Minnows in the Marsh: The Gulf’s Canary in the Coal Mine?

Several weeks ago, researchers published a seminal study on how the Deepwater Horizon oil spill has harmed fish in coastal marshes.  To date, most studies on wildlife affected by the spill focus on acute and direct effects.  But equally important are sub-lethal effects, such as impaired reproduction and embryonic development, which are far more difficult to observe.  Indeed, sub-lethal effects are “critically important for predicting longterm population-level impacts of oil pollution,” according to the researchers.

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The study tracked the effects of oil from the Deepwater Horizon spill on Gulf killifish (Fundulus grandis) during the first 4 months of the spill.  At one of the study sites, researchers found that although sampled water and fish tissue did not show abnormally high levels of oil, there were “significant biological effects” on the fish and an increased risk of health problems.  For example, juvenile fish had genetic evidence of exposure to polycyclic aromatic hydrocarbons (PAHs), which can lead to cardiac impairment in adulthood.  The researchers also found that the spill contaminated marshes at a time coinciding with “the spawning season for many marsh animals, including killifish, and reproductive effects are predictive of long-term population-level impacts from oil spills.”

This study has several important implications.  It shows that although seafood from the Gulf of Mexico may be safe for human consumption, affected wildlife may continue to suffer population declines.  As a result, it could be a long time before the public is “made whole” again following an oil spill, as required by the Oil Pollution Act of 1990.  Last year, we had questioned whether the government was properly assessing how the spill may have harmed many coastal marsh species.  In particular, we saw no evidence that the protocols created to assess natural resource damages resulting from the spill were comprehensive enough to cover the Saltmarsh topminnow (Fundulus jenkinsi), a species endemic to Gulf marshes and now being considered for listing under the U.S. Endangered Species Act, in part because of the spill.  It’s easy to lose sight of these inconspicuous, non-iconic animals, which is why this recent study is especially important.

Another underappreciated aspect of the Gulf spill is that if it results in species being listed under the Endangered Species Act, the public and other business will bear the cost of listing and recovering the species, as well as complying with the restrictions of the act generally.  This cost should be shifted to the companies responsible for the spill as part of the Natural Resource Damage Assessment process.

Journal reference:
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: 10.1073/pnas.1109545108

Gulf Killifish. Credit: USGS

Saltmarsh Topminnow. Credit: Joseph R. Tomelleri

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- who has written 19 posts on dotWild.

Ya-Wei Li is the Senior Director of Endangered Species Conservation at Defenders of Wildlife.

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