1,720,969 research outputs found
Replication Data for: Arctic cold seeps alter dissolved organic matter composition at the Svalbard continental margin and the Barents Sea
No full textAbstract: Dissociating gas hydrates, submerged permafrost, and gas bearing sediments release methane to the water column from a multitude of seeps in the Arctic Ocean. The seeping methane dissolves and supports the growth of aerobic methane oxidizing bacteria (MOB), but the effect of seepage and seep related biogeochemical processes on water column dissolved organic matter (DOM) dynamics is not well constrained. We compared dissolved methane, nutrients, chlorophyll, and particulate matter concentrations and methane oxidation (MOx) rates from previously characterized seep and non-seep areas at the continental margin of Svalbard and the Barents Sea in May and June 2017. DOM molecular composition was determined by Electrospray Ionization Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). We found that the chemical diversity of DOM was 3 to 5 % higher and constituted more protein- and lipid-like composition near methane seeps when compared to non-seep areas. Distributions of nutrients, chlorophyll, and particulate matter however, were essentially governed by the water column hydrography and primary production. We hypothesised that the organic intermediates directly derived from seepage or indirectly from seep-related biogeochemical processes, e.g. MOx, can modify the composition of DOM leading to distinct DOM molecular-level signatures in the water column at cold seeps
Replication data for: Cold Seeps and Coral Reefs in Northern Norway: carbon cycling in marine ecosystems with coexisting features
No full textThis dataset contains water column measurements, dissolved organic matter compositions, hydrographical profiles and 16S rRNA data collected from the Lofoten-Vesteralen seep site at Northern Norway. Data are presented along with the R codes for the replication of analyses, and figures that were added in our submitted paper.
We recommend using R (v4.3.1) and R Studio (2023.06.1) which can access all codes and data. Running codes in the given order will create corresponding data tables and all the figures that were used in the article.Cold seeps and cold-water corals (CWCs) coexist on Northern Norway’s continental shelf at the Hola trough between Lofoten and Vesterålen. Here, cold seeps release methane from the seabed, yet none reaches the sea-surafce. Instead, the methane dissolves and disperses in the ocean where it is ultimately consumed by methane-oxidizing microorganisms. These microorganisms metabolize methane and release carbon dioxide and dissolved organic matter (DOM), which impact the biogeochemical habitat of CWCs in close vicinity of cold seeps. We investigated the biogeochemistry of carbon, carbon isotopes, nutrients, dissolved organic matter compositions, and microbial diversity in the water column. Our results indicated that dissolved inorganic carbon concentrations were 29% higher near cold seeps with modified carbon's isotopic compositions. The hydrophysical parameters and surface-to-bottom control of sinking particles mainly govern water column productivity and nutrient cycle. DOM compositions implied that the seep-associated microbiomes modify DOM's chemical diversity and isotopic composition at CWCs and the entire water column near cold seeps.
We suggest cold seeps and CWCs coexist in Northern Norway's continental shelves; however, enhanced water temperatures and consequent increase in methane release at cold seeps may mitigate the ecological role and functioning of CWC reefs in the future
Replication data for: Compositions of dissolved organic matter in the ice-covered waters above the Aurora hydrothermal vent system, Gakkel Ridge, Arctic Ocean
No full textThis dataset contains water column measurements, dissolved organic matter compositions, and hydrographical profiles collected from Aurora Hydrothermal vents at Gakkel Ridge, Arctic Ocean. Data are presented along with the R codes for the replication of analyses, and figures that were added in our submitted paper.This study provides an extensive characterization of the water column in the Aurora hydrothermal vent area. To the best of our knowledge, this is the first attempt to differentiate hydrothermal plume and non-plume dissolved organic matter compositions in the deep ocean (<4000 m), at ice-covered Arctic high latitudes (82.9 N).We recommend using R Studio (v1.4) to run R project file (.Rproj) which can access all codes and data. Running codes in the given order will create corresponding data tables and all the figures that were used in the article
Replication Data for: Elevated methane alters dissolved organic matter composition in the Arctic Ocean cold seeps
No full textThis dataset contains water column measurements, dissolved organic matter compositions, and hydrographical profiles collected from the Norskebanken seep site at Northern Svalbard, Arctic Ocean. Data are presented along with the R codes for the replication of analyses, and figures that were added in our submitted paper.
We recommend using R (v4.3.1) and R Studio (2023.06.1) to run R project file (.Rproj) which can access all codes and data. Running codes in the given order will create corresponding data tables and all the figures that were used in the article.Cold seeps release methane (CH4) from the seafloor to the water column, which fuels microbially mediated aerobic methane oxidation (MOx). Methane oxidising bacteria (MOB) utilise excess methane, and the MOB biomass serves as a carbon source in the food web. Yet, it remains unclear if and how MOx modifies the composition of dissolved organic matter (DOM) in cold seeps. We investigated MOx rates, DOM compositions and the microbial community during ex-situ incubations of seawater collected from an active cold seep site at Norskebanken (north of the Svalbard archipelago) in the Arctic Ocean. For comparison, we used seawater collected from a control site (a non-seep environment). Samples were incubated with and without methane amendments. Samples amended with methane (~1 µM final concentration) showed elevated rates of MOx in both seep and non-seep incubations. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analyses showed that the number of DOM formulas (i.e., molecular diversity) increased by up to 39 % in these incubations. In contrast, the number of formulas decreased by 20 % in samples not amended with methane, both from non-seep and seep locations. DOM composition was thus altered towards a more diverse and heterogeneous composition along with elevated methanotrophic activity in methane-amended conditions. In addition to microbial DOM production, abating microbial diversity indicates that elevated DOM diversity was potentially related to grazing pressure on bacteria. The diversity of DOM constituents, therefore, likely increased with the variety of decaying cells contributing to DOM production. Furthermore, based on a principal coordinate analysis, we show that the final DOM composition of non-seep samples amended with methane became more resemblant to that of seep samples. This suggests that methane intrusions will affect water column DOM dynamics similarly, irrespective of the water column’s methane history. </p
Biogeochemistry of dissolved organic matter in Arctic Ocean waters charged with methane
Full text linkDissolved organic matter (DOM) is defined as organic matter that is smaller than a nominal pore size filter (e.g., 0.7 µm) that passes through during the filtration of aquatic samples. It comprises the largest reservoir of reduced carbon (700 Pg C) in the oceans. The DOM pool is in close interaction with all the elemental cycles and food chains in the ocean and is an essential component in the marine microbial loop.
Methane is seeping from numerous geological sources in the Arctic Ocean associated with multiple mechanisms that elevate methane production and release. Independent of the mechanism, however, liberated methane is predominantly consumed in the water column by methanotrophic bacteria (MOB), which use methane as a source of carbon and energy during an aerobic enzymatic reaction called methane oxidation (MOx). In sedimentary fluid flow systems such as cold seeps or hydrothermal vents, the amount of methane release and subsequent MOx would be substantial and further trigger other ecosystem processes such as bacterial growth and heterotrophic consumption and consequent mechanisms that alter DOM composition in the water column.
Since methane is one of the most potent greenhouse gasses in the atmosphere and due to its subsequent effect on global warming, it has been quantified extensively in the oceanic environments and its fate in the water column has been investigated in different types of geological settings. However, the effects of methane emanation and methane-driven processes on DOM dynamics in the water column have been merely constrained. The main objective of this thesis was to unravel the modifications of DOM composition in relation to methane release in the Arctic Ocean cold seeps and hydrothermal vents
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
