Freshwater mussels (order Unioniformes) fulfill an essential role in benthic aquatic communities, but also are among the most sensitive and rapidly declining faunal groups in North America. Rising water temperatures, caused by global climate change, industrial discharges, drought, or land development, could further challenge imperiled unionid communities. The aim of our study was to determine the upper thermal tolerances of the larval (glochidia) and juvenile life stages of freshwater mussels. Glochidia of 8 species of mussels were tested: Lampsilis siliquoidea, Potamilus alatus, Ligumia recta, Ellipsaria lineolata, Lasmigona complanata, Megalonaias nervosa, Alasmidonta varicosa, and Villosa delumbis. Seven of these species also were tested as juveniles. Survival trends were monitored while mussels held at 3 acclimation temperatures (17, 22, and 27uC) were exposed to a range of common and extreme water temperatures (20-42uC) in standard acute laboratory tests. The average median lethal temperature (LT50) among species in 24-h tests with glochidia was 31.6uC and ranged from 21.4 to 42.7uC. The mean LT50 in 96-h juvenile tests was 34.7uC and ranged from 32.5 to 38.8uC. Based on comparisons of LT50s, thermal tolerances differed among species for glochidia, but not for juveniles. Acclimation temperature did not affect thermal tolerance for either life stage. Our results indicate that freshwater mussels already might be living close to their upper thermal tolerances in some systems and, thus, might be at risk from rising environmental temperatures.

This article discusses the issue of lead contamination of drinking water, noting the various regulatory-driven measures that have been adopted in the U.S. since 1986 to address this public health issue. The article summarizes the literature on the dynamics of tap water lead contamination and discusses this widespread source of lead exposure in the context of the latest research evidence.

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Freshwater mussels are among the most sensitive aquatic organisms to many contaminants and have complex life-cycles that include several distinct life stages with unique contaminant exposure pathways. Standard acute (24-96 h) and chronic (28 d) toxicity tests with free larva (glochidia) and juvenile mussels are effective at generating data on contaminant effects at two discrete life stages but do not incorporate effects on brooded glochidia. We developed a novel partial life-cycle assay that incorporates exposures to brooding adult female mussels and used this method in combination with acute toxicity tests to assess adverse effects of perfluoroctanesulfonic acid (PFOS) and perfluoroctanoic acid (PFOA) on freshwater mussels. Fatmucket (Lampsilis siliquoidea) were exposed to PFOS at two life stages: brooding glochidia (in marsupia) for 36 d and free glochidia in water for 24 h. In standard acute tests with glochidia (24-48 h exposures) and juveniles (48-96 h exposures) of fatmucket and black sandshell (Ligumia recta), glochidia were 8 to 25 times more sensitive than juveniles. Perfluoroctanesulfonic acid significantly reduced the duration of glochidia viability and reduced probability of metamorphosis at concentrations 3,000 times lower than the most sensitive acute endpoint (24-h EC50). The partial life-cycle test is adaptable to a variety of endpoints and research objectives and is useful for identifying adverse effects at contaminant concentrations below those required for an acute lethal response.

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The toxicity of cyanide to the early life stages of freshwater mussels (order Unionida) has remained unexplored. Cyanide is known to be acutely toxic to other aquatic organisms. Cyanide-containing compounds, such as sodium ferrocyanide and ferric ferrocyanide, are commonly added to road deicing salts as anticaking agents. The purpose of the present study was to assess the acute toxicity of three cyanide compounds (sodium cyanide, sodium ferrocyanide, and ferric ferrocyanide), two road salts containing cyanide anticaking agents (Morton and Cargill brands), a brine deicing solution (Liquidow brand), and a reference salt (sodium chloride) on glochidia (larvae) and juveniles of the freshwater mussel Villosa iris. Sodium ferrocyanide and ferric ferrocyanide were not acutely toxic to glochidia and juvenile mussels at concentrations up to 1,000 mg/L and 100 mg/L, respectively. Lowest observed effect concentrations (LOECs) for these two chemicals ranged from 10 to >1,000 mg/L. Sodium cyanide was acutely toxic to juvenile mussels, with a 96-h median effective concentration (EC50) of 1.10 mg/L, although glochidia tolerated concentrations up to 10 mg/L. The EC50s for sodium chloride, Liquidow brine, Morton road salt, and Cargill road salt were not significantly different for tests within the same life stage and test duration (range, 1.66-4.92 g/L). These results indicate that cyanide-containing anticaking agents do not exacerbate the toxicity of road salts, but that the use of road salts and brine solutions for deicing or dust control on roads may warrant further investigation.

Freshwater mussels fulfill an essential role in aquatic communities, but are also one of the most sensitive and rapidly declining faunal groups in North America. Rising water temperatures, caused by global climate change or industrial discharges, can further challenge impaired unionid communities, but thermal stress is almost certainly not the only stressor affecting freshwater mussels. Metals, such as copper (Cu), are a common source of toxicant exposure in aquatic environments. The toxic effects of Cu on the early life stages of freshwater mussels have been well studied, and freshwater mussels are more sensitive to Cu than most aquatic organisms. The purpose of the present study was to determine the effect of a sublethal copper concentration on the upper thermal tolerance of three species, Lampsilis siliquoidea, Potamilus alatus, and Ligumia recta, of juvenile freshwater mussels in 48- and 96-h tests. Thermal tolerance was determined over a range of experimental temperatures (20-42 degrees C) at three acclimation temperatures (17, 22, and 27 degrees C). Median lethal temperatures (LT50s) were calculated in the absence and presence of Cu, and at 48 h ranged from 34.6 to 44.4 degrees C (mean 37.7 degrees C) without Cu, and from 33.8 to 38.9 degrees C (mean 35.8 degrees C) with Cu. The LT50s at 96 h ranged from 32.5 to 35.6 degrees C (mean 34.5 degrees C) without Cu and from 33.0 to 35.4 degrees C (mean 34.2 degrees C) with Cu. Potamilus alatus had a significantly lower 48 h LT50 with Cu than without Cu at the 22 degrees C acclimation temperature; there were no other significant differences in LT50s attributed to Cu. Survival trends showed limited evidence of interactive effects between copper and temperature for all three species, suggesting the combined stress of elevated temperatures and copper exposure to freshwater mussels should be further explored.