Nutrients and warming temperatures are feeding a bloom of blue-green algae called Lyngbya in area waters, according to scientists with Manatee County.
As has been the case over the last two years, Lyngbya is accumulating in the waters of Robinson Preserve and in the Intracoastal Waterway, Sarasota Bay and Tampa Bay, according to a report by county environmental scientists distributed to county commissioners by Acting County Administrator Scott Hopes last week.
Excessive Lyngbya, a cyanobacterium, is common locally when warm temperatures combine with nutrient-rich waters to form mats, according to the report.
The nutrients phosphorus and nitrogen were contained in the 215 million gallons of polluted water released into Tampa Bay at Port Manatee last month from one of the closed Piney Point phosphate plant’s gyp stack retention ponds. An accidental leak detected on March 26 led to the intentional discharge that ended April 9 and kept the stack from collapsing.
Contact with Lyngbya can result in itching, burning, pain, rash, blisters and cell death, resulting in loss of superficial layers of the skin, according to the report. Airborne toxins from the algae can cause eye and respiratory irritation.
Excessive growth of lyngbya can result in damage to seagrass beds and oyster bars, foul odors, oxygen depletion in the water and fish kills. It also can cause harmful algal blooms such as red tide, also associated with detrimental human health effects. Low levels of red tide were reported last week in Manatee County by the Florida Fish and Wildlife Conservation Commission.
The mats are formed when naturally-occurring Lyngbya on the bay bottom is exposed to increased temperatures, sunlight and nutrients, causing rapid growth, according to the report. Longer days and clear water conditions cause Lyngbya to rapidly produce oxygen, causing bubbles to form and become embedded in its filaments, which makes the algae float to the surface to be carried by tides and winds, sometimes forming mats. Accumulations often increase along shorelines, like Robinson Preserve.
“It is not feasible to remove the extraordinary biomass of Lyngbya during these bloom events on a bay-wide scale,” the report states. “The scale at which removal would have to occur in such a large and open system is not likely feasible and cost prohibitive.”
No cyanotoxins – the neurotoxins produced by blue-green algae – were detected in water samples taken in Tampa Bay on May 4 in response to last month’s Piney Point discharge, according to the Florida Department of Environmental Protection. Results taken from samples on May 6 are pending.
Exposure to cyanotoxins can cause hay fever-like symptoms, skin rashes, respiratory and gastrointestinal distress, and, if consumed, liver and kidney damage, according to the U.S. Environmental Protection Agency.
