Distribution of Cyanobacteria and Microcystin in Lakes of the US Driven by Combination of Lake, Watershed, and Climate Characteristics.
Citation:
Handler, A., J. Compton, M. Dumelle, M. Weber, R. Hill, L. Jansen, M. Brehob, M. Pennino, AND R. Sabo. Distribution of Cyanobacteria and Microcystin in Lakes of the US Driven by Combination of Lake, Watershed, and Climate Characteristics. National Atmospheric Deposition Program Technical and Science Spring Meeting, Madison, WI, April 29 - May 03, 2024.
Impact/Purpose:
Harmful cyanobacterial blooms can produce toxins which impair freshwater ecosystems used for drinking water, recreation, and habitat for aquatic biota. With increased awareness and reporting of cyanobacteria blooms, water managers need information about how to prioritize monitoring locations in surface waters that may be affected. This presentation highlights analyses that combine data from the National Lakes Assessments field assessments and a variety of watershed, climate, and lake characteristic to model the risk of toxic blooms in lakes across the US. This presentation will be to the Critical Loads of Atmospheric Deposition working group of the National Atmospheric Deposition Program which is attended by research scientists and well as practitioners and managers that are concerned with understanding the ecological impacts of atmospheric deposition of nutrients.
Description:
With increasing concerns about freshwater cyanobacteria blooms, there is a need to identify which waterbodies are at risk for developing these blooms, especially those that produce cyanotoxins. To address this concern, we developed spatial statistical models using the US National Lakes Assessment, a survey with over 3500 spring and summer observations of cyanobacteria abundance and microcystin concentration in lakes across the conterminous US. We combined these observations with other nationally available data to model which lake, watershed, and climate factors best explain the presence of harmful cyanobacterial blooms. We found that both higher cyanobacteria abundance and probability of microcystin detection was associated with higher nitrogen and phosphorus nutrient inputs to the landscape, and lakes with a lower baseflow index, shallower depth, and longer fetch. In both models, nutrient inputs were more strongly associated with blooms in the eastern and central portions of the US compared to the west. Additionally, nitrogen inputs were more strongly associated with higher probability of microcystin in deep lakes compared to shallow lakes. Both models had spatial covariance, indicating there are similarities in lakes that are closer in space beyond that captured by the covariates in the models. Models fit data well with squared correlation coefficient between observed and fitted values for the cyanobacteria abundance of 0.48 and an AUC of 0.92 for the probability of microcystin detection. These models help identify which lakes are more vulnerable to harmful cyanobacteria blooms and can help estimate blooms risk in unobserved locations.