Lakes in warm ecoregions - overview

The pristine status

Click to enlargeIn southern Europe most deep lakes are artificial (reservoirs), while shallow lakes are more common, though less frequently occurring than in the formerly glaciated areas of central and northern Europe. Mediterranean lakes are ice-free throughout the year, and are thus monomictic, with long summer stratification and a single circulation period in winter.

Human impact

As naturally dry systems, Mediterranean countries are characterized by high demand for freshwaters. Being a stable source of this scarce resource, lake systems in these regions are often heavily managed, placing considerable pressure on the Lake ecosystem. Water withdrawals from aquifers and diversion of surface waters, result in extreme water level fluctuations, and high levels nutrients inputs are also threatening water quality.

Climate change impact

Climate change in the Mediterranean might decisively accentuate fluctuations in the depth of water and favour increased nutrient concentrations in combination with a high rate of internal recycling from the sediment. The increase in global temperature will both further decrease the supply of dissolved oxygen via reduced saturation relative to air and increase the biological oxygen demand. In arid zones, more frequent droughts and low water level-induced anoxia may lead to local extinctions.

For further reading

• Jeppesen E, Beklioglu M & Søndergaard M. REFRESH Deliverable 3.12: Review on processes and effects of temperature regimes in lakes and threats due to climate change on current adaptive management and restoration efforts. link to article
• Jeppesen E, Mehner T, Winfield IJ, et al. (2012) Impacts of climate warming on the long-term dynamics of key fish species in 24 European lakes. Hydrobiologia, 694, 1–39.
  link to article
• Nõges P, Nõges T, Ghiani M, Sena F, Fresner R, Friedl M, Mildner J (2011) Increased nutrient loading and rapid changes in phytoplankton expected with climate change in stratified South European lakes: sensitivity of lakes with different trophic state and catchment properties. Hydrobiologia, 667, 255–270.
  link to article