Remotely sensed cyanobacterial intensity predicts likelihood of lake blooms and toxins across the contiguous US

Cyanobacterial harmful algal blooms (CHABs) can produce toxins that impair freshwater ecosystems used for drinking water, recreation, and habitat for aquatic biota. With CHABs increasing in extent and intensity globally, water managers need information about how to prioritize lake monitoring. We combined the Cyanobacterial Assessment Network (CyAN) remote sensing data with the U.S. EPA National Lakes Assessments completed in 2007 and 2012 to predict the likelihood of measuring CHABs in lakes across the U.S. We use logistic regression modeling to relate the likelihood of lakes exceeding health recommendation thresholds associated with CHABs based on summer bloom intensity as measured by CyAN. We then used the model to extrapolate the likelihood of exceeding risk thresholds to all lakes monitored via CyAN. We find that the interannual mean bloom intensity from CyAN can be used to estimate the relative risk of lakes exceeding thresholds for cyanobacteria cell density, microcystin, and chlorophyll a during the period of 2007-2012. Such information can help inform setting priorities for lake water monitoring in regional contexts.

Impact/Purpose

Cyanobacterial harmful algal blooms (CHABs) can produce toxins which impair freshwater ecosystems used for drinking water, recreation, and habitat for aquatic biota. With CHABs increasing in extent and intensity globally, water managers need information about how to prioritize lake monitoring. This presentation to the contacts at the Oregon Health Association highlights an analysis from Pacific Ecological System Division scientists that combines data from the remote sensing Cyanobacteria Assessment Network (CyAN) and the National Lakes Assessments completed in 2007 and 2012 to predict the likelihood of CHABs. By developing models based on the subset of lakes that are captured in the CyAN data and those that are sampled in the NLA, the likelihood of exceeding health thresholds associated with CHABs can be extrapolated to all lakes monitored via CyAN. The state leads in EPA Region 10 that are responsible for harmful algal bloom monitoring and management are the audience for this presentation. Their feedback on this analysis is invaluable to creating a product that helps managers set lake monitoring priorities.

Citation

Handler, A., J. Compton, Ryan A Hill, AND S. Leibowitz. Remotely sensed cyanobacterial intensity predicts likelihood of lake blooms and toxins across the contiguous US. EPA Region 10 State HABs Leads Meeting, NA, April 15, 2021.