The ionic concentrations,conductivity and pH of water in the Lake Chany complex in West Siberian Russia change from the mouth to the interior of the lake. This difference is indicative of marked evaporation of lake water from the closed water body system in the dry climate of Western Siberia. The carbon isotope composition of particulate organic matter (POM, composed mainly of phytoplankton) clearly changes, along with the pH of the water, reflecting the concentration of dissolved CO 2 . Carbon and nitrogen isotope signatures of Chironomus plumosus larvae, a benthic invertebrate that may feed on bulk lake sediment, systematically increase, along with those of POM and sediment organic matter (SOM), through the lake chain. Both sulfate-sulfur and nitrogen isotope compositions of the POM and SOM increase with distance from the estuary into the Lake Chany complex. Heavier sulfur and nitrogen isotope recycling from the sediment, caused by microbial sulfate reduction and denitrification, respectively, may have led to the increased sulfate-sulfur and nitrogen isotope compositions of the POM and SOM.
In lacustrine ecosystems, benthic grazers are generally thought to feed on sediment detritus and microalgae, although there is a paucity of information on food resource use within populations. In this study, we investigated individual level trophic signatures for grazing snails, Lymnaea stagnalis, along with primary consumers and producers in the same habitat, using carbon and nitrogen stableisotope analyses. In addition, we tested whether ontogeny and parasite presence influence food resource use. The large variation in d 13 C and d 15 N isotopic signatures indicated that individuals within a population feed on different food sources. Snails appear to have much greater individual variance in trophic behaviour than the other lacustrine species sampled (larval chironomid Chironomus plumosus, amphipods, Gammarus lacustris, zooplankton Ceriodaphnia sp. and Simocephalus vetulus). Moreover, variation among snails was not explained by shell length or the presence of parasitic infections. Habitat heterogeneity and resource availability at the microhabitat level may be the primary factors determining individual food sources.
We investigated spatial changes in the isotope ratios of the plankton food web in Lake Chany, Siberia, Russia, especially at an estuarine transition zone of the lake. The d 13 C values of particulate organic matter (POM) varied among the sampling sites, and increased with increasing pH of the lake water. This may reflect a shift by phytoplankton from using CO 2 to using bicarbonate for photosynthesis with increasing pH. The d 13 C values of zooplankton community also changed at each site along with those of the POM. This was indicative of carbon isotope changes of plankton food webs between the stations along an environmental gradient.
The first five microsatellite markers for the ide, Leuciscus idus , and four microsatellite markers for the Siberian roach, Rutilus rutilus , were designed. Cross-amplification of ide markers was examined in Siberian roach and vice versa. The number of alleles per locus ranged from three to 13 in ide and from two to eight in roach. The expected heterozygosity ranged from 0.313 to 0.909 in ide and from 0.119 to 0.775 in roach. These markers could be used to evaluate the genetic population structure of these species and other fish from the Cyprinidae family.
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