Parasite and chemical effects on freshwater snail survival, egg production, and shell strength

Background/Question/Methods

Benthic animals are exposed to multiple stressors that may disrupt their vital rates or survival.  I studied the effects of two chemical stressors, nitrate and 1-butyl-3-methyl imidazolium bromide (bmimBr), a room temperature ionic liquid, and a parasite, the trematode Acetodextra amiuiri, on the survival, growth rate, egg production, and shell strength of the freshwater snail Physa acuta.  Room-temperature ionic liquids (ILs) are a new class of chemicals being proposed as environmentally-friendly solvent substitutes for industrial applications.  While ILs are relatively benign to the atmosphere because they are non-volatile, their impacts on aquatic organisms and communities are largely unknown.  An experimental regression design was used to model the effects of stressors on Physa vital rates.  
Results/Conclusions

Lethal concentrations (LC50) of chemical stressors were lower in combination with parasites than when presented to snails alone.  Nitrate and bminbr alone and in combination affected Physa growth rates.  Physa egg production increased with increasing nitrate concentrations, but was unaffected by sublethal bminBr concentrations.  bminBr significantly reduced Physa shell strength. These results suggest that IL toxicity to Physa is modified by environmental factors and more realistic tests of IL toxicity are necessary to understand their potential impact on aquatic organisms.