| Summary: | Global warming is expected to raise the mean annual temperatures all over the world by 0.3-4.8°C, but the impact of climate change is predicted to be particularly pronounced in the Arctic region. The increasing temperatures will likely have major impacts on Arctic ecosystems. Some climate-related environmental changes have already been observed, including changes in freshwater communities and food webs. According to earlier studies, increasing temperatures affect e.g. species composition, densities and emergence times of aquatic insects. In this experimental study, the impact of warming on Chironomidae, along with other aquatic insect families, was studied. The study was conducted in Hengill region, Western Iceland, with several spring-fed streams of various temperatures. Two parallel streams were selected for this study: a cold (mean summertime temperature 6.6°C) and a warm (mean summertime temperature 22°C) stream. The cold stream was divided with a dam, and the downstream section was warmed up with approximately 4°C, using the heat of the warm stream. The effects of this warming on the diversity, density as well as emergence times of Chironomidae and other aquatic insects were observed. The results show that warming up of the cold stream alters its species and family composition and increases densities of emerging flies, while the diversity was mostly unaffected. No significant changes were found in the emergence times. These findings suggest that global warming could threaten certain species and drastically change the community structure of stream ecosystems. Það er áæltað að loftlagshlýnun muni hækka hita um 0,3-4,8°C í heiminum, og mest á norðurhveli jarðar, sérstaklega á heimskautasvæðum. Þegar er vart við umhverfisbreytingar sem hægt er að rekja til loftslagsbreytinga, t.d. á vatnasamfélögum og fæðuvefjum. Eldri rannsóknir hafa sýnt að hitaaukning hefur áhrif á t.d. tegundasamsetingu og klaktíma vatnaskordýra. Í þessari tilraun voru rannsökuð áhrif hlýnunar á rikmý (Chironomidae) og önnur vatnaskordýr. ...
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