SCCF: Red tide continues to persist on islands, beaches
The worst red tide outbreak Southwest Florida has seen continues to linger on beach fronts up and down the Gulf Coast.
The most recent chart from the Florida Fish and Wildlife Conservation Commission, as of Sept. 26, shows continual high levels of the red tide organism, Karenia-brevis.
“In Southwest Florida, reports of fish kills were received for multiple locations in and/or offshore of Pinellas, Manatee, Sarasota, Charlotte, Lee and Collier counties,” said the online update.
Dr. Eric Milbrandt, director of the Sanibel-Captiva Conservation Foundation’s Marine Laboratory, gave his insight on the red tide events along Sanibel and Captiva, as well as Fort Myers Beach.
“Cell counts are still medium to high on Sanibel,” he said of the red tide testing. “FWC reporting from Sept. 21 indicates that there are still large patches of Karenia in Southwest Florida in the Gulf. The interior waters of San Carlos Bay and Pine Island Sound Matlacha Pass are low to background.”
Milbrandt said the zero oxygen zone is a big reason why dead fish, crabs and other marine life are continuing to wash up on shores.
“Now we are dealing with the effects of the massive mortality of marine life. Many artificial reefs – some that I’ve scuba dived on last Thursday – are completely devoid of fish and invertebrates,” he said. “This is because of large hypoxic zone (zero oxygen) deeper than 15 feet in the lower water column. This layer has unknown size but will not support fish.
“The mortality caused by the red tide toxin resulted in a lot of dead marine life and consequently, a lot of decomposition and oxygen depletion. Algae blooms on their own can cause oxygen depletion as well,” Milbrandt continued. “We continue to sample in the Gulf using dissolved oxygen sensors that measure the entire water column and we’ve measured this layer from Blind Pass to the middle of Estero Island out 10 miles. Other researchers from FGCU are sampling from the Florida Institute of Oceanography research ship this week to help determine the overall size of the hypoxic dead zone.”
He noted that it is “difficult to predict” if Lee County will continue to see drastic fish kills on its shores in the coming months because of the red tide and “dead zones.”
“We observed dead fish near the Sanibel lighthouse on Thursday. The red tide events typically occur this time of year until a strong cold front mixes the Gulf of Mexico. The fronts are typically in November-February,” Milbrandt said. “If you mean drastic as in large numbers like July, I think the initial event killed most of the fish that couldn’t move away. When conditions improve, they will move back or juveniles will be ‘seeded’ from other areas in the Gulf.”
A positive aspect of the most recent developments is that shallow waters have seen a reduction in the red tide organism, while places on Sanibel are showing little to no Karenia brevis.
“Actually the shallow waters have been lower to background this week,” he said. “We’ve looked at samples in Ding Darling NWR (Sanibel) and there are few to no Karenia, while the samples from the Beach (Fort Myers Beach) remain medium to high.”
The next red tide update by the FWC was made available on Sept. 29.