PARTICLE CAPTURE AND DEPOSITION BY DEEP-SEA SPONGES FROM THE NORWEGIAN-GREENLAND SEA

Particle uptake and deposition by the 2 most abundant deep-sea demospo nge species from the Norwegian and Greenland Sea (Thenea abyssorum) an d the deep fjords of western Norway (Thenea muricata) were studied in flume experiments. Fluorescent particles of 1, 2, 3, 6, 10 and 16 mu m diameter (microspheres, Duke Scientific Corporation(R)) with a densit y of 1.05 g cm(-3) were used at 2 current velocities, 1.5 and 5 cm s(- 1). Both species ingested small particles exclusively (<6 mu m and <10 mu m, respectively), with a preference for the smallest fraction at b oth current speeds. The results suggest that the size spectrum actuall y ingested depends on the supplied particle sizes rather than on curre nt velocity. Current velocity fields around dead specimens were record ed and turbulence intensity calculated in order to determine the influ ence of the sponge acting as a biogenic structure on the near-bottom c urrent regime. Disruption of flow conditions was detected as far as 14 cm downstream and several cm laterally from the biogenic obstacles. B ulk biodeposition rates calculated from sponge biomass and volume of i ngested particles range between 7 and 10 mg d(-1) g(-1) ash-free dry w eight.