BP Plc’s oil spill in the Gulf of Mexico may be exacerbating a natural phenomenon that causes fish, crabs, eels and shrimp to swarm the shoreline to escape oxygen-depleted sea waters.
Called “jubilees” by locals because of the opportunity to scoop up seafood in buckets, they typically appear during the summer along the Gulf Coast. This year, scientists say jubilees have occurred in open water for the first time, raising concern that low-oxygen areas are expanding because of the more than 4 million barrels of oil BP’s Macondo well leaked into the Gulf.
Low oxygen in the water because of oil and methane from the BP spill contributed to a “jubilee-like effect” in late June off the coast of Fort Morgan, Alabama, at the mouth of Mobile Bay, Monty Graham, a senior marine scientist at the Dauphin Island Sea Lab in Alabama, said in a telephone interview. Catfish, shrimp, crab and flounder piled up along an offshore sandbar, until the sharks moved in, Graham, 45, said.
“Most of us believe it had something to do with the oil,” said Robert Shipp, 67, chairman of the Marine Sciences Department at the University of South Alabama. There was a “consensus” among faculty at the University of South Alabama and the Dauphin Island Sea Lab that oil played a part in the event, which was “quite different” from the naturally occurring jubilees in the Gulf’s Mobile Bay, Shipp said.
Seasonal jubilees can sometimes be predicted based on winds and tides, and don’t have a negative effect on fish populations, he said.
First recorded in Mobile Bay in 1867, jubilees typically occur when strong winds churn oxygen-deprived, or hypoxic, water from the bottom of the bay to the surface. The hypoxic seawater forces suffocating fish, stingrays and other marine animals toward shore in search of oxygen.
This summer, more fish may wash up in coastal coves where microorganisms break down oil droplets and use up oxygen, Shipp said in a telephone interview. Crude came ashore in Fort Morgan as recently as the week of Aug. 8, he said.
A group of scientists said in a memo made public Aug. 16 that as much as 79 percent of BP’s leaked crude remains in the Gulf, challenging an Obama administration assessment that the oil is mostly gone.
BP’s spill has created a 22-mile (35-kilometer) underwater plume of degrading oil that’s migrating across the Gulf, according to another group of scientists, from the Woods Hole Oceanographic Institution in Falmouth, Massachusetts. The trail of crude will remain in waters for months as microbes break it down, they said in a statement released Aug. 19.
“Oil residues on the bottom and in the water columns could exacerbate and make worse this phenomenon,” Kent Mountford, an environmental historian who has studied estuarine ecology for 46 years, said in a telephone interview. Mountford, 73, works for Cove Corp., an environmental consultancy, in Lusby, Maryland.
Hypoxic seawater, referred to as dead zones, can be made worse by larger amounts of fertilizer and sewage runoff from rivers, which feed algae blooms that consume oxygen. The Gulf’s dead zone this year measured 7,722 square miles (20,000 square kilometers) as of July 31, twice as big as last year, according to an NOAA study.
It’s hard to tell how fish populations may be affected by increased instances of hypoxia and jubilees, said Graham, the Dauphin Island scientist. It may take up to five years, as juvenile fish mature, to see an effect, he said.
Jubilees have been recorded in places such as the Chesapeake Bay off the U.S.’s East Coast and Japan’s Omura Bay. In Texas, jubilee-like events are called “fish kills,” Bill Balboa, 50, a biologist at the Texas Parks & Wildlife Department, said in a telephone interview.
“A lot of them happen in enclosed bodies of water like harbors and canals,” he said.
In Mobile Bay, Alabama, which usually gets at least one a year, jubilees are seen as major social events -- part entertainment, part food gathering, Graham said.
“There’s always been a lot of excitement associated with jubilees, hence the name,” he said.
Michael Hutchison, 55, who’s lived in Point Clear, Alabama, since 1988, wades along the shoreline during a jubilee scooping crab and fish into a canoe. He said he’s not worried about oil polluting his catch because the bay is flushed with nine freshwater rivers.
As of last week, 22 percent of the Gulf of Mexico was closed for fishing due to concern about contamination from the oil spill, down from 36 percent at the height of closures on June 21, according to the National Oceanic and Atmospheric Administration Fisheries Service.
The U.S. Food and Drug Administration has said shrimp from Mobile Bay are safe to eat, and NOAA Fisheries reports its tests have found no contaminated samples. Alabama is still awaiting test results from crabs, Chris Denson, 35, a biologist with the Alabama Department of Conservation and Natural Resources, said in a telephone interview.