Outcomes of Chronic Arsenic Exposure on Aquatic Insects

Arsenic is a widespread contaminant of aquatic systems worldwide, and though the toxic effects on vertebrates are well understood, the impacts of chronic arsenic exposure on lower trophic levels of insects have received little attention. The overall goal of this dissertation was to investigate the sublethal effects of arsenic on aquatic primary consumers, and how they could transfer arsenic from aquatic to terrestrial environments. I investigated the effects of arsenic on survival, growth, and reproduction of Chironomus riparius. There was a significant increase in the time between male and female emergence when exposed to 1000 μg/l as larvae, and a significant decrease in the number of eggs produced per egg mass. Total arsenic body burdens decreased 72% between larval and adult stages. Larvae of Culex tarsalis and Culex quinquefasciatus exposed to arsenate or arsenite were assayed against Bacillus thuringiensis var. israelensis or Lysinibacillus sphaericus microbial pathogens to determine shifts in survival curves resulting from arsenic accumulation. Arsenic did not affect growth and survival of these mosquitoes compared to controls. Culex tarsalis was the more sensitive species, but both species were tolerant to arsenic exposure. X-ray absorption spectroscopy was used to map the localization and biotransformation of arsenic in various life stages of C. riparius and Cx. tarsalis. Chironomus riparius larvae accumulated arsenic in the midgut, while adults had arsenic distributed throughout the exoskeleton. There was evidence for reduction of arsenate to arsenite, and production of an As-thiol. In Cx. tarsalis, arsenic was found throughout the larval and adult bodies. Behavioral assays on Cx. tarsalis revealed no effects of prolonged arsenic exposure on frequency or duration of measured behaviors, including time spent resting, gliding, diving, and swimming. There was a limited effect of exposure on predator avoidance behaviors, but interactions made patterns difficult to discern. The trophic transfer potential of arsenic from aquatic to terrestrial environments was evaluated by feeding contaminated Cx. tarsalis to aquatic and terrestrial predators. Results suggest that overall the trophic transfer of arsenic is more likely to occur within an aquatic system, although transfer to terrestrial predators may play an important role in arsenic cycling during periods of mass emergence of insect prey