ZOOPLANKTON DYNAMICS DURING THE ONSET OF WINTER IN A NORTHERN NORWEGIAN FJORD - VERTICAL-DISTRIBUTION AND METABOLIC-ACTIVITY IN RELATION TOPHYTOPLANKTON AND SEDIMENTATION

The study was conducted at a permanent station (depth of 80 m) in Ramf jorden (ca. 70 degrees N), a branch of Balsfjorden near Tromso, Norway , in November/December 1989. Phytoplankton and zooplankton were collec ted and sedimentation rates were measured every 3 to 4 days; zooplankt on respiration was determined in the laboratory. Phytoplankton concent rations were extremely low and tended to decrease during the investiga tion period, while zooplankton abundance was still at about 65 % of it s annual peak level. Depth distribution was markedly different between copepod species. Pseudocalanus acuspes and Acartia longiremis were mo re abundant in the surface layer while concentrations of Microsetella norvegica and Microcalanus pusillus were higher in deep water. Weight- specific respiration and faeces concentrations in the surface layer we re higher than at depth. It is hypothesized that P. acuspes and A. lon giremis remain active in winter and, by feeding, conserve part of the biomass in the pelagial.