Investigations on the plankton community of Balsfjorden, Northern Norway. The phytoplankton 1976–1978. Environmental factors, dynamics of growth, and primary production

Abstract

Measurements of incident and sub-surface radiation, plant nutrients, particulate carbon and nitrogen, and ‘in situ’ carbon assimilation were performed from February 1976 to November 1978. The onset, culmination, and magnitude of the spring bloom is described. The dynamics of the phytoplankton spring bloom were highly governed by incident radiation. The spring bloom probably ended because of lowered sub-surface irradiance, due to increased cell densities, and a high degree of mixing of the water column. The spring bloom ended with higher nutrient values than in more southerly areas. The summer situation was comparable with other areas with a ‘chemostat’-growth system. Grazing was probably also an important factor in regulating phytoplankton biomass during summer. Primary production estimates were comparable to other fjords and coastal areas (100 gC/m³ per year) along the Norwegian coast and were probably underestimated due to the methods applied.