Succession of aquatic invertebrates in recently deglaciated terrain: mapping the magnitude and impact of climate change

With human impact minimised, possible effects of climate change should be more easily detected in pristine Arctic environments. Both the glacial history of the Arctic and expected future temperature change caused by the greenhouse effect indicates that th e amplitude of temperature change is greater here than in temperate regions. The Arctic environment is harsh with relatively simple freshwater ecosystems consisting of species adapted to low levels of nutrients, very short productive season, and low tempe ratures. Chironomidae (Insecta: Diptera) is as larvae the most common insect group in freshwaters. In Arctic ecosystems, the chironomids are disproportionately important compared to lower latitudes and forms a key organism. Because the distribution of chi ronomids is restricted by environmental conditions, and because Arctic ecosystems are vulnerable to environmental stress, Arctic chironomids are ideal to examine both the magnitude and impact of climate change. A climate warming may lead to increased ra tes of faunal succession and replacements, including primary succession in lakes formed subsequent to glacial retreat. Such an impact may also affect the terrestrial ecosystem through the input of energy and nutrients from adult chironomids. By examining how the present chironomid fauna is influenced by the primary physical and chemical factors at Bylot Island, Arctic Canada, we plan to predict how the fauna may respond to high latitude climate scenarios as provided by General Circulation Modelling. To pr ovide more reliable GCM scenarios, chironomid-inferred temperatures for the last millenium will be used to evaluate the variability modes of the hind-casting mode of the GCM. By examining the fundaments for life in recently formed lakes, we also meet the need to examine the problematic late glacial and early Holocene no-analogue phases in palaeoclimatic inferences. During these phases the fauna may or may not reflect the ambient environment we wish to reconstruct.