Long-term history of chemoautotrophic clam-dominated faunas of petroleum seeps in the Northwestern Gulf of Mexico |
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Authors: | Prof Dr Russel Callender Prof Dr Eric N Powell |
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Institution: | (1) Virginia Graduate Marine Science Consortium, University of Virginia, Madison House, 170 Rugby Rd, 22903 Charlottesville, VA, USA;(2) Haskin Shellfish Research Laboratory, Rutgers University, 6959 Miller Ave., 08349 Port Norris, NJ, USA |
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Abstract: | Summary Chemoautotrophic clam-dominated assemblages are commonly associated with petroleum seepage on the continental slope of the
Gulf of Mexico. We examine the persistence and resilence of these communities by evaluating downcore trends in abundance,
biomass, and trophodynamics in communities from four separate petroleum seep sites on the Louisiana continental slope. Some
petroleum seep sites retained optimal habitat for some species continuously over geologically-relevant periods of time. More
commonly, however, habitat optimality varied substantially over time scales of hundreds of years. Thus, one important characteristic
of these sites was the degree of persistence of the chemoautotrophic biota. A fauna typically was persistent over a time span
of a few hundred years, but was typically not persistent over a longer time span. The mechanisms producing local extinction
remain unclear, however temporal variations in juvenile survivorship seem to be substantially larger than temporal variations
in larval settlement, to the extent that the heavily taphonomically-biased record of juvenile individuals permits such a conclusion.
When local extinctions occurred in the chemoautotrophic biota, the biota was replaced by a normal slope biota or a mixture
of a normal slope biota and the juveniles of chemoautotrophic species that failed to survive to adulthood. Thus, the only
faunal transitions were between specific chemoautotrophic faunas and the non-chemoautotrophic fauna. Not one distinctive faunal
transition between two chemoautotrophic faunas was observed. Accordingly, each discrete chemoautotrophic fauna was resilient
over long time scales; time scales of geological importance. |
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Keywords: | Clam-Fauna Cold-Seep Methane Seeps Chemoautotrophy Gulf of Mexico Recent |
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