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

Abstract

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.