--> Abstract: Macrofauna and Foraminifera from Slope and Shelf Methane Seeps on the Eel River Margin, by L. A. Levin, A. E. Rathburn, G. J. Mahn, C. M. Christopher, D. H. Zachary, L. Harris, and R. Michener; #90920 (1999).

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LEVIN, LISA A., ANTHONY E. RATHBURN, GIESKES, JORIS, MAHN; CHRISTOPHER, MARTIN, CHRISTOPHER; DAVID, HELD, ZACHARY, Scripps Institution of Oceanography, La Jolla, CA; LESLIE HARRIS, Los Angeles County Museum, Los Angeles, CA; and ROBERT MICHENER, Boston University, Boston, MA

Abstract: Macrofauna and Foraminifera from Slope and Shelf Methane Seeps on the Eel River Margin

We studied the taxonomic and isotopic composition of infauna from methane seeps on the Eel River margin (500 m and 35-55 m) to examine community structure, the importance of chemosynthesis for macrofaunal nutrition and the influence of methane seep environments on the distribution and stable isotopic signatures of benthic foraminifera. Taxa were categorized as seep specialists, seep tolerant and seep avoiders, based on comparisons with non-seep samples and other available data for the California margin. Both protozoan and metazoan seep infauna appeared to consist mainly of normal slope species found in productive settings. Abundances of living benthic foraminifera in the top 1 cm are quite high at the 500 m site. Differences in vertical distribution patterns between species are evident. Stable isotopic analyses of living (Rose Bengal stained) specimens of 7 species of benthic foraminifera, shell material from two Calyptogena pacifica valves, and authigenic carbonate from clam beds confirm the presence of methane-influenced pore waters. Only a few macro-infaunal taxa exhibited isotopic signatures indicative of chemosynthetically-based food chains.

AAPG Search and Discovery Article #90920©1999 AAPG Pacific Section Meeting, Monterey, California