Tracer analysis of methanogenesis in salt marsh soils.

Differences in paths of carbon flow have been found in soils of the tall (TS) and short (SS) Spartina alterniflora marshes of Sapelo Island, Ga. Gaseous end products of [U-C]glucose metabolism were CO(2) and CH(4) in the SS region and primarily CO(2) in the TS region. Sulfate concentration did not demonstrably affect glucose catabolism or the distribution of end products in either zone. [U-C]acetate was converted to CO(2) and CH(4) in the SS soils and almost exclusively to CO(2) in the TS soils. Sulfate concentration did not affect acetate metabolism in the SS soils; however, a noticeable effect of sulfate dilution was seen in TS soils. Sulfate dilution in TS samples resulted in increased methane formation. Total glucose and acetate metabolism were similar in TS and SS soils despite differences in end products. A microbial community characterized by fermentative/sulfate-reducing processes has developed in TS soils as opposed to the fermentative/methanogenic/sulfate-reducing community found in SS soils.