The biomass, community structure, and spatial distribution of the sedimentary microbiota from a high-energy area of the deep sea

Abstract

Sediments from an abyssal area subjected to high-energy currents showed a total cellular biomass, measured as extractable phospholipid, 6 to 10 times greater than that of other sediments of comparable depths, and approximately one-third that of a subtidal estuarine sediment. Community structure of these abyssal sediments, assessed by ester-linked phospholipid fatty acids, was characterized by increased bacterial dominance and a greater proportion of anaerobic bacteria when compared to a subtidal estuarine sediment. Although there is geochemical evidence for mixing of sediments to depths > 10 cm below the sediment surface, biomass in the 9 to 10 cm layer is approximately one-third of the 0 to 1 cm layer. A distinct community structure occurs in this deeper stratum, as reflected by increased proportions of fatty acids typical of anaerobic bacteria. A three-level, nested sampling design allowed an assessment of spatial distribution of microbial assemblies. The major source of variance was among subcores within a box core. This small-scale patchiness parallels that determined for a subtidal estuarine sediment.