The effects of UV-B radiation on tire deterioration and the ecology of Aedes albopictus and Cx. pipiens mosquitoes
Villena Carpio, Oswaldo Clever
Leisnham, Paul T
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Although recycling programs have reduced stockpiles of scrap tires in the U.S., vast numbers of tires are still deposited throughout landscapes nationwide. Among the most important environmental impacts of tires is their degradation when exposed to ultraviolet (UV) radiation and, in the presence of water, the resulting leaching of numerous soluble inorganic (e.g., zinc) and organic contaminants (e.g., benzothiazoles). Studies have shown clear toxicological effects of tire leachate on a few focal aquatic taxa, but there is a lack of knowledge on the effects of tire leachate on most aquatic communities. This project investigates the relationship of scrap tire contamination on the ecologies of the two most broadly distributed mosquitoes in the Eastern U.S., the invasive Aedes albopictus and resident Culex pipiens, which engage in strong competition for microbial food in tire habitats. The main objectives of this project were to: (1) Assess the impacts of UV-B radiation conditions that mimicked full-sun, shade, and no-UV settings in the field on the metabolic rates and fitness of Ae. albopictus and Cx. pipiens larvae and associated microbial fauna; (2) Compare the effects of full-sun, shade, and no-UV radiation on the degradation of tires; (3) Test the hypothesis that tire leachate from tire degradation promotes condition-specific competition between Ae. albopictus and Cx. pipiens; and (4) Test the effects of tire leachate on Ae. albopictus and Cx. pipiens oviposition. Overall, the results of my dissertation indicate that UV-B can have strong effects on the ecologies of both Ae. albopictus and Cx. pipiens, both through direct negative effects on metabolic processes and fitness, and indirectly through the degradation of tires and the leaching of contaminants. The most ecologically interesting impacts of UV-B exposure may be via the promotion of condition-specific competition whereby Cx. pipiens appears to have greater competitive effects on Ae. albopictus under conditions that promote greater tire degradation. Tire leachate does not appear to alter the oviposition behavior of both Ae. albopictus and Cx. pipiens. Therefore, the effects of tire leachate on larval ecology is likely to be important in dictating the distribution and abundance of both species in tire habitats.