Macrobenthic nematodes as biological indicators in a Mediterranean lowland river in Central Italy: a case study.

Abstract

To test their effectiveness as biological indicators, the distribution of macrobenthic nematodes (retained by a sieve with mesh opening of 0.280 mm) along the River Arrone (Central Italy) was studied in seven soft-bottomed sites variously affected by organic pollution. Significant positive relationships were found between environmental parameters (orthophosphate, ammonium, BOD 5 in the water, and silt/clay and organic matter in the sediments) and densities of both total nematodes and the most abundant species (Tobrilus diversipapillatus, Dorylaimus asymphydorus and Tobrilus gracilis). Relationships were also found between taxa and some biotic indices (EBI modified by GHETTI 1986, and BWMP modified by ALBA TERCEDOR & SANCHEZ-ORTEGA 1988), commonly used in surveillance studies in which nematodes are not considered. Principal Component Analysis performed on nematode taxa densities clearly illustrates these relations, the first component is identified as chemical and biotic gradients and the second as organic matter content and granulometric gradient. The results of this study were compared with the literature reports of taxa found in the River Arrone. All the data suggest that the analysis of the nematode communities can be a promising tool in water quality assessment studies of lowland rivers, because of the good relations between this zoological group and physico-chemical parameters and biotic indices.