Effects of Suspended Food Availability on the Feeding Mode and Burial Depth of the Baltic Clam, Macoma balthica

Abstract

Previous studies showed that siphon cropping by epibenthic predators reduces the size of inhalant siphon of the Baltic clam Macoma balthica (L.), causing the clams to reside at shallower burial depths in the sediment and making them more vulnerable to lethal predation. This indirect interaction is further complicated because M. balthica facultatively switches between suspension-and deposit-feeding in response to the availability of suspended food particles. Laboratory experiments showed that the proportion of clams deposit feeding with exposed siphons increased with decreasing food concentrations in the water column and this resulted in shallower burial depths in the sediment. The clams showed similar responses in feeding mode and burial depth to the concentrations of suspended food indirectly manipulated by the presence and/or density of either interspecific (suspension-feeding soft-shelled clam Mya arenaria L.) or intraspecific competitors. J. lin and A. H. Hines, Smithsonian Environmental Research Center, P. O. Box 28, Edgewater, MD 21037, USA (present address of JL: Dept of Biological Sciences, Florida Inst. of Technology, 150 West University Blvd, Melbourne, FL 32901-6988, USA).Higher-order interactions and indirect effects involving multiple trophic levels and environmental factors are widespread in marine (e.g., Dungan 1986, Schmitt 1987, Kneib 1988, Peterson and Black 1988, Wilson 1989, Posey and Hines 1991, freshwater (e.g., Morin 1986, Miller and Kerfoot 1987, Sih 1987, Sadinski and Dunson 1992, Werner 1992, and terrestrial communities (e.g., Miller 1985, Wilson 1986). An understanding of these complex multispecies interactions is essential to synthetic theories of population and community structure. The complexity of the interactions, however, often makes it difficult to detect higher-order interactions andlor distinguish direct and indirect effects (Connell 1983).The Baltic clam Macoma balthica (L.) offers an ideal model system to exaInine the role of indirect effects and complex interactions on trophic interactions. It is a facultative suspension and deposit feeder. Bubnova (1972) and'Olafsson (1986) hypothesized that M. balthica suspen-

Influences of nutritional state and temperature on suspension-feeding rates and mechanics in the spionid polychaete Polydora cornuta

“…These algal concentrations occur naturally in coastal waters during bloom and non-bloom conditions, respectively (Lin & Hines 1994, Navarro & Thompson 1995, Hughes et al 2000, Lucas et al 2000 and these temperatures correspond to temperate-zone spring/summer and winter conditions, respectively (Vedel 1998, Hughes et al 2000, Jordana et al 2000. Each worm was conditioned separately, with its pipettor tip held upright, in a plastic container holding 4.5 l of artificial seawater and with vigorous aeration to maintain algae in suspension.…”

Community structure and bioturbation potential of macrofauna at four North Sea stations with contrasting food supply

“…Changes in benthic community structure have been associated with biotic factors such as con~petition and predation (Rhoads & Young 1970, Weinberg 1984 and abiotic factors such as water depth (Hyland et al 1991), current velocity (Wildish & Peer 1983), sediment stability (Probert 1984), sedimentation rate (Schaffner et al 1987, Aller & Stupakoff 1996, oxygen concentration (Levin et al 1991), silt content (Eleftheriou & Basford 1989) and organic loading (Dauer & Conner 1980). In particular, the amount and the nutritional quality of the organic material in the sediment is believed to play a key role influencing the biomass (Grebmeier et al 1988), vertical distribution (Lin & Hines 1994) and trophic structure of rnacrofaunal communities (Marsh & Tenore 1990). On the other hand, macrofauna affects the distribution of organic matter in sediments by bioturbation (Wheatcroft 1990, Blair et al 1996.…”

Microalgae, macrofauna and sediment stability: an experimental test of a reciprocal relationship

“…This may reflect the ability of post-juvenile M. balthica to adopt suspension, as well as deposit, feeding (Lin & Hines 1994), thus reducing its dependence on benthic food sources such as microalgae. The absence of any significant treatment impacts on Cerastoderma edule, an obligate suspension feeder (Kamermans et al 1992), further supports the suggestion that the microphytobenthos are important for deposit, but not suspension, feeding organisms.…”