Conversion of the particulate fraction of seaweed detritus to bacterial biomass

The efficiency with which particulate organic carbon from seaweed detritus was transformed to bacterial carbon was determined in the laboratory by comparing changes in bacterial numbers with changes in the organic carbon content of detritus in incubation experiments lasting between 2 and 36 days. In general, the efficiencies were highest (43%) in the shortest incubations and declined with increasing length of experiment to a mean of 22% at 36 days. Nitrogen enrichment of the cultures accelerated decomposition and increased bacterial abundance but did not lead to higher conversion efficiencies than those observed without enrichment. Of the initial detrital carbon, 54% was rapidly leached into the seawater and a further 23% was removed by microbial activity. The remaining material was relatively refractory and had a low C:N ratio. The results indicate that the C:N ratio of detritus is not a good indication of its nutritional value.