Tiniest victims of the Gulf of Mexico oil spill may turn out to be most important

By Bob Marshall, The Times-Picayune
May 14, 2010, 7:00PM

To the watching world the environmental threat that BP’s oil disaster poses to the nature-rich Louisiana coast is captured in images of beautiful birds or furry creatures crippled by thick black goo. But scientists who know these estuaries best are more concerned about a less photogenic community. The grass, microscopic algae and critters living in the wafer-thin top layer of marsh mud – called the benthic community – are the fuel that drives the whole system. If it’s covered with oil, everything above, including birds, fish and cute, furry critters, will be in trouble. And so will the humans who rely on the marsh for storm protection and seafood production. “The top two millimeters of that marsh muck is where the action is in a coastal estuary,” said Kevin Carman, dean of the College of Basic Sciences at LSU. “That’s the base, the food that fuels the whole system. If you lose that in a large enough area it could have a disproportionate impact on the food web, and everything that depends on it: fish, shrimp, oysters, all the species that rely on the estuary.” Half of the all the life created in the one of the world’s most productive estuaries takes place in this slimy zone just seven-hundredths of an inch thick. It’s a world too small for the human eye to detect and involves creatures few people have ever heard of, but one that looms huge for the larger critters in the system. … “It’s an incredible engine for a wide range of life,” Carman said. It’s a system that shows great resilience and continues to hum along in the face of nature’s toughest blows, from hurricanes to freezes. But scientists worry how well it would cope with the giant oil spill that could be washing ashore for weeks on end, because that has never happened before. However, they can paint a worst-case scenario from the many smaller, inland spills that have hit state’s interior coastal wetlands during the 80 years the oil industry has been here. It’s a frightening picture. “If the toxic components of the oil kill those invertebrates foraging on the algae, then the algae will grow out of control,” Carman said. “The analogy would be if you removed cattle grazing in a field, the grasses would just take over. Same thing here.” The algae eventually would form a thick mat over the marsh mud, preventing sunlight and oxygen from penetrating below its surface. “That would make it harder for anything to grow in the sediments below,” he said. Those toxic components would dissipate in a mater of days or weeks, and the grazers might return. But if components of the oil known as asphaltenes – the thick black tars – settled on the surface, the damage could be worse. “If the algae can’t get sunlight, they die,” said Carman. “If they die, the invertebrates have no food, and the whole web is disrupted.” …