Boreal chironomid communities and their relations to environmental factors — the impact of lake depth, size and acidity

The relationship between chironomid community composition and certain lake characteristics was investigated using canonical correspondence analysis (CCA) on literature-retrieved data sets from 38 localities in North America and 43 in northern Europe. Three separate analyses were performed, classifying the chironomids to subfamily, genus or species level. The results demonstrate that the occurrence and abundance of chironomids are a function of lake depth, size and acidity. The subfamily Diamesinae-Prodiamesinae was a good indicator of large deep lakes with higher pH values. Subfamily Orthocladiinae was an indicator of relatively small lakes with low pH and conductivity, while Tanytarsini occurred in lakes with relatively high pH value. Tanypodinae and in particular Chironomini appeared less influenced by the analyzed environmental factors than other chironomids. At the genus level, Ablabesmyia and Zalutschia and subgenus Psectrocladius and Monopsectrocladius dominated in small shallow lakes with low values of pH and conductivity, whereas Prodiamesa, Cryptotendipes, Thienemaniella, Paratendipes, Stempellina and Cricotopus dominated in large deep lakes with high pH. The most common chironomids, the genera Procladius, Tanytarsus and Chironomus, were less correlated with the environmental factors in the boreal lakes, although some Chironomus species appeared to be indicative of acid lakes.