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Position of ocean current plays role in harmful Florida red tide algae blooms, study finds

A major ocean current in the Gulf of Mexico plays an important role in sustaining Florida red tide blooms, according to research conducted by the University of Miami.

Researchers at the Rosenstiel School of Marine and Atmospheric Science are suggesting that the position of the Loop Current can serve as an indicator of whether the algal bloom will be sustained and provide warning of possible hazardous red tide conditions in coastal areas.

The Loop Current moves from the Caribbean Sea into the Gulf of Mexico before looping west and south, exiting through the Florida Straits. While it is a permanent current, the Loop Current changes shape and orientation, depending upon the season as well because of fluctuating wind and temperature patterns.

Red tides are caused by a higher-than-normal concentration of the Karenia brevis microscopic organism, which is most commonly found in Florida and the Gulf of Mexico.

"Nutrients are needed to sustain a large red tide," Associate Professor Josefina Olascoaga of the Department of Ocean Sciences at the University of Miami said. "Low mixing rates and sufficient isolation are needed to keep it from dispersing. Other factors are not well known."

Algae blooms have also occurred after unusually high water temperatures and extreme weather events such as hurricanes, floods and drought, the U.S. National Ocean Service said.

The paper on "Historical Analysis of Environmental Conditions During Florida Red Tide" was published in the December of 2015 issue of the journal Harmful Algae.

The research looked at the position of the Loop Current during red tide events between 1993 and 2007, Olascoaga said.

"We cannot predict blooms well yet," she said. "We know statistically when and where a red tide is more likely, but cannot make accurate predictions at this time. However, from our research, we can be fairly confident that a red tide will not develop when the Loop Current is [in] its southern position."

"If it is in a northern position, a red tide is possible but not inevitable," she added. "So we cannot say if there will be or not a bloom if the Loop Current is in a northern position, but we know now that if a bloom forms, it is more likely to persist."

The blooms can cause problems for both humans and marine life, the Florida commission said.

For people with severe or chronic respiratory conditions, such as emphysema or asthma, red tide can cause serious illness due to respiratory irritation. The toxins can also accumulate in oysters and clams, which can lead to shellfish poisoning in people who eat the contaminated shellfish, the commission said.

The red tide organism also produces toxins that can kill fish and other sea life.

A red tide bloom currently persists along Pinellas, Manatee, Sarasota, Charlotte and Lee counties in Southwest Florida, according to the Florida Fish and Wildlife Conservation Commission.

A 2014 Florida red tide outbreak in the northeastern part of the Gulf of Mexico covered an area as large as the state of Connecticut.