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Seasonal composition and activity of sulfate-reducing prokaryotic communities in seagrass bed sediments
Citation:
Smith, A. C., J. E. Kostka, R D. Devereux, AND D F. Yates. Seasonal composition and activity of sulfate-reducing prokaryotic communities in seagrass bed sediments. AQUATIC MICROBIAL ECOLOGY. Inter-Research, Luhe, Germany, 37(2):183-195, (2004).
Impact/Purpose:
To better understand interactions of communities of Sulfate-reducing prokaryotes with aquatic plants and their role in carbon and nutrient cycles
Description:
Sulfate-reducing prokaryotes (SRP) play a key role in the carbon and nutrient cycles of coastal marine, vegetated ecosystems, but the interactions of SRP communities with aquatic plants remain little studied. The abundance, activity, and community composition of SRP was studied in relation to plant growth state in a Thalassia testudinum seagrass bed and in adjacent unvegetated areas. The community composition of SRP was determined using restriction fragment length polymorphism (RFLP) screening and amino acid sequence comparisons of the dissimilatory bisulfite reductase (dsr) genes amplified and cloned directly from sediment samples. The majority of unique DSR sequences clustered within the Desulfobacteriaceae, possibly representing new SRP genera. Some DSR sequences grouped according to the presence of vegetation, although the relationship did not appear to be strong. Depth-integrated sulfate reduction rates were three to five times higher in vegetated (52. 5 mmol m-2d-1 in summer and 20.4-26.5 mmol m-2d-1in winter) as compared to unvegetated sediments (10.7 mmol m-2d-1 in summer and 3.6-7.6 mmol m-2d-1in 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 as compared to unvegetated sites in the summer during the period of maximum growth for seagrasses; whereas no statistically-significant difference was observed for counts between sites during the winter, SRP counts from MPNs accounted for approximately 1% and 0.01% of bacterial direct counts in vegetated and unvegetated sediments, respectively. The diversity of SRP in seagrass sediments, as indicated by dsr sequences, was high and did not appear to covary with the other environmental paramenters tested. Our results indicate that seagrass growth state enhances the abundance and activity of SRP but has little effect on their community composition.