Naples Daily News

Black water devastates coral in Keys

A new area of black water has formed off Sanibel Island

Sunday, August 11, 2002


More than half of the coral on the north side of the Florida Keys was destroyed in the past 12 months, and researchers who've been monitoring Keys coral since 1996 say the black water event from last spring is to blame.



Click here for our complete coverage of the black water issue.


"I'm sure that's what caused it," said James Porter, a leading coral expert who heads the research team. "It's something to do with the water chemistry, but it's beyond anything we know about."

Porter said his team of researchers measured a 60 percent loss of over one year, "which is the highest rate of loss we have ever seen anywhere in the Florida Keys in a single year," he said. "Even Hurricane Georges did not do this kind of damage."

Five coral species were completely wiped out in areas Porter monitors in the content Keys, a crowd of patch reefs and mangrove islands just north of the island chain. He noted the demise of centuries-old boulder corals, and large numbers of other bottom dwellers such as sea squirts, sea biscuits and sponges.


Sanibel Island pilot Jim Anderson said he took this picture Aug. 1 around 10 a.m. The view is across the northward bend in Sanibel Island, looking toward Captiva. The black mass of water was within yards of shore and stretched to sea almost a mile, Anderson said. He did not know how far south it went. Photo courtesy of Jim Anderson

Joining Porter in his assessment of the area's sea life is marine collector Ken Nedimyer.

"Most of the brain corals in the Northwest Channel are dead," Nedimyer said. "I could go on. The Middle and upper Keys look good, but the Lower Keys and Key West were hammered. But we're not supposed to worry because this is a natural phenomenon."

Officials in the spring characterized the event as naturally occurring and similar to a 100 years flood.

No assessment is yet in on the area hundreds of square miles in size and farther north where satellite pictures showed the water pooled for months beginning in November 2001 and then washed over the Keys.


New concerns

What worries some environmentalists and others along the Southwest Florida coast is the appearance in recent weeks of another mass of black water that formed off Sanibel Island near where the Caloosahatchee River — an outlet for Lake Okeechobee — empties into the Gulf of Mexico.

Jim Anderson, a Sanibel pilot, said he at first thought the water was oil. Others who live along the Caloosahatchee River say they've seen a drop in water quality there over recent weeks.

"I noticed when waves come on shore, the water is thick and black," said Mitrah Bakhtian, who's lived along the river for seven years.

Satellite pictures show a cloud of dark water hugging the Florida coast and concentrating south of Cape Romano, though this water mass isn't as large as the one in the spring.


True color satellite imagery shows a dark mass of water moving south along the Florida coast. Though it looks similar to the black water event that decimated Keys' coral reefs, researchers are collecting samples and say they haven't yet ruled out naturally occurring phenomena. Photo courtesy of the Goddard Space Flight Center

"The images are a bit similar to what we saw in the winter black water event, but they are less dark and appear more brownish and they cover less (area) and are closer to the coast," said Chuanmin Hu, a researcher at the University of South Florida's Institute for Marine Remote Sensing. "This may or may not be the same thing we observed in the winter."

Hu checked the satellite data after hearing reports of black water, but he said there is no ongoing monitoring and interpreting program in place.

Scott Willis, spokesman for the Florida Marine Research Institute, said scientists are collecting water samples from the current mass of water and will be looking at those this week. Fishermen spotted the first event in January when it had become a mass bigger than Lake Okeechobee occupying the area between Cape Romano and the Florida Keys. It slowly moved south across the Keys by April.

Satellite pictures at the time showed the water had trailed along the west coast of Florida from the Caloosahatchee and intensified when it reached western Florida Bay off the Shark River just below Marco Island and Naples.

Researchers concluded later that the black water was a complex interaction among red tide and other algae blooms mixing with river runoff, said Beverly Roberts of FMRI.

Few in the scientific community would say if they think July's dark water is a repeat event, and Roberts said it could just as likely be normal river runoff.

Fresh water is much darker than sea water and would float along the surface of the gulf.

"That can extend miles into the gulf," she said.



Water from Lake Okeechobee

Whether or not this black water is a repeat of the spring, it comes as Florida water officials seek to manage water levels in Lake Okeechobee, an increasingly complicated task in recent years.

Water managers have three choices when it comes to draining the lake: they can send it east to the St. Lucie River, west to the Caloosahatchee or south through the Everglades. Complicating matters is the fact that the lake water is rich in nutrients and causes problems no matter which way they send it.

The lake's level peaked above 18 feet in October 1999, a level U.S. Army Corps of Engineers feared would cause the dike surrounding the lake to fail. In response, water managers flung open the spillways leading into the Caloosahatchee and St. Lucie rivers.

The district released about 2 million gallons of lake water per minute into the Caloosahatchee over roughly a month.


What worries some environmentalists and others along the Southwest Florida coast is the appearance in recent weeks of another mass of black water that formed off Sanibel Island near where the Caloosahatchee River empties into the Gulf of Mexico.

By June 2000, the lake was lowered to 13 feet.

The district and Army Corps were forced to re-examine their water-management policies for the lake after public outcry arose over algae blooms and fish kills in the Caloosahatchee.

Today, water managers try to keep the lake between 13 1/2 and 15 1/2 feet to avoid major releases such as those in 2000, said Karen Estock, head of the Army Corps South Florida Operations office in Clewiston.

Water management officials also use so-called "pulse releases," 10-day-long periods in which they keep spillways open. And releases don't happen unless scientists, local and state politicians and concerned citizen groups give their blessing.

"That's always our goal— let people know what we're going to do, get some feedback and them make our decision," Estock said. "It's science and politics."

There have been two recent "pulse releases." One ran from July 15 to July 25. Another began Aug. 1 and will continue until Aug. 10.

In both cases, the decision to let the water out of the lake came after its level jumped above 14 1/2 feet. Water management officials try to keep levels lower during the rainy season, Estock said.

The release's intensity reached a peak a week ago, when nearly 3,500 cubic feet per second of water rushed into the Caloosahatchee through the Moore Haven lock, where the river meets Lake Okeechobee.

However, the lake's level has increased slightly due to rainfall.



Lake water quality

The amount of fresh water directed down the Caloosahatchee is a problem, environmentalists and the state agree, and most people also agree it's a combination of lake releases, farm and urban runoff.

What worries people like David Guest, an attorney for the environmental law firm Earth Justice, is what's in the water.

Lake Okeechobee is more than just a place to fish. It's also where agricultural interests around the lake pump excess water to keep farm fields dry. What comes with the water is loads of nitrogen and, to a lesser degree, phosphorus, according to the water district's own reports.

Together, they're food for a host of organisms that, though generally harmless, can choke waterways when they can grow out of control.

Guest said the water backpumped from farms is bad for creatures in the Caloosahatchee and could just as well be bad for the Gulf.

"When you have algae or maybe the black tide and when that arrives and finds nutrient-rich water, is it a surprise that it grows out of control?" he asked.

Porter, whose team recently identified a new disease decimating elkhorn coral in waters up and down the Keys, said the black water is a mystery and that research and monitoring needs to go on.

"I'm deeply concerned by that event," he said, "as much because I don't know what it means as I know what it did. I don't think anyone knew how important this was because it had never happened before."

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