Understanding the implication of changes in climate and river flow conditions on freshwater mussels

Elaine Langone, Room 241

Alterations to flow regimes are predicted to increase with water management and changing climatic conditions and are thus likely to affect aquatic species. Freshwater mussels are a key group of benthic organisms that could be highly impacted by streamflow alterations, primarily due to their sedentary nature and often long-life spans. Some mussel species are known to live up to 150 years as determined from annually-deposited shell growth rings (annuli). While counting shell annuli can provide useful information on basic population demographics, it is possible that additional information could be gleaned from measurements of the width of annual growth bands. We test this possibility using shell thin-sections from the federally endangered dwarf wedgemussel (Alasmidonta heterodon). We collected shells from 185 individuals from 5 locations in northern Atlantic Slope rivers and, combined with quantitative survey data, developed estimates of mussel age distribution for these populations. Incremental growth measurements were then made on a subset of shells from two locations. Using estimates of mussel “time of death”, annual growth measurements were aligned with instream-flow and regional climatic variables. Multivariate analyses were used to identify suites of environmental variables that best predicted patterns in annual shell growth. These results could be beneficial for predicting the effects of changing flow regimes on freshwater mussel growth; identifying optimal flow conditions for maximizing mussel growth and presumably condition; and for informing water management decisions for maintaining healthy populations of this rare and endangered species.