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SCCF Marine Lab monitoring recent red tide bloom

By SCCF - | Dec 16, 2020

SCCF Red tide sampling on Dec. 3.

Scientists at the Sanibel-Captiva Conservation Foundation’s Marine Lab have been tracking a red tide bloom that came to their attention on Thanksgiving Day, Nov. 26, according to officials.

Satellite imagery provided by SCCF’s colleagues at the National Oceanic and Atmospheric Administration indicated the development and transport of a red tide (Karenia brevis) algae bloom toward Sanibel on Thanksgiving.

The sequence of satellite images showed a large patch that had the optical characteristics of a dinoflagellate bloom. Since the first week of December, volunteers and staff have collected water samples from Bowman’s Beach, Tarpon Bay Road Beach, and Lighthouse Beach. At that time, the number of Karenia brevis, the single-cell dinoflagellate that causes red tide, were low, less than 100,000 cells per liter.

On Dec. 6, counts were high, or 20 million cells per liter at Gulfside City Park beach and at Tarpon Bay Road Beach. The Dec. 8 counts showed 1 million cells per liter, or medium concentration at the Donax Road beach access. The Dec. 9 counts of Karenia brevis on Sanibel beaches were low, coming in at less than 100,000 cells per liter.

A research cruise on Dec. 3 collected samples along six offshore transects from Captiva to the Sanibel Lighthouse. Water samples were collected for microscopic cell counts, nutrient concentrations, and dissolved-oxygen concentrations. Several patches of discolored water were encountered on the cruise and it was later confirmed that there were more than 10 samples with medium concentrations (100,000-1,000,000 Kareniacells per liter) and a few with high concentrations, or greater than 1 million.

The patches were between five miles to 10 miles south and west of Sanibel with the highest concentrations near the Sanibel Lighthouse. The SCCF will continue to follow the satellite imagery, which showed a possible dense patch south of Sanibel, along the southern Lee County coast.

To learn more about red tide, visit www.sccf.org/water-quality/red-tide-resources.