ABSTRACT
The “Dreissena-Monitor” is a recently developed early warning system for the aquatic environment. It is based on the valve movements of up to 2×42 specimens of the zebra mussel Dreissena polymorpha. The dynamic limits of two of the parameters recorded by the system—(1) the percentage of open mussels, and (2) the number of valve movements—are exceeded when the actual running average is less or greater than a “long-term average” minus or plus its threefold standard deviation. With consideration being given to the normal behaviour of the mussels, and the response of the system during several toxicity tests, reliable alarm-thresholds are established (1) for one experimental channel in comparison to the second one (necessary, e.g., during toxicity tests), and (2) for the whole system during operation for continuous water control purposes. The way this alarm function works is described with the aid of examples.
