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Intensifying Red Tide Threatens Islands’ Recovery

February 22, 2023

By Leah Reidenbach, SCCF Research & Policy Associate

Understanding how releases from Lake Okeechobee are connected to the red tide bloom that has lingered off the Southwest Florida coast since October tells us that it could have been worse if flows weren’t curbed at first. It also tells us that releases may now be fueling the bloom with nutrient loading, jeopardizing the much-needed restoration of our islands’ tourism economy.

Most of all, it tells us that striking a healthy balance between Lake Okeechobee levels, ecology, and safety, and the environmental effects of flows to the Northern estuaries is impossible with the current infrastructure and water management practices. 

Lake Okeechobee levels have an important impact on water flows to the Caloosahatchee River. Since Hurricanes Ian and Nicole, Lake Okeechoobee levels have been too high and were at a level that is designated as the “Intermediate sub-band” by the Army Corps of Engineers in their Lake Operation Release Schedule known as LORS08. Under this operating schedule (developed in 2008), the Corps was directed to release up to 4,000 cubic feet per second (cfs) at S-77 (the lock and dam closest to the Lake) and up to 1,800 cfs at S-80 (the St. Lucie Estuary on the east coast). 

These flows would have caused major environmental issues to both coasts if they had been implemented, which would have further devastated our community after going through Hurricane Ian. Instead of implementing high-volume releases, the Corps utilized a makeup release tool, sending us a 7-day average of 2,000 cfs and “banking” the difference for releases later in the wet season.

After watching the Lake slowly recede for months, it is now in what is designated as the “Low sub-band” and LORS08 directs the Corps to release up to 450 cfs at S-79 and 200 cfs at S-80. However, they are going to continue sending us 2,000 cfs at S-79 and 500 cfs to S-80 to use water that is stored in the bank and to continue to lower Lake levels. 

Unfortunately, despite efforts to curtail high-volume releases to our estuary, we are still experiencing red tide on our coast. While 2,000 cfs is technically within the RECOVER2020 optimum flow envelope for salinity (750 – 2,100 cfs), this performance measure does not account for seasonality or nutrient loading. 

Being at the high end of the flow envelope during the dry season does not mimic the natural reduction of flows that would be seen during the dry season and could potentially interfere with spawning season in March and April. Further, the additional nutrient loading from Lake Okeechoobee could be intensifying the current red tide bloom around Sanibel.

The red tide bloom has been patchy on our coast since October and was exacerbated by runoff from Hurricane Ian. Reports of fish kills this past month have been frequent along Sanibel beaches and reports of mild to severe respiratory irritation have also been reported. 

In the past week, the Florida Fish & Wildlife Conservation Commission (FWC) has detected bloom levels of Karenia brevis in 22 samples in Lee County and the Florida Department of Health has issued health alerts for the presence of red tide near Lynn Hall Park (Fort Myers Beach), Gasparilla Island State Park (Boca Grande Pass), Turner Beach (Captiva), Blind Pass Beach (Sanibel), and Lighthouse Beach Park (Sanibel). Shellfish harvesting areas in Pine Island Sound and Matlacha Pass have been closed due to the presence of K. brevis.

When red tide intensifies, it’s not only bad for wildlife and human health, but it is also bad for tourism. Sanibel is typically viewed as an escape from the overly developed cities of Fort Myers and Cape Coral, and we have just begun reopening our beaches and businesses to the public. Although our beautiful island isn’t recovered, red tide is stymying our ability to bring back the tourism economy that many businesses on Sanibel and Captiva depend on. 

Even with the completion of Everglades restoration, a healthy balance between Lake Okeechobee levels, ecology, and safety, and the environmental effects of flows to the Northern estuaries is not always possible. Achieving that balance is increasingly at the mercy of the weather and a changing climate, requiring an urgent response. 

Water managers must send more water south to the Everglades where it is needed, and more water storage and treatment in the Caloosahatchee watershed are absolutely necessary to buffer periods of high and low flows and reduce nutrient loading. Our islands’ economy and our future depend upon it.

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