A paleolimnological approach, based on chironomid
stratigraphical analysis, was applied to
investigate consequences of long-term
environmental and climate changes. The fossil
larval head capsules preserved in lake sediments
are used for chironomid analysis. The six
subarctic freshwater ecosystems under study are
located in the central part of the Kola Peninsula.
The results of study of postglacial chironomid
colonization and changes in chironomid assemblages
to environment and climate changes through
Holocene in a subalpine shallow lake located near
treeline are presented in one of the dissertation
chapters. This is first Holocene chironomid
stratigraphy from Kola Peninsula. The lake
chironomid fauna showed a marked response to the
major and minor climatic oscillations,
demonstrating that large-scale temperature change
had an overriding influence on the distribution of
chironomid midges. In the chironomid fauna history
there are seven distinct phases reflecting
climatic changes. The pioneer Holocene chironomid
fauna of the lake included cold stenotherms
typical of oligotrophic lakes. Rising temperatures
after initial deglaciation stage caused a sharp
decline in the abundance of cold-water taxa, an
establishment of chironomid taxa associated with
warmer water, a sharp dominant shift, and a rapid
increase in total chironomid abundance. Following
significant changes towards a warmer and more
humid climate, and a likely progressive changes in
the vegetation of the area surrounding the lake,
resulted in subsequent increase in total
chironomid abundance and new dominant shift. The
middle Holocene was characterized by an appearance
and an increase in the abundance of meso-eutrophic
taxa, reflecting some increases in lake
productivity. The highest values of taxa richness
and species diversity in the chironomid
assemblages took place during
deglaciation/colonization of the lake as well as
during strong Holocene cooling (the end of Boreal
and the Little Ice Age of Subatlantic). During
last century the development of the lake is
affected by human impact associated with
atmospheric contamination. This caused an aquatic
moss expansion on the lake bottom and a reduction
of habitat heterogeneity for chironomid larvae, a
marked increase of one taxon dominating, and a
decrease in the species diversity and evenness of
chironomid assemblages. Additionally, changes in
the structure of chironomid assemblages related to
long-term anthropogenic acidification,
eutrophication, and contamination by metal-rich
waters from copper-nickel smelter of the lakes are
studied. The other dissertation chapters report
changes in the structure of chironomid assemblages
of the lakes affected by anthropogenic
acidification, eutrophication or contamination by
metal-rich waters from copper-nickel smelter.
Three developmental stages are distinguished from
the chironomid fauna history of the ecosystem,
which has suffered from the metal contamination
caused by the smelter activities.