Long-term Effects of Gulf Oil Spill on Shrimp, Other Species is Still Unknown

Gulf of Mexico shrimp, along with all seafood, has been tested extensively to assure that it’s safe for consumption in the wake of the BP oil spill, but the long-term effects on fish species from that oil, and the chemicals used to fight it, are still largely unknown. Possible effects on the growth and mortality of Gulf shrimp could come from a variety of factors, including alterations in the food they eat or the species who prey on them, changes in the marsh they inhabit, or changes in their own biology.

(By Benjamin Alexander-Bloch, The Times-Picayune) –Hanging ominously over the Gulf studies is the specter of the collapse of the Pacific herring fishery in Alaska’s Prince William Sound in 1993, four years after the Exxon

-Valdez oil spill. In part, that threat looms because the scientific community never made a conclusive determination about what caused that decline and whether that oil spill was the driver, or whether perhaps a virus or fungal infection played a major role.

While the Exxon-Valdez spill occurred during the herring spawning season and BP’s Macondo well began spewing around the white shrimp spawning season, the difference is that herring spawn at the age of 4, whereas shrimp are an annual crop, spawning each year and living only about a year. So, presumably a quicker decline would be seen in shrimp.

Last fall, LSU released a study showing that the Gulf killifish, a marsh minnow known locally as cocahoe, showed signs of  hydrocarbon poisoning. But Andrew Whitehead, lead author of the study, made clear that the species would have to be monitored for several more years to know whether it would affect the species’ reproduction and population levels.

He also noted that his study held no implications for the safety of eating Gulf seafood because the levels that affect the tiny cocahoe are much too low to affect humans.

The federal Natural Resource Damage Assessment, or NRDA, is looking at some of the BP spill’s potential effect on shrimp. BP has pledged to spend $1 billion on “early restoration” projects, with Louisiana in line to get $200 million, but the company and other parties responsible for the spill may eventually have to spend as much as $20 billion on natural resource projects.

The state is conducting toxicity testing to evaluate survival, reproduction, growth and disease responses of representative Gulf species to the BP oil and dispersants, but those tests are part of the non-cooperative work plans, so the state is keeping the work confidential.

Another study approved by the state and BP is examining Louisiana marsh oiling. Of 123 sample sites, the study described 66 marsh sites in Louisiana in the fall of 2010 as having received heavy oiling, 42 as receiving moderate, light or very light oiling, and 15 areas as receiving no oiling.

Then there are ongoing studies exploring potential oil affects on the spawning stocks of species that rely on marshes for nursery habitat, and on the state of the food shrimp eat during their growth stages.

In addition, the Gulf Research Initiative is funding $500 million worth of environmental studies in the Gulf of Mexico. One such study looks at potential oil spill effects on the mortality, development and growth of the larval, juvenile and adult stages of three Gulf species, including white shrimp.

Steve Murawski, a University of South Florida oceanographer, and a colleague earlier this month gave a presentation in Florida discussing fish they’d found with skin lesions in the Gulf last summer, many of them in areas where oil had been present. Murawski conditioned his findings though, saying that areas where fish with lesions were found also might have had natural oil seeps, leaky pipelines or rigs unrelated to the BP spill.

“It’s complicated and I’m unwilling to point a finger at anyone until I have pretty clear answers,” said Murawski, who served as NOAA’s chief fisheries scientist from 2004 until 2010.

One of the main problems is there isn’t much pre-spill data. For example, Murawski admitted that the rate of fish skin lesions before the spill isn’t documented. At least, he said, his study will provide an assessment of the current health that will help determine a threshold for future assessments in case of disasters down the line.

Skin lesions are nothing new in the Gulf. In 2009, fish with lesions began showing up at higher rates in Alabama’s Mobile Bay, and an evaluation by the Alabama Department of Conservation and Natural Resources and Auburn University determined the lesions likely were caused by a sudden surge of fresh water from earlier flash floods, and temperature changes.

“GoMRI In the news” is a reposting of articles about GoMRI-funded research (published by various news outlets).  The author’s interpretations and opinions expressed in these articles is not necessarily that of GoMRI.