MEPS 154:241-252 (1997)  -  doi:10.3354/meps154241

Particle uptake and deposition by the 2 most abundant deep-sea demosponge species from the Norwegian and Greenland Sea (Thenea abyssorum) and the deep fjords of western Norway (Thenea muricata) were studied in flume experiments. Fluorescent particles of 1, 2, 3, 6, 10 and 16 µm diameter (microspheres, Duke Scientific Corporation^®) with a density of 1.05 g cm^-3 were used at <\n>2 current velocities, 1.5 and 5 cm s^-1. Both species ingested small particles exclusively (<6 µm and <10 µm, respectively), with a preference for the smallest fraction at both current speeds. The results suggest that the size spectrum actually ingested depends on the supplied particle sizes rather than on current velocity. Current velocity fields around dead specimens were recorded and turbulence intensity calculated in order to determine the influence of the sponge acting as a biogenic structure on the near-bottom current regime. Disruption of flow conditions was detected as far as 14 cm downstream and several cm laterally from the biogenic obstacles. Bulk biodeposition rates calculated from sponge biomass and volume of ingested particles range between 7 and 10 mg d^-1 g^-1 ash-free dry weight.

Deep sea · Sponge · Suspension feeding · Biodeposition · Biogenic structure · Flow regime