Satellite Imagery Can Track Harmful Algal Blooms

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A joint collaboration between EPA, NOAA, NASA, and USGS scientists has demonstrated that satellite imagery can be used to track the frequency of harmful algal blooms.  The satellites can accomplish this by measuring certain algal pigments in the water.

Harmful algal blooms can occur in all types of surface waters, including the Nation’s lakes and reservoirs. These blooms can affect summer recreation and affect businesses, ruin aquatic habitats and important fisheries, and even cause health risks associated with exposure to the toxins that these blooms can produce. In freshwaters, harmful algal blooms caused by cyanobacteria, also called blue-green algae, are most common. Cyanobacteria can produce cyanotoxins, which pose a range of health risks to humans, pets, livestock, and wildlife. 

 “This research is an excellent example of how we’re using space-age techniques to help address an age-old problem,” said USGS scientist Keith Loftin, one of the CyAN project’s lead scientists. “We are providing the science necessary to identify satellite-based approaches (with acknowledgement of known limitations) that stakeholders can use to efficiently manage resources for the protection of human health.”

Image shows varying pigment levels from a satellite perspective of lakes in the United States
Map of the frequency of observed cyanoHAB occurrence above the World Health Organization (WHO) high threshold for risk of 100,000 cells per milliliter (cells mL−1) in central Florida lakes from 2008 through 2011. A value of 1 indicates that the pixel was observed to have cyanoHABs above the WHO threshold in all observations, and a value of 0 indicates that the pixel had no cyanoHABs above the threshold. Modified from figure 7, Clark and others, 2017.(Public domain.)

Scientists developed a satellite-based approach to assess the frequency of harmful cyanobacterial blooms over time at two test regions that included recreational and drinking-water resources in Florida and Ohio. When verified on the ground, the satellite-approach reliably estimated the frequency of the cyanobacterial blooms, meaning the same approach could likely be used nationwide, particularly as satellites of sufficient resolution and sensing capabilities become available.

In addition, the study looked at the usefulness and limitations of currently available remotely sensed satellite data for identifying the frequency and severity of harmful algal blooms in the Nation’s lakes and reservoirs. The scientists found that the resolution and sensing capabilities of existing satellites were limiting factors in whether or not they could measure the harmful algal blooms in lakes that are greater than 1 hectare (2.47 acres).

Nationwide, cyanotoxins have been implicated in human and animal illness in at least 43 states. In August 2016 alone, at least 19 states had public health advisories because of cyanotoxins, according to the EPA.

 “Toxins from these harmful algal blooms are an issue throughout the country,” said Blake Schaeffer, one of the CYAN Project’s lead scientists. “That’s why we’re putting a focus on developing methods to track the frequency and location of algal blooms using satellite technology”.  

Current satellite sensor technology is not equipped to detect cyanotoxins.  Instead, satellite imagery provides information on algal bloom location and can therefore help scientists and the public health community target specific locations for field crews to test for the presence of algal toxins.

Logical next steps include development of methods for measuring spatial extent and applying those methods nationally to evaluate the frequency and locations and extent of harmful algal blooms in lakes and reservoirs so that resource managers can make informed decisions about bloom prevention and minimization of exposure risk.

This study can be accessed here and is part of a larger effort of the USGS Environmental Health Mission Area to provide information that will help resource managers to understand how to effectively minimize potential risks to the health of humans and other organisms exposed to cyanotoxins and other biogenic toxins through recreational, drinking, and other exposure routes.

This study was supported by the NASA Ocean Biology and Biogeochemistry Program/Applied Science Program, the U.S. Environmental Protection Agency, the National Oceanic and Atmospheric Administration and the U.S. Geological Survey Toxic Substances Hydrology Program.