Dr. Harwood's Research Group

Overview

In 2021, United States production of sodium chloride (NaCl) reached a total of 40 million tons, with 42% of the salt consumed by highway deicing (USGS, 2022). While the ecological impacts from road salts have been recognized since the 1970s, the effects of salinization on freshwater macroinvertebrate communities is of increasing concern not just from acute toxicity but from ecosystem level effects (Mason et al., 1999; Williams et al., 1999; Blasius & Merritt, 2002; Ramakrishna & Viraraghavan, 2005; Corsi et al., 2010; Findlay & Kelly, 2011; Harless et al., 2011; Hintz et al., 2017; Jones et al., 2017; Schuler et al., 2017; Schuler & Relyea, 2018; Nutile & Solan 2019). An estimated 40 percent of the United States' urban streams have chloride levels that exceed safe guidelines for aquatic life (Stumpf et al. 2009).  Sodium chloride (NaCl) is the primary salt used for roadway de-icing (Lilek, 2017) and previous studies have evaluated the toxicity of NaCl to aquatic ecosystems (Blasius & Merritt, 2002; Gardner & Royer, 2010; Elphick et al., 2011; Harless et al., 2011; Van Meter et al., 2011; Van Meter & Swan, 2014; Hintz et al., 2017; Jones et al., 2017; Schuler et al., 2017; Schuler & Relyea, 2018). However, other “eco-friendly” de-icing agents such as beet-deicer have also been promoted with little evidence that they reduce ecosystem level effects (Nutile & Solan 2019).  

The proposed research will further evaluate the potential of ecosystem level effects of both sodium chloride and beet deicer by further evaluating their effects of the feeding behaviors of macroinvertebrates critical in the food web. Preliminary data indicates that NaCl may have an impact on the ability of Daphnia magna to filter green microalgae and Hyalella azteca to shred conditioned leaves when exposed to sublethal concentrations of NaCl. RESS participants will research factors that may influence these changes in feeding rates (e.g., concentrations, organism age, temperature, etc.) to better understand the potential consequences of freshwater salinization on aquatic systems and the mechanisms for food-web level effects.

RESS participant experiences 

This project will require RESS participants to develop and practice a range of interdisciplinary skills from creating salt solutions, caring and maintaining animals, and collecting, interpreting, and analyzing data. Participants will receive the necessary training to culture their aquatic organisms. They will learn to evaluate the acute toxicity of these chemicals to the species of interest under varying conditions and how to apply that information to develop longer-term experiments that evaluate different endpoints. Furthermore, participants will learn how to evaluate data using current statistical methods and software and how to communicate that information to fellow students and scientists. This research will be presented locally to the Alma community as well as at the Society of Environmental Toxicology and Chemistry national meeting. Presenting this research at a national conference will provide them with invaluable experiences communicating with other scientists from the various sectors.