Search results for "Stable isotope ratio"
showing 10 items of 200 documents
Chironomid incorporation of methane-derived carbon in plankton- and macrophyte-dominated habitats in a large shallow lake
2018
1. While 13 C-depleted carbon derived from biogenic methane can substantially contribute to the benthic secondary production in deep stratified lakes, its role in shallow lakes is less clear. We investigated the dynamics of δ13 C and δ15 N in the larvae of Chironomus plumosus throughout an annual cycle in two ecologically distinct basins (open-water plankton-dominated and sheltered macrophyte- covered) of a large (270 km2 ), shallow, polymictic and eutrophic lake (Võrtsjärv, Estonia, North Europe). The larval stable isotopic compositions were linked to the presence of methane-oxidising bacteria (MOB) in larval guts and sediments. 2. Molecular detection of MOB revealed their presence in vari…
Methane oxidation in industrial biogas plants-Insights in a novel methanotrophic environment evidenced by pmoA gene analyses and stable isotope label…
2018
Abstract A broad methanotrophic community consisting of 16 different operational taxonomic units (OTUs) was detected by particulate methane monooxygenase A (pmoA) gene analyses of reactor sludge samples obtained from an industrial biogas plant. Using a cloning-sequencing approach, 75% of the OTUs were affiliated to the group of type I methanotrophs (γ-Proteobacteria) and 25% to type II methanotrophs (α-Proteobacteria) with a distinct predominance of the genus Methylobacter. By database matching, half of the total OTUs may constitute entirely novel species. For evaluation of process conditions that support growth of methanotrophic bacteria, qPCR analyses of pmoA gene copy numbers were perfor…
Cribra orbitalia as a potential indicator of childhood stress: Evidence from paleopathology, stable C, N, and O isotopes, and trace element concentra…
2016
Cribra orbitalia (CO), or porotic hyperostosis (PH) of the orbital roof, is one of the most common pathological conditions found in archaeological subadult skeletal remains. Reaching frequencies higher than 50% in many prehistoric samples, CO has been generally attributed to a variety of factors including malnutrition (e.g., megaloblastic anemia) and parasitism. In this study, we tested the relationship between CO, trace element concentrations, and stable isotope values (δ13C, δ15N, δ18O) in subadult skeletons from a 17th to 18th century cemetery in the historic town of Jēkabpils, Latvia. A total of 28 subadults were examined, seven of which (25%) showed evidence of CO. Bioarchaeological ev…
Parasite infection alters host stable-isotope composition under controlled feeding
2016
1) Stable isotopes are widely used for studying trophic relationships, but variation driven by environmental conditions or food availability complicates the interpretation of trophic dynamics. Parasites are ubiquitous and known to affect physiological functions of their hosts, but only few studies have assessed the effects of parasites on isotope composition of hosts. 2) We measured the changes in two of the most commonly used stable isotopes in food-web studies, nitrogen (i.e. 15N:14N ratio; denoted as δ15N) and carbon (13C:12C; δ13C) in Daphnia hosts exposed to infection by a parasitic micosporidian in the laboratory. Isotopic signatures of hosts fed a standardised controlled diet were co…
Long-term summer temperature variations in the Pyrenees from detrended stable carbon isotopes
2015
Abstract Substantial effort has recently been put into the development of climate reconstructions from tree-ring stable carbon isotopes, though the interpretation of long-term trends retained in such timeseries remains challenging. Here we use detrended δ13C measurements in Pinus uncinata tree-rings, from the Spanish Pyrenees, to reconstruct decadal variations in summer temperature back to the 13th century. The June-August temperature signal of this reconstruction is attributed using decadally as well as annually resolved, 20th century δ13C data. Results indicate that late 20th century warming has not been unique within the context of the past 750 years. Our reconstruction contains greater …
Persistent link between Caribbean precipitation and Atlantic Ocean circulation during the Last Glacial revealed by a speleothem record from Puerto Ri…
2020
The sensitivity of tropical Atlantic precipitation patterns to the mean position of the Intertropical Convergence Zone (ITCZ) at different time scales is well‐known. However, recent research suggests a more complex behavior of the northern hemispheric tropical rain belt related to the ITCZ in the western tropical Atlantic. Here we present a precisely dated speleothem multi‐proxy record from a well‐monitored cave in Puerto Rico, covering the period between 46.2 and 15.3 ka. The stable isotope and trace element records document a pronounced response of regional rainfall to abrupt climatic excursions in the North Atlantic across the Last Glacial such as Heinrich stadials and Dansgaard/Oeschger…
Petrography and carbonate isotope stratigraphy from MIS AND-1B core, Antarctica: Evidence of the early Pliocene warming event
2011
Abstract A large portion of ANDRILL (ANtarctic geological DRILLing) core AND-1B recovered in the Western Ross Sea and spanning the early Pliocene has been investigated in order to obtain a detailed carbonate isotope record from Antarctic margin sediments through the early Pliocene warming event. Petrographic observations and mineralogical analyses reveal the authigenic nature of the carbonate and small proportions of Fe and Mg incorporated within the calcite lattice. High productivity conditions testified by ~ 80 m-thick diatomite interval (383 to 460 mbsf) well fit with the composite nature of the authigenic carbonate generally characterizing organic matter-rich sediments. As is known, sed…
Carbon and nitrogen stable isotope ratios of soils and grasses as indicators of soil characteristics and biological taxa
2019
Abstract The use of stable isotope techniques can assist in understanding interactions of plants with various abiotic and biotic processes. In the research, we focused on carbon (C) and nitrogen (N) isotopes because they are the most important resources influencing plant function and the biogeochemical cycles. The 13C/12C and 15N/14N ratios in plants and in soils and the relationships between these ratios and biological and environmental factors of widely distributed native C3 plants (couch grass, plantain and yarrow) collected from two sites in St. Petersburg, Russia were studied. The soil characteristics of the sites were rather different. This had a significant effect on the isotope rati…
Sr-isotope analysis of speleothems by LA-MC-ICP-MS: High temporal resolution and fast data acquisition
2017
Speleothems are well established climate archives. A wide array of geochemical proxies, including stable isotopes and trace elements are present within speleothems to reconstruct past climate variability. However, each proxy is influenced by multiple factors, often hampering robust interpretation. Sr isotope ratios (87Sr/86Sr) can provide useful information about water residence time and water mixing in the host rock, as they are not fractionated during calcite precipitation. Laser ablation multi-collector-inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) has rarely been used for determination of Sr isotope signatures in speleothems, as speleothems often do not possess appropriate…
Carbon stable isotope composition of charophyte organic matter in a small and shallow Spanish water body as a baseline for future trophic studies
2015
<p>Quantitative descriptions of foodweb structure based on isotope niche space require knowledge of producers’ isotopic signatures. In freshwater ecosystems charophytes are one of the main components of submerged vegetation and the feeding base for many herbivorous consumers, but knowledge about their organic carbon isotopic signatures is sparse. In this study, the δ<sup>13</sup>C organic values (and organic %C and %N) of the four species of submerged macrophytes (three charophytes - <em>Chara hispida</em>, <em>Nitella hyalina</em> and <em>Tolypella glomerata </em>- and one angiosperm, <em>Myriophyllum spicatum</em>) growing …