Climate Change and the European Water Dimension

Climate Change
and the
European Water Dimension
Chapter VI.A. Case Study on Specific
Lakes
Key Points
• Lake Mondsee: an increase in spring water temperature leading
to an earlier onset of thermal stratification, a longer stratified
period during summer, higher summer surface temperatures,
and a trend of rising deep-water temperature. a high degree of
synchrony in timing of physical and chemical parameters has
been established.
• Esthwaite Water: The chlorophyll concentrations measured in
the lake are substantially lower if the winter is wet. When the
winter is cold, appreciable numbers of Daphnia survive in the
open water. When the winter is mild, , the Daphnia cannot ingest
enough food to survive and the Eudiaptomus then dominate.
Relatively small changes in the winter water temperature can
have a significant effect on the long-term dynamics of a key
planktonic species. The historical variations in the winter
characteristics show that this lake is very sensitive to year-toyear
variations in the weather. These weather-related variations
influence the physical, chemical and biological characteristics of
the lake.
• Lake Erken: In eutrophic lakes with long water residence times,
eutrophication problems might become serious in a warmer
future climate. 1970’s and 1980’s data showed that earlier ice-out
and higher temperatures in May lead to increased phosphorus
concentration and phytoplankton biomass in summer, and an
overall doubling with climate scenarios.
• Lake Võrtsjärv: In non-stratified shallow lakes the changes of
the lake depth affect the average illumination of the mixed water
column, resuspension intensity, nutrient release from
sediments, and denitrification rate. These factors control the
growth and composition of phytoplankton that is the first link of
the pelagic food web. Cold winters characterised by low water
level cause several winter fish-kills. In warmer and wetter climate
the probability of both the summer blue-green blooms and
winter fish-kills should decrease.
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