Deepwater oil spill impact continues

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Despite reports of low concentrations of oil in the Gulf of Mexico, a study has found that the Deepwater oil spill has had dramatic effects on fish.

The team from Louisiana University undertook a combined field and laboratory study and found that the effects of the oil spill in the Louisiana marshes on fish was wide-ranging; affecting reproduction and genetic material and damaging gills leading to developmental abnormalities and even death.

These effects persisted long after the visible oil had disappeared from the marshes. This means that whilst environmental chemistry indicated that the levels of oil were low, the fish were far more sensitive and accurate predictors of the presence of oil.

Fernando Galvez, Andrew Whitehead and team looked at gene expression in killifish in the lab and from the wild and found that even at low levels, the consequences of the spill were far-reaching.

George Gilchrist, acting deputy director of NSF's Division of Environmental Biology, which funded the research said: "Joining remote-sensing of the spill with gene expression data from wild-caught killifish, these scientists have captured the effects of low-level exposure to pollutants on the long-term health of fish. It's a landmark study in applying genomic technology to wild animal populations under stress."

The work found that the gene expression in the tissues of the fish suggested they may be at risk of developmental abnormalities, impaired reproduction even death. The gills were also damaged and less able to repair themselves; a key problem when gills are critical for maintaining fish body functions.

Associate Professor Whitehead said: "Though the fish may be 'safe to eat' based on low chemical burdens in their tissues, that doesn't mean that the fish are healthy or that the fish are capable of reproducing normally,"

The study also found similar cell responses in developing fish embryos.
Whitehead added: "This is of concern because early life-stages of many organisms are particularly sensitive to the toxic effects of oil, and because marsh contamination occurred during the spawning season of many species."

Dr Whitehead also emphasised that previous work had highlighted the influence of sub-lethal levels of oil and that this was what was being seen here: "…sub-lethal biological effects, especially those linked with reproduction, are most predictive of the long-term effects of oil in many fish species, such as herring and salmon."

For more information see the paper: Andrew Whitehead, Benjamin Dubansky, Charlotte Bodinier, Tzintzuni I. Garcia, Scott Miles, Chet Pilley, Vandana Raghunathan, Jennifer L. Roach, Nan Walker, Ronald B. Walter, Charles D. Rice, and Fernando Galvez.Science Applications in the Deepwater Horizon Oil Spill Special Feature: Genomic and physiological footprint of the Deepwater Horizon oil spill on resident marsh fishes. PNAS, September 26, 2011 DOI:

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