¹LimCo International, An der Aa 5, D-49477 Ibbenbüren, Germany
²Water Transport Company Rhine Kennemerland (WRK), P.O. Box 10, NL-3430 AA Nieuwegein, The Netherlands

^*Corresponding author, Email: limco.int@t-online.de

Abstract

The Multispecies Freshwater Biomonitor (MFB) based on quadropole impedance conversion technique is a "biological early warning system" (BEWS) for online water quality biomonitoring. The aim of this study was to test the MFB with two crustaceans (Gammarus pulex and Daphnia magna) in a drinking water processing plant at the River Rhine: 1) Sensitivity of the test species to short-term acid pulses and alarm-responses in the MFB were studied in the laboratory. 2) Long-term monitoring with Gammarus pulex and Daphnia magna in the MFB was performed in situ. A decrease in pH, especially below pH 6.8, resulted in a significant behavioural response of both species according to the Stepwise Stress Model. After a first escape response of D. magna, both species reacted similarly with decreased activity and G. pulex additionally with increased ventilation. G. pulex survived better than D. magna. The behavioural effects remained in the recovery phase. Long-term monitoring showed stable locomotory behaviour and better survival of G. pulex when compared to D. magna. The MFB can be recommended for drinking water control using G. pulex as test species.