Red tide shows up at low levels in the Indian River Lagoon, causing concern for manatees

FWC focus on Indian River Lagoon as feeding efforts continue to save manatees

BREVARD COUNTY, Fla. – In the wake of the worst year for manatee deaths on record, Florida wildlife officials last week found yet another potential killer of the threatened species in the Indian River Lagoon — red tide.

While only at background levels now, the toxic algae’s presence in the sea cow’s most important habitat in Florida portends a tough summer ahead for the threatened species, News 6 partner Florida Today reports.

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The closed, almost stagnant nature of the 156-mile-long lagoon — which has few inlets to let ocean water flush out algae — heightens the risk to manatees and other marine life, should red tide reach bloom levels this summer.

If the algae thickens to concentrations high enough to emit lethal levels of toxins, it could be fatal for the manatees when they broach the water surface to breathe, inhaling the poisons.

It also can sicken, or at very extreme levels, kill bottlenose dolphins. A red tide in Southwest Florida killed at least 174 bottlenose dolphins in that region in 2018, according to the National Oceanic and Atmospheric Administration.

It could also claim the lives of countless fish and other marine life, and can can cause respiratory and neurological symptoms in humans, when the toxins aerosolize in sea spray.

On Wednesday, June 15, the red tide algae, called Karenia brevis, was observed at background levels in a sample drawn from the Indian River Lagoon at NASA Causeway, according to the Florida Fish and Wildlife Conservation Commission data released late Friday

FWC’s testing did not show any red tide off of Brevard’s beaches.

FWC also found background and very low concentrations offshore of Collier County in Southwest Florida over the past week.

“Background” means the level was less than 1,000 cells per liter, which isn’t expected to cause any ill effects. But when levels exceed 1,000 cells per liter, people can experience respiratory irritation and shellfish harvesting can close.

When levels reach more than 100,000 cells per liter, considered a “medium” concentration, fish will die and satellites will pick up the increase in chlorophyll at the water’s surface. At more than 1 million cells, considered “high,” the water turns red and the death toll gets worse.

The advent of red tide in the Indian River Lagoon comes on the heels of last year’s record 1,101 manatee deaths in Florida.

Through June 10 this year, 588 manatees have died, compared with 799 through June 10 last year and a five-year average of 419 for that time frame. FWC suspects most of last year’s manatee deaths were from starvation. This year, 330 manatees have died in Brevard, 56% of the the total.

The deaths rate in 2021 prompted the state agency last winter to embark on a first-ever pilot program to feed manatees lettuce in the wild — from the Florida Power & Light Co. power plant in Port St. John.

In October 2018, red tide rose to “high” levels in Brevard, Indian River, and St. Lucie counties, according FWC sampling, triggering beachside fish kills. The toxic algae caused carcasses of mullet, mackerel, menhaden and ladyfish to wash up ashore.

There have been no reports of fish kills suspected to be related to red tide over the past week.

The next status report will be issued on Friday, June 24.