WEST PALM BEACH — The South Florida Water Management District (SFWMD) and the Florida Department of Environmental Protection (FDEP) continue to routinely sample water from Lake Okeechobee to check for cyanobacteria (commonly called blue-green algae) and microcystin toxins that are sometimes produced by cyanobacteria.
On Aug. 5, South Florida Water Management District staff collected samples from 28 locations on Lake Okeechobee. No microcystin toxins were detected in 11 of the samples. Barely detectable “trace” levels of toxins of less than 1 part per billion (ppb) were detected in 11 of the samples.
The Environmental Protection Agency (EPA) considers levels below 8 ppb to be safe for human recreational contact. According to the EPA study, this level is based on the assumption a small child might accidentally swallow water while swimming in a freshwater lake, pond or river.
Four locations found levels of more than 1 ppb and less than 4 ppb. Two samples had toxin levels above the level considered safe for human recreational contact. The sample from L004 site test found 28 ppb microcystin. The L004 site is in the Martin County portion of the lake, about 6 miles west of Port Mayaca. The sample from the LZ40 test site had 24 ppb. The LZ40 sample site is about 12 miles offshore, near the center of the lake, in the Palm Beach County portion of the Big O.
Microcystis aeruginosa was the dominant taxon in all of the samples with total microcystin levels greater than 1 ppb. Two stations that had trace levels of total microcystins were dominated by Cylindrospermopsis raciborskii. The U.S. Geological Survey has documented 28 different species of cyanobacteria on the Lake Okeechobee Waterway. About 25% of cyanobacteria are capable of producing toxins. Even cyanobacteria capable of producing toxins do not always do so.