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Tolerance to road salt deicers in chronically exposed urban pond communities
Van Meter, R. AND C. Swan. Tolerance to road salt deicers in chronically exposed urban pond communities. Presented at The Association of Southeastern Biologists Meeting, Athens, GA, April 04 - 07, 2012.
Presentation for Association of Southeastern Biologists in Athens, GA.
Freshwater salinization is a concern in urban aquatic ecosystems that receive road salt runoff from vast expanses of impervious surface cover. Our study was designed to evaluate the effects of chloride contamination on urban stormwater pond food webs and to assess the tolerance of pond dwelling organisms that are chronically exposed. From May – July 2009, we employed a 2x2x2 full-factorial design to manipulate chloride concentration (low = 177 mg L-1 Cl- / high = 1067 mg L-1 Cl-), gray treefrog (Hyla versicolor) tadpoles (presence/absence) and source of stormwater pond algae and zooplankton inoculum (low conductance/high conductance urban ponds) in 40,600-L mesocosms. Phytoplankto biomass (chlorophyll [a] µg L-1) was 53% greater in mesocosms receiving high conductance inoculum and high chloride as compared to the low conductance inoculum and low chloride treatment. High chloride reduced periphyton biomass by 15% and increased total zooplankton density by 80%, although different zooplankton taxa showed varied responses to chloride exposure. Tadpoles reared in high chloride that reared metamorphosis in fewer days than the average were also 18% greater in mass at metamorphosis relative to tadpoles in the low chloride treatment. Our results indicate differential susceptibility to chloride salts among algal resources and zooplankton taxa and suggest that phytoplankton, adult copepod zooplankton and gray treefrog larvae may be more tolerant of the high salt loads often present in urban stormwater ponds. Changes in ecosystem structure in urban ponds receiving and retaining chloride can be anticipate with predominance toward salt tolerant taxa.