Monterey Bay cold-seep biota: Assemblages, abundance, and ultrastructure of living foraminifera

Although there is a growing body of evidence indicating benthic foraminifer a inhabit hydrocarbon and cold seep environments, biochemical and ultrastru ctural data on seep foraminiferal communities are not available. Therefore, sediments collected from cold seeps in Monterey Bay, CA (900-1000m), were examined for the presence of live benthic foraminifera. Results from three independent methods (ATP assay, ultrastructural. analysis, rose Bengal stai ning) indicate that certain species inhabit the Clam Flat and Clam Field se eps. Abundances in our seep samples were lower than in comparable non-seep sites, although not atypical for these bathyal depths. Of 38 species repres ented at these two seep sites by cytoplasm-containing specimens, only Spiro plectammina biformis was restricted to the seep environment. However, becau se S. biformis is also known from non-seep sites in other areas, it should not be considered as endemic to seeps. Ultrastructural studies show abundan t peroxisomes in seep specimens, which may allow inhabitation of such envir onments. One specimen of Uvigerina peregrina had prokaryotes nestled in tes t pores, suggesting that bacteria may play a role in the survival of forami nifera in this seep environment. (C) 2001 Elsevier Science Ltd. All rights reserved.