SSRP Abstract

Board 5: Exploring Local and Regional Variation in NaCl Tolerance in Daphnia pulicaria

Student Scientists: Makenna Juergens ’23 and Abigail Doza ’23
Research Mentor: Amy Downing (OWU Department of Biological Sciences)

Environmental policies are designed to protect natural ecosystems and humans that depend on them. Researchers are exploring if the EPA legal limit of salt allowed in freshwater ecosystems due to road de-icing is sufficient to protect freshwater ecosystem quality. Previous studies have shown that Daphnia, an ecologically important freshwater invertebrate, may be sensitive to salt concentrations lower than the EPA legal limit. Our study focuses on finding the maximum livable salt concentration for the species Daphnia pulicaria.

Anthropogenic activity has adverse effects on freshwater ecosystems. For example, road deicing adds excess salt (NaCl) into the water, a known detriment to freshwater organisms. Freshwater ecosystem health is largely indicated by the invertebrate species Daphnia — an important bioindicator and integral part of the food web. Previous studies have found that the lethal concentration of NaCl at which 50% of the Daphnia population dies (LC50) occurs between 900 and 2,000 mgCl/L in lab conditions. In order to determine underlying factors contributing to this LC50 range, we are collaborating with labs globally to observe the variation of Daphnia salt tolerance on local, regional, and global scales. In this study we studied the NaCl tolerance of local Daphnia pulicaria populations sampled from three lakes in Madison County, OH (Prairie Oaks Metro Park; Darby Lakes Residences). Our results suggest that the LC50 for our systems occurs between 900 and 1,200 mgCl/L and that there does not appear to be substantial variation between family lines within the same pond, but there is evidence of slight variation between populations in different ponds. These results will be compared with those of labs participating in the study to determine global variation in Daphnia salt tolerance and to explore factors that might determine salt tolerance, such as previous exposure to salt in native ponds, local environment conditions, and genetics. This study will help us understand to what degree anthropogenic activity impacts freshwater ecosystems as well as improve environmental policy and EPA guidelines on how much salt can be used for winter road maintenance.