Freshwater mussels of the Unionida are globally in decline and knowledge of the sensitivity of their vulnerable
life stages to stressors is crucial for their conservation. Increasing salinity, e.g., due to road deicing, has been
proposed as an important stressor, but its impact on the complex interaction between mussel larvae and their
obligate attachment to fish hosts remains largely unknown. This study tested the acute toxicity effects of environmentally
relevant chloride concentrations on larvae of European Anodonta anatina mussel as well as the impacts
on attachment rates of the larvae to their fish host. Chloride concentrations above 727 mg⋅L−1 significantly
affected glochidia viability and the 24 h EC50 value was determined at 2505 mg⋅L−1
. Successful attachment of
glochidia to the host fish Phoxinus phoxinus was negatively correlated with increasing chloride concentration
and became significant at concentrations N2909 mg⋅L−1
. Comparable responses could be observed by separately
counting fin and gill attached glochidia, while gill attachment showed the highest correlation with overall attachment
rates. These results indicate a potential threat from short-term elevated chloride concentrations during
runoff events on sensitive life stages of freshwater mussels. Consequently, we propose additional chloride sensitivity
tests on other mussel species as well as the reduction of salt peak input loading into freshwater bodies
through a 3R-principle (restriction of use, retention of runoff for peak concentration avoidance and replacement
by alternatives) in areas where endangered mussels occur.
Capsule: Freshwater mussels of the Unionoida are globally in decline and knowledge on the sensitivity of the
most vulnerable larval stages to salinity is crucial for their conservation
Freshwater mussels of the Unionida are globally in decline and knowledge of the sensitivity of their vulnerable
life stages to stressors is crucial for their conservation. Increasing salinity, e.g., due to road deicing, has been
proposed as an important stressor, but its impact on the complex interaction between mussel larvae and their
obligate attachment to fish hosts remains largely unknown. This study tested the acute toxicity effects of environmentally
relevant chloride concentrations on larvae of European Anodonta anatina mussel as well as the impacts
on attachment rates of the larvae to their fish host. Chloride concentrations above 727 mg⋅L−1 significantly
affected glochidia viability and the 24 h EC50 value was determined at 2505 mg⋅L−1
. Successful attachment of
glochidia to the host fish Phoxinus phoxinus was negatively correlated with increasing chloride concentration
and became significant at concentrations N2909 mg⋅L−1
. Comparable responses could be observed by separately
counting fin and gill attached glochidia, while gill attachment showed the highest correlation with overall attachment
rates. These results indicate a potential threat from short-term elevated chloride concentrations during
runoff events on sensitive life stages of freshwater mussels. Consequently, we propose additional chloride sensitivity
tests on other mussel species as well as the reduction of salt peak input loading into freshwater bodies
through a 3R-principle (restriction of use, retention of runoff for peak concentration avoidance and replacement
by alternatives) in areas where endangered mussels occur.
Capsule: Freshwater mussels of the Unionoida are globally in decline and knowledge on the sensitivity of the
most vulnerable larval stages to salinity is crucial for their conservation
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