Hydrography, nutrients, suspended organic matter, and primary production in a shallow fjord system on the west coast of Norway

Abstract

Abstract The investigation was carried out at three stations in a coastal area, characteristic for the west Norwegian coast. 21 cruises cover the period February to October 1982. The hydrography (T °C, S %º, O2/H2S), the nutrient concentration (NO3 -, SiO2, PO4 3-), suspended organic biomass (chlorophyll a, phaeophytin, particulate organic carbon, and nitrogen), and in situ 14C-assimilation were measured at fixed depths. The predominant northerly and southerly winds and the resulting on-shore and off-shore transport of water had a significant influence on the hydrography at the outer station in Raunefjorden, somewhat less at the intermediate station in Kviturdvikpollen, but were of minor influence at the permanently stratified inner station in Vågsböpollen. Hydrogen sulphide occurred in the bottom water of both Vagsbopollen and Kviturdvikpollen from June to October. Maximum concentrations were up to 6 times higher than reported in a study 18 years ago in the same localities. The concentrations of nutrients and suspended organic matter were highest in Vågsböpollen and Kviturdvikpollen. Highest suspended concentrations were found at the oxic/anoxic interface. In Raunefjorden the nutrient and suspended organic matter concentrations were strongly influenced by upwelling of nutrient-rich water. The annual primary production at the three stations ranged from 180 to 230 g C/m2 per year. The topography of the fjords, the fresh-water run-off, and changes in the predominantly longshore wind stress are essential for an understanding of the phytoplankton dynamics in the area.