Are Australian Chironomids tolerant of water pollution?

![CDATA[Chironomids or ‘midges’ are regarded by many Australian aquatic scientists with a mixture of suspicion and fear. They are a family of freshwater insects (in the order Diptera) that are sometimes perceived to be tolerant of polluted water and often appear to numerically dominate otherwise interesting macroinvertebrate samples. This study is one of very few in Australia to focus specifically on Chironomids and their relationship to water pollution using the ‘Chironomid Pupal Exuvial Technique’ developed in the Northern Hemisphere. We conducted a one--‐year seasonal collection of exuviae (pupal skins) from stream edges. We assessed the response of Chironomidae to impaired water quality by collecting samples in 15 study sites within the Western Blue Mountains region of New South Wales. The sources of water pollution included sewage effluent and mining and industrial (saline/heavy--‐metal) contamination. Chironomid community assemblages were modified by both pollution types to a variable degree. Multivariate analysis indicated that polluted water was generally associated with mild ecological differences. At three sites (two sewage and one acid mine drainage) the ecological impact was severe with species richness much lower (75 %) than at reference sites. Several sites with impaired water quality had similar Chironomid species richness to that at reference sites. Unlike the North Hemisphere, there was no seasonality of Chironomid exuviae detected, which indicates that this technique has potential for year--‐round application.]]