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Marine Ecology Progress Series

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MEPS 293:99-108 (2005)  -  doi:10.3354/meps293099

Variations in seep mussel bed communities along physical and chemical environmental gradients

Derk C. Bergquist1,3,*, Clint Fleckenstein1, Julie Knisel1, Brett Begley1, Ian R. MacDonald2, Charles R. Fisher1

1Department of Biology, Pennsylvania State University, 208 Mueller Laboratory, University Park, Pennsylvania 16802, USA
2Physical and Life Sciences Department, Texas A&M University—Corpus Christi, 6300 Ocean Dr. ST320, Corpus Christi, Texas 78412, USA
3Present address: Department of Zoology, University of Florida, 223 Bartram Hall, Gainesville, Florida 32611-8525, USA

ABSTRACT: This study examined the faunal communities associated with beds of the hydrocarbon seep mussel Bathymodiolus childressi in the Gulf of Mexico and the relationships between these communities and local environmental characteristics. Mussels, their associated fauna and accompanying water chemistry parameters were collected at 17 locations across 4 hydrocarbon seep sites. A total of 19 species, mostly seep endemics, were identified. Species richness and fauna density were significantly and negatively correlated with methane concentration and were significantly and positively correlated with oxygen concentration. Canonical Correspondence Analysis (CCA) separated polychaetes, alvinocarid shrimp and gastropods along gradients of methane and oxygen concentrations. Polychaetes and alvinocarid shrimp tended towards lower oxygen and higher methane concentrations and gastropods tended towards higher oxygen and lower methane. The larger-sized predaceous gastropods and decapods were associated with lower sulfide and higher oxygen concentrations. The proportion of the community comprising of endemic species was significantly and positively correlated with mussel biomass and shell surface area. Other measures of habitat complexity (mussel density, shell surface area and biomass) explained little of the variation in the associated faunal communities. The results suggest that oxygen and methane availabilities play a substantial role in structuring these communities with several dominant seep heterotrophs partitioning resources among different microenvironments.

KEY WORDS: Benthic community · Chemical gradient · Habitat complexity · Bathymodiolus childressi · Cold seep

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