Zgrupowania skąposzczetów dennych (Oligochaeta) Kanału Gliwickiego i Kanału Kędzierzyńskiego oraz związanych z nimi zbiorników antropogenicznych

Abstract

Most of the studies on bottom oligochaetes have been carried out in lakes and rivers, whereas other various anthropogenic water environments have been treated sporadically. Only dam reservoirs are rather well known in this field of study, while the surveys concerning the occurrence of these animals in ditches, drain canals and navigable canals have been conducted only occasionally. The previous investigations referred mainly to the role of canals in the spread of alien freshwater species into new water systems. The scarcity of studies on bottom oligochaetes in navigable canals and anthropogenic reservoirs was the reason for undertaking this study in two canals (the Gliwicki canal and the Kędzierzyński canal) and in the three sand pits (Dzierżno Duże, Dzierżno Małe, Pławniowice) connected with them. The sites studied are located in a heavily industrialised region of Southern Poland (Upper Silesian Industrial Area). The investigations were carried out from 2002 to 2005. Oligochaeta were sampled from bottom sediments by means of standard quantitative methods using a core sampler (20 cm2) from 31 sampling stations. Immediately prior to sampling the oligochaetes, water samples and sediments were collected from each sample site. The zoocenological studies of the oligochaete communities were carried out using the following indices: domination, frequency, the Shannon-Wiener index and the Pielou index. Different tools based on oligochaetes were used for the evaluation of the biological quality of studied environments. The resulting data were evaluated and interpreted by different statistical tests using Statistica for Windows ver. 7.0 and the Canoco program for Windows ver. 4.5. In the environments studied Oligochaeta were dominants and formed from 73% (in Pławniowice) to 95% (in the Gliwicki canal) of the benthic fauna. In addition to them, Amphipoda, Gastropoda, Bivalvia and Diptera larvae were observed in all the environments. Isopoda and Hirudinea occurred in sand pits as well. In total, 25 oligochaete species from the families Tubificidae (with 11 species of the subfamily Naidinae and 12 species of the subfamily Tubificinae) and Lumbriculidae (2 species) were found in the environments studied. Amongst them only Potamothrix bavaricus (Oeschmann) is rare in Poland. Along the Gliwicki canal different oligochaete communities were observed. The community was poor in species from the first section below the Gliwice port, whereas the section before the Kędzierzyn-Koźle port was more diverse. The obtained results showed that diversity of oligochaete communities may be caused by the amount of bottom sediment pollution (heavy metals and WWA15), the sediment granulation, as well as the pollution of the water by organic contaminants, salinity and nutrients. The studies revealed different responses of oligochaete species to sediment pollutions. Limnodrilus hoffmeisteri and L. claparedeanus were the most tolerant. The result of the surveys indicated that the bottom oligochaetes are a useful tool for evaluating the water quality and bottom sediments in the anthropogenic environments studied. The IOBS index and the percentage of Tubificinae without hair chaetae in dorsal bundles were the most valuable for classifying bottom sediments, whereas diversity indices had great value for classifying the water quality. The classification of the Gliwicki canal sediments was proposed on the basis of the IOBS index and the percentage of Tubificinae without hair chaetae. In the Gliwicki canal and Dzierżno Duże similar oligochaete communities were recorded. Both of these environments are supplied by water from the Kłodnica river. The communities in Dzierżno Małe and Pławniowice were different, first of all, in species richness. All the sand pits, in spite of their connection with the Gliwicki canal, had no effect on the Oligochaeta species occurring in it.