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AME 37:183-195 (2004)
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Abstract
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Seasonal composition and activity of sulfate-reducing prokaryotic communities in seagrass bed sediments
April C. Smith1, Joel E. Kostka1,*, Richard Devereux2, Diane F. Yates2
1Department of Oceanography, Florida State University, Tallahassee, Florida 32306-4320, USA 2US Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Gulf Ecology Division, Gulf Breeze,
Florida 32561, USA
*Corresponding author. Email: jkostka@ocean.fsu.edu
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ABSTRACT: Sulfate-reducing prokaryotes (SRP) play a key role in the carbon and nutrient cycles of coastal marine, vegetated ecosystems; however, the interactions of SRP communities with aquatic plants remain little studied. The abundance, activity, and
community composition of SRP were studied in relation to sediment geochemical gradients and plant growth state in a Thalassia testudinum seagrass bed and in adjacent unvegetated areas. Geochemical analyses indicated significantly higher
concentrations of microbial respiration products in vegetated sediments during summer than during winter. Depth-integrated sulfate reduction rates were 3 to 5 times higher in vegetated (52.5 mmol m2 d1 in summer and 20.4
to 26.5 mmol m2 d1 in winter) compared to unvegetated sediments (10.7 mmol m2 d1 in summer and 3.6 to 7.6 mmol m2 d1 in winter), and depth-integrated
activities further showed a strong correlation with seagrass biomass. Most probable number (MPN) counts of SRP were 10 times higher in vegetated compared to unvegetated sites in the summer during the period of maximum growth for seagrasses, whereas no
difference was observed for counts between sites during the winter. The community composition of SRP was determined using restriction fragment length polymorphism (RFLP) screening and amino acid sequence comparisons inferred from partial dissimilatory
bisulfite reductase (dsrA and B) genes that were PCR-amplified and cloned from DNA extracted from sediment samples. The majority of unique DSR sequences were not affiliated with any known SRP group, and clustered at levels indicative of new
SRP. Some DSR sequences grouped on the basis of originating from vegetated or unvegetated sediments, although the relationship did not appear to be strong. The diversity of SRP in seagrass bed sediments, as indicated by dsr analysis, was high and
did not appear to covary with the other environmental parameters tested. Our results indicate that seagrass growth state enhances the abundance and activity of SRP, while SRP community composition remains relatively stable across the environmental
parameters tested.
KEY WORDS: dsr gene · Seagrass · Sulfate reduction · Sediment geochemistry · Sulfate-reducing bacteria
Full text in pdf format
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Published in AME Vol.
37, No. 2
(2004) on November 11
Print ISSN: 0948-3055; Online ISSN: 1616-1564.
Copyright © Inter-Research, Oldendorf/Luhe, 2004
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