MICROBIAL-GROWTH AND ACTIVITY DURING THE INITIAL-STAGES OF SEAGRASS DECOMPOSITION

Microbial O2 consumption and bacterial growth associated with decaying Zostera marina increased rapidly in the first 24 h of incubation at the sediment surface. During this period, the detrital complex lost 20% of its initial dry weight. An additional 20% of the original dry weight was lost in the next 13 d, and 73% was lost over the entire 6 wk incubation period; changes in the rate of weight loss were consistent with changes in the patterns of bacterial activity. While the initial response of the detritus-associated bacteria was rapid and substantial, less than 7.5% of the detrital carbon lost during the first 48 h of incubation was metabolized (assimilated plus respired), although 52.6% was metabolized during the 28 d to 42 d period. Of the plant carbon metabolized, over 80% was mineralized to CO2. The results suggest that if bacterial transformation of plant litter is an important link in the transfer of primary production to aquatic food webs, water column bacteria function as a link and not the bacteria associated with detrital particles.