Search results for "Stable Isotopes"
showing 10 items of 167 documents
Invasive crayfish increase habitat connectivity: a case study in a large boreal lake
2013
Several studies have shown that distinct compartments of lake ecosystems are coupled via transportation of organic matter, nutrients and energy across habitat boundaries. Here we evaluate the potential of the invasive signal crayfish (Pacifastacus leniusculus (Dana)) to modify energy pathways in large boreal lakes. Using a stable isotope mixing model and calculation of the isotopic niches we estimated the contribution of different food sources to the diets of crayfish captured from different habitats, and from that inferred their potential to transport energy across the littoral-profundal gradient. The crayfish caught from the littoral area utilized mainly littoral food sources, whereas the…
Theoretical study of supernova neutrino and antineutrino scattering off the stable cadmium and lead isotopes
2017
In this thesis work, an extensive study of neutrino- and antineutrino-nucleus interactions is performed. The work is focused on supernova-neutrino scattering off the stable cadmium and lead isotopes. The studied nuclei are of interest for the investigations of neutrino-properties and for neutrino-detection experiments. The adopted nuclear-structure models are based on the quasiparticle random-phase approximation (QRPA) and the microscopic quasiparticle- phonon model (MQPM) and the cross-sections calculations are based on the Donnelly-Walecka formalism. The computed cross sections are folded with a two-parameter Fermi-Dirac distribution to obtain realistic estimates of the nuclear responses …
Response of microbial biomass and carbon dynamics to changing hydrological conditions in old peat deposits
2018
Peatlands play key roles in the global ecosystem carbon (C) balance, as important C-stores. Their efficiency as long-term C-stores or atmospheric C sink is affected by the rate of microbial mineralization. Most studies on the climate change effects on the microbial communities and C-cycling in peatlands have focused on the surface layers. This thesis compared microbial biomass, community composition and internal C cycling processes in drained vs. natural peat profiles with focus on deep old peat. Using the phospholipid fatty acid (PLFA) and rRNA gene analyses, the study particularly looked at the impact of long-term drainage and the short-term effects of temperature and water content on the…
Formation of microbial organic carbonates during the Late Jurassic from the Northern Tethys (Amu Darya Basin, Uzbekistan): implications for Jurassic …
2020
23 pages; International audience; The Late Jurassic was a period of major global carbon cycle perturbations with episodes of anoxia leading to regional accumulation of organic matter in sediments worldwide. The Tubiegatan section (SW Gissar Mountains, Uzbekistan) located in the Northern Tethys, shows atypical organic-rich limestone and marl deposits (up to 6% of total organic carbon) marked by pronounced negative excursions of δ13Ccarb (amplitude of ca. 12‰) and δ13Corg (amplitude of ca. 4‰) recorded during the Middle Oxfordian (Transversarium Zone). A transdisciplinary approach including sedimentology, palynofacies characterization, mineralogy, organic and inorganic geochemistry was carrie…
Diet composition and seasonal feeding patterns of a freshwater ringed seal (Pusa hispida saimensis)
2015
The Saimaa ringed seal (Pusa hispida saimensis) is one of the few freshwater seal populations worldwide. The major conservation issue of this critically endangered population is bycatch mortality. We used digestive tract content and stable isotopes (d13C and d15N) to estimate the diet and seasonal feeding patterns for gaining better understanding of the seals feeding habits and potential conservation implications. The diet was similar across age groups. Altogether 15 fish species were identified and the most important were smelt (Osmerus eperlanus), ruff (Gymnocephalus cernuus), perch (Perca fluviatilis), vendace (Coregonus albula) and cyprinids. The high d15N values suggested that the seal…
A stable isotope study of the hydrological and carbon cycle in meromictic lake, Lovojärvi
2012
Lake Lovojärvi, at its deepest point of 17.5 m, is permanently stratified forming two water layers. The mixolimnion (the upper layer, from 0 to 10 m depth) is affected by seasonal changes while the monimolimnion (bottom layer, from 10 to 17.5 m depth) does not mix and is not affected by seasonal changes. As a result, the lake stores large quantities of dissolved inorganic carbon and methane. I used a multiple stable isotope approach to gain insight into the carbon cycle and water balance of Lovojärvi. The δ18O and δ2H profiles reveal that at the 7 m depth in the mixolimnion, there is a sub-surface stream whose isotopic characteristics are similar to surface streams from a nearby mire, sugge…
Chemical and isotopic characterization of rainwater in volcanic, urban and industrial areas of Sicily (Italy)
2021
The chemical composition of rainwater depends on (i) the dissolution of gases and particulate matter emitted by different sources, (ii) the chemical and physical reactions occurring during local and regional scale transport, and (iii) removal processes. The source of major and trace elements dissolved in rainwater can be both natural (e.g. sea salts, volcanic emissions, geogenic dust, biogenic material) and anthropogenic (e.g. industrial plants, vehicular traffic, domestic heating, vessel traffic). A group of trace elements has been recently brought to attention, especially for their possible environmental impacts, the Technology-critical elements (TCEs): Ga, Ge, In, Te, Nb, Ta, Tl, the Pla…
Growth and population structure of perch in relation to diet in a small humic lake, Valkea-Kotinen
2011
Lake Valkea-Kotinen is a long-term ecological monitoring site in the Evo region of southern Finland .The aim of this study was to investigate the growth and population structure of perch (Perca fluviatilis L.) in relation to diet in Valkea-Kotinen in order to provide reference data for a study investigating effects of increased loading of dissolved organic matter to nearby Lake Alinen Mustajärvi. Valkea-Kotinen was predominantly inhabited by small benthivorous perch. The growth relationship between opercular bone and total length of perch in the lake is similar to those earlier analysed for nearby lakes. Compared to wider growth rates, the growth of perch was slow and similar to those in si…
Trophic ecology of piscivorous Arctic charr (Salvelinus alpinus (L.)) in subarctic lakes with contrasting food-web structures
2019
The trophic ecology of piscivorous Arctic charr (Salvelinus alpinus (L.); charr) in the food webs of large subarctic lakes is not well understood. We assessed charr diets, parasites, growth, maturity, and stable isotope ratios in Fennoscandian subarctic lakes dominated by monomorphic or polymorphic whitefish (Coregonus lavaretus (L.)) populations. Charr density was low in all lakes, except in profundal habitats. Charr shifted to piscivory at small size (16–25 cm total length) and consumed a range of prey-fish sizes (2–25 cm). Cannibalism was observed in a few individuals from one monomorphic whitefish lake. Charr matured at 37–51 cm (5–8 years old), grew to 52–74 cm maximum observed length …