Barák V.1,2*, Jahelková V.1, Simon O.1, Bílý M.1, Douda K.2
The effects of contaminants are traditionally considered one of the main reasons of the global declines of freshwater mussels including endangered freshwater pearl mussel Margaritifera margaritifera (Linnaeus, 1758) (FPM). The objective of our study was to develop and test a robust design for the in situ investigation of the multiple point-source pollution-caused effects on FPM. A declining FPM population occurring in the Malše River (Czech Republic, Central Europe) has reportedly been disturbed by the impact of municipal pollution from a point sources but there is a lack of data documenting these effects due to the inherent episodicity of the pollution events. Therefore, a 30-km-long river stretch was delimited of the impacted and both the upstream and downstream control sections. At each of total 15 sites, 2−4 open water mesh cages with juvenile mussels were located. Five water samples were taken at each site at intervals of 6−8 days during one-month experiment. As it had been assumed, survival rates of FPM within impacted section were lower than at control sites (73‒95% and 91‒100% of the upstream and downstream control values, respectively). An acute effluent-induced toxicity could be detected within studied river. Several potential stressors (ammonia and nitrite, low DO levels) have been found to be elevated and were associated with the adverse mussel development. This study highlights the importance of freshwater mussel species sensitivity to sudden adverse changes in ambient water quality. The methodology applied here may provide a useful tool for assessing and managing water quality in streams with FPM and possibly other freshwater bivalves.
Keywords: in situ monitoring, freshwater pearl mussel, water quality, effluent-induced toxicity
Acknowledgements: The study was supported by IGA Faculty of Environmental Sciences CZU Prague [No. 20194213], the Czech Science Foundation [No. 19-05510S] and the European Regional Development Fund [No. CZ.02.1.01/0.0/0.0/16_019/0000845].