Seasonal variation in hydrography, nutrients, and suspended biomass in a subarctic fjord: Applying hydrographic features and biological markers to trace water masses and circulation significant for phytoplankton production

Abstract

Abstract Investigations of the hydrography, nutrients, fluorescence, and suspended biomass in the basin of the north Norwegian fjord Balsfjord, revealed highly variable hydrographic features from March to early October 1996. Among those are (a) an inflow of more saline water in spring, probably of deep origin outside the fjord, which was slowly diluted until August, (b) an inflow of phytoplankton- and nutrient-rich, but nitrate-low surface water into the deep basin in March-early April and late April to June, respectively, and (c) the intrusion of phytoplankton-rich layers at variable times and depths throughout the water column, probably of surface origin. An extended spring bloom took place between early April to early June and resulted in biomass accumulation in the upper 30 m up to 23 g C m-2. The spring bloom was dominated by the haptophyte Phaeocystis pouchetii (Hariot), which is reflected in the depletion of nitrate and phosphate during the bloom, while silicate prevailed.