Trophic dynamics in antarctic benthic communities. I. In situ ingestion of microalgae by Foraminifera and metazoan meiofauna

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Abstract
Benthic microalgal production and the ingestion and subsequent metabolism of algal carbon by Foraminifera and several metazoan meiofauna were measured in situ in McMurdo Sound, Antarctica. The benthic microalgal community was dominated by the diatom Amphora antarctica. Microalgal biomass and production were 15 .+-. 4.8 mg chl a m-2 (mean .+-. SD) and 6.0 .+-. 1.9 mg C m-2 d-1, respectively. Weight-specific ingestion rates of microalgae by the foraminifers Astrammina rara and Astrorhiza sp. were ca 2.5 to 3.5 ng C mg wet wt-1 d-1; these rates were 2 to 3 times lower than those of the burrowing anemone Edwardsia meridionalas, small polychaetes and clams. All the meiofauna examined appeared to biosynthesize new cellular material from the ingested alagal carbon. The patterns and rates of polymer synthesis differed significantly for the protozoan and metazoan meiofauna: Foraminifera synthesized 2 to 5 times more protein and 3 to 5 times less lipid than metazoans. The different patterns of polymer synthesis of the meiofauna likely reflect differences in prey preference, metabolic rates, and the pathways and rates of digestion of the ingested prey. This study suggests that there may be differences in the patterns of metabolism and trophic status of co-occurring meiofauna.