Benthic-pelagic coupling and suspension-feeding bivalves: Linking site-specific sediment flux and biodeposition to benthic community structure

Suspension-feeding bivalves play an important role in coastal ecosystems by affecting near-bed hydrodynamics and, subsequently, rates of biodeposition . We designed a high-resolution field study to investigate rates of sedimen tation and biodeposition around individuals within beds of the large pinnid bivalve, Atrina zelandica, and to link these rates with sediment biogeoche mical characteristics and macrofaunal community structure. The study was co nducted at three sites arrayed along a gradient of increasing suspended ses ton concentration, enabling us to assess changes in the strength of the Atr ina-macrofauna interaction with background sedimentation. Sedimentation rat es and inputs of organic carbon and nitrogen were higher close to individua l Atrina (less than or equal to 10 cm) compared to further away (> 30 cm). Seafloor sediments nearer Atrina were enriched in carbon and nitrogen and h ad more diverse and abundant macrofaunal assemblages. The strength of this interaction decreased with increasing background sedimentation. Although ot her mechanisms, both biotic and abiotic, may explain some of these patterns , we have identified variations in macrofaunal community structure that at least partly can be linked to site-specific sedimentation, at the small sca le of single Atrina, nested within the larger landscape scale of Atrina bed s, emphasizing Atrina's role in habitat modification, both structurally and functionally.