Zooplankton of subarctic Imandra Lake following water quality improvements, Kola Peninsula, Russia

The composition, species richness and abundance of zooplankton communities were studied in two highly contaminated areas: (1) mainly by heavy metals a nd other toxic and non-toxic matter, and (2) mainly by fine particles of ne pheline and other minerals and organic matter, in the large, subarctic Iman dra Lake (northwestern Russia), based on data collected between 1978 and 19 90. Reduction in the relative abundance of the typical inhabitants of north ern oligotrophic lakes and their substitution by tolerant-to-pollution, wid ely distributed, circumpolar species were the general trends for the commun ities. In both lake areas, water quality changes occurred in response to re ductions in contamination of metals, mineral particles and organic matter i n the mid 1980s. Water chemistry improvements, including decreased concentr ations of pollutants, have resulted in partial recovery of zooplankton comm unities, increase in species richness, density of individuals, and shifts i n composition of the dominance group. However, both lake areas are still co ntaminated and re-establishment of communities typical of a non-polluted la ke did not occur between the mid 1980s and mid 1990s. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.