Changes in physical and chemical limnology and plankton during the spring melt period in a subarctic lake

The springtime limnology of subarctic Lake Saanajarvi, NW Finnish Lapland, was studied in 1999 with particular interest on the estimation of the effects of acid pulse. No clear pH depression was seen during the study year with exceptionally thin snow cover, in contrast to the year 1997, when a clear episodic decline in surface water pH was measured. In contrast to many Arctic lakes, no phytoplankton spring bloom was observed, probably because of the combination of low nutrient concentrations, dilution effect, flushing and rapid change in light climate. Low temperatures and limited food resources, resulting in long life cycles of zooplankton and with a clear winter maximum, may be the main factor controlling the atypical succession of zooplankton in Lake Saanajarvi.