Twin Cities WRS Seminar

Using Predictive Lake Modeling to Assess the Development of Cyanobacteria Blooms: Lake ecosystem responses to nutrient stressor gradients


Dr. Erik Smith
U.S. Geological Society

November 10, 2017


The U.S Geological Survey (USGS) has developed mechanistic, bio-physical lake models that simulate trophic dynamics and track changes in algal populations, including dominance by Cyanobacteria. For three deep, cold-water Sentinel lakes, calibrated models captured the trajectories of phytoplankton seasonal succession over time at multiple depths. Model simulations successfully tracked the seasonal dominance of cyanophytes as well as the development of lake-specific algal biomass distributions. Calibrated models were used to evaluate changes in biomass of major algal groups under changing nutrient loading and meteorological stressor gradients. In Lake St. Croix, a multi-basin, riverine glacial scour lake, a calibrated model was able to simulate the spatial and temporal development of a Cyanobacteria bloom that is known to produce algal toxins. Sensitivity analysis of the Lake St. Croix model revealed how specific parameters were driving algal bloom dynamics. Model simulations provided an understanding of how cyanobacterial production and biomass accumulation in Lake St. Croix results from complex interactions between algal physiology, lake stratification, and hypoxia in the deep pools of the lake.

Dr. Erik Smith has been a full-time hydrologist with the U.S. Geological Survey (USGS) since 2005. Erik started with the USGS Iowa Water Science Center, working as a supporting scientist on the USGS Agricultural Chemicals Transport (ACT) project. From 2009-2011, Erik moved to Minnesota to complete work on a PhD in the Water Resources Science program. Since graduating from the University of Minnesota in late 2011, Erik has been a full-time hydrologist with the USGS Minnesota Water Science Center. His current research focuses on CE-QUAL-W2 modeling of several Minnesota lakes (including Sentinel Lakes), turbidity response of Lake Houston to Hurricane Harvey, and groundwater sustainability issues related to water use and agricultural drainage.