The use and application of freshwater midges (Chironomidae: Insecta: Diptera) in geographical research

Abstract

The potential of applying the analysis of freshwater midges (Chironomidae) for current questions in geographical research is examined. Chironomids are cosmopolitan in distribution and frequently the most abundant insects found in freshwater ecosystems. The capacity of the family to tolerate large gradients of pH, salinity, depth, oxygen concentration, temperature and productivity enables members of the Chironomidae to occupy virtually every available niche present in freshwater environments.In addition to wide distribution and abundance, Chironomidae are well suited for paleolimnological studies because the larvae possess chitinous head capsules which are well-preserved in lake sediment and relatively easily recovered and identified. As a result, chironomids are increasingly being used to track a number of natural and anthropogenically induced limnological changes resulting from atmospheric contamination, eutrophication and increased lake water salinity. Other areas in which subfossil chironomid analysis has provided valuable insight include climate change, phylogentics and biogeography and aquatic ecosystem dynamics and development.Details describing the biology and ecology of the Chironomidae that are directly relevant to their use in paleoenvironmental and biogeographical studies are presented. The methodology describing the recovery and identification of subfossil chironomid remains is reviewed. A generalized overview of the statistical methods that are commonly employed in relating the modern distribution of chironomids to specific aspects of the environment, i.e., the calibration dataset approach, is briefly discussed. Case studies that highlight the various uses and applications of chironomid analysis in areas of paleoenvironmental and biogeographical research relevant to geographers are described. Lastly, the current status of chironomid research in academic geography is discussed and suggestions of potential future research directions are made.