BlogsGoMOSES 2019

Benthic fauna in the Gulf: living in oily times

Written by Sean Beckwith, Web Content Developer for USFCMS

NEW ORLEANS, LA –  As a non-“fish person,” I have to admit that I sometimes forget about…the fish.   In my own research, I’ve mostly focused on the chemical compounds in seawater, like CO2, or on corals and shelled organisms, which are benthic (bottom-dwelling) creatures.

Yesterday’s Session 4 at the GoMOSES conference reminded me that “benthic fauna” also include fish that interact with the bottom creatures and with the sediment, such as grouper, snapper and tilefish, to name a few.  These fish search for their food primarily along the bottom, and some even make homes within the mud.

Session 4, “Environmental Setting, Stressors, and Their Influence on Resilience of Benthic Fauna in the Gulf of Mexico”, was chaired by USFCMS researchers Dr. Patrick Schwing and Dr. Isabel Romero and colleagues from Boston University, University of Southern Mississippi, Rice University, and Texas A&M University.  The 12 talks included in the session addressed large-scale (ocean circulation, sea surface temperature, storm runoff) and localized (oil pollution, agricultural runoff, fishing pressure) stressors to account for changes in the benthic community in the years following the Deepwater Horizon (DWH) blowout.

In the second half of the session, Dr. Erin Pulster (USFCMS/C-IMAGE) raised the question as to what truly represents baseline data given that 1) previous spills, 2) natural oil seeps, 3) leaky wells, and 4) river discharges (especially the Mississippi) create a Gulf that is, at any given time, fairly oily.  Her research asks the open question, “How do we quantify recovery?” in light of an oily baseline.

With spikes in the concentration of polycyclic aromatic hydrocarbons, a carcinogenic micropollutant, found in fish muscle tissue following the DWH event, researchers are fairly confident the oil spill was to blame in most of the fish examined but are careful to consider all sources of oil release into the Gulf.  Research continues on the best methods for teasing apart the various sources of oil pollution.

Going back to Monday’s workshop on “Fighting the Next War” on oil spills, Dr. Schwing had given a nice overview of similar troubles in the benthic environment, but with the focus on foraminifera (so, not fish).  An alarming takeaway from his talk was that 80 to 90% of the benthic meiofauna (little guys living in the sediment) and macrofauna (slightly bigger guys living on or in the sediment)  around the DWH well-head showed moderate to severe impacts following the 2010 blowout.  For foraminifera specifically, there was an 80 to 93% decrease in density (of their populations) and a 33 to 40% decrease in diversity, based on several study areas in the northern Gulf of Mexico in proximity to the blowout.

Still to come…a report on oil spill impacts to fishes of the deep pelagic zone (>200 m).

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