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The Effects of Low Sulfate Concentrations on Modern Microbial Mat Communities: A Long Term ManipulationMicrobial mats were widespread during the first ca. 2 Ga. of our biosphere's history. To better understand microbial ecosystems and their biomarkers under the low sulfate levels present in early oceans, we attempted a long-term (ca. 1 year) manipulation of sulfate in modem mats. Mats collected from salt ponds at Guerrero Negro, Baja Calif. Sur were incubated in a Greenhouse "Collaboratory" at Ames. Mats were maintained in artificial seawater brine containing either: 1) sulfate levels normal for these mats (70 mM), or 2) brine in which sulfate was replaced by chloride. Sulfate concentrations in the "low sulfate" brine gradually approached their lowest (to date) value of 0. 1 mM as sulfate was consumed and/or diffused out of the mat over a period of ca. 4 months. During that period of time, a number of differences between the treatments emerged. Relative to the "low sulfate" mats, "normal sulfate" mats had: 1) lower consumption of oxygen in the lower levels of the mat, 2) higher efficiencies of oxygenic photosynthesis, and 3) higher rates of nitrogen fixation. Rates of methane production by the mats increased greatly as sulfate concentrations fell below ca. 0.2 mM. In contrast, "low" and "normal" sulfate mats had similar net rates of exchange of O2 and dissolved inorganic C between the mats and overlying water. Reduced sulfate levels have diverse impacts upon these ecosystems.
Document ID
20020054451
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Bebout, Brad
(NASA Ames Research Center Moffett Field, CA United States)
Carpenter, Steve
(NASA Ames Research Center Moffett Field, CA United States)
DesMarais, David J.
(NASA Ames Research Center Moffett Field, CA United States)
Discipulo, Mykell
(NASA Ames Research Center Moffett Field, CA United States)
Hogan, Mary
(NASA Ames Research Center Moffett Field, CA United States)
Turk, Kendra
(NASA Ames Research Center Moffett Field, CA United States)
Date Acquired
August 20, 2013
Publication Date
January 1, 2002
Subject Category
Life Sciences (General)
Meeting Information
Meeting: 2nd Astrobiology Science Conference
Location: Moffett Field, CA
Country: United States
Start Date: April 7, 2002
End Date: April 11, 2002
Funding Number(s)
PROJECT: RTOP 344-38-00-05
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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