Water quality and contaminants have been frequently identified as critical stressors for freshwater mussels, many species of which are highly imperiled throughout North America and the world. Nutrient pollution, specifically nitrate, has become one of the most prevalent causes of water quality degradation globally, with increasing anthropogenic input from suburban and agricultural runoff, municipal wastewater, and industrial waste. Nitrate acute toxicity is generally low for aquatic species, but the potential effects of nitrate exposure are largely unknown for freshwater mussels, particularly during the parasitic stage of their complex lifecycle. Therefore, this study was designed to determine the effects of short-term nitrate exposure at environmentally relevant concentrations on juvenile production in two freshwater mussel species. Lampsilis siliquoidea and L. fasciola glochidia were exposed to nitrate (0, 11, or 56 mg NO3-N/L) for 24 h before inoculation on a primary host, Largemouth Bass (Micropterus salmoides). Glochidia attachment, metamorphosis success, and total number of juveniles produced were monitored on individual fish. Exposure of L. siliquoidea glochidia to 56 mg NO3-N/L nitrate resulted in a significant (p = 0.02) 35% reduction of total juveniles produced, a combined result of moderate decreases in both glochidia attachment and metamorphosis success. A similar trend (28% reduction; p = 0.06) was evident with 11 mg NO3-N/L. No effects were apparent for L. fasciola, suggesting species-specific differences in responses even among closely related species. These results are the first to suggest that glochidia exposure to nitrate may adversely affect juvenile recruitment in some species. Findings from these studies are important for improving characterization of the hazards of nitrate pollution to aquatic life and this work will help better define the role of water quality in assessing habitat suitability for mussel conservation efforts.
Bibliographical noteFunding Information:
Funding for this project was provided by the U.S. Fish and Wildlife Service Science Support Partnership in partnership with the U.S. Geological Survey through Cooperative Agreement number G15AC00213 with the University of Georgia. Additional support was provided by the University of Georgia Interdisciplinary Toxicology Program and the Warnell School of Forestry and Natural Resources at the University of Georgia . We thank Chris Barnhart at the University of Missouri and Paul Johnson from the Alabama Aquatic Biodiversity Center for providing the mussels used in these experiments. We thank Jace Nelson, Bob Ratajczak, and Matt Urich for their assistance with fish care. This study was conducted under the auspices of the University of Georgia Animal Use Protocol No. A2016 06-030-Y2-A2.
© 2018 Elsevier Ltd
- Early life stages
- Unionid mussels