Bivalve Feeding and the Benthic Boundary Layer

Benthic suspension feeders particularly some bivalves have strong structuring effects on rocky shore communities which are commonly dominated by the Mytilidae in most oceans (see Paine 1984). This dominance may be related to at least two important aspects of their ecology the sestonic nature of their food and their sessile mode of life. The food of seston feeders is produced in a three-dimensional environment which flows over the animals. Under favourable conditions this food is continuously replenished by currents sinking and reproduction of planktonic organisms. Thus owing to their sedentary nature and feeding behaviour there is strong coupling between the pelagic and benthic environments through bivalves. Energy from the pelagos is channeled directly to the benthos via the filtering activity of the organisms and is eventually used for various metabolic and growth activities (see Dame and Patten 1981). Given the above it can be postulated that the biomass of other feeding guilds (e.g. carnivores which depend directly on primary consumers and perhaps even grazers through the elimination of algal growth by sessile animals Dayton 1973) as well as the overall structure of intertidal communities is dependent on the “success” or “failure” of the suspension feeders. Thus given the central position of suspension feeders as structuring agents of the intertidal communities energy flow from the pelagos to the benthos can be determined by measuring energy flow through this guild. Similar principles hold for subtidal macrofaunal assemblages. Wildish and Peer (1983) for example reported similar relationships between the pelagos and benthos in the Bay of Fundy where suspension feeders contributed over 88% of the total macrofaunal production.