Gulf oil spill: Florida braces for impact

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As the powerful Loop Current, a surge of warm water that circulates in the eastern Gulf of Mexico, moved north within 30 miles of the spill, scientists predicted that it would catch the the oil and sweep it around the Florida peninsula. The oil could then contaminate the Everglades National Park, along with mangrove swamps, coral reefs, sea grass and the animals and fish that depend on them, they said. Beaches in Miami and along Florida’s eastern coast could be tarred.

“Where it hits will be devastating,” said James Fourqurean, a sea grass ecologist with Florida International University. “But it is not going to hit everywhere.”

“Filaments of the Loop Current are within tens of kilometers of the oil spill,” said Robert H. Weisberg, an oceanographer at the University of South Florida who has been modeling the movement of the spill. Once the current catches the spill, he said, “the speed of the current is such that it only takes a week before oil will be at entrance of the Florida straits and another week until it gets as far as Miami.… Whether the oil gets into the Florida Bay or the Everglades depends on what local winds are doing when oil is flowing past.”
Weisberg said he could not predict the exact timing. “But it appears to be imminent,’ he said. ‘It looks like it is going to happen sooner rather than later...The Loop Current moves very fast.” As for the oil’s trajectory, he said, “Whatever comes will flow west of Dry Tortugas and towards Cuba before it comes back north.” For the oil to get into the vicinity of shallow water in the Florida Bay, Weisberg said, the current ‘would have to take oil into passes from south to north. It is difficult to get a lot of oil into the Florida Bay.’

Elaborating on the nature of the Loop Current, Weisberg explained, “The Loop Current is always there. The question is how far north it extends. The current extends father north into gulf until it sheds an eddy. A piece breaks off and moves west. The rest shifts to south. That process of moving north and eddy shedding repeats itself. It happens every eight to 16 months. Right now it is in the process of moving north.’

Weisberg said that if the oil remains in deep water, “there is not an immediate threat to the western coast of Florida.” But he added, “The longer the oil leaks, the more it gets in shallow water along the northern coast, and it make its way south closer to shore.“
“Fortunately,’ he said, ‘we are coming out of a strong wind season and going to a weaker wind season.” As for Miami’s beaches, he said, “whether oil makes landfall anywhere depends on what the winds are doing at that point in time. It is likely there could be oil on beaches in Miami.“

If oil gets into the Florida Bay, which is part of the Everglades ecosystem, “it would be a horrible thing to happen, “ said Fourqurean, the sea grass ecologist, who has studied the Florida Bay for 25 years.

Fourqurean said that about 7,000 square miles of sea grass, flowering plants that live under the ocean, are located along the Florida Shelf, the Florida Keys National Marine Sanctuary, Florida Bay and Biscayne Bay. Sea grasses form the base of the food chain for commercial and economically important species of fish and other animals in South Florida, he added.

Forqurean said that the Florida Bay is “a net evaporation basin. More water evaporates out
than water is rained into it. It is a sink.... If a surface slick runs along the southern tip of the Florida peninsula, it could be pulled into the Florida Bay and could remain resident there for years. And Florida Bay is part of Everglades National Park.”
However, Forqurean added that “one of the good news pieces is that sea grasses are relatively resistant to oil spills. The only time that sea grasses are drastically harmed is when oil ponds up at low tide and inches across the bed. The bad news is that all the animals that shelter in sea grass beds are very susceptible to oil. Especially larval forms. Oil is very, very toxic to animals.... Animals that live completely submerged are poisoned by slightly soluble components of the oil. Oil has elements that are toxic to anything with gills....Turtles and manatees have to breathe air so they come up to the surface. And oil on the surface is sludgier, so that is a physical problem as well as directly toxic.”

Jerome Lorenz, an ecologist with Audubon of Florida, said the oil spill is “a major concern” for mangroves, a tropical tree that lines the shores in south Florida. “If oil enters the ecosystem, it would blanket the surface and destroy the productivity of wetlands,” he said. “Once it is in there, it can’t be cleaned. It will take decades to get the oil out of the system.’

Mangrove forests are essential in feeding a variety of birds and crocodiles, and their productivity is crucial to the health of the Everglades, Lorenz said, adding that most colonies of giant wading birds occur in mangrove swamps. Oil could have a devastating effect on game fish species as well as wading birds, such as Roseate spoonbills, osprey, herons, pelicans, he said. ‘Game fish spend a portion of their juvenile life in those habitats. Redfish, snapper species, sea trout…”

Richard Dodge, director of the Oceanographic Center and National Coral Reef Institute at Nova
Southeastern University in Florida, said, “The third part of the triumvirate of Florida coastal ecosystems are the coral reefs. The United States has a lot of coral reef ecosystems, and Florida has 84% of U.S. coral reef ecosystems. So when you look at mangroves, sea grass and corals, you are looking at a huge economy that generates lots of jobs.’Dodge said that corals, a combination of animals and plants, are affixed to the ocean floor, like sea grass. ‘So floating oil on top of the water can be benign,’ he said. ‘But it depends on the duration and the frequency. Oil can dissolve in the water column and have toxic materials, if you have a big spill or chronic spills.”

Dodge said that if the slick is thin, the oil mixes with water and becomes emulsified, and typically travels along as a layer under the surface. “That could have a direct effect on coral reefs,” he said. “If the oil is emulsified, more toxicity is available. The effect on coral reefs could be copious: effects on reproductive health, bleaching, mortality. “ But he added, “Fortunately oil spills usually are floating and corals are fairly deep.”

Dodge added that when reefs are nearby, “The method of choice to mitigate the oil is not dispersants… Chemical dispersants are very toxic to coral reefs. “
“Coral reefs are almost at their breaking point already,” he said. ‘Global warming is leading to bleaching from higher temperatures, and ocean acidification. And all the pollution effects. We don’t want to add more insults to an ecosystem that is a source of concern.”

--Margot Roosevelt