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Threats to coral include warmer water, pollution

Two species of coral are considered threatened as the vital organisms face more danger than ever.

By CURTIS KRUEGER
Published March 5, 2007

Kim Ritchie, a microbiologist at Mote Marine Laboratory in Sarasota, scuba dives past a cluster of elkhorn coral at Looe Key Reef on Feb. 13. The brown areas of the coral are healthy, but the large grey area is dead. Elkhorn is a threatened species.
	[Times photo: Ted McLaren]

ADVERTISEMENT [Times photo: Ted McLaren] Elkhorn coral polyps protrude from their hard skeletons at Looe Key Reef in the Florida Keys National Marine Sanctuary.

Walter C. Jaap, a St. Petersburg marine ecologist, vividly recalls the reefs off the Florida Keys he saw during research dives in the 1970s:

Thousands of chocolate brown and golden corals teeming with fish. Snapper, goatfish and grunts darting into thickets of the darker colored elkhorn coral to escape predators like barracudas. Other fish finding refuge by swimming into the golden staghorns.

These gardens of coral covered 40 to 50 percent of the reefs that Jaap and fellow scientists visited. But when he returned to monitor them from 1996 to 2005, the coral cover had dropped to 7.2 percent.

"It's pretty barren," said Jaap, now a consultant after retiring from the state Fish and Wildlife Research Institute.

Last year the National Marine Fisheries Service declared elkhorn and staghorn coral to be threatened species. They were the first corals to be listed in such danger.

And the news is not getting better.

Coral reefs, a key feature of Florida's ecology and tourism, have been called underwater rainforests because they abound with a diversity of life, at least when they're healthy. They also are a good measure of the state of Florida's seas.

"Coral reefs," says Jaap, "are probably a good parallel to the canary in the coal mine."

The canary's in trouble.

Florida coral is facing more danger than ever. And it's not just one threat, but many: hurricanes, pollution, unexplained diseases and maybe even global warming.

"The overall state of Florida's coral is pretty bleak," said marine science professor Pamela Hallock Muller of the University of South Florida.

* * *

Kim Ritchie, a microbiologist from Mote Marine Laboratory in Sarasota, is diving in 15 feet of water at Looe Key Reef in the Florida Keys. She pulls out a syringe, and takes a sample from the very edge of a bronze, antlerlike branch of elkhorn.

Ritchie goes to this reef every month, looking for mucus and bacteria. Which does sound obscure. But by studying the slime and the bugs, she is hoping to unravel a mystery about what keeps coral alive, and what kills them.

The mucus covering these coral contains an antibiotic, which can fight disease. But this protection vanishes when water temperatures get too high. Water temperatures have been high in recent years, which could explain why so much coral in Florida and the Caribbean is suffering from disease.

"I'm looking at coral health to figure out why they're getting diseases," Ritchie said.

Scientists like Ritchie shuttle between the reefs and the labs because they believe that to understand threats to Florida's coral, they need to understand coral itself.

Coral can look like underwater plants, and their skeletons can form rock-solid structures.

But they're actually animals, related to sea anemones and jellyfish. Individual coral animals, called polyps, have mouths they can open to swallow plankton. Coral polyps tend to spend their lives stuck together in large colonies, so they're not hunters.

Fortunately for shallow-water species like the elkhorn and staghorn, they have another way of getting food: They derive nourishment from tiny algae that seep inside their tissue from the water.

The algae are essentially plants, and therefore survive by photosynthesis, the same process tree leaves use to drink in the energy of the sun.

This explains one of the threats: Coral need the algae to thrive; algae need sunlight to live; murky water means less sunlight. Every time dredging or construction stirs up sediment, or storms churn the water, that hurts the algae and the coral.

Of course hurricanes have battered Florida for eons, but they may inflict more damage now that coral is in such a weakened state, scientists say.

Other threats include:

- Higher-than-normal water temperatures. Warm waters in 2005 damaged coral throughout the Caribbean Basin, including South Florida reefs. The highly sensitive coral expel the helpful algae when warm waters combine with other environmental factors, depriving the coral of food. The process is called coral bleaching, because they turn bone-white.

Global warming is likely to blame for the warmer waters, many scientists say.

Jaap said that when he first began researching coral, bleaching happened about once a decade. "Now it seems to go on every other year or every third year or sometimes in consecutive years," he said.

- Scientists are studying several possible sources of pollution such as pesticides and fertilizer that drain off the lawns of suburban Florida.

Fertilizers contain nutrients that can cause algae to grow, but not necessarily the helpful algae that corals rely on. The wrong types of algae can work against coral by competing for resources.

- Unexplained diseases. They are affecting coral more often than before, and "we don't know why they're there or what causes them," said Erin McDevitt, of the state Fish and Wildlife Conservation Commission.

"When you start to add the cumulative impact of multiple stressors is when you start to see decline," she added.

Times Staff Writer Curtis Krueger can be reached at 727 893-8232 or at ckrueger@sptimes.com.

[Last modified March 5, 2007, 01:38:15]