Biomonitoring miejskiego odcinka Dzierżęcinki z wykorzystaniem makrozoobentosu w celu renaturyzacji koryta rzeki

Biomonitoring of the Dzierżęcinka river, a natural watercourse passing through Koszalin, was conducted in 2006. Three sites were selected, at which macrozoobenthos was three times extracted using 0.5mm mesh benthic net. 45 samples were taken. 5 qualitative and quantitative samples from each site, 4 of the former and 1 of the latter type. Analysis consisted of taxonomic affiliation, number and biomass of extracted organisms. Basing on the research results the ecological condition of the investigated parts of the Dzierżęcinka river was determined with the use of the following indices: TBI (Trent Biotic Index), Saprobe Index S, BMWP-PL index (Biological Monitiring Working Party which has been adapter to the Polish conditions), the EPT index (Ephemeroptera to Plectoptera to Trichoptera) First site was situated at the spout point of the Dzierżęcinka river to Koszalin, at 4-Marca street. The ecological condition of the waters oscillated between average for BMWP-PL to good for TBI and the Saprobe Index S. At the same time the EPT index reached low values, which signifies small number of desirable insect larvae sensitive to pollutants. The reason for this mediocre watercourse condition at this site may be a busy street adjacent to the research site, which is the source of partial contamination of water with pollutants from petroleum incineration, waterdrain collectors, which may introduce certain pollutants into the river and waters coming through drainage ditches between Bonin and Koszalin. Second site was situated in the center of the city near the mill. It has the lowest grade in all ecological indices. The lowest number of organisms, in addition to the minimal number of taxons was observed here. The cause of such a poor state may be the closeness of the city center and the Młyńska street (one of the busiest streets in Koszalin) , waterdrains, numerous water birds in the nearby pond whose droppings undoubtedly negatively influence the functioning of water flow. Third site, situated in the vicinity of the bridge, shows satisfactory BMWP-PL, TBI and S indices. Despite these values, the site was characterized by the greatest biodiversity during all dates of research. The reason for this is the sandy and pebbly riverbed, which provides proper ecological niches for a greater number of macrozoobenthic species. Thus it seems, that in order to broaden biodiversity of benthic organisms, actions toward diversifying their environment should be taken. For that reason renaturalization of the Dzierżęcinka riverbed should be based on introduction of varied habitat elements such as: rocks, pebbles, gravel slide-offs, fallen tree-trunks, washed root systems and branches, which create proper conditions for feeding, rest and hiding from predators. Recreation of those elements in respect of bottom morphology parts of the Dzierżęcinka river, will enrich the river in greater number of zoobenthic species, which will influence the self-purification process of the water and the circulation of matter in the ecosystem.