Toxic Tides: Another Reason To Worry About Hurricanes

When Hurricanes Charley, Frances, Ivan, and Jeanne struck Florida in the summer of 2004, they killed 116 people, left thousands homeless, and caused billions of dollars in damage. Now, scientists suggest that the storms may also have triggered an intense, widespread Gulf of Mexico algae bloom that afflicted the state's western coast throughout 2005.

DANGER ZONE. The red-and-yellow patch of Gulf of Mexico water off Tampa Bay shows the origin of last year's huge red tide, which may have been fueled by nutrient-rich groundwater discharges boosted by 2004 hurricanes. Hu, et al.

Commonly called red tides regardless of their color, toxic algal blooms frequently occur in the shallow waters off Florida's west-central coast. The organism primarily responsible for red tides there undergoes population explosions that scientists have been working to explain for more than a century, says Chuanmin Hu, an oceanographer at the University of South Florida in St. Petersburg. Toxins produced by the algae accumulate in shellfish, kill sea creatures, and irritate the eyes and respiratory systems of boaters and beachgoers.

At its peak, the 2005 red tide covered more than 67,000 square kilometers of shallow coastal waters—an area larger than the state of West Virginia. Hu and his colleagues now suggest that blame for the bloom falls on algae-boosting nutrients that reached the Gulf via the discharge of groundwater beneath the Gulf's surface. That seepage was driven by precipitation that had collected on land during and after the 2004 hurricanes.

One theory holds that red tides are fueled by phosphorus- and nitrogen-bearing plant nutrients brought to the region by local rivers or carried there from the Mississippi River by ocean currents. However, Hu calculated, those sources probably provided only one-fifth the amount of nitrogen that was needed to sustain the algal bloom.

Another model suggests that iron-rich dust wafting across the ocean from the Sahara triggers red tides. However, satellite data show that no more African dust came to Florida's Gulf coast in 2005 than in any of the previous 8 years, Hu found.

Hu points out that the four big hurricanes of 2004 dropped more than 38 centimeters of rain on central Florida in a single month, a rate of precipitation that hadn't been seen since 1970. After several months, enough water had accumulated in local aquifers to increase the rate of discharge below the Gulf's surface. That water carried algae-boosting nutrients, Hu's team asserts in the June 16 Geophysical Research Letters.

Groundwater seeping from land often carries at least 10 times the concentration of nutrients that seawater does (SN: 10/15/05, p. 248: Available to subscribers at http://www.sciencenews.org/articles/20051015/bob9.asp). Therefore, underwater springs can have a substantial effect on coastal ecosystems, says Ivan Valiela, a marine biologist in a Boston University laboratory in Woods Hole, Mass. "Even a small flow can have a large effect," he notes.

Under normal conditions, underwater springs in Tampa Bay carry more than one-fourth of the nitrogen-bearing nutrients that reach coastal waters, says Kevin D. Kroeger, a research chemist at the U.S. Geological Survey in St. Petersburg. The time needed for rain to reach the coast via aquifers hasn't been measured in Florida, but it's reasonable to estimate that an increased flow rate would show up in a few weeks or months, he notes. "It's a theory worth studying," says Kroeger.

If you have a comment on this article that you would like considered for publication in Science News, send it to editors@sciencenews.org. Please include your name and location.

I live in Florida, my research indicates that nutrient rich run offs are not the problem. If this were the case, then the red tide blooms would be more severe in the estuaries, where nutrient pollution is heaviest. The red tide would follow the estuary plumes into the Gulf of Mexico. In fact, the estuaries are safe havens for fish from the red tide. The natural filter feeders in the Gulf of Mexico, the large schools of Menhadden fish, have been decimated by over fishing. Without these natural enemies of the K. Blevins algae, the algae bloom and cause toxic conditions.

The real problem here in Florida is a marine research community that is not committed to defeating the Red Tide. The marine biologists have a mind set, that tells them that it is the pollution of man that is causing the problem, and because of that, they squander research dollars on locating the red tide, and not finding strategies that will defeat it. The Marine Fisheries Commission, is more interested in catching fishing law violators, who take hundreds of pounds of fish illegally, than stopping the red tide, which kills millions of tons of fish.

Case in point, there is a man in Venice Florida that claims to have an inexpensive cure for red tide infected waters. Without getting into a discussion as to the effectiveness of his treatment, you would think that the State Officials and researchers would have an interest into what he has achieved. No, they are not interested in talking to him, I have spoken to the gentleman personally, and he says that the researchers are not interested because THEY did not come up with the solution. The state officials follow that lead, because they don't know diddly about red tide science issues. The nexus of researchers who study the problem (as opposed to solving the problem) and politicians spewing tax dollars, keeps the marine laboratory funded. I live in Florida, my research indicates that nutrient rich run offs are not the problem. If this were the case, then the red tide blooms would be more severe in the estuaries, where nutrient pollution is heaviest. The red tide would follow the estuary plumes into the Gulf of Mexico. In fact, the estuaries are safe havens for fish from the red tide. The natural filter feeders in the Gulf of Mexico, the large schools of Menhadden fish, have been decimated by over fishing. Without these natural enemies of the K. Blevins algae, the algae bloom and cause toxic conditions.

Government is not about solving problems, Government needs victims, and so, dances around the solution.

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.