Preliminary assessment of parasites in alien and native freshwater mussels in Europe

The Powell River (Virginia and Tennessee, USA) supports several threatened and endangered species of freshwater mussels and fishes. Coal mining in the Powell River watershed began in the 1800s. Surface mining increased in intensity in the 1980s; active surface mining permits currently occupy 38% of the upper watershed. Temporal changes in freshwater mussel assemblages have been documented, but data have not been extensively compared between studies or with other taxa. The objectives of this study were to evaluate spatial and temporal trends in recent (2000âEUR2013) and historic (1899âEUR1999) freshwater mussel and fish data and to relate these trends to water quality measurements and the prevalence of surface mining. Upper reaches of the river currently have far fewer freshwater mussel species than were observed in the earliest surveys (1899âEUR1913). A significant negative relationship between number of species observed and river km was first observed in the 1970s and this trend has persisted. Quantitative and qualitative data from multiple studies at specific sites indicate declining mussel densities and species numbers as early as the 1970s and 1980s, which corresponds to initial elevation of major ion concentrations (relative to 1949), extremely high iron concentrations, and observed blackwater events and mussel dieâEURoffs. Fish assemblage data from both recent and historic collections also demonstrate significant negative relationships between river km and metrics such as percent darters and percent intolerant species. Impaired fish communities were first observed in the Powell River in the 1960s, with complete extirpation of certain species occurring in the late 1970s. Major ion concentrations in the Powell River doubled between 1949 and 1978 and doubled again by 2006. However, whether these concentrations cause changes in freshwater mussel and fish assemblages or contribute to persistence of changes that occurred over 30 years ago is unclear and will be discussed.