ROAD EFFECTS ON BIOGEOCHEMICAL CYCLING

Roads are distributed pervasively throughout much of North America, posing a suite of negative effects on native habitats. In addition to fragmentation effects and roadkill, contaminants and nutrients are deposited onto roads, and carried into adjacent habitats. In northern, less-developed areas, road salt is chief among these. In temporary aquatic habitats, which are typically small and shallow, and known to host a unique assemblage of species found nowhere else, such contaminants can become highly concentrated, altering chemical cycling and posing sub-lethal and toxic effects to native species. While laboratory studies have demonstrated the negative effects of singular contaminants, few studies have experimentally investigated the responses of populations in altered habitats. Similarly, the impact of salinization on biogeochemical cycles, particularly dissolved organic carbon (DOC), nitrogen and trace metal cycling, is lacking. In recognition of this data gap, we examined the influence of roadway proximity on 1) the potential for trace metal uptake, and 2) carbon and nitrogen cycling. We used a combination of water quality analysis, and laboratory mesocosm experiments to investigate the responses to road proximity in five forest and five roadside temporary wetlands located in northeastern Connecticut. Roadside ponds demonstrate increases in trace metals and decreases in organic carbon and nitrogen. Separate laboratory experiments document significant decreases in DOC and nitrogen removal as well as shifts in DOC quality. These water chemical results were combined with amphibian population studies that demonstrated a shift in amphibian populations consistent with an evolutionary response to road adjacency. Together, these results suggest that even in relatively undeveloped settings, roads can dramatically reshape wetland environments, altering not only the composition and cycling of nutrients and contaminants, but also the very evolutionary basis of occupant species.