The effects of salinity exposure on multiple life stages of a common freshwater mussel, Elliptio complanata

Abstract

There is growing concern over the effects of increased salinization on freshwater organisms, which are largely unknown for unionid mussels. Adult and larval Elliptio complanata were exposed to low-level salt concentrations to determine the effects on mussel survival, physiology, and reproduction. Adults were exposed to salt concentrations of 0 parts per thousand (ppt), 2 ppt, 4 ppt, and 6 ppt NaCl and monitored over 7 d for mortality. Treatment groups exposed to 6 ppt and 4 ppt experienced 50% mortality at day 3 and day 4, respectively, with complete mortality by day 7. No mortality was observed in the other treatments. Adults were also exposed to sublethal salinity levels of 1 ppt and 2 ppt NaCl for 4 wk to determine physiological consequences of prolonged salinity exposure. Mussels exposed to 1 ppt and 2 ppt experienced reduced metabolic rates within the first 24 h of exposure that recovered to control levels in the 1-ppt treatment within 7 d. Metabolic recovery did not occur in the 2-ppt treatment by the end of 28 d. Glochidia exposed to 3-ppt NaCl during attachment to their host fish suffered a reduction in attachment success and metamorphosis, resulting in a 10-fold reduction in the number of juveniles produced per host fish. The present study demonstrates that low levels of salt can have a dramatic effect on the reproduction, physiology, and survival of freshwater mussels.

Freshwater Mussel Population Status and Habitat Quality in the Clinch River, Virginia and Tennessee, USA: A Featured Collection

“…Freshwater mussel sensitivity to major ions has been most studied in laboratory settings for NaCl solutions in reconstituted waters of varying hardness. Such studies have found acute toxicities for NaCl to vary widely among freshwater mussel species (Valenti, ; Bringolf et al ., ; Gillis, ), among life stages (Bringolf et al ., ; Blakeslee et al ., ), and with water hardness (Gillis, ). Gillis () also found acute toxicity to native mussel glochidia at lower NaCl concentrations in laboratory reconstituted waters than in natural river waters, suggesting that the full range of water chemistry is influential as demonstrated for laboratory test organisms by Mount et al .…”

RNA sequencing analysis of transcriptional change in the freshwater mussel Elliptio complanata after environmentally relevant sodium chloride exposure

“…To establish E. complanata as an experimental model for salt stress in freshwater ecosystems, we sought to establish the range of acute NaCl doses that are lethal , the physiological impacts of sublethal exposures of various durations , and whether transcriptional responses of genes implicated in the salt response in other species (e.g., NKA, Hsp70s, aquaporins, and the taurine synthesis pathway) are also expressed in a manner consistent with expectation (present study). These initial steps are important so that the subsequent prioritization of candidate biomarker genes has a sound biological footing.…”

“…Assembly and annotation of the transcriptome to support RNA‐Seq and other analyses are described in Cornman et al . Details of the collection of mussels, their housing and care in the laboratory, and salinity exposures are described briefly in the present study and more fully in Blakeslee et al .…”

“…Its abundance and broad ecological niche have led to the adoption of the species as a sentinel of aquatic contamination and an experimental model for freshwater mussels, including studies of how salinity affects mussel physiology and longevity. For example, previous work has established that acute exposures of ≥4 ppt sodium chloride (NaCl; ≥2.4 ppt chloride) for 7 d are lethal to adult E. complanata . Concentrations in the interval of 1 to 2 ppt NaCl (0.6–1.2 ppt chloride) do not increase mortality but reduce metabolic rate and disrupt reproduction over exposures ranging from 1 d to 1 mo .…”

Can salinity trigger cascade effects on streams? A mesocosm approach

“…Aquatic invertebrates regulate their ionic balance at an energetic cost (Bradley, 2008;Jonusaite et al, 2011), which can be translated into less energy available for other biological functions and reduced fitness. Although not many studies are available, there are evidences that elevated salinities can reduce egg hatchling (Kefford et al, 2004;Paradise, 2009), larval recruitment (Blakeslee et al, 2013) and growth Johnson et al, 2014), and increase time to emergence of larvae as flying adults (Hassell et al, 2006;Lob and Silver, 2012;Hale et al, 2014). One important sub-lethal effect that has yet to be investigated is changes in predation efficiency (i.e.…”