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Development of the species number of macrozoobenthos and of the oxygen contents

The rise of the average annual oxygen content of Rhine water at the German-Dutch border reflects the pleasing success in the field of wastewater treatment in the period 1990 – 2006.

Parallel to improved oxygen content, micro-organism species, that is macrozoobenthos has distinctly increased, even though river training has clearly changed its composition and little demanding immigrant species prevail.

Since 1995, the species number has more or less remained constant, however, many insect species abundant more than 100 years ago, such as the ephemera Oligoneuriella rhenana are still missing. Presumably, this is also due to the monotonous structure of river banks.