Predicting aquatic insect growth rates and voltinism as a function of temperature and body mass

Background/Question/Methods

Aquatic insects grow slowly at low temperatures characteristic of many arctic, alpine, and profundal habitats, resulting in multi-year developmental periods. Despite low productivity, such prolonged development can lead to accumulation of high population biomass when multiple year classes coexist, providing a substantial resource for insect consumers. We ask how climatic warming may alter larval growth rates, population structures, and the overall productivity of such communities. Understanding the temperature dependence of aquatic insect growth in shallow arctic ponds is complicated by highly fluctuating temperatures throughout much of the growing season. We use predictions from the metabolic theory of ecology (MTE) to model growth rates and developmental times of aquatic insects as a function of body size and temperature. 

Results/Conclusions

Models were calibrated using insect growth data from arctic tundra ponds near Barrow, Alaska in the 1970s, including chironomid species in the genera Chironomus and Tanytarsus. We also use these models to calculate apparent effective temperatures as a function of field-derived estimates of growth rates and developmental times. Results indicate sufficient habitat warming to reduce the developmental period of Chironomus from 7 years three decades ago, to 6 years in the early 21^st Century.