Algae bloom growing near Port Mayaca; Phosphorus-rich runoff from St. Lucie basin feeding algal bloom near Port Mayaca

OKEECHOBEE — As a bright green algae bloom grew on Lake Okeechobee near Port Mayaca this week, area fishermen did not appear concerned. Algae is just part of the lake’s ecology and it’s common to see algal blooms on the lake, especially when the summer temperatures rise. But large blooms — this year fed by heavy nutrient flow into the lake at Port Mayaca — do raise concerns for water quality experts.

The Florida Department of Environmental Regulation continues to monitor algae blooms on Lake Okeechobee and collect samples everywhere algae blooms are found. So far, all but one of the samples collected on the lake this summer have shown no toxins. One sample collected on July 27 near Indiantown came back at 1.9 micrograms/liter.

Some – not all – blue-green algae can produce toxins, and even those that are capable of producing toxins are not necessarily always producing toxins, explained Dee Ann Miller of the Florida Department of Environmental Protection. You also can’t tell whether algae is producing toxins or not just by looking at it. That is why toxin analysis is performed to see if the algae is producing toxins and if so, at what levels – and why we routinely monitor and retest persistent blooms, she explained.

According to SFWMD records, backflow from St. Lucie Waterway at Port Mayaca is feeding that bloom. The water in the C-44 canal has been backflowing into the lake since June. That water is about three times higher in phosphorus than the water in Lake Okeechobee.

According to SFWMD tests, phosphorus loads in the C-44 water at the C44S80 station (Port Mayaca) were 390 parts per billion (ppb) on July 13 and 297 ppb on July 20. Phosphorus levels in water tested at the S3083 station (on the C-44 canal in Martin County) were 464 ppb on July 5 and 324 on July 17. By comparison, Florida Department of Environmental Regulation reports estimate the phosphorous in the lake water at about 100 ppb.

SFWMD Water Quality Bureau Chief Stuart Van Horn said a large agricultural area in Martin County contributes to the high nutrient levels in the runoff into the C-44 canal. He said phosphorus levels in recent flows are typical for that watershed.

“The water in Lake Okeechobee is a little over 100 pbb phosphorus,” he explained. “Any of the watershed discharges with high phosphorus concentrations are going to provide a food source for the algae.

“The C-44 discharge is part of that food source.”

Other areas with discharges high in phosphorus include Taylor Creek/Nubbin Slough and Indian Prairie.

Earlier this week, the flow from the C-44 into the lake at Port Mayaca was more than 1,000 cubic feet per second (cfs). On Thursday, the flow was 739 cfs.

No water has flowed through the Moore Haven lock in either direction since the start of the rainy season.

“Because reducing nitrogen and phosphorous levels can help decrease the intensity and duration of algal blooms, in addition to algal bloom monitoring and response, DEP is actively working with other agencies and local governments to identify and implement restoration projects to improve water quality. This includes Everglades Restoration projects as well as restoration projects in the Lake Okeechobee, St. Lucie and Caloosahatchee basins,” Ms. Miller stated.

Tracking the blooms

The Florida Department of Environmental Protection website (https://depnewsroom.wordpress.com/algal-bloom-sampling-results) provides daily updates on algal bloom reports and testing. So far, no toxins have been detected in Lake Okeechobee.

Even without the unusual water flows this year, it is likely there would be algae blooms on the lake.

According to the Florida Department of Environmental Regulation, blue-green algae, or cyanobacteria, is a type of bacteria found naturally in freshwater environments. This bacteria is a microorganism that functions like algae or a plant in that it feeds through photosynthesis and derives its energy from the sun. Blue-green algae can be found all over the world, and occur in Florida’s freshwater and brackish habitats, such as lakes, rivers and estuaries.

• On June 28, an algae bloom was reported in Lake Okeechobee, Latitude 27.0840, Longitude -80.8561 (several miles offshore, south of Buckhead Ridge.) FDEP took water samples. The dominant algae was Dolichospermum circinale; while this species of algae is capable of creating a toxin, no toxins were detected in the water. Dolichospermum circinale does not form mats; it may form small clusters or filaments.

• On July 17, an algae bloom was reported in Indian River Lagoon south of the Sebastian Inlet. The dominant taxon was identified as Lyngbya majuscula. No toxins were detected.

• On July 18, the Florida Department of Environmental Regulation responded to a surface algae bloom reported in Lake Okeechobee in Glades County (several miles offshore, south of Brighton Seminole Reservation). The dominant algae was Dolichospermum circinale. No toxins were detected.

• On July 24, an algae bloom was reported on Lake Okeechobee, Latitude 26.9072, Longitude -80.6596 (south of Port Mayacca). FDEP found the dominant taxon is Microcystis aeruginosa. No toxins were detected in the water.

• On July 27, an algae bloom was reported on Lake Okeechobee near Taylor Creek. The dominant taxon was identified as Microcystis aeruginosa. No toxins were detected.

• On July 27, an algae bloom was reported on Lake Okeechobee near Indiantown. Dominant taxon was Microcystis aeruginosa. Total microcystin was 1.9 micrograms per liter. (Levels above 10 micrograms/liter are considered potentially hazardous.)

• On Aug. 1, an algae bloom was reported south of Port Mayaca. Small algae fragmented clumps were seen within the water. The algae was barely noticeable from the surface. Samples were collected. Results were not available at presstime.

• On Aug. 1, an algae bloom was reported on Lake Okeechobee near Pahokee. The bloom covered about 100 square meters and was described by FDEP as a bright green, continuous, high density bloom. Samples were taken. Results were not available at presstime.

• On Aug. 2, an algae bloom was reported at Central Marine in Martin County.
Report algae blooms

DEP encourages residents and visitors to report algal blooms to help us respond as quickly and efficiently as possible to observed algal blooms. To report an algae bloom, call 855-305-3903.

An algae bloom on Lake Okeechobee near Port Mayaca has turned the water near the shore bright green. Since June more than 22 billion gallons of nutrient-laden water has backflowed into the lake from the St. Lucie watershed at Port Mayaca, feeding the lake’s natural algae and contributing to the spreading bloom. According to SFWMD data, the water entering the lake from the C-44 is three times higher in phosphorus than the lake. Photo by Eric Kopp.

Publisher/Editor Katrina Elsken can be reached at kelsken@newszap.com

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