Abstract:

Abstract The basic environmental variables and adaptability of phytoplankton communities to low light and salinity were studied with incubation experiments in Kongsfjorden, a high Arctic fjord of Spitsbergen, in late summer 2006. The results showed a significant halocline occurred in the water column. The depths of euphotic zone were between 25 m and 30 m with a decrease tendency from outer fjord to inner fjord. The chlorophyll peaks were observed in water column between 10 and 20 m depths. The experiment results illustrate that, the chlorophyll a concentrations maintain or decrease slightly in darkness after one-day or one-week incubation. The chlorophyll a concentrations showed an initial decline when exposed to nature light after one-week incubation in darkness, and then increase significantly. In the salinity experiment, the maximal growth rate was observed at a dilution ratio 10%, however, higher dilution ratios (≥40%) had a obvious negative effect on phytoplankton growth. The study reveals the phytoplankton in fjord in late summer have the ability of darkness adaption. It also suggests that the inflow of glacial melting water is helpful for phytoplankton growth in outer fjord where the dilution rates are low.

Key words: phytoplankton, light, salinity, Kongsfjorden, Arctic