Biotic enrichment of intertidal sediments by experimental aggregates of the deposit-feeding bivalve Macoma balthica

Abstract

Experimental aggregates of the bivalve Macoma balthica, established on a sandy tidal flat in the North Sea, are preferentially colonized by small zoobenthos. The tellinids stay buried at 3 to 6 cm while their long inhalant siphons pick up deposits from the surface. The short exhalant siphons terminate within the sediment. High abundance of diatom-feeding Turbellaria at the surface, and bacteria-feedmg and predatory species in the subsurface suggest enhanced growth of rnicroalgae, bacteria and their grazers, stimulated by M. balthica. No such 'gardening' effects are observed within aggregates of the suspension-feeding cockle Cerastoderma edule, where exhalant siphons are flush with the surface. Both bivalve aggregates, however, displaced the tube-dwelling polychaete Pygospjo elegans.