Report: Macrozoobenthos: Weser estuary – Long-term changes (2001)»
Description
Effluents from a titanium dioxide factory have been discharged into the Weser estuary since 1969. As part of a monitoring programme, the long-term changes of the eulitoral benthos in the mesohaline section of the estuary were examined using mapping data from 1968, 1980 and 1992. With the help of cluster analyses, eight Benthos associations could be defined and described, the number of which decreased from 1968 (7) to 1992 (3). This loss of diversity of communities is likely to indicate a loss of environmental quality without mentioning the direct causes. At the same time, distribution areas of many species as well as the total benthos biocoenosis had shifted upstream, due to the long-term increase in salinity. Some of the most striking changes are: 1) a sharp decline in the brackish water algae Vaucheria sp., demonstrably not caused by waste water from TiO2 production, and 2) the establishment of the Polychaete Marenzelleria c.f. wireni since 1986, which has immigrated to many estuaries of the southern North Sea during the 1980s. In the framework of environmental control investigations, the long-term changes of intertidalbenthic assemblages in the mesohalinic section of the estuary have been studied by a comparison of survey data from 1968, 1980 and 1992. By means of cluster-analysis eightbenthos assemblages could be identified and described, the number of which declined from1968 (7) through 1992 (3). This loss of assemblage diversities presumably indicates an environmental deterioration without direct reasons being recognisable. It was accompanied by a shift of individual species distribution and of the whole estuarine Benthic Community in the upstream direction which clearly is induced by a long-term increase of salinity. Two of the most conspicuous changes were 1) A strong decrease of the brackish-water algae Vaucheria sp. in the period 1968 to 1980, which could be ascertained, was not an effect of the wastes from TiO2-production, and 2) an immigration of the polychaete Marenzelleria c.f. wireni since 1986, which is a new species in many estuaries of the southern North Sea.
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Tags
- makrozoobenthos-abundanz-makrofauna-artenzusammensetzung-nlwkn-biologische-kartierung-vergleich-abwasser-titandioxid-eulitoral-mesohalinikum
- wesermündung-weser