Since 2005, great cormorants have been observed on the Lake Góreckie (Wielkopolski National Park) shoreline. The population of these birds occurring within the lake has gradually increased. In autumn 2008, more than 100 individuals were observed. In the period 2009-2012 the number of birds occupying the island periodically exceeded 250 individuals. So far, there is no breeding colony of great cormorants, but the birds have established a roosting colony on the island. In the period 2009-2012 we conducted research on the impact of the colony of great cormorants on the accumulation of nitrogen, phosphorus and other elements in soils beneath the colony and transfer of chemical elements from the colony to a nearby freshwater ecosystem. Our results show that a relatively small and recent colony of great cormorants can significantly affect the chemistry of soil. Compared to a control, the soil beneath the colony was characterized by statistically higher concentrations of nitrogen and phosphorus. A significant accumulation of nutrients was observed in the topsoil zone (to a depth of about 20 cm). Enrichment of soil in chemical elements has resulted in their further transport to a nearby lake. Compared to the control, the groundwater and surface runoff from the colony area revealed several-fold higher concentrations of nitrogen and phosphorus. The maximum abundance of cormorants in the roosting colony was reflected in the elevated concentrations of nitrogen and phosphorus in the littoral water near the colony. Our study demonstrates that the roosting colony of great cormorants can play a significant role in accelerating the eutrophication of surface waters.
Anna Borysiak, Janina Borysiak, Tomasz Joniak and Barbara Nagengast
Translocation of Nuphar lutea (L.) Sibth. & Sm. from the A2 road near Nowy Tomyśl (Poland) into alternative sites
A translocation of Nuphar lutea (L.) Sibth. & Sm. was made from its primary location in Prądówka, situated in the path of the construction site of the A2 motorway, into replacement biotopes. All rhizomes were taken out of the water and used to prepare cuttings. These were divided into three approximately homogeneous groups. Each group was introduced into different replacement water bodies with environmental conditions that resembled those of the biotope in the Prądówka site. Two of the water bodies were fish ponds. A third was a so called ‘ecological water body’ (settling pond, settling basin) that collected fall effluents delivered from the surface of motorway. The results of the examination of the physical-chemical features of water and bottom sediments from the Prądówka peat pit, two fish ponds and four settling basins are presented in the article. Biological and autecological features of the species Nuphar lutea, which are significant from the aspect of the growth of the seedlings within the alternative sites, have been discussed. A year after translocation it was observed that in the case of fish ponds, 83% and 75% of the introduced plants survived, while in the settling basin only 50%. A conservation project was undertaken by the investor in order to compensate for the negative effects of the A2 motorway within the area of the European Ecological Natura 2000 Network.
Progressing eutrophication of waterbodies requires measures to be undertaken that aim at halting or reversing negative changes in the environment. Chemical restoration is one of the most common methods used for lake treatment, where iron or aluminium phosphate coagulants are applied. However, their chemical qualities pose the risk of acidification and aluminium ion release, which become toxic in acidic conditions. The influence of coagulants on aquatic plants, including charophytes that are very valuable from the ecological perspective, is little recognised. For this reason, the aim of the research was to define changes in the growth pattern of the charophyte Chara hispida under the influence of an aluminium coagulant. The research was carried out in mesocosms (0.8 m3) located in situ in a lake. Polyaluminium chloride was applied once to each chamber in doses of 50.0, 100.0 and 200.0 ml m−3. Coagulant concentrations reflected aggressive restoration aimed at precipitation of phosphates, suspension and water colour at the same time. It was proved that the coagulant had inhibited the growth and slightly reduced the length of branchlets, and simultaneously elongated internode cells. Changes in the total length as well as the length of branchlets were caused by a strong pH decrease of the environment which simultaneously induced higher aluminium solubility and toxicity. Elongation of internode cells was caused by reduced light availability, resulting from high water turbidity in the first stage of coagulant’s application, and then from the charophytes’ thallus being covered by a coagulated suspension precipitated from water.