Assemblage-level estimation of nontanypodine chironomid growth and production in a southern Illinois stream

Abstract

AbstractChironomid midges are abundant and important components of freshwater communities, but estimating their production is problematic because of taxonomic difficulties, short generation times, and overlapping cohorts. We measured growth rates of nontanypodine chironomid larvae from a 3rd-order stream in southern Illinois, USA, at different temperatures to estimate assemblage-level production using the instantaneous growth method. We collected Chironomini, Tanytarsini, and Orthocladiinae larvae, separated them into small (0–3.9 mm), medium (4–7.9 mm), and large (8–12 mm) size classes, and then reared larvae in a controlled environment for 3 to 7 d at temperatures ranging from 5 to 28°C. We measured lengths of individual larvae before and after each trial and estimated biomass using a length–mass regression. Instantaneous growth rates (g) across all size classes ranged from 0.008 mg mg−1 d−1 at 5°C to 0.24 mg mg−1 d−1 at 22°C. Instantaneous growth rates of small larvae increased linearly with temperatur...