Remotely Detecting Harmful Algal Blooms in the Great Lakes

Remotely Detecting Harmful Algal Blooms in the Great Lakes

The National Aeronautics and Space Administration (NASA) Glenn Research Center partnered with the National Oceanic and Atmospheric Administration’s (NOAA) Great Lakes Environmental Research Laboratory and the State of Ohio to address the recurrence of harmful algal bloom (HAB) events in the Great Lakes.

Generally within a 4- to 8-week period in late summer, HABs pose a significant threat to humans and wildlife, form, spread, and then disappear. HABs commonly contain a toxin called microcystin, which poses a threat to human health and wildlife. For humans, microcystin can cause serious liver damage and has been linked to pansteatitis, a condition in which body fat becomes inflamed. Some scientists suggest a link between the presence of microcystin in drinking water and some forms of liver and colorectal cancer.

The toxin also can cause mass deaths of fish, and consuming them proves harmful. Early detection can minimize threats of toxic drinking water, provide alerts to close recreational areas around the Great Lakes, and decrease the potential for toxic fish entering the marketplace. Current remote sensing technologies used to monitor these events are limited. High-resolution satellite data (i.e., Landsat) provide spatial data, but are not capable of providing the spectral resolution needed to differentiate a HAB from a non-harmful algal bloom. Water sampling methods, which are time-consuming and expensive, had been prevalent.

The NASA-NOAA-Ohio collaboration used a hyperspectral imager mounted to NASA research aircraft. Hyperspectral imaging divides the electromagnetic spectrum into a multitude of bands that can be used to identify a spectral “signature” for a range of organism types. Hyperspectral imaging was used to detect the pigment phycocyanin, an indicator of microcystis, in low concentrations. NASA aircraft flew several missions over the Great Lakes while NOAA collected water samples for direct comparison. The hyperspectral imager scanned several sites in the central and western basins of Lake Erie, documenting concentrations of the algal pigment phycocyanin. The teams calibrated the results between the aerial remote sensing and the water sample measurements.

The close match suggested the unique hyperspectral signature for HABs, potentially allowing scientists to identify their formation early and reliably through remote sensing. The Great Lakes are the nation’s most important freshwater resource, with more than 60 million people in the region utilizing them for drinking water, transportation, recreation, food production, and manufacturing.

The Great Lakes:

  • Contain over 80 percent of the U.S. supply of surface freshwater
  • Contain 18 percent of the total global supply of freshwater
  • Provide more than 500 beaches for recreation • Supply drinking water to more than 40 million U.S. and Canadian citizens
  • Provide 56 billion gallons of water daily for municipal, agricultural, and industrial use.

These numbers demonstrate the imperative nature of monitoring the Great Lakes to address toxic conditions and underscore the importance of improved technologies to do so.