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Isotopic evidence for chemosynthesis‐based nutrition of macrobenthos: The lightness of being at Pacific methane seeps
Author(s) -
Levin Lisa A.,
Michener Robert H.
Publication year - 2002
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2002.47.5.1336
Subject(s) - chemosynthesis , petroleum seep , cold seep , food web , oceanography , geology , trophic level , macrobenthos , bathyal zone , isotopes of carbon , methane , ecology , benthic zone , total organic carbon , biology , paleontology , hydrothermal vent , hydrothermal circulation
The importance of chemosynthetic nutritional pathways was examined for macrofaunal invertebrates (≫300 µm) from methane seeps in the Gulf of Alaska (4,413–4,443 m), on the Oregon margin (590 m), and on the northern California slope [Eel River margin] (520 m) by use of natural abundance stable isotopic data. Seep macrofauna exhibited lighter Δ 13 C and Δ 15 N values than those in nonseep sediments, but isotopic signatures varied among seep sites. Macrofaunal isotopic signatures indicated chemosynthetically fixed carbon sources with a significant contribution from methane‐derived carbon (MDC) in macrofauna from sediments of pogonophoran fields (average Δ 13 C, 246.44‰, 32%–51% MDC) and Calyptogena phaseoliformis beds (average Δ 13 C, 240.89‰, 12%–40% MDC) in the Gulf of Alaska and in microbial mat sediments on the Oregon margin (average Δ 13 C, 243.80‰, 20%–44% MDC). Lesser influence of MDC was noted in macrofauna from sediments of Calyptogena pacifica beds on the Oregon (average Δ 13 C, 233.38‰, 0%–27% MDC) and California ( Δ 13 C, 225.10‰, 0%‐22% MDC) margins and from California microbial mat sediments ( Δ 13 C, 222.23‰, 0%–5% MDC). Although most macrofauna appeared to be heterotrophic, light Δ 15 N and Δ 13 C values together provided evidence for chemoautotrophic symbioses in selected taxa. Carbon isotopic signatures were consistent with consumption of methane‐oxidizing archaea by some dorvilleid polychaetes (Δ 13 C, 290.62‰ and 273.80‰) and with grazing on filamentous sulfur bacteria by gastropods and polychaetes from the Oregon and California seeps. The importance of chemosynthetic trophic pathways varies regionally and among microhabitats, taxonomic groups, and feeding guilds.