Influence of salinity and suspended matter on benthos of an Arctic tidal flat

Abstract

Abstract An Arctic tidal flat in Spitsbergen (Svalbard Archipelago) was studied along a transect from the river on the landward side to the adjacent fjord in July 1996 and 1997. The concentration of suspended particulate matter ranged from 500 mg l−1 in the river to 50–200 mg l−1 over the tidal flat and to less than 20 mg l−1 in the surface water of the fjord. Sedimentation rates ranged from 10 g m− 2 d− 1 close to the river mouth to 60 g m− 2 d− 1 on the tidal flat and reached maximum values of over 500 g m− 2 d− 1 just across the tidal flat break, characterized by a sharp salinity and depth gradient. Macrozoobenthos biomass increased from 1 g ww m− 2 in the tidal flat to over 50 g ww m− 2 in the fjord basin. The number of macrobenthos species increased from 3 to 70 across the steep depth/salinity gradient. Diversity was little different between stations exposed to heavy and low sedimentation in the fjord. The critical zone of environmental change appears to be very narrow and is situated just on the tidal shelf break, where zoobenthos changes as sharply as the salinity/depth gradients.