PH19 Biomonitoring
Exhibit Hall
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(PH222) Benthos of the River Blaukrantz, S. Africa, affected by domestic and agricultural pollution.

Janssens de Bisthoven, L1, Gerhardt, A1, 1 LimCo International, Ibbenbueren, Germany

ABSTRACT- The first/second order stream Blaukrantz, Eastern Cape, S. Africa, was sampled in austral autumn for benthos (surber) at 5 sites on a stretch between Grahamstown and 25 km downstream to assess the general water quality with commonly used biotic indices, and the chironomid community and deformities. The first section, a few 100 m from the spring, showed already an extremely degraded quality. At the outskirts of the town, the presence of a purification plant discharge was beneficial to the quality of the stream. Further downstream, where the valley was characterised by small-scale husbandry and agriculture, interspersed by natural bush vegetation, the macrozoobenthos was dominated by detritivores, showing a poor quality and a high saprobicity. The chironomids are currently being analysed to assess whether they would provide a more differentiated assessment than the macrobenthos, including an indication for the presence of heavy metals and/or pesticides.

Key words: chironomidae, benthos, water quality assessment, biomonitoring

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