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|Title:||Climate-Related Changes in Terrestrial and Freshwater Ecosystems. 4.4. Freshwater Ecosystems|
|Authors:||SMITH Benjamin; BLENCKNER Thorsten; NOGES PEETER; NOGES Tiina|
|Publisher:||Springer Berlin Heidelberg|
|ISBN:||978-3-540-72785-9 (Print) 978-3-540-72786-6 (Online)|
|Type:||Articles in books|
|Abstract:||A number of studies from the Baltic Sea region report evidence of change in freshwater systems attributable to recent climate change or variability. Impacts described from particular lakes or rivers and their ecosystems during recent decades include: ¿ A longer annual ice-free period and earlier breakup of ice cover leading to community structure changes such as dominance shifts among phytoplankton taxa, changed successions, reduced species diversity, and transformations from a clear-water (macrophyte-dominated) to turbid (phytoplankton-dominated) state. ¿ Increased water temperatures leading to increased primary production, higher lake biomass and the incidence of phytoplankton blooms in some northern European lakes. ¿ Changes in fish communities associated with the effect of warmer early summers on zooplankton biomass. ¿ Increased nutrient loads and/or increased contributions of nutrients from diffuse sources under a warmer and wetter climate, with dominance shifts in phytoplankton assemblages as a possible result. A description of the potential impacts of future climate changes on freshwater ecosystems emerges from a handful of experimental and modelling studies, extrapolation of recent observed trends, and understanding of mechanisms. Potential impacts of such a climate development include the following: ¿ Warmer water temperatures combined with longer stratified and ice-free periods in lakes could accelerate eutrophication, particularly in the western and southern Baltic Sea Basin. Shallow lakes and littoral zones may be particularly vulnerable. ¿ Cold-water fish species may be extirpated from much of their current range while cool- and warm-water species expand northwards. ¿ Altered lake nutrient status: increased remineralisation and higher diffusion rates of nutrients in warmer water would be expected to increase nutrient availability, especially in lakes with longer water residence times. Reduced N:P status combined with higher temperatures could result in phytoplankton community structure shifts favouring N-fixing and warm-temperature species, including cyanobacteria. ¿ Increased influxes of humic substances to ecosystems downstream of boreal and arctic peatlands would steepen light attenuation with negative impacts on lake periphyton and benthic communities, while potentially increasing the contribution of northern lakes to regional CO2 emissions and climate forcing.|
|JRC Institute:||Institute for Environment and Sustainability|
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