EFFECTS OF SUSPENDED FOOD AVAILABILITY ON THE FEEDING MODE AND BURIALDEPTH OF THE BALTIC CLAM, MACOMA-BALTHICA

Previous studies showed that siphon cropping by epibenthic predators r educes the size of inhalant siphon of the Baltic clam Macoma balthica (L.), causing the clams to reside at shallower burial depths in the se diment and making them more vulnerable to lethal predation. This indir ect interaction is further complicated because M. balthica facultative ly switches between suspension- and deposit-feeding in response to the availability of suspended food particles. Laboratory experiments show ed that the proportion of clams deposit feeding with exposed siphons i ncreased with decreasing food concentrations in the water column and t his resulted in shallower burial depths in the sediment. The clams sho wed similar responses in feeding mode and burial depth to the concentr ations of suspended food indirectly manipulated by the presence and/or density of either interspecific (suspension-feeding soft-shelled clam Mya arenarin L.) or intraspecific competitors.