Chironomids (Diptera) and oxy-regulatory capacity: An experimental approach to paleolimnological interpretation

Abstract

We measured the ability to regulate oxygen uptake of 16 chironomid taxa from lakes in low-arctic West Greenland by means of oxygen microelectrodes in custom-made respiration chambers. The respiration patterns were modeled using piecewise linear regression with break-point and simple hyperbolic functions. The mathematical constants obtained from the controlled laboratory experiments were good ecophysiological indicators of species-specific "oxy-regulatory capacity." The oxy-regulatory capacity of different chironomid communities was calculated for subfossil assemblages collected from 52 lakes in West Greenland. The overall assemblage structure was expressed using detrended correspondence analysis (DCA). The oxy-regulatory capacity was as strongly correlated to DCA axis 1 (r = 0.72-0.86, p < 0.001), as were surface water temperature (r = 0.82, p < 0.001) and nutrients (r = 0.47-0.86, p < 0.001). Warm-water chironomid assemblages characterized by taxa such as Chironomus, Dicrotendipes, Ablabesmyia, and Procladius had a high oxy-regulatory capacity. Cold-water assemblages were dominated by oxy-conformers such as Heterotrissocladius, Micropsectra, Hydrobaenus, and Diamesa. An expression of the oxy-regulatory capacity of a given chironomid assemblage can be directly inferred from a simple model using weighted averaging of the ecophysiological mathematical constants. The autecological information from controlled experiments provides important additional information for interpretations in chironomid paleolimnology. The results can also be used to identify secondary changes or mismatches in multiproxy down-core paleoclimate studies.