Aquatic Sciences Meeting, Albuquerque 2001

SS14 Microbial Diversity (Disciplinary Connections)

Date: Tuesday, February 13, 2001, Time: 2:15:00 PM

Location: Mesilla

Molina, M, , US EPA and University of Georgia, Athens, USA, molina.marirosa@epa.gov

Burke, R, A, US EPA, Athens, USA, burke.roger@epa.gov

Hodson, R, E, University of Georgia, Athens, USA, hodson@arches.uga.edu

MICROBIAL DIVERSITY IN SURFACE SEDIMENTS: A COMPARISON OF TWO ESTUARINE CONTINUUMS

The microbial diversity in estuarine sediments of the Altamaha and Savannah Rivers in Georgia were compared temporally and spatially using phospholipid fatty acid (PLFA) analysis. Surface sediment samples collected along a salinity gradient were also analyzed for ATP, TOC, and C stable isotopes of sediments and individual PLFAs. Both the Savannah and Altamaha contained similar concentrations of total PLFAs and ATP. However, the Savannah contained higher concentrations of phototrophic indicators (16:1w3 and 20:5w3) and lower concentrations of i15:0, i16:0 and 10Me16:0 (Gram + bacteria). The Shannon Diversity Index indicated significant within river differences due to season, but no difference between rivers. During March and October ‘97 (lowest diversity in both rivers) the sediment del 13C indicated areas of C3 deposition at the mouth (-27.6 per mil). The signal was more enriched in 13C (-16.8 to -21.5 per mil) at the mesohaline area, indicating higher inputs from marine and C4 sources. 13C-PLFAs indicated selective C utilization by specific groups of the microbial community. The data suggest that in these rivers, the quality of the natural fluctuation of organic C may be more important than anthropogenic influences in determining the diversity and structure of microbial communities in surface sediments.

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Aquatic Sciences Meeting, Albuquerque 2001

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