Tracking Lake Okeechobee muck may help state deal with green slime
Tracking muck from Lake Okeechobee as its waters flow east and west to the St. Lucie and Caloosahatchee rivers can shed light on a much-hated Florida problem: harmful algae blooms.
The South Florida Water Management District will invest about $1 million over the next four years to study how sediment moves to the coastal estuaries, carrying nutrients that fuel the green, stinky stuff that has repeatedly tainted the lake and rivers on both sides of the state.
Measuring nitrogen and phosphorus levels and figuring out how these nutrients are transported downstream is crucial to combating the blooms and improving water quality in Florida’s increasingly slimy waters. The District said that while there are studies on Lake Okeechobee and estuary sediments and their dynamics, there’s no research focusing on sediment discharges to the Caloosahatchee and St. Lucie rivers.
“We know by your own data that there is a lot of silt and sediment that enter the estuaries,” Mark Perry, executive director of the Florida Oceanographic Society in Stuart, told board members during the District’s monthly meeting on
Thursday. “We are all very concerned about this and applaud the District’s efforts.” He added that over the last 10 years data showed 205,000 metric tons of sediment has been transported to the rivers.
Fine-grained sediments like silt, muck and other small particles cover 44% of the total bed area of Lake Okeechobee and can be suspended by wind and waves, carrying downstream the main food source for algae, the district said. The new study will be conducted in cooperation with the U.S. Geological Survey.
During the 2018 summer of slime, Lake Okeechobee was smothered by thick layers of green gunk, harmful blue-green algae blooms that killed fish and contaminated the water with microcystin, a toxin produced by algae that can stay in the water for months and leads to liver damage and gastrointestinal and respiratory illnesses in people. Another toxin known as BMAA has been associated with brain diseases in marine animals, according to a study that found the substance in the brains of dead dolphins from Florida.
Water in Lake O has a high concentration of nutrients because of runoff from surrounding agricultural lands, urban storm-water reservoirs and septic tanks. The lake is a key water source for South Florida, used to replenish drinking water supplies for some communities and for irrigation by farmers. It’s also the heart of the Central Everglades region and a gatekeeper between the watershed from the north and the southern Everglades.
But managing the lake is tricky, and water discharges have often done more harm than good. Two years ago, releases from Lake O coincided with a red tide that swept up and down the Gulf Coast, filling beaches with dead fish and other marine life. Scientists say the polluted lake water flushed down the Caloosahatchee River likely exacerbated the phenomenon.
For the past few years the state has launched efforts to better understand what exactly causes these blooms and has implemented surveillance infrastructure to measure nutrients in the water. Last year, a BlueGreen Algae Task Force, an advisory board, was created to help the state Department of Environmental Protection deal with the problem.
Blue-green algae was found in some water samples tested by the Department of Environmental Protection in early July, though no toxins were present in the samples. There were 37 reported site visits from July 2 though July 9, with 36 samples collected. Algal bloom conditions were observed at 17 sites, the
DEP said.
Between July 6 and 8, the District staff performed routine monitoring on Lake Okeechobee and observed algal bloom conditions at 14 of the 28 stations they visited.