Stable isotope analysis of food webs in wetland areas of Lake Balaton, Hungary

Stable carbon (delta(13)C) and nitrogen (delta(15)N) isotopes were used to analyze the source and transformation of organic matter in the food web of the Kis-Balaton Water Protection System (KBWPS). The extent of the isotopic shift between trophic levels deviated significantly from typical values of 1 parts per thousand for carbon and 3.5 parts per thousand for nitrogen. The delta(13)C enrichment factor in food chain benthos > cyprinid prey fish > predatory fish (pike-perch, pike) was over 2 parts per thousand in the KBWPS. Variability in delta(13)C in the KBWPS reservoir would be dampened because of the high ratio of dissolved inorganic carbon and also it may reflect inputs of terrestrial organic carbon through the main inflow. The trophic fractionation of N-15 appears to be more pronounced in fish than in invertebrates. The isotopic shift in the food web of the reservoir proved to be lower than 3.5 parts per thousand and was 2.9 parts per thousand. Our isotope evidence indicated that there might be strong competition for food resources between bream and prussian carp on the one hand and between common carp and roach on the other. Pike-perch and pike depended on omnivores such as bream and prussian carp as food. KeyWords Plus: CARBON; NITROGEN; DIE