Toxicity of various road‐deicing salts to Asian clams (Corbicula fluminea)

Abstract

Humans are altering environments by destroying habitats, introducing species, and releasing pollution. One emergent pollutant is the salinization of freshwater habitats from road-deicing salts. Government agencies have set thresholds to protect freshwater ecosystems, yet these values are exceeded in many systems. The present study investigated the tolerance of Asian clams (Corbicula fluminea), a common invasive bivalve, to the common road salt (sodium chloride [NaCl]) and 2 alternatives (magnesium chloride [MgCl ] and calcium chloride [CaCl ]). Experiments conducted at 4 and 8 d revealed that Asian clams are very salt tolerant. The median lethal concentration after 4 d of exposure (LC50 ) estimate was 2162 mg Cl /L for MgCl , 3554 mg Cl /L for CaCl , and more than 22 581 mg Cl /L for NaCl, which were all significantly different from each other (p ≤ 0.05). The LC50 values were significantly different (p ≤ 0.05) from each other and from the LC50 values, and were estimated to be 1769 mg Cl /L for MgCl , 2235 Cl /L for CaCl , and 10 069 mg Cl /L for NaCl. Mortality was determined using 2 methods: either no response after exposure or no response after being in freshwater following exposure. For the majority of the LC50s, these methods were not significantly different (p > 0.05). The high salt tolerance of Asian clams is a concern because of their transportation in ballast water between aquatic ecosystems. Furthermore, salt-tolerant organisms may outcompete sensitive organisms in salinized ecosystems, which may alter ecosystem services. Environ Toxicol Chem 2018;37:1839-1845. © 2018 SETAC.

Road Salt Impacts Freshwater Zooplankton at Concentrations below Current Water Quality Guidelines

“…Finally, our study considered NaCl because it is the most common deicing agent applied to roads and other paved surfaces and is responsible for the increase in Cl – concentration in Jevins Lake. Regions where alternative chloride salts are applied may have more severe consequences for aquatic organisms because they are more toxic than NaCl (KCl > MgCl 2 > CaCl 2 > NaCl; refs and , but see Hintz and Relyea for sublethal effects on trout (CaCl 2 > NaCl >MgCl 2 )). Road salt may also contain a variety of other contaminants, which could increase toxic effects on daphniids.…”

Regulations are needed to protect freshwater ecosystems from salinization

“…specific conductance) might be more appropriate, and would be more informative than no ionic measurements [35]. However, frequent measures of specific conductance could easily be coupled with infrequent ion-specific testing, and the relative influence of each ion can then be modelled [35,39].…”

“…Although many of the documented effects of ion contamination come from studies focusing on the effects of sodium or chloride [15,29], each ion associated with salinization can uniquely affect physiological processes in organisms [13,[35][36][37][38]. Additionally, experimental research suggests that ions such as magnesium, potassium and sulphate, are more toxic to freshwater organisms than sodium or chloride [15,28,37,39]. Regardless of which ions have the strongest toxicological effects, the toxicity of specific ions differs among freshwater organisms, and the toxicity of specific ions often depends on the presence, ratio, and concentration of additional ions [28,[40][41][42].…”

“…Regardless of which ions have the strongest toxicological effects, the toxicity of specific ions differs among freshwater organisms, and the toxicity of specific ions often depends on the presence, ratio, and concentration of additional ions [28,[40][41][42]. For example, when associated with chloride, magnesium and calcium have been shown to be more toxic to freshwater invertebrates than sodium [33,37,39]. However, the concentration of sodium has been demonstrated to determine the toxicity of potassium salts [40].…”

Lakes at Risk of Chloride Contamination

“…In reality, salt sensitivity of freshwater organisms varies by taxa, with invertebrates typically being more sensitive than fish . Some species, such as the glochidia of certain freshwater mussels are impacted at chloride concentrations below the EPA water quality thresholds, while other species, such as invasive Asian Clams ( Corbicula fluminea ) and the Common Reed ( Phragmites australis ) can thrive above these thresholds. , The fact that some invasive taxa are salt tolerant is particularly concerning as they may be able to outcompete more sensitive, native taxa. In addition, other water quality characteristics (e.g., water hardness) can influence the vulnerability of species to chloride toxicity.…”