Published ingestion rates of total dry material (inorganic and organic) by benthic invertebrate deposit feeders and detritivores feeding at 15°C could be explained almost entirely by organic content of the ingested material and body size; the relation was consistent for 19 species from 3 phyla. Since ingestion rate of total dry material varied inversely with the organic content of the food, organic matter ingestion (C) was essentially a function of body size (W): [Formula: see text] where C is mg day and W is mg dry weight. These animals may maintain a rate of intake of organic matter which is independent of the organic content of the food source by: (1) Actively adjusting their feeding rates according to some perception of food "quality", and/or (2) Adapting their feeding rates to different environments on an evolutionary time scale.

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In order to investigate the controls of bacterial abundance and production in marine sedinlents, bacterial production determined by uptake of 3~-t h y m i l n e , microalgal production and sediment oxygen uptake was investigated monthly for 1 yr in 2 benthic systems, an intertidal mudflat and an intertidal sandflat. There was a closer coupllng between these rates in the sandflat than m the mudflat that may have been due to the more d y n a m~c nature of the sandflat. The parameters measured in h s study fell into 2 groups based on the similarity between their annual totals or mean abundances for the mudflat and for the sandflat. Although microalgal biomass, gross production, and sediment oxygen uptake were similar for both areas, bactenal biomass, bacterial productlon, and sedlment organic carbon were all 4 to 5 times higher in the mudflat than in the sandflat. Estimated annual turnovers of the bacterial population were 52 for the sandflat and 59 for the mudflat. Temperature was the factor that had the greatest influence on bactenal productlon, explairung 55 to 57 % of seasonal variation in specific growth rate. Bactena appeared to respond to the increase In temperature in late winter-early spring more quickly than the rest of the sediment community; this would imply that the input of organic matter to the benthos from an early spring bloom, occurring in colder waters, might result in a less efficient transfer of energy to the macrofauna than would occur with a later bloom.