Abstract
Elevated CO2 could alter the productivity of heterotrophic aquatic ecosystems through effects on allochthonous litter inputs. The effects of atmospheric CO2 concentration, light availability to trees and tree species, on leaf detritus quality as a food resource for eastern treehole mosquitoes (Aedes triseriatus) were examined. Larvae were reared in laboratory microcosms (simulated treeholes) with naturally-senesced, abscised foliage from seedlings of red oak (Quercus rubra) and paper birch (Betula papyrifera) grown in ambient and elevated atmospheric CO2 environments. Elevated CO2 did not have significant effects on any measure of mosquito performance. In contrast, host species and light availability had dramatic effects on mosquito development time and survival; light availability had additional effects on adult size. Mosquito reproductive potential (± SE) averaged 8.4 ± 1.5 females female-1 generation-1 when litter input was from birch-sun leaves, but was 19.6 ± 1.8 when the litter was from birch-shade leaves and 13.0 ± 1.8 when from oak-sun leaves. Mosquito development time was nearly halved when the litter input was from oak-sun leaves versus birch-sun leaves, suggesting a potential for even greater demographic effects (e.g. two generations per year instead of one could yield a 20-fold increase in annual growth rate). Trophic transfer rates ( mg insect detritivore g litter-1 d-1) were 3-fold greater on birch-shade leaves than on birch-sun leaves. Changes in insolation and tree species composition can have important consequences for forest ecosystems, because of effects on litter quality that impact microbial saprobes and, ultimately, invertebrate detritivores.