EFFECTS OF ELEVATED ATMOSPHERIC CO(2) ON WATER CHEMISTRY AND MOSQUITO (DIPTERA: CULICIDAE) GROWTH UNDER COMPETITIVE CONDITIONS IN CONTAINER HABITATS

Abstract

We investigated the direct and indirect effects of elevated atmospheric CO(2) on freshwater container habitats and their larval mosquito occupants. We predicted that a doubling of atmospheric CO(2) would (1) alter the chemical properties of water in this system, (2) slow degradation of leaf litter, and (3) decrease larval growth of Aedes albopictus (Skuse) mosquitoes raised on that litter under competitive conditions. Effects of elevated CO(2) on water quality parameters were not detected, but the presence of leaf litter significantly reduced pH and dissolved oxygen relative to water-filled containers without litter. Degradation rates of oak leaf litter from plants grown under elevated CO(2) atmospheres did not differ from breakdown rates of litter from ambient CO(2) conditions. Litter from plants grown in an elevated CO(2) atmospheres did not influence mosquito population growth, but mosquito production decreased significantly with increasing larval density. Differences among mosquito density treatments influenced survivorship most strongly among male Ae. albopictus and time to emergence most strongly among females, suggesting fundamental sex-determined differences in response to competition. Results of this and other studies indicate that direct and indirect effects of doubled atmospheric CO(2) are minimal in artificial containers with freshwater.

Fig. 1

Mean (± SE) nitrate concentration (A), pH (B), and DO (C) in cups containing leaf litter plus water and cups with water only. n = 16 for each mean on weeks 1–9. Week 0 means were based on n = 5 cups which were added to illustrate starting values and were not included in the repeated-measures ANOVA. One nitrate measurement (22.5 mg/L) in the water treatment on week 6 was excluded after significance testing for outliers.

Fig. 2

Mean (± SE) nitrate concentration in cups located in different experimental environments (n = 8 for each mean). One outlier (22.5 mg/L) in the ambient environment on week 6 was excluded.

Fig. 3

Mean (± SE) estimated finite rate of population increase (λ′). Different letters indicate significant differences among Ae. albopictus density treatments (F = 90.08, df = 4, 40, P < 0.0001), but litter type and the litter type × density treatment interaction were not significant (all F < 3.75, P > 0.05).

Fig. 4

Mean (± SE) survivorship and time to emergence for the significant Ae. albopictus density effect. Open and filled symbols show male and female bivariate means, respectively. Different lower case and capital letters indicate significant differences among means. Mass values were omitted because they contributed little to the density effect.