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Analysis of the qualitative signature of fatty acids in tissues of organisms is an increasingly utilized tool in studies of trophic ecology in aquatic and terrestrial ecosystems. Here, we studied a colonial waterbird, the black-headed gull Chroicocephalus ridibundus, nesting in three colonies. We aimed to investigate whether fatty acid composition of its eggs is affected by the location of the colony (reflecting the spatial variation in habitat composition and, in turn, female diet at the time of egg formation), and the egg laying sequence (reflecting the temporal variation in female diet). We found that the composition of fatty acids in eggs of black-headed gulls differed among colonies, but not among subsequent eggs within the clutch. We interpret these results in the context of spatial differences in the diet of females breeding in different colonies and a lack of temporal variation in the diet of individual females. The pattern of the ratio of omega-3 to omega-6 fatty acids reflected the contribution of aquatic/terrestrial prey to their diet, and was consistent with the area of water courses around the colonies. High levels of omega-6:omega-3 can promote inflammation and thus lead to increased susceptibility to antigens. Further studies with prey sampling are required to reconstruct the diet composition of females during egg formation in more detail. [ABSTRACT FROM AUTHOR]

Biogeochemical effects to Polish terrestrial ecosystems resulting from atmospheric nitrogen deposition were forecasted until the target year 2020. To this end recently updated critical loads of nutrient nitrogen were applied and the nitrogen deposition projections for the sequence of decades from 1980 until the target year 2020, based on the Current Legislation (CLE) and Maximum Feasible Reductions (MFR) emission scenarios. The predictions were done by use of the Very Simple Dynamic (VSD) Model developed within the Working Group on Effects of the UN ECE Convention on the Long-Range Transboundary Air Pollution CLRTAP. The calculations were done for three main forest ecosystems and three selected semi-natural ecosystems encompassing the whole territory of Poland with the spatial resolution defined by a grid cell of 1 x 1 km size. The study concluded with maps of CLnut(N) exceedances and expected nitrogen concentrations in soil as chemical criterion, assigned to different eutrophication risk categories for each deposition scenario. The obtained results show that in spite of the realistic (CLE scenario) and extreme (MFR) nitrogen emission reductions until 2020, more than 99% and 80% of total area of terrestrial ecosystems of Poland, respectively, will be exposed to excessive nitrogen deposition. Results of this study as well as studies done on the European scale reveal that the nitrogen emission reductions determined by the Gothenburg Protocol are still insufficient and may lead to negative ecological effects including loss of ecosystems biodiversity. This substantiates a demanding need for the revision of the CLRTAP Gothenburg Protocol. [ABSTRACT FROM AUTHOR]