| Abstract: | Biomass and respiration (oxygen consumption) of bacteria, microfauna, and meiofauna were measured in coarse sand sediment from Brown's Bank (172 m) off Nova Scotia, Canada. Community biomass, excluding macrofauna, had a median value of 35 mg C m−2, dominated by bacteria (51%), microfauna (25%), and a minor meiofauna component (2·5%). Protozoan microfauna were mostly microflagellates (colourless cryptomonads). The experimental design allowed partitioning of benthic metabolism without using subtraction from whole community rates. Addition-removal experiments with fauna separated into size categories were used to construct a respiration-biomass regression for all taxa. Respiration rates for faunal groups were then calculated from their biomass in the natural sediment. Total microbial and meiofaunal community respiration had a median rate of 0·55 ml O2 m−2 h−1 which was partitioned into median proportions of bacteria (50%) microflagellates (27%), and metazoan meiofauna (4%). Correlations among faunal biomass values from incubated vials of sediment suggested that bacteria were important prey for protozoans. With added biomass of meiofauna, protozoans also became a potentially important source of prey. The results demonstrated the significance of microflagellate protozoans in these sediments and their metabolic and trophic importance relative to meiofauna and even bacteria. |
