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Abstract

Bacteria of the Cytophaga-Flavobacterium-Bacteroides (CFB) group (phylum Bacteroidetes),
in particular members of the class Flavobacteria, are among the most prominent heterotrophic
organisms in marine pelagic systems. They have also previously been found to be important
in the initial biopolymer degradation of sedimentary organic matter. The Flavobacteria community
was analysed in inshore, marine sediments subject to regular inputs of highly labile organic carbon
in order to understand the importance of this group in carbon degradation. We used denaturing gradient
gel electrophoresis and real-time PCR in a statistically robust manner, over 2 consecutive years,
to demonstrate that the number of Flavobacteria in the sediment increased and community composition
shifted with organic loading. Further community shifts occurred after cessation of organic loading,
and population numbers also decreased. Flavobacteria appear to be important in the initial
responses of the sediment microbial community to organic loading, regardless of sediment type, but
flavobacterial composition was not predictable. The highly dynamic nature and large diversity (functional
redundancy) of the Flavobacteria in these sediments may contribute to this unpredictable
response.