Clay Sprays May Control Harmful Algal Blooms

Harmful algal blooms, or HABs, can harm fish, birds and even people who are exposed to the toxic algae. HABs come in many forms, including a red tide that regularly affects Florida waters, a brown tide organism, and Pfiestera piscicida, an algae associated with fish kills. Scientists are unsure of exactly what causes the blooms, but a Woods Hole Sea Grant research team may have come up with a way to treat the increasingly common occurrences. Don Anderson and Mario Sengco are testing the use of clay to manage and control HABs. Clay, mixed with seawater, is sprayed over the algal bloom, where it binds with the harmful organisms and sinks to the bottom. In laboratory experiments meant to mimic field conditions, results showed that the clay removed 80 to 90 percent of the toxins in 2-hour treatments.

Korea and Japan have used clay to control HABs periodically. In Korea clay is used mainly in aquaculture operations, which provide about 30 percent of Korea’s fish. The concept has not caught on yet in the U.S., mainly due to water quality concerns. The WHOI project uses only native clay types, many of which come from the Florida coast in the Gulf of Mexico. Further research on water quality issues and the future feasibility of clay use to treat HABs is currently taking place. CONTACT: Mario Sengco, WHOI Sea Grant, Postdoctoral Investigator, Biology Department, WHOI, 508-289-2749, Email: msengco@whoi.edu