SANIBEL ISLAND, FL (WWSB) - Red tide is visible on Lido Beach about 65 miles north of where discharged water from Lake Okeechobee hits the gulf via the Caloosahatchee River.
We drove down to sanibel island today to find out why that's probably too far to be feeding these particular blooms.
Dr. Rick Bartleson has been startled by the number of red tide cells he's counting daily, or the dead marine life he's been asked to examine.
"It's more than we've seen in past red tide events since I've been here," says Bartleson, who has worked for the Sanibel-Captiva Conservation Foundation since 2006.
The roads to the SCCF Marine Laboratory are lined with trash bags of dead fish and visible red tide algae. Not far is the mouth of the Caloosahatchee River, emptying discharged water -- and most recently toxic blue-green algae -- from Lake Okeechobee into the Gulf of Mexico.
However, Bartleson is one of many scientists saying one algae is not causing the other.
"The blue-green algae isn't causing the red tide to bloom," says Bartleson. "We already had a lot of red tide out there, they already have a lot of nutrient sources."
Red tide experts at Mote Marine Laboratory say Karenia Brevis alga forms offshore, and is a saltwater species unlike the freshwater cyanobacteria forming in Lake O.
Bartleson says it's unlikely Lake Okeechobee water is even coming as far north as Sarasota.
"We have some water that goes up to redfish pass, but it doesn't make it to Boca Grande," says Bartleson. "You definitely don't get it all the way up to Sarasota."
What can end up feeding red tide, though, is something we can't see in the water coming down the Caloosahatchee. High levels of nutrients like phosphorous and iron have been coming down the discharged water this year, according to Bartleson. Phosphorous levels in the lake are high, he says, due to back-pumping water from sugar cane farms to the south. Then, due to a high amount of debris from Hurricane Irma in all lakes, rivers, and estuaries, oxygen levels in freshwater bodies have dropped, causing levels of iron to increase in the water running off into the coast. Both nutrients, phosphorous and iron, can cultivate algae like red tide.
"If you take a glass of phytoplankton, and you add nutrients, you get a bloom in that glass," Bartleson says as an example.
Mote scientists say Karenia Brevis (red tide) can draw nutrients from 12 different sources, so it's very difficult to determine what's inside a specific sample. However, they agree nutrient dumping can lead to unhealthy oceans, and help sustain red tide blooms.
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