- Florida's Threatened Reefs (Video Sequence) - QUICKTIME - WINDOWS MEDIA

HARBOR BRANCH "Green Tide" Research Program

Caulerpa brachypus -- Invasive macroalgae species from the Pacific first discovered in Florida waters by Brian Lapointe and colleagues in mid-2001. Species is currently overgrowing sponges, corals and other harmful macroalgae bloom species in northern Palm Beach County. It has been spotted as far north at Fort Pierce and is expected to continue spreading north and south from Palm Beach County, though the area it currently covers has not been determined. Dive operators and fisherman have reported that the species is now becoming so thick it is forcing fish and lobster away from reefs.

Caulerpa taxifolia -- Cousin of Caulerpa brachypus, native to the Caribbean and other tropical seas. In its native regions, where waters are typically nutrient-poor, it grows in small patches and does not pose a problem. In 1989 it was released into the Mediterranean Sea by the Oceanographic Museum of Monaco. Because it is a tropical species officials did not expect it to survive the winter, though one scientist called for removal of the small initial patch that had taken hold to prevent its spread. His warnings were ignored and by the time the problem was recognized it was too late to control. The species now covers over 10,000 acres of the Mediterranean and has caused billions of dollars in damage. The Mediterranean problem is the subject of the book Killer Algae by Alexandre Meinesz. When small patches of Caulerpa taxifolia were spotted in California in 2000, it was quickly destroyed to prevent spread.

Codium isthmocladum -- Species has always been present on local reefs, but before the 1990's was only found in small concentrations. Between 1989 and 1992 it began blooming on reefs in mats up to six feet thick that smothered sponges, corals and other reef life. Though still a problem, much of the Caulerpa isthmocladum on local reefs is now being overgrown by Caulerpa brachypus.

Caulerpa verticillata -- Though prevalent on many reefs now, it had traditionally been found only in nutrient enriched nearshore waters such as around mangroves. Before 1998 it had not been reported on Palm Beach County reefs. Much of the Caulerpa verticillata on local reefs is also now being overgrown by Caulerpa brachypus.

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Stable Nitrogen Isotopes -- One of the key measures Dr. Lapointe will be using to tie the spread of harmful macroalgae species to pollution is stable nitrogen isotopes. Isotopes are atoms of an element that have more or less than the typical number of neutrons, and counting the number of isotopes in a given sample relative to the number of normal atoms in the sample gives a substance's isotope signature. Lapointe's team will be analyzing samples of the various types of macroalgae to determine their nitrogen isotope signature, specifically, they will be measuring the ratio of less common "15N" isotopes to the most common "14N" isotopes. A living organism's signature is similar to that of its nitrogen source. Therefore, if the algae spread is being fueled by pollution the isotope ratios in macroalgae samples should be similar to that of pollution sources from land such as sewage water, which has a higher percentage of 15N isotopes than seawater. In previous work, Lapointe found that macroalgae isotope ratios were closest to pollution around sewage outfalls and near more heavily populated areas.

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How pollution, specifically nitrogen in the form of ammonium is delivered onto reefs:

• Nitrogen in the form of ammonium from septic tanks contaminates groundwater and surface waters, which eventually make their way into the ocean and out to reefs.

• Six ocean outfalls off southeast Florida deliver about 400 million gallons per day of secondarily treated wastewater, which is still high in ammonium, into the ocean at a depth of about 90 feet.

• At Class I injection wells throughout Florida, secondarily-treated wastewater is pumped about 3000 feet below the ground. Class V injection wells pump storm water, rather than sewage, to less than 100 feet underground. Both processes allow inadequately treated and ammonium-rich water to get into especially permeable portions of the aquifer between about 60 and 100 feet down. This aquifer layer runs beneath coastal water and out to where blooms are occurring, where some of the polluted water escapes.

Some researchers have argued that macroalgae blooms are driven by nutrients supplied by deeper ocean water that upwells to shallower areas around reefs at certain times of year. Arguments against this upwelling theory include:

• Nitrogen isotope ratios for macroalgae at reefs in question are typically close to those of sewage and significantly higher than the isotope ratios for upwelled nitrogen.

• There is evidence that macroalgae prefer ammonium, the form of nitrogen common in polluted waters, as compared to nitrate, the form found in upwelled water.

• Sporadic upwelling has always been around, but harmful macroalgae blooms on Florida reefs did not begin until the late 1980's.