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Rapid expansion of the Asian clam Corbicula fluminea (O. F. Müller, 1774) : a new alien species in the mollusk community of the Vistula

Bonk M., Zając K., Lipińska A. M.

Oceanological and Hydrobiological Studies

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2018

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Vol. 47, No. 1

75--86

EN

A new large population of the Asian clam Corbicula fluminea (O. F. Müller, 1774) was found within a reach (ca 210 km long) of one of the largest European rivers, the Vistula. The largest population and the largest individuals were found at the outlet of a channel collecting heated water from the cooling process at the Połaniec power station and adjacent parts of the river. In the northern part of the study area, bivalves occurred at the channel margins, in groyne fields, and in the shallows of sand banks or sandbars. The clams were less numerous in places where the river was regulated with straightened banks and stone ripraps. Twenty-five other taxa of mollusks were found altogether at the sampling stations where Corbicula was observed, including other non-indigenous mollusk species.

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Long-term changes of mollusc assemblages in bottom sediments of small-isolated lakes of different trophic state

Kołodziejczyk A., Lewandowski K., Stańczykowska A.

Polish Journal of Ecology

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2009

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Vol. 57, nr 2

331-339

EN

It is a common view that increase of the trophic state of lakes has a negative effect on littoral invertebrate macrofauna, molluscs among them. However, the available data are often contradictory, and the decline of particular species is often observed only at a very pronounced raise in trophic state. The aim of this work was to present the changes of the composition and abundance of bottom malacofauna taking place during last 30 years in five small (area from 0.12 to 1.74 km[^2]), mainly shallow (mean depth from 3.7 to 11.8 m) lakes of different trophic state (eutrophic and mesotrophic), connected by a small river (Masurian Lakeland, Northeastern Poland). The research were conducted in years 1997 and 2006 and were compared with published data, collected in 1976. The trophic state of the lakes studied was still constant during the period of investigations. In the studied lakes the decrease of number of bottom mollusc species was observed in subsequent years. The previously recorded there alien, invasive species, Potamopyrgus antipodarum (J.E. Gray, 1843) and Lithoglyphus naticoides (C. Pfeiffer, 1828) also disappeared. Dreissena polymorpha (Pallas, 1771) remained the dominant species in most of the lakes. These changes were recorded in four eutrophic lakes as well as inone mesotrophic lake. The decline of the species in individual lakes didn't follow any regularity. Some mollusc species disappeared and value of similarity index between malacocenoses in these lakes decreased. It seems, that the trophic state was not the cause of disappearance of some mollusc species from the studied lakes. However, the effect of frequent anoxia in littoral zone related to eutrophication was raised up as the possible cause. The decline is of long-term character, probably resulting from small size and relative isolation of the lakes, which impede their recolonisation.

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Ten years of change in ground-layer vegetation of European beech forest in the protected area (Ojców National Park, South Poland)

Łysik M.

Polish Journal of Ecology

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2008

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Vol. 56, nr 1

17-31

EN

Long-term changes in ground-layer vegetation of unique stand of Carpathian beech forest Dentario glandulosae-Fagetum considered partly as a natural succession due to climatic changes and partly as a response to canopy dynamics, were investigated in the Ojców National Park (South Poland). Species composition and structure of the herb layer in the permanent research area were compared in 1993 and after ten years. About 77% of the study area was changed in this period, but the spatial pattern of distribution and intensity was highly mosaic. The mean intensity of changes calculated according to formula (1) derived from changes in percent cover of species was 42%. Herb cover decreased by about 15%, probably due to the rapid development of natural recruitment of trees in the study area (48% of area was covered by dense tree recruitment). In the same time the number of plant species and vegetation types (homogeneous vegetation patches of the size at least 1m2, that differed from neighbouring patches in species composition and/or species share) increased substantially. It is probably due to greater variation of light condition in ground layer created as a result of canopy gaps dynamics (the area of windthrow mounds in the study area increased approximately eight times between 1993 and 2003). There was a significant decline of species typical for beech forests, especially of vernal geophytes like Dentaria glandulosa W.K. and Isopyrum thalictroides L. Although it is too early to predict any directional changes, it is possible that the beech forest community will change into the Tilio-Carpinetum association in some parts of study area. Nowadays the expansion of invasive alien species Impatiens parviflora DC. is the great threat to the forest vegetation of the protected study area and the Ojców National Park. This species in 10 years managed to displace native species in 3% of the study area. The drastic decrease in herbaceous plants cover connected with increase in tree seedlings and saplings, systematic decline of vernal geophytes and typical beechwood species, diversification of ground vegetation structure and composition, and finally occurrence of non-native invasive plant species inform about highly dynamic nature of climax beech forests and generally of temperate forests. Changes are induced probably by both changing climate and overstorey dynamics.