Northeastern North America (NENA), has experienced an increase in both the abundance and geographic distribution of mosquitoes. Additionally, there has been over a doubling in dissolved organic matter (DOM) concentrations in many inland water bodies throughout this region. The increases in DOM reduce water transparency and therefore underwater exposure to solar ultraviolet radiation (UVR). DOM thus provides water borne pathogens and diseases a refuge from UVR. Yet almost nothing is known about the effects of solar UVR and DOM on disease vectors such as mosquito larvae. It is known that mosquito larvae are common in shaded habitats and most species require constant contact with the water-air interface to breathe through their breathing siphons which increases their potential exposure to damaging UVR. However, essentially nothing is known about their susceptibility to damage by solar UVR or potential mechanisms of protection. I hypothesize that 1) solar UVR kills mosquito larvae, (2) exposure to DOM provides protection from lethal solar UVR and 3) the presence of photoenzymatic repair radiation (PRR) does not increase survivorship. Experiments using UV-lamps and solar radiation manipulated the presence of DOM and PRR to test first instar Culex pipiens and C. restuans larval survivorship after exposure to UVR.
Results/Conclusions
Exposure to solar UVR significantly decreased larval survivorship (p < 0.001). The presence of DOM during UVR exposure significantly increased survivorship (p<0.001). Unexpectedly, pre-exposure to DOM also significantly increased survivorship following exposure to solar UVR. There was no evidence of PRR (p =0.865). These findings confirm that DOM provides protection against lethal solar UVR for mosquito larvae, and that mosquitoes primarily rely on environmental mediators such as shading from DOM more than organismal mechanisms of protection such as photoenzymatically activated DNA repair. Our study suggests that solar UVR as an environmental regulator of mosquito larvae and extends the current hypothesis that declines in water transparency will lead to increases in not only water borne pathogens and diseases, but to disease vectors as well.