Science Foundation

Chloride is naturally occurring in freshwater lakes but can have adverse ecological impacts if concentrations rise above background levels. Many lakes worldwide have experienced increased chloride concentrations in recent decades. Regional drivers include natural processes (e.g., sea salt deposition and drought) and anthropogenic influences (e.g., runoff from road salt and agricultural fertilizer, and discharge of industrial effluent). While lake chloride trends and drivers have been studied at the watershed scale, there have been few regional trend analyses. We have compiled a dataset of long-term (> 10 years) chloride concentrations in over 500 freshwater lakes, ponds, and reservoirs worldwide (>0.04 ha), predominantly in the United States, Canada, and Europe. The geographic and morphometric range of lakes in this dataset allows us to assess the influence of lake and watershed parameters, ecoregion, climate, near-shore road density, and coastline proximity on relative changes in chloride concentrations. In the United States, we generally find urban lakes have strong positive trends in chloride concentrations, whereas remote lakes have stable or decreasing chloride levels. In states with seasonal road-salt application, the percent impervious surface, a proxy for road density, within 200 m of a lake is strongly correlated with increases in chloride. Additionally, preliminary analyses indicate potential threshold effects of chloride concentrations on phytoplankton and zooplankton communities. At high chloride concentrations, we find significant decreases in planktonic abundance and richness. The water quality and plankton ecology of freshwaters worldwide are vulnerable to changing salt concentrations; proper management is crucial to reduce or maintain lake salt concentrations.