A toxic, red algae bloom has left a trail of dead fish, fleeing tourists and abandoned beaches along 240km of southwestern Florida coastline, prompting the governor to issue a state of emergency.

Toxins released by the algae have poisoned dolphins, manatees, tonnes of fish and even contributed to the death of an 8m-long whale shark. The deluge of dead and rotting wildlife strewn across beaches has threatened to upturn the vital Florida tourist season.

Governor Rick Scott, (R), said yesterday that he was allocating US$100,000 in additional funds to scientists cleaning up the expanding swath of affected Gulf Coast waters. He also diverted half a million dollars for local communities and businesses that have seen tourists vanish as the pungent smell of the algae and dead animals permeates the summer air.

Scott has stepped up efforts to clean up Lee County with an additional US$900,000 in funds, a news release said. The county straddles a high concentration of algae tracked by Florida wildlife officials and had received relief funds. A severe algae tide prompted a state of emergency in 2016 for similar reasons.

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Red algae collects in seawater for most of the year, but the last two months have produced a non-stop assault of high concentration for reasons that have eluded researchers, said Kelly Richmond, a spokeswoman for the Florida Fish and Wildlife Conservation Commission.

The toxins can aerosolise in the wind that drifts ashore, triggering respiratory problems or worsening conditions like asthma. That has compounded the urge for many tourists and some locals to flee.

"It's a spiralling effect," Richmond said.

The naturally occurring algae - known as a red tide or red bloom for tarnishing clear water with a red or brown hue when in high concentrations - has affected the shore since last October.

High concentrations of the bloom stretch from Naples in the south to Anna Maria Island in the north, she said.


Officials believe the algae to have been a factor in the deaths of manatees, sea turtles and potentially dolphins, Richmond said today. Scientists also believe the toxins contributed to the death of a whale shark that washed ashore in July on Sanibel Island, which is in Lee County.

It is the first known death of a whale shark caused by red bloom.

Longboat Key has removed five tonnes of dead fish, AP reported, and even big fish like the Goliath grouper and Snook are among the dead species.

Sea turtles have been dying at three times the normal rate this year, and officials have pointed to red tide poisoning. More than 450 stranded and dead sea turtles have been recovered in effected counties, and the Florida Wildlife Research Institute believes as many as 300 died from toxic indigestion, AP reported.

Algae tides have been documented in Florida for centuries, and even Spanish conquerors noted "fish kills" near Tampa, state officials said.