DescriptionAs the Northeastern United States continues to develop, the need for increased applications of salt on roads, sidewalks and parking lots will follow. The increased incidence of severe weather impacts from climate change is likely to exacerbate these applications, potentially heightening the frequency and severity of impacts upon the health of local freshwater ecosystems. Mayflies and stoneflies are halosensitive bioindicators that provide important indications of water quality degradation; similarly, heat shock proteins (HSPs) have been used as biomarkers tracking molecular responses to disturbance. Developing a method using aquatic phases of these organisms for ecological risk assessments will provide time for critical decision making prior to species loss. We quantified the heat shock response of mayflies and stoneflies to sub-lethal doses of sodium chloride (NaCl) to provide an early identifier of at-risk communities. To develop a reliable molecular approach for detecting NaCl stress, we (1) evaluated HSP70 expression across the insect body to better understand how NaCl stress is introduced to macroinvertebrate nymphs; (2) explored dose-response curves of HSP70 expression under laboratory conditions of heat and NaCl treatments; (3) quantified HSP70 expression from field collected specimens to assess levels of ecological stress across the state. This led to a proof of concept protocol which also involved the temporal course of the heat shock response in macroinvertebrates experiencing salt and temperature stress. We gathered stonefly nymphs from a local NH stream from May - July 2017 and assayed their expression levels of HSP70 following exposure to NaCl and increased temperature. Western blotting was used to quantify differences in expression in nymphs across stresses, with results suggesting a window of 24-72 hours in which expression peaks.