SHORT-TERM SEDIMENTATION PATTERN OF ZOOPLANKTON, FECES AND MICROPLANKTON AT A PERMANENT STATION IN THE BJORNAFJORDEN (NORWAY) DURING APRIL MAY 1992

Sedimentation rates were determined daily over a 2 wk period (late Apr il - early May 1992) under post spring bloom conditions at a permanent station in the Bjornafjorden, Norway. Samples collected using floatin g sediment traps deployed at 50 and 100 m depth showed that sedimented seston, particulate organic matter, carbonate and lithogenic + opal f ractions were, on average, twice as high at 100 m (221, 99, 51 and 76 mg m-2 d-1, respectively) as at 50 m (119, 62, 27 and 34 Mg M-2 d-1, r espectively). Faecal pellets made up the bulk of sedimenting matter, a ccounting for 87 and 92 % of the average total organic carbon recorded at 50 and 100 m, respectively. The remaining sedimented matter consis ted mainly of tintinnids. Diatoms cells and resting spores, coccolitho phorids and flagellates contributed a minor fraction. It is postulated that the vertical flux of faecal pellets was determined by a combinat ion of 3 factors: (1) relatively high standing stock of actively grazi ng mesozooplankton dominated by calanoid copepods and appendicularians , which are known for their high faeces production rates; (2) a relati vely high abundance of the cyclopoid copepod Oithona similis, which is reported to feed on faecal pellets produced by calanoid copepods, sug gesting that coprophagy in the water column was high; (3) a phytoplank ton community dominated by diatoms and coccolithophorids, whose minera l skeletons accelerate sinking rates of faecal pellets.