PERFORMANCE OF 2 ARTIFICIAL SUBSTRATE SAMPLERS FOR MACROINVERTEBRATESIN BIOLOGICAL MONITORING OF LARGE AND DEEP RIVERS AND CANALS IN BELGIUM AND THE-NETHERLANDS

Harmonization exercises organized by the European Communities in the 1 970s on biological water assessment methods for running waters, becaus e the usual methods were difficult or impossible to apply, explicitly stressed the need for development of standardized sampling procedures for monitoring large and deep rivers and canals. To meet this objectiv e, an extensive monitoring campaign was organized in Belgium and The N etherlands to test the efficiency of artificial substrates colonized b y macroinvertebrates as an alternative for natural communities sampled with a handnet. Two types of artificial substrates were tested: a Bel gian substrate, composed of a plastic netting filled with medium-sized pieces of brick, and a Dutch substrate consisting of a stainless stee l box filled with marbles. The collected biocoenoses were compared qua litatively and quantitatively. Water quality was assessed by means of several biotic indexes. The results show that both the Belgian and the Dutch artificial substrate sampler can replace the usual samples obta ined by means of a handnet, and provide a correct assessment. A major drawback of the use of artificial substrates in uncontrolled monitorin g sites remains the unforeseen losses. For that reason the cost price of the substrates may have to be considered when making a selection.