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Satellite monitoring of cyanobacterial harmful algal bloom frequency in recreational waters and drinking water sources
Clark, J., B. Schaeffer, J. Darling, E. Urquhart, JohnM Johnston, A. Ignatius, M. Myer, K. Loftin, J. Werdell, AND R. Stumpf. Satellite monitoring of cyanobacterial harmful algal bloom frequency in recreational waters and drinking water sources. ECOLOGICAL INDICATORS. Elsevier Science Ltd, New York, NY, 80:84-95, (2017).
Harmful algal blooms are environmental events that occur when algal populations achieve sufficiently high density to result in negative environmental or health consequences (Smayda, 1997). Blooms associated with photosynthetic prokaryotes (cyanobacterial harmful algal blooms, or cyanoHABs) occur worldwide and have been documented across the United States (Loftin et al., 2016). Nationally, many states have issued health advisories or closed recreational areas due to potential risks from cyanoHAB exposure (Chorus, 2012; Graham et al., 2009). CyanoHABs typically result from a combination of excess nutrients (Michalak et al., 2013) and other environmental conditions such as warming temperatures and water column stratification (Paerl and Huisman, 2008). Alterations in land use practices, such as urbanization or agricultural practices, can change sediment loading and increase nutrient delivery in watersheds (Lunetta et al., 2010) known to influence cyanobacterial growth. CyanoHABs produce an array of potential toxins, nuisance odors in recreational and potable waters, cause hypoxia, and surface scums are generally visually unappealing (Codd et al., 2005a). Additional consequences of blooms include economic and infrastructure costs such as loss of revenue in recreational systems, loss of revenue in business that rely on potable water, undesirable potable water, and increased drinking water treatment costs (Dodds et al., 2009; Steffensen, 2008).
Cyanobacterial harmful algal blooms (cyanoHABs) cause extensive problems in lakes worldwide, including human and ecological health risks, anoxia and fish kills, and taste and odor problems. CyanoHABs are a particular concern because of their dense biomass and the risk of exposure to toxins in both recreational waters and drinking source waters. Successful cyanoHAB assessment by satellites may provide a first-line of defense indicator for human and ecological health protection. In this study, assessment methods were developed to determine the utility of satellite technology for detecting cyanoHAB occurrence frequency at locations of potential management interest. The European Space Agency's MEdium Resolution Imaging Spectrometer (MERIS) was evaluated to prepare for the equivalent Sentinel-3 Ocean and Land Colour Imager (OLCI) launched in 2016. Based on the 2012 National Lakes Assessment site evaluation guidelines and National Hydrography Dataset, there were 275,897 lakes and reservoirs greater than 1 hectare in the 48 U.S. states. Results from this evaluation show that 5.6 % of waterbodies were resolvable by satellites with 300 m single pixel resolution and 0.7 % of waterbodies were resolvable when a 3x3 pixel array was applied based on minimum Euclidian distance from shore. Satellite data was also spatially joined to US public water surface intake (PWSI) locations, where single pixel resolution resolved 57% of PWSI and a 3x3 pixel array resolved 33% of PWSI. Recreational and drinking water sources were ranked by cyanoHAB occurrence frequency above the World Health Organization high threshold for risk of 100,000 cells mL-1 in Florida and Ohio. Ranking identified 158 recreational waterbodies, from 2008-2011, with values above the WHO high threshold ranging from <0.1 % of pixels in Kirwan Lake, OH to 99 % of pixels in Lake Apopka, FL. The method presented here may serve as an indicator of locations with higher exposure to cyanoHABs and therefore can assist in prioritizing management resources and actions across recreational and drinking water sources.