LAKE OKEECHOBEE — What effect will the wind and rain from Hurricane Dorian have on Lake Okeechobee? It’s too soon to tell.
The winds and rain associated with Hurricane Dorian made it impossible for NOAA to get reliable satellite images. The most recent available image is from Sept. 1, and NOAA notes that it may not be accurate due to the winds at the time the image was taken.t
For the week before the storm (Aug. 23-29), NOAA satellite imagery for Lake Okeechobee indicated that “bloom potential” appeared to be covering approximately 35% of the lake, with the heaviest bloom potential then appearing in the southern portion of the lake, according to the Florida Department of Environmental Regulation report. “Bloom potential” means the satellite image detected levels of chlorophyll in the water that indicate a probable concentration of cyanobacteria. Cyanobacteria, often called “blue green algae,” can be present when it is not visible to the human eye.
The South Florida Water Management District collected samples at the Franklin Lock on the Caloosahatchee River on Aug. 26, and from the St. Lucie Canal on Aug. 28.Toxins were not detected at Franklin Lock. The S-308 structure sample was dominated by Microcystis aeruginosa and only trace levels (0.27 ppb) of total microcystins were detected.
DEP collected samples at four locations in the southern portion of Lake Okeechobee on Aug. 28 in areas with the highest bloom potential. Algae was observed in the water column and on the surface at the time of collection. All four samples were dominated by Microcystis aeruginosa. Total microcystins in the were 192.9 ppb, 71.75 ppb, 26.33 ppb and 1.1 ppb. Of those samples taken in the bloom area in the south portion of the lake that day, the sample with the lowest level of toxins was taken at the Pahokee Marina.
South Florida Water Management District revisited the St. Lucie Lock Aug. 29 and observed “green layer on the surface of the water moving upstream.” Tests indicate it was a mixed algae bloom with no dominant species.
No water from Lake Okeechobee has been released to the St. Lucie Canal since March. For most of the wet season, water was backflowing from the St. Lucie Canal into Lake Okeechobee at the Port Mayaca Lock because the water level in the canal was higher than the water level in the lake. That water control structure is driven by gravity flow. Since the middle of August, Port Mayaca has been closed with no flow either direction. In anticipation of Hurricane Dorian, the U.S. Army Corps of Engineers allowed some flow from the St. Lucie Canal through the St. Lucie Lock in order to lower the water level in the canal in anticipation of local basin flooding from the storm. All of the water that has flowed through the St. Lucie Canal since March is local basin runoff.
FDEP staff continues to monitor blooms in the New River area near Fort Lauderdale. A sample collected at West Canal and 16th was dominated by Microcystis aeruginosa and had a total microcystin concentration of 0.79 ppb, according to the report.
“Different types of blue-green algal bloom species can look different and have different impacts,” the report states. “However, regardless of species, many types of blue-green algae can produce toxins that can make you or your pets sick if swallowed or possibly cause skin and/or eye irritation due to contact.
“We advise to stay out of water where algae is visibly present as specks, mats or water is discolored pea-green, blue-green or brownish-red,” the report continues. “Additionally, pets or livestock should not come into contact with the algal bloom-impacted water, or the algal bloom material or fish on the shoreline.”