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PH20 On-line Water Toxicity Monitoring
(PH232) Daphnia magna (Crustacea) in the Multispecies Freshwater Biomonitor: responses to natural and artificial photoperiod.
Gerhardt, A1, Janssens de Bisthoven, L1, Schmidt, S1, 2, 1 LimCo International, Ibbenbueren, Germany2 University of Applied Sciences (FH), Jena, Germany
ABSTRACT- Daphnia magna is a standard test species in aquatic ecotoxicology and has been used in the so-called Dynamic Waterflea Assay for online biomonitoring of water quality for up to 30 years. In one type of this biomonitor swimming activity of a group of phototactic clones of daphnids exposed in a test chamber between two alternating light sources are used. The aim of this study was to elaborate the best test conditions for Daphnia magna in the Multispecies Freshwater Biomonitor (MFB). Survival and swimming behaviour of single and groups (5, 10) of daphnids exposed in test chambers (9 cm length) of different diameter (2cm, 3cm) were recorded on line during 48 h under natural (12h light: 12h dark) and artificially alternating (2h light: 2 h dark) photoperiod. Test chambers contained three levels in vertical arrangement, where behaviour was recorded quantitatively using tetrapole impedance conversion technology. Daphnia magna clearly exhibited a natural diurnal activity pattern with phototactic behaviour, consisting of elevated night activity in the top compartment of the test chamber and elevated day activity in the bottom part of the chamber. The behaviour of daphnids was independent of the diameter of the chamber. Increasing number of daphnids per test chamber resulted in decreasing clarity of the diurnal vertical movement pattern. Survival did neither depend on the number of daphnids per chamber nor on the chamber diameter. Exposure of single individuals in large 3-level test chambers is recommended for Daphnia magna in the MFB, because of 1) clarity of design, 2) statistical power and 3) phototaxis can be used as additional toxicity parameter to overall swimming behaviour and survival.
Key words: daphnia magna, phototaxis, behaviour, multispecies freshwater biomonitor
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