Preliminary report on a study of toxicity in mussels as related to dinoflagellate populations in Norwegian coastal waters

Shellfish Committee

The Annual Phytoplankton Cycle of a Landlocked Fjord near Bergen (Nordåsvatn)

1. Quantitative phytoplankton records for 1941 and 1942 from Nordåsvatn near Bergen were used for a discussion of the annual phytoplankton cycle of this land-locked fjord. 2. Ice covered the surface till late in April 1942 and retarded the onset of the spring diatom vegetation, which reached its maximum in early May, while in the coastal waters outside it occurs in March. 3. Between the spring diatom maximum and an autumnal increase in the diatom population in the middle of September, irregular changes in the phytoplankton population took place. These were due partly to succession, partly to influx of water from the outside. 4. The summer plankton consisted of a few diatoms, coccolithophorids in increasing numbers from June (mainly Coccolithus Huxleyi and Calypirosphaera oblonga) and dinoflagellates. The ceratia had their maximum in the middle of September, while other dinoflagellates (Peridinium trochoideum, Prorocentrum micans and Oxytoxum mucronatum) occurred in considerable quantities at various times. 5. The causes of the heterogeneous composition of the phytoplankton as to ecological types are discussed. 6. The main factors influencing phytoplankton abundance in the fjord are enumerated, including local factors which are effective in Nordåsvatn, such as pollution by sewage, ice cover and currents

Phytoplankton observations in offshore Norwegian coastal waters between 62°N and 69°N - I. Variation in time of the spring diatom maximum 1968-71

An attempt was made to trace yearly fluctuations in the timing of the spring diatom maximum along the Norwegian west coast, 62°N-69°N. Qantitative data on the diatom population at 281 stations with 0 m samples and 120 stations with additional samples from the 10, 20 and 30 m levels, collected in March-April during the four years 1968-71, were used. A delay of about three weeks from the southern to the northern part of the area, as previously observed, was again established. The years 1970 and 1971 were years with an early maximum while 1969 was a definitely late year within the whole area. The time variation in 1968-71 recorded in the Trøndelag and Helgeland subareas, showed trends different from those of the neighbour areas. The phytoplankton data were not adequate for a detailed analysis of the factors responsible for the timing of the maximum each year in the respective parts of the investigated area

Seasonal changes in the phytoplankton at various points off the Norwegian West Coast : (Observations at the permanent oceanographic stations, 1945-46)

1. Quantitative phytoplankton samples from four of the Permanent Oceanographic Stations of the Institute of Marine Research of the Fisheries Directorate, Bergen: Utsira and Sognesjøen in the southern part of the Norwegian west coast and Skrova and Eggum in the northern part, covering all seasons of the year, were examined by the sedimentation method. The results were correlated with hydrographic data, supplied by Dr. JENS EGGVIN. 2. The main features of the annual phytoplankton cycle at these points of the outer coastal region are described. Common are the winter poverty and the spring increase, which occurred about three weeks earlier at the southern stations than at the northern ones. During the remainder of the year: late spring, summer and autumn, the seasonal changes were notably different at all four localities. Essential annual changes at the same locality were also observed. 3. Factors of general nature: the different light supply due to geographical position and the delayed vernal stabilization at the northern stations, conditioned by a smaller fresh-water supply, were pointed out as main factors causing the delay in spring phytoplankton growth in the north. Extensive winter mixing, inducing a more pronounced dilution of the winter population in the north, may also result in smaller phytoplankton stocks in early spring. 4. The difference in the changes taking place after the spring increase were tentatively tracecl back to hydrographical factors. The impression was gained that, at this time of the year, the outer coastal waters constitute a mosaic of vegetation areas, conditioned by the variation in the degree of stabilization and by the local admixture of adjoining water masses, the fjord waters to the east and offshore waters to the west. At the Eggum station the effect of local hydrographical conditions seemed to be very pronounced. 5. The composition of the populations was described in some detail. The occurrence of large populations of Euglenaceae in May-June at the northern stations is a noteworthy feature. 6. No detailed analysis of the ecological factors which are at play has been feasible, but the ecological situation at the various seasons was discussed. 7. A brief review of the present situation in phytoplankton research of Norwegian coastal waters was presented, especially in view of its application to fisheries problems