Stay in the know about wildlife, water quality, and ecosystems on Sanibel and Captiva Islands and in Southwest Florida

Red Tide Counts Down; Lake O Too High

December 7, 2022

Over the past couple of weeks, water quality has been improving with fewer fish kills, increased water clarity, and a reduction of red tide concentrations around Sanibel.

Flows to the Caloosahatchee Estuary from S-79 have been in the optimal flow envelope for 41 days and releases from Lake Okeechobee have begun to supplement flows from the watershed as the dry season progress. The current Lake regulation schedule (LORS08) currently recommends up to 4,000 cfs from S-79.

“However, there is concern that high flows could result in excess nutrient loading which could fuel red tide,” said SCCF Policy Associate Leah Reidenbach, who produces the weekly Caloosahatchee Conditions Report for water managers and policymakers.

On Dec. 3, the US Army Corps of Engineers increased the flow at S-79 to a seven-day average of 2,000 cfs from 1,200 cfs. Lake Okeechobee is high for this time of year after Hurricanes Ian and Nicole so releases, combined with decreased inflow, and increased evaporation can help lower the lake. To decrease flows from the LORS08 guidance, the Corps is utilizing a water banking tool which allows them to reduce flows now and “save” them for beneficial releases (up to 2,800 cfs) later in the dry season when LORS08 guidance falls below 2,800 cfs.

“This will benefit us now by preventing excess nutrient flows and by providing beneficial flows in the dry season,” said Reidenbach. “The drawback to this plan is the Lake is currently too high which is bad for its ecology and fewer outflows lead to a slower rate of decline of lake levels. When Lake Okeechobee is too high during this time of year it can cause the nutrient-rich sediment on the bottom of the Lake to get stirred up, making phosphorous available to blue-green algae.”

The sediment can get washed into the marshes where cattails can take over and outcompete native species. High lake levels also reduce light availability for submerged aquatic vegetation and reduce habitat availability for millions of migratory birds that need shallow water for feeding. There are often many tradeoffs to consider when managing a large system with a diversity of needs.

“We will continue to monitor this dynamic system, which can change rapidly from week to week during these times when tough decisions need to be made,” she said. “The science and data that is generated from the SCCF Marine Lab, our Policy team’s dedication to monitoring and advocating for the Estuary, and our collaboration with stakeholders allow us to give conditions updates and recommendations to the Corps every week in our Caloosahatchee Conditions Report.”

Click here to sign up for the report, which is emailed out every Wednesday afternoon.


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