Indicators for Climate Change Impacts - Lakes in cold ecoregions, Shallow lakes
Stratification
| Stressor type | Temperature |
|---|---|
| Responding parameter group | Hydromorphological parameters |
| Responding parameter | Stratification |
Response description
Higher temperatures result in earlier onset and prolongation of summer stratification. As a result, changing mixing processes occur and systems may change from dimictic to warm monomictic. A lack of full turnover in winter might lead to a permanent thermocline in deeper regions (below shallow seasonal thermocline).
Secondary effects
Changes in mixing processes lead to decreased nutrients entrainment. Less intense mixing and increased thermal stability result in oxygen depletion in deeper regions with subsequently phosphate and ammonium (i.e. nutrients in general) release from the sediment. Anoxia in the hypolimnion leads to benthic species extinctions, especially sensitive chironomids. Nutrient (N, P) availability leads to eutrophication with several effects such as increased algae growth, (further) oxygen depletion during night times, extinction of sensitive species such as brown trout (Salmo trutta).
Specification of relevant ecosystem type
Relevant for all small lakes in cold ecoregions.
Relevant ecoregion(s) according to Illies
Borealic Uplands (20), Tundra (21), Fennoscandian Shield (22), Taiga (23)
Suggested indicator
Duration of summer stratification as reflected by water temperature
Justification of indicator
Water temperature well reflect the status of lake stratification.
Reference(s)
Pettersson, K. & K. Grust (2002): Seasonality of nutrients in Lake Erken ? effects of weather conditions. Verhandlungen Internationale Vereinigung Limnologie 28: 731-734.
Bleckner, T., A. Omstedt & M. Rummukainen (2002): A Swedish case study of contemporary and possible future consequences of climate change on lake function. Aquatic Sciences 64: 171-184.
