Constructed wetlands are an important environmental technology because they can serve as a tertiary wastewater treatment among other functions, removing nutrients and pollutants that remain in the water after the primary and secondary treatments. It is hypothesized that tertiary treatment wetlands (TTWs) may function similar to natural wetlands in their ability to support plant and wildlife communities, but remaining pharmaceuticals have been demonstrated to cause developmental abnormalities in anurans using wastewater treatment wetlands. In a controlled experiment, we evaluated larval anuran development in water from secondary and tertiary treated wastewater versus rain-filled pond water. We compared these results to changes in nutrient availability and common pharmaceutical and personal care products.
Results/Conclusions
Tadpoles took 21% longer to metamorphose in pond water and grew to only 70% the size of tadpoles from secondary and tertiary treated wastewater. Survival was 2.2 times higher in wastewater relative to pond water. We also noted that size-corrected leg length was larger in tadpoles from wastewater but size-corrected head size was smaller than individuals from pond water. No malformations were noted in individuals from pond water but 5.5% of individuals from wastewater exhibited minor malformations. Overall, larval anurans developed faster to larger sizes in wastewater relative to pond water with tadpoles from TTWs more closely resembling those from secondarily treated wastewater relative to pond water. Both sources of treated wastewater had elevated concentrations of diphenhydramine, which has been studied as an analgesic for amphibians. Ongoing behavior trials suggest that tadpoles are sluggish and move less in wastewater that may result from increased exposure to diphenhydramine and would contribute towards less energy expenditures in wastewater. Increased growth in wastewater may confer higher long-term survival despite low rates of malformations suggesting that TTWs may serve as high quality habitat for anurans and other wildlife.