COCCOLITHS IN SEDIMENT TRAPS FROM THE NORWEGIAN SEA

The fine fraction of surface sediment samples in the Norwegian Sea shows an unexpectedly high amount of calcareous nannoplankton. Investigations, using time-series sediment traps in the Lofoten Basin (69°N, 1983/84), near Bear Island (75°N, 1984/85) and in the Fram Strait (78°N, 1984/85) provided information about the accumulation of this material in relation to the strong seasonality of biological production. Coccolith identification and counting, by means of a scanning electron microscope, indicated that the coccolith assemblages in the traps consist almost entirely of the two speciesEmiliania huxleyi andCoccolithus pelagicus. These species dominated the flux rate of the nannoplankton carbonate. A further eight species only made minor contributions to the flux. In the Lofoten Basin a distinct seasonality could be recognized in both standing crop and carbonate flux. Also the relationship between the two main species and the proportion of intact coccospheres showed an annual cycle. In the sample series of the two northerly traps the seasonality was less distinct. In general, the coccolith flux decreases towards the North. This was particularly evident for the smaller speciesE. huxleyi, while the number of massiveC. pelagicus coccoliths - and so the coccolith carbonate flux - diminished only slightly. Additional investigations on water samples from the Norwegian Sea revealed species compositions that differed greatly from those in the sediment traps. This suggests that selective processes change the relative species proportions during sedimentation. © 1990 Elsevier Science Publishers B.V.