Environmental characteristics and microbial plankton activity of freshwater environments at Kongsfjorden, Spitsbergen (Svalbard)

Abstract

Physical, chemical and microbiological features of a range of High Arctic freshwater lakes, located in the vicinity of Kongsfjorden, north-west Svalbard, are described for the first time. The lakes were chosen to include both upland and coastal systems and those in proximity of human activity. Sampling was undertaken during April (late winter) and in July/August (summer). The lakes all proved to be oligotrophic with low DOC concentrations (< 2 mg/l) and most were relatively light transparent (K dPAR 0.13-0.26 m -1 ) but high inorganic particle loadings or wind-induced sediment resuspension significantly reduced light penetration in certain lakes. In the clear lakes/pools, a substantial proportion of incident UV-A and UV-B radiation often penetrated the entire water column. With short-wave radiation in High Arctic locations currently increasing the light penetration data presented here suggest that planktonic biota in the shallow lakes and pools will be subject to UV influence. Phytoplankton populations were sparse (1-3 μg chlorophyll-a/l) and virtually absent in winter with seasonal activity focussed on the short summer season. Evidence of under-ice planktonic activity was observed in only one lake. Patterns of microbial numbers and activity observed within and between lakes appeared to be related to lake volume, catchment features and high summer water temperatures (up to 15 °C). In particular, the proportion of viable (electron transport system activity) bacteria increased with temperature within each study system and a trend of increasing percentage viability was also seen in bacterioplankton along the relatively weak eutrophication gradient.