Gulf oil spill: Has it caused a new fish kill? (UPDATED)

By Margot Roosevelt, Los Angeles Times
August 23, 2010

Dead fish


Louisiana state biologists Monday were investigating whether a large fish kill at the mouth of the Mississippi River was caused by oil or dispersants from the BP spill in the Gulf of Mexico. The gulf also contains a vast dead zone created by agricultural runoff along the river.

"By our estimates, there were thousands, and I’m talking about 5,000 to 15,000 dead fish," St. Bernard Parish President Crag Taffaro said in a news release Monday. "Different species were found dead, including crabs, sting rays, eel, drum, speckled trout, red fish, you name it, included in that kill."

The fish were found floating at the top of the water, collected along plastic booms that were placed to contain millions of gallons of oil from the spill that was touched off by the April 20 explosion of BP’s Deepwater Horizon drilling rig. The oil flowed into the gulf until July 15 when the gusher was capped.

A half-mile long swirl of thick substance with several tar balls and a strong smell of diesel was discovered Monday around Louisiana’s Grassy Island, St. Bernard Parish officials announced. Skimmers were collecting the scum.

"There is what we believe to be some recoverable oil in the area," Taffaro said. "We will be sampling that and recovering what we can. We don’t want to jump to any conclusions because we’ve had some oxygen issues by the Bayou La Loutre Dam from time to time.

"The Marine Division of Wildlife and Fisheries is on it … It does point to the need for us to continue to monitor our waters."

According to St. Bernard Parish spokeswoman Karen Bazile, the fish were found in the Mississippi River Gulf Outlet, a 76-mile shipping shortcut from the Gulf of Mexico to New Orleans that was dug by the U.S. Army Corps of Engineers in the 1960s. "It is blamed for massive wetlands loss and is widely believed to have worsened the flooding from Hurricane Katrina," she said in an e-mail. "Since that storm, the federal government has paid for a rock structure across the channel at Bayou La Loutre to stop the flow of salt water, also putting an end to shipping in the channel."

UPDATE: On Monday evening, St. Bernard Parish oil disaster information officer, Jennifer Belson, said that preliminary testing by the state’s Wildife & Fisheries indicated that the cause of the fish kill was "hypoxia" or lack of oxygen. "But we don’t have the final testing back," she said. Hypoxia is most often caused by an excess of nitrogen and phosphorus from agricultural fertilizer or human waste, but it can also be caused by chemical dispersants, which were used extensively after the oil spill.

Ralph Portier, an environmental scientist at Louisiana State University, cautioned in an interview that, "A lot of things can explain a fish kill, which is not uncommon during the hot summer weather in Louisiana. It could be the nutrient-rich environment with a lot of heat. It could be rainfall. It could be changes in salinity or upwelling from disturbed sediment."

The Mississippi River Gulf Outlet, he noted, is "like a dead end canal with water that does not mix as much as you would like it to."  If oil were the cause, he said, he would expect a more gradual, rather than a sudden fish kill.

But he said he could not rule out that the fish kill could be related to the oil spill. Fresh water, which has been diverted into the marshes since the spill, can change salinity levels and affect fish, he noted. The fish kill announcement, he said, "goes to show how sensitive the (oil spill) issue is. You can imagine the angst of a lot of people in the sea food industry when they hear about a fish kill now."

— Margot Roosevelt

Photo: A dead fish lays along and oil boom deployed along the Louisiana shore in May. Credit: Carolyn Cole / Los Angeles Times