Changes in the Nitrate-reducing Community of an Anaerobic Saltmarsh Sediment in Response to Seasonal Selection by Temperature

Measurement of the nitrate-reducing potential by bacteria in saltmarsh sediment, using a thermal gradient block incubator, revealed seasonal physiological changes in the community. A mesophilic part of the nitrate-reducing community was always present, although it achieved maximum development at the end of the summer and minimum development at the end of the winter. In contrast, a distinct psychrotrophic part of the community achieved maximum development at the end of the winter but disappeared during summer. Chemostat enrichment of nitrate-reducing bacteria at 10 °C isolated predominantly Pseudomonas spp., but Vibrio spp. predominated in enrichments at 25 °C. The observed seasonal changes in situ might reflect differential seasonal selection of these two groups of bacteria.