A combination of rotting fish and algae blanketing the bottom of the Gulf of Mexico is creating a dead zone off Southwest Florida, two scientists say.
“Nothing is what we saw,” said Florida Gulf Coast University researcher and professor Bob Wasno, who dove in the Gulf recently. “We went out to Edison reef and everything was dead. For the hour dive we did, we saw three snapper and three porkfish, and quite frankly they looked pretty lost.”
Wasno said everything from sand dollars to sea urchins and coral are now dead offshore.
Red tide has enveloped the area since October but has been particularly bad this summer.
The county and islands have collected millions of pounds of fish and sea creatures after a large Red Tide outbreak. Where does it go in the end? Fort Myers News-Press
Millions of pounds of fish and sea life have been collected from Lee County beaches and shorelines in the past several weeks.
Hundreds of sea turtles, dozens of manatees and dolphins and even a whale shark have been recovered from local beaches this summer.
The dead animals are starting to pile up on the sea floor.
“The whole floor of the reef site was covered in a rose-colored flocculate, it just looks like snot across the bottom,” Wasno said.
A dead zone is an area of water with oxygen levels too low to support most marine life. It’s basically an area where the marine food chain has stopped working.
“There are some pockets of hypoxic (or anoxic) conditions out there,” Wasno said. “The algae dies and the fish die and the process of decomposition takes up a lot of oxygen. That’s most likely the reason behind these hypoxic zones. They get you coming and going. First comes the red tide and then the hypoxia.” Hypoxia refers to very low oxygen and apoxia to the absence of oxygen.
Although local beaches have at times been blanketed with dead wildlife, that’s only a fraction of what is actually being killed by the massive red tide.
The rest is either floating at the surface offshore or is at the bottom of the Gulf.
And the dead sea life, along with the algae, is causing even more death.
“The bloom is killing things and as they decompose on the bottom they’re taking up oxygen,” said Rick Bartleson, a water quality scientist with the Sanibel-Captiva Conservation Foundation. “That’s typical dead zone conditions.”
Bartleson said he and others measured an area about 25 square miles in size that showed hypoxic, or dead zone conditions.
“Thursday we were Southwest of Sanibel and we found anoxia from 30 feet to about 20 feet, so that’s 10 feet of depth with no oxygen on the bottom,” Bartleson said.
Typically water from the bottom would mix with the upper layers, which oxygenates that water.
But heavy releases from Lake Okeechobee and runoff after events like Tropical Storm Gordon are keeping the layers from separating because fresh and saltwater don’t mix well.
‘The surface water is fresher,” Bartleson said. “A lot of freshwater goes out into the Gulf and that’s increasing the stratification of the water, so there’s not a lot mixing.”
Counts along the Southwest Florida coast have ranged from natural, background conditions to 1 million cells per liter and higher.
Fish kills and breathing irritation in humans can start when levels reach 10,000 cells per liter, according to the Florida Fish and Wildlife Conservation Commission.
Wasno said although local beaches are much cleaner than they’ve been in recent weeks, the red tide is still lurking offshore.
A change in the weather could push the red tide back onshore, and the dead wildlife with it.
‘Eight to 20 miles offshore it was just dead fish littering the surface, of all kinds of makes and models,” Wasno said. “So with the weather we’ve had the last couple of days, we’re not seeing the dead fish (on the beaches) but that doesn’t mean they’re not out there.”