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Sediment quality assessment of flowing waters in South-West
Germany using acute and chronic bioassays
T.A. Ziehla,b,
A. Schmittc
aInstitute of Microbiology,
University of the Saarland, im Stadtwald, 66041 Saarbrücken,
Germany
bInstitute for Biology Ii, University of Freiburg, Stefan-Meier-Straße
19, 79104 Freiburg, Germany
cState-owned institute for Health and Environment, Ma/starter
Straße, 66117 Saarbrücken, Germany
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Abstract
Four bioassays were selected to examine sediment-elutriates
of three flowing waters in the Saarland (South-West Germany). The
aims of this study were the determination of the most sensitive
bioassay for a sediment assessment within routine screening procedures
and the comparison of a recently developed long-term bacterial assay
with other commonly used and standardized bioassays.
Sediment samples were elutriated with water and also
with dimethyl sulphoxide in order to extract organic compounds.
An expected accumulation of toxicants in the sediments was checked
by additional examination of surface water at respective sampling
sites, applying bioassays as well as chemical analysis methods.
Whereas the sensitivity of the Daphnia magna
assay was relatively low, the Scenedesmus subspicatus chlorophyll
fluorescence test denoted the presence of high loads of nutrients
at all sites. The results obtained using the Vibrio fischeri
short-term bioassay suggested that an ecotoxicological risk can
be excluded.
The long-term luminescent bacteria assay is a further
development of the short-term V. fischeri -assay. Prolonging
the test duration from 30 mm to 24 h should track down subacute
toxicities, thus leading to a greater degree of sensitivity. However,
the prolongation caused severe problems in respect of an accurate
interpretation of the results. The long-term assay is not suited
for routine deployment without major improvements.
The extractable content of metals, pesticides, polychlorinated
biphenyls and chlorinated hydrocarbons remained below their threshold
values by several orders of magnitude.
The use of dimethyl sulphoxide as solvent caused a decrease
of bioluminescence in both bacterial assays. The inhibition was
caused by toxic metabolic products of di methyl sulphoxide formed
by autochthonous bacteria from the sediment samples during the elutriation
procedure. Thus, the use of dimethyl sulphoxide is not recommended
for examinations of environmental samples when applying a 'luminescent
bacteria assay. © 2000 Elsevier Science Ltd and AEHMS. All
rights reserved.
Keywords: Daphnia magna; Scenedesmus subspicatus:
Vibrio fischeri; Dimethyl sulphoxide; Elutriation;
G-value
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