TAMPA, Fla., Aug 7 (Reuters) - The largest red tide bloom seen in Florida in nearly a decade has killed thousands of fish in the Gulf of Mexico and may pose a greater health threat if it washes ashore as expected in the next two weeks, researchers said on Thursday.
The patchy bloom stretches from the curve of the Panhandle to the central Tampa Bay region. It measures approximately 80 miles (130 km) long by 50 miles (80 km) wide.
Red tide occurs when naturally occurring algae bloom out of control, producing toxins deadly to fish and other marine life. The odorless chemicals can trigger respiratory distress in people, such as coughing and wheezing.
"It could have large impacts if it were to move inshore," said Brandon Basino, a spokesman for the Florida Fish and Wildlife Conservation Commission (FWC). "It has been killing a lot of marine species, especially fish, as it waits offshore."
The agency has received reports of thousands of dead fish, including snapper, grouper, flounder, crabs, bull sharks, eel and octopus. This is the largest bloom seen since 2006.
The phenomenon has existed for centuries, but such a large bloom is being closely monitored in Florida because it could impact beach tourism and commercial fishing.
A smaller red tide bloom, closer to shore, contributed last year to a record number of deaths among Florida manatees, an endangered sea mammal.
"I have seen analogies that equate red tide with a forest fire," said Kellie Dixon, manager of the ocean technology program at the Mote Marine Laboratory in Sarasota, Florida. "There is an ecosystem reset."
Researchers at that laboratory recently helped deploy two underwater robots, nicknamed Waldo and Bass, to collect data on the slow-moving red tide, which could linger for months or be rapidly dispersed by a storm.
To map the bloom and try to predict its movement, state wildlife officials also organized this week a three-day boating expedition, sending researchers to test water samples across 2,000 square miles (5,180 sq km).
The team found evidence of red tide at the bottom of the ocean, where it is expected to be swept by currents and carried to land, potentially affecting beaches north and south of Tampa.
"It looks like it's coming in," said Alina Corcoran, an FWC research scientist on the expedition, adding that the bloom would not arrive at once. "All of southwest Florida is not doomed. This is normal. It happens all the time." (Reporting by Letitia Stein; Editing by Scott Malone and Sandra Maler)