OKEECHOBEE — Scientists, anglers and Lake Okeechobee residents would like to see more testing of the waters of Lake Okeechobee. Environmental groups and coastal residents have also called for more testing.
To solve the concerns about cyanobacteria (also known as blue green algae) in the big lake, more information is needed about where, when and what kind of blue-green algae is present in the 730-square-mile lake.
Currently the South Florida Water Management District conducts water sampling from 17 stations on Lake Okeechobee. SFWMD tests for microcystin, a toxin that can be produced by some kinds of cyanobacteria known to live in the big lake, from six stations on the lake each month.
Mike Krause, at Okeechobee Fishing Headquarters, said fishing guides would welcome more testing. He believes more tests would prove that Lake Okeechobee’s waters are safe for both the humans and the fish.
Dr. Paul Gray of Florida Audubon, is also calling for more tests. He said he hopes the state’s new task force on blue-green algae will recommend funding for regular weekly testing of the lake’s waters on a grid patter with at least 20-30 sample sites.
The Florida Department of Environmental Protection only collects and tests samples when an algal bloom is reported. The occasional samples done when algal blooms are reported are not enough to provide the data needed to really understand the algal blooms and the extent of toxins present (if any), said Dr. Gray.
The National Oceanic and Atmospheric Administration satellite imagery predicts concentrations of cyanobacteria based on chlorophyll levels. But clouds can obscure the lake when the satellites pass over, so NOAA does not get a usable image every week. The NOAA images cannot determine what kind of cyanobacteria is present nor can NOAA tell if the cyanobacteria present is one of the types capable of producing toxins. The NOAA images do not predict toxins. Lake Okeechobee is home to about a dozen types of cyanobacteria, according to University of Florida studies, but only a few are capable of producing toxins. Another factor to consider: Cyanobacteria that is capable of producing toxins does not always do so.
The photographs taken by the satellites can show algae on the surface, but that blur of green on the image is a combination of other algae and blue-green algae. Without testing there is no way to tell if that green spot includes cyanobacteria or not.
Another reason regular testing is warranted — even when no blue-green algae is visible — is that Lake Okeechobee is fished both by recreational fishermen and commercial fishermen. According to the Florida Fish and Conservation Commission, more than a million pounds of fish is harvested from the lake each year by commercial fishermen for sale to fish houses and restaurants.Many winter visitors enjoy fishing for – and eating – Speckled Perch. Some low-income lake area residents also catch fish year round to supplement the family’s food supply.
Earlier this week, U.S. Congressman Brian Mast introduced legislation that would “require the U.S. Army Corps of Engineers to prioritize public health, including prevention of toxic cyanobacteria, the integrity of the Herbert Hoover Dike, Everglades restoration and tribal water quality laws.” Rep. Mast wants the corps to consider whether or not the lake water contains toxins before releasing it to coastal estuaries. Without a system of regular testing, the corps would have no way to know if the water contains toxins.
Most samples taken from Lake Okeechobee this summer by FDEP had no toxins or very low levels of toxin, well below the 8 micrograms per liter level set this year by the Environmental Protection Agency as safe for human contact. Previously, the World Health Organization set the level for human recreational contact at 10 micrograms per liter.
A single sample, taken June 5 about 10 miles southwest of Port Mayaca tested above the safe level with microcystin content of 17.6 micrograms per liter. Microcystis aeruginosa was dominant in the sample. A sample taken closer to Port Mayaca that same day was mixed algae and had no microcystin. A sample taken June 5 at Port Mayaca had 1.48 micrograms per liter microcystin. Microcystis aeruginosa was dominant in that sample.
The large algal bloom near Port Mayaca had disappeared by the following week. On June 12, a sample taken at the Port Mayaca Lock had 1.08 micrograms per liter of microcystin.
Since June 12, only three samples were taken from Lake Okeechobee.
On June 17, two samples were taken of an algal bloom at the water control structure at Canal Point. Microcystis aeruginosa was dominant in both samples. One sample had 4.95 micrograms per liter of microcystin. The other had 6.35 micrograms per liter. The bloom was impounded against the control gates and was about 12 meters wide.
On June 20, a sample was taken near the lock at Port Mayaca. Tests showed it was mixed algae with no dominant species.