The studies have revealed that Potamothrix bavaricus (Oeschmann, 1913), generally rare in Poland, is a common species in the benthic oligochaete fauna of different anthropogenic freshwater habitats in a heavily industrialised area of Poland. It was often found in habitats with significant salinity, a high total hardness and a large content of nutrients. The evident resistance to various pollutants enables the settlement of P. bavaricus in such habitats, which are unsuitable for other oligochaete species.Industrial regions are seldom the subjects of hydrobiological investigations. They are not considered interesting from a biological point of view. The natural environment of these areas is devastated to a high degree because they have been impoverished repeatedly.
In Poland, the region of Upper Silesia was for decades influenced by the coal-mining industry. As a result of this activity, numerous freshwater habitats originated either intentionally (as channels) or accidentally (as subsidence ponds). Because this area is devoid of freshwater stagnant habitats, the anthropogenic water bodies play a significant role as valuable refuges for many freshwater species of plants and animals.
In anthropogenic water bodies, rare animal species or those considered rare, often occur more frequently than in natural habitats. In particular, species with the ability to migrate and with considerable ecological tolerance are inhabitants of such environments. For this reason, these water bodies are considered valuable in environmental protection.
As in natural water bodies, Oligochaeta are a significant component of the bottom fauna in anthropogenic habitats. They play an important role in mineralisation of organic matter, in the exchange of elements between the bottom and the water column, and as food for many different animals.
The earliest investigations on freshwater Oligochaeta of anthropogenic water bodies in Upper Silesia showed the presence in this area of Potamothrix bavaricus, which was known only in several localities in other regions of Poland.
The aim of the present paper was to determine the condition of P. bavaricus occurrence in the anthropogenic freshwater habitats of the industrialised area of Upper Silesia (Southern Poland).During the study period, the occurrence of P. bavaricus was found in all 14 study sites. In certain water bodies from 3 to 10 other oligochaete species (Dero digitata, Nais elinguis, Nais simplex, Nais communis, Ophidonais serpentina, Psammoryctides albicola, Tubifex tubifex, Limnodrilus hoffmeisteri, Limnodrilus udekemianus and Limnodrilus claparedeanus) common in Poland were also observed. The water in the majority of these habitats was characterised by elevated salinity, resulting from the inflow of salt water from coal mines, by a high concentration of nutrients and by high total hardness.
The occurrence of P. bavaricus in the Gliwicki channel (study sites 11–14), which is extremely polluted not only with salt water and nutrients but with heavy metals and various organic pollutants as well, is noreworthy. This shows the considerable resistance of P. bavaricus to different environmental pollutants.
No significant correlations were found between the density of P. bavaricus and the parameters of the water.
In the majority of the study sites, specimens of P. bavaricus were a permanent element of the bottom oligochaete fauna. They comprised up to several per-cent of the oligochaete community in particular habitats. The average density of P. bavaricus was from 21.4 individuals m?2 in site 4 to 228.6 individuals m?2 in site 7.P. bavaricus has been recorded in various natural lakes and ponds , lower river courses and small streams. However, it should be noted that the occurrence of oligochaete in post-industrial water bodies has only rarely been the subject of studies to date.
P. bavaricus is a palearctic species of Ponto-Caspian origin but has also recently been distributed in North and South America, in the Near East as well as in Australia and New Zealand in addition to Europe.
It has been found both in freshwater, which indicates its high tolerance for salinity. The research in Upper Silesia also confirms this. found P. bavaricus in hard, highly eutrophicated waters in Germany, which is also in agreement with the observations of this study, because the waters of the investigated environments were hard and rich in nutrients. have indicated that P. bavaricus has been found in a wide range of temperature (13–35 °C), conductivity (300–11600 ?S cm?1), content of chlorides (3–3207 mg L?1), dissolved oxygen (2.5–16 mg L?1) and nitrates (0–70 mg L?1) in habitats in Israel. This shows that it is a euryoic species that is able to occupy new environments unfavourable for other oligochaete species. concluded that P. bavaricus, being a euryhaline species, is a very successful competitor in a wide variety of water types. It can be reasoned that P. bavaricus appears and creates permanent populations in such habitats as examined in this study. In various kinds of anthropogenic environments, the occurrence of rare or non-typical species has often been observed, which could result from a lack of pressure from potential competitors. This study also confirms this because in general the biodiversity of biocenosis in the habitats was low and grazing pressure or competition had no significant effect.
As was observed by, the abundance of P. bavaricus in the bottom oligochaete fauna was differentiated and amounted to from several to hundreds of specimens. observed that this species in the waters of Australia was often abundant when present. The density of P. bavaricus in Upper Silesia was similar in comparison with the above-mentioned research.
According to, a whole set of species of the genus Potamothrix have a great dispersal capacity and can be easily spread on the feathers of water birds. Because the region where these investigations were carried out is the nesting area of many bird species, one may expect an increase in the number of water habitats colonised by P. bavaricus from year to year.
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