THE NET PHYTOPLANKTON IN KONGSFJORDEN, SVALBARD, JULY 1988, WITH GENERAL REMARKS ON SPECIES COMPOSITION OF ARCTIC PHYTOPLANKTON

Examination of 17 samples collected by a 20 mu m meshed net in Kongsfj orden, Svalbard, 8-18 July 1988, Showed a dominance of dinoflagellates and the chrysophyte Dinobryon balticum in the surface layers, whereas the diatom and the haptophyte Phaeocystis pouchetii abundance increas ed with depth. The diatom Pseudo-nitzschia granii appeared together wi th P. pouchetii through the whole water column, and Actinocyclus curva tulus was one of the few diatoms present also in the surface samples. Two samples, from 15 and 50 m, respectively, were cleaned of organic m aterial and mounted in Naphrax for a more critical identification of t he diatoms. We were able to group the species according to habitats, e specially types of ice. The planktonic Thalassiosira antarctica var. b orealis, T. hyalina, T. nordenskioeldii, Bacterosira bathyomphala, Cha etoceros furcellatus, C. socialis and Fragilariopsis oceanica were pre sent mainly as resting stages representing a post-bloom situation. The se species and T. gravida appear early in the season and may have star ted to grow already under the ice. Fragilariopsis cylindrus and F. oce anica seem to have a closer affinity to ice than Thalassiosira and Cha etoceros spp. although they are common in the plankton. Some Nitzschia species which are usually regarded as typical sea-ice diatoms and hav e thicker and older ice as the main habitat were present only in small cell numbers in the plankton samples. The last component, evidently i ntroduced from Atlantic water in the Norwegian Sea, consisted of diato ms with a more oceanic distribution, e.g. Fragilariopsis pseudonana an d a small form of Thalassiosira bioculata.