Why Is Seaweed Killing Florida's Coral Reefs?

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For ten days the scientists lived at Aquarius while conducting their experiments. Because the lab is underwater, scientists can spend eight to ten hours a day working at depths of 60 to 120 feet (18 to 36 meters). If the scientists dove to these depths from a surface vessel, they would be limited to 30 minutes of diving a day because of the risks of becoming ill from decompression, which can be lethal.

Study of Nutrient Levels

Beach's goal was to determine what factors—such as sunlight and nutrients—affect the growth of D. menstrualis. His colleague Linda Walters of the University of Central Florida in Orlando focused on how the plant can propagate so rapidly.

Beach installed a number of nutrient dispensers near a patch of the seaweed and measured the rate of photosynthesis that occurred over ten days. He will analyze the data to find out whether there was a sudden growth spurt that correlated with the higher nutrient levels.

Walters studied how the plant replicates by fragmentation. When fragments of D. menstrualis break off from the main plant, they can put out roots within hours of landing on sponges, corals, and sand, Walter explained.

"Dictyota is very fragile and breaks easily," she said. "The more fragments are dispersed, the faster Dictyota replicates."

While Beach and Walters study D. menstrualis, other scientists are trying to aid recovery of the corals by restocking the reefs with sea urchins. If Beach finds, however, that high nutrient levels are responsible for the overgrowth of the seaweed, broader measures may be needed to save the coral reefs, such as revising Florida's water-quality standards.

A story describing attempts to restore the reefs by replenishing the sea urchin population was reported on National Geographic Today, shown only on the National Geographic Channel, at 7 p.m. ET/PT in the United States.

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