Cyanobacterial harmful algal blooms (CyanoHABs) are serious environmental, water quality, and public health issues worldwide. CyanoHABs produce toxins and odorous compounds that can adversely affect public drinking water supplies, as well as recreation, fisheries, and tourism.
A method to systematically derive quantitative information on spatiotemporal distributions of CyanoHAB magnitude is needed, to allow for effective evaluation of recreational and drinking water lakes. In this study, we present a method for estimating CyanoHAB magnitude in freshwater lakes using satellite observations.
CyanoHAB magnitude was estimated as the spatiotemporal mean of satellite-derived areal CyanoHAB biomass, which is calculated from Medium Resolution Imaging Spectrometer (MERIS) and Ocean Land Color Imager (OLCI) sensors. CyanoHAB magnitudes in all satellite-resolvable Contiguous United States (CONUS) lakes were calculated for the entire MERIS (2003 - 2011) and OLCI (2016 - present) time series. These CONUS lakes were further ranked based on median magnitude over the years.
More than 2,000 lakes were evaluated, with the majority of these lakes in Minnesota, Maine, Michigan,Texas, and Florida. About 40% of all the lakes had CyanoHAB magnitude of potentially high risk (based on World Health Organization guidelines), compared with 1/3 of lakes in the National Lake Assessment having cyanotoxins. These lakes were found in all regions of the country.
Ranking of lakes provides actionable insight, which can be used by water quality managers to prioritize management strategies. The same method could be transferred to other geographic regions and therefore be applied to lakes around the world for assessing CyanoHABs.