The Bloom That Vexes

In a popular Keys diving spot, marine researchers find two species of algae that tend to favor polluted waters

To the untrained eye, the mass of turfy green may have appeared to be just another strange sea plant common to Looe Key reef in the Florida Keys. No big deal. Food for the fish, perhaps, or somewhere for them to hide. To Bill Matzie, though, it was, in his words, "dismaying and disappointing."

For six years, Matzie has studied the reef while working as an assistant to Brian Lapointe, a marine research scientist who has scrutinized Looe Key for fourteen years. Matzie knows its fauna and its flora. But on a research foray in February, he stumbled across an alga neither he nor Lapointe had ever seen out there: Cladophora fuliginosa, soft clumps that resemble divots of Bermuda grass. A subsequent trip to the five-square-mile reef turned up another related alga: Cladophora crispata, a drifting, diaphanous plant that looks a little like pale-green cotton candy. As of this past week, Matzie reports, the algal duo had spread across several acres of the reef.

The presence of the two species could be extremely bad news for the reef, one of the world's most beautiful and popular diving destinations and a major economic engine for the Florida Keys. Algae blooms can cause turbidity, blocking out light and smothering coral, sponges, and sea grasses. Moreover, these particular species like to feed on phosphorus and nitrogen, nutrients commonly associated with sewage and agricultural runoff, so the presence of the algae might be an indication that the reef is being polluted. (The nutrients themselves can contribute to harmful sedimentation on the reef, as well.)

A University of South Florida scientist has confirmed the identities of the algae, and Lapointe and Matzie have also sent the specimens to a botanist at the Smithsonian Institution in Washington, D.C., and are awaiting his analysis. While both Cladophora fuliginosa and Cladophora crispata have been detected elsewhere in the Keys, neither normally grows in offshore waters. Looe Key reef is located in the Lower Keys, about five miles south of Big Pine Key, on the Atlantic side.

"The two Cladophora species are generally associated with near-shore environments high in nutrients," says Matzie, who made the discovery while monitoring the reef as part of a study funded by the U.S. Environmental Protection Agency. "You might find them in an in-shore canal or under a mangrove island where there's a lot of bird waste. But they're not associated with offshore, coral reef environments."

News of the discovery has been making its way slowly through South Florida's marine-science community, where it is being greeted with equal measures of concern and caution. "This is a piece of information that could be of great interest," says John Hunt, a Marathon-based research administrator for the Florida Department of Environmental Protection. "But until we know the abundance of this kind of algae out there, and growth rates, and things of that nature, we should be very careful about claiming that this is a significant change in that region."

Adds Steven Miller, science director of the National Undersea Research Center, a federally funded facility in Key Largo: "Algae have really complicated life histories. Light, temperature, and nutrients all have an effect. So it's not a simple matter to discover something like this and ascribe a cause to it. It could be a signal that significant changes are going to happen, or it could all be gone tomorrow."

A spokeswoman for the Florida Keys National Marine Sanctuary, which includes the Looe Key reef site, says sanctuary officials have heard about the finding but haven't yet investigated Lapointe's and Matzie's claims. "As far as any conclusions, we don't have any until we can get out and take a look at the size of what [Lapointe and Matzie are] calling a bloom," says spokeswoman Alyson Simmons.

Lapointe ventures a couple of preliminary theories regarding possible causes of the algae growth: sewage leaking out of septic tanks, cess pits, and deep injection wells in the Keys; or nitrogen-rich topsoil washing through the Everglades into Florida Bay, through the channels that run between the Keys, and into the Atlantic. He hopes to present his preliminary findings at several marine-science forums this summer, including the eighth International Coral Reef Symposium in Panama City, Panama, later this month.

 
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