PARTICLE-FLUX, AND COMPOSITION OF SEDIMENTING MATTER, IN THE GREENLAND-SEA

Vertical flux of particulate material was recorded with moored sedimen t traps during 1988/1989 in the Greenland Sea at 72 degrees N, 10 degr ees W. This region exhibits pronounced seasonal variability in ice cov er. Annual fluxes at 500 m water depth were 22.79, 8.55, 2.39, 3.81 an d 0.51 g m(-2) for total flux (dry weight), carbonate, particulate bio genic silicate, particulate organic carbon and nitrogen, respectively. Fluxes increased in April, maximum rates of all compounds occurred in May-June, and consistently high total flux rates of around 100 mg m(- 2)d(-1) prevailed during the summer. The increasing flux of biogenic p articles measured in April is indicative of an early onset of algal gr owth in spring. Small pennate diatoms dominated in the trap collection s during April, and were still numerous during the high flux period wh en Thalassiosira species were the most abundant diatoms. During May-Ju ne, up to 22% of the Thalassiosira cells collected were viable-looking cells. The faecal pellet flux increased after the May-June event. The refore we conclude that the diatoms settled as phytodetritus, most lik ely in rapidly sinking aggregates. From seasonal nutrient profiles it is concluded that diatoms contribute 25% to new production during spri ng and 50% on an annual basis. More than 50% of newly produced silicat e particles are dissolved above the 500 m horizon. High new production during spring does not lead to a pronounced sedimentation pulse of or ganic matter during spring but elavated vertical export is observed du ring the entire growth period.