Temperature trend in the eastern Gulf of Mexico since 1975. Data from NOAA. Graphic: Climate Central

By Angela Fritz
15 August 2018

(The Washington Post) – Red tide is killing Florida’s southwest coast. Fish, manatees, sea turtles — some of them endangered — and nine dolphins have washed up dead on the beaches, and all of them are confirmed or suspected to have been poisoned by the algal bloom. The body of a young whale shark was found on a beach in late July, and biologists believe that it was the first known whale shark to have been killed by red tide.

Now the toxic algae — Karenia brevis — is working up the coast from Sanibel Island to Tampa Bay. Respiratory irritation in humans has been reported as far north as Manatee County, just south of Tampa Bay, where high concentrations of the algae were measured last week. The water off Pinellas County — Clearwater, Largo, St. Petersburg — had elevated concentrations of red tide beyond a normal “background” state for the first time this month.

Florida Gov. Rick Scott declared a state of emergency for seven counties on the southwest coast Tuesday.

Algal blooms are common in Florida and along the rest of the Gulf Coast, but they don’t always get this bad. This one began in 2017 and, over the past few months, has slowly ballooned into a nightmare scenario for residents and business owners — not to mention the thousands of animals that have died.

There are several ways human activity can exacerbate a bloom, but the main culprit is allowing nitrogen-rich material such as fertilizer to run off into natural water sources. The same fertilizer that helps sugar cane, tomatoes, and corn grow in the Sunshine State feeds algae when it reaches the ocean.

Humans are also playing a role by driving up global temperatures via greenhouse gas emissions. In a letter published by the journal Environmental Science & Technology, researchers at the University of Florida and the University of North Carolina said that “climate change will severely affect our ability to control blooms, and in some cases could make it near impossible.”

As air and ocean temperatures increase, the environment becomes more hospitable to toxic algal blooms in several ways, according to scientists and the Environmental Protection Agency.

In freshwater such as the Great Lakes, a different kind of “algae” — cyanobacteria — flourishes at warmer temperatures. Combined with fertilizer runoff, red tides due to cyanobacteria have spiraled out of control in recent years, particularly in western Lake Erie. In freshwater cases, the harmful algal bloom doesn’t just threaten wildlife, it also threatens the water that people drink and bathe in. In 2014, Toledo’s water supply was so poisoned with cyanobacteria toxins that the entire city had to drink bottled water for three days, according to the Cleveland Plain Dealer. [more]

How climate change is making ‘red tide’ algal blooms even worse

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