The floating nurseries of the Gulf of Mexico are in the wrong place at the wrong time. Home to the larvae of more than 120 species of fish, the nurseries congregate along the US coast – precisely where the Deepwater Horizon oil slick is wreaking havoc.
Ecologists in the region say the oil is already hitting the nurseries, as well as the feeding grounds of the world's biggest fish, the whale shark.
"This could not have come at a worse time," says Jack Rudloe, owner of Gulf Specimen Marine Lab in Panacea, Florida. "Everything is spawning right now."
The coastal wetlands, which serve as nurseries to key commercial species like shrimp, have been the focus of environmental concern thus far. Once hit, they are very difficult to clean up.
"But the spawning grounds for offshore fish are being impacted now," says Jim Franks, a fisheries scientist at the University of Southern Mississippi at Ocean Springs.
Winter rains wash nutrients into the ocean, triggering spring plankton blooms along the northern loop current in the Gulf – perfect food for baby fish. Floating mats of Sargassum seaweed line up along the currents, providing shelter from predators.
As a result of these perfect conditions, more than 120 species spawn in the Sargassum mats, including the endangered bluefin tuna. All are at risk. "There are slicks in bluefin spawning areas now," says Franks. "The adult fish might swim away from the oil to spawn, but the spawn will just drift right into it."
Sean Powers, a marine scientist at the University of South Alabama in Mobile told Associated Press that his team have seen Sargassum mats in the same area as the oil slick during air surveys.
The whale shark, the world's biggest fish, also feasts on the spring plankton blooms, sometimes in groups of up to a hundred. "The oil is in their territory," says Franks. "We have no idea what they'll do, but when you're as big as a bus and you eat a lot, you may not be able to avoid it. The whole food web could be affected."
Olof Linden of the World Maritime University in Malmö, Sweden, points out that a ban or reduction in fisheries resulting from the spill could be good news for local stocks. In fact, he says, the fisheries closure after a similar blow-out at the Ixtoc 1 wellhead in the southern Gulf of Mexico in 1979 actually benefitted stocks, by giving them a break from fishing pressure.
But that small benefit will be somewhat outweighed by the timing and location of this spill. "The northern and southern Gulf have very different biota," says Franks.
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