Algae and Daphnia (waterfleas) forewarn drinking water sector Biomonitors, instruments which measure the biological effects of different substances on organisms, detect substances which cannot be detected using chemicals anaylsis methods. This is also valid for combinations of substances which are present in the water in large concentrations. A well-functioning monitor is necessary since our modern society uses over one hundred thousand different substances. It is unlikely whether they can all be measured using chemical analysis. In the measuring plants in Eijsden and Lobith biomonitors are used as alarm systems.
On 24th and 25th September 2006, the Algae Toximeter in Eijsden triggered an alarm.
Algae convert sunlight (photo). Chlorophyll needs sunlight to convert the cells to a higher energy level, to makes the growth of algae possible. The chlorophyll does not absorb all the sunlight but gives some off as energy (i.e. fluorescence). Algae Toximeters measure fluorescence and on these two days the fluorescence emitted by the algae increased considerably. And this means that the algae absorbed less sunlight and thus produced less growth.