Gradients in activity and biomass of the small benthic biota along a channel system in the deep Western Greenland Sea

Sediments sampled during summers 1999-2002 with the German ice-breaker RV “Polarstern” were analyzed to estimate benthic microbial activity and biomass of the smallest sediment-inhabiting organisms (size range: bacteria to meiofauna) along a channel system in the deep western Greenland Sea at about 75°N. Biochemical investigations were expanded by direct counts of bacteria and meiofaunal organisms, including foraminiferans. A total of 36 stations was sampled along the Ardencaple Canyon, extending over 200 km in north-easterly direction from the Greenland continental rise towards the central Greenland Basin. Stations were grouped in defined regions, generally with sampling sites inside the canyon plus accompanying sites on the northern and southern levees. An additional eight stations were sampled along a depth transect crossing the Greenland continental margin and traversing the channel in its midsection. All parameters investigated confirmed no differences between stations within the channel compared to stations on the levees, opposing the hypothesis that the Ardencaple Canyon displays a major pathway for suspension-driven shelf drainage flows. However, investigations showed some general trends in the data: parameters indicating food availability at the seafloor and total microbial biomass generally decreased with increasing water depth and distance from the Eastern Greenland continental margin. Along the depth transect crossing the Greenland margin both parameters exhibited increased values at deep stations on the continental rise. The position of these stations coincides with the position of the ice edge during sampling in summer 2000. Increased food availability and microbial biomass in the sediments most probably reflect raised levels of primary productivity and enhanced sedimentation in the marginal ice zone, thereby pointing to a close pelago-benthic coupling. Bacterial activities in the sediments showed a different picture with generally increasing values with increasing distance from the continental margin, which could probably be explained by a change in bacterial assemblages.