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Research Article
1 March 1979

Microbial Biomass and Activity Distribution in an Anoxic, Hypersaline Basin


The Orca Basin is a hypersaline depression in the northern Gulf of Mexico with anoxic conditions observed in the lower 200 m of the water column. Measurements of adenosine 5′-triphosphate, heterotrophic potential, and uridine uptake made above and across the interface into the anoxic zone revealed the presence of an active microbial population approximately 100 m above the interface. Biomass and activity decreased at and just below the interface but increased near the bottom, consistent with similar observations made in the Cariaco Trench. The maximum adenosine 5′-triphosphate concentration above the interface of 5.9 ng/liter (2,173 m) is about eight times greater than the value found in oxygenated waters of corresponding depth in the absence of an anoxic zone. The maximum adenosine 5′-triphosphate concentration in the anoxic zone is approximately 15 times greater than that found in oxygenated water of similar depth, suggesting anoxia will support the development of a larger bacterial population. Our findings suggest that autotrophic bacteria may be the dominant physiological group in the region just above the interface.

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Published In

cover image Applied and Environmental Microbiology
Applied and Environmental Microbiology
Volume 37Number 3March 1979
Pages: 466 - 470
PubMed: 16345355


Published online: 1 March 1979


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Paul A. LaRock
Department of Oceanography, Florida State University; Tallahassee, Florida 32306
Ray D. Lauer
Department of Oceanography, Florida State University; Tallahassee, Florida 32306
John R. Schwarz
Department of Marine Biology, Texas A&M University, Galveston, Texas 77550
Kathleen K. Watanabe
Department of Oceanography, Florida State University; Tallahassee, Florida 32306
Denis A. Wiesenburg
Department of Oceanography, Texas A&M University, College Station, Texas 77843

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