Search results for "RCT"

Terrestrial Inputs Drive Seasonality in Organic Matter and Nutrient Biogeochemistry in a High Arctic Fjord System (Isfjorden, Svalbard)

2020

Climate-change driven increases in temperature and precipitation are leading to increased discharge of freshwater and terrestrial material to Arctic coastal ecosystems. These inputs bring sediments, nutrients and organic matter (OM) across the land-ocean interface with a range of implications for coastal ecosystems and biogeochemical cycling. To investigate responses to terrestrial inputs, physicochemical conditions were characterized in a river- and glacier-influenced Arctic fjord system (Isfjorden, Svalbard) from May to August in 2018 and 2019. Our observations revealed a pervasive freshwater footprint in the inner fjord arms, the geochemical properties of which varied spatially and seaso…

Variations in plasma lipids and in the LDL peak particle size after acute myocardial infarction

2002

Recent changes in chironomid communities and hypolimnetic oxygen conditions relate to organic carbon in subarctic ecotonal lakes

2018

A key question in aquatic elemental cycling is related to the influence of bottom water oxygen conditions in regulating the burial and release of carbon under climate warming. In this study, we used head capsules of Chironomidae larvae to assess community and diversity change between the past (estimated as Pre-Industrial Period) and present and to reconstruct changes in hypolimnetic oxygen conditions from 30 subarctic ecotonal lakes (northeastern Lapland) using the top-bottom paleolimnological approach applying surface sediment (topmost 0-2 cm) and reference (4-5 cm) samples. Subsequently, we tested the findings against dissolved organic carbon (DOC) concentration of the sites. We found tha…

Carbon dynamics in highly heterotrophic subarctic thaw ponds

2015

Abstract. Global warming has accelerated the formation of permafrost thaw ponds in several subarctic and arctic regions. These ponds are net heterotrophic as evidenced by their greenhouse gas (GHG) supersaturation levels (CO2 and CH4), and generally receive large terrestrial carbon inputs from the thawing and eroding permafrost. We measured seasonal and vertical variations in the concentration and type of dissolved organic matter (DOM) in five subarctic thaw (thermokarst) ponds in northern Quebec, and explored how environmental gradients influenced heterotrophic and phototrophic biomass and productivity. Late winter DOM had low aromaticity indicating reduced inputs of terrestrial carbon, wh…

Biogenic Fenton process - A possible mechanism for the mineralization of organic carbon in fresh waters.

2020

To explore the mechanisms that mineralize poorly bioavailable natural organic carbon (OC), we measured the mineralization of OC in two lake waters over long-term experiments (up to 623 days) at different pH and iron (Fe) levels. Both the microbial and photochemical mineralization of OC was higher at pH acidified to 4 than at the ambient pH 5 or an elevated pH 6. During 244 days, microbes mineralized up to 60% of OC in the 10-mu m filtrates of lake water and more than 27% in the 1-mu m filtrates indicating that large-sized microbes/grazers enhance the mineralization of OC. A reactivity continuum model indicated that the acidification stimulated the microbial mineralization of OC especially i…

Norway-Russia disaster diplomacy for Svalbard

2020

Abstract The Arctic is frequently framed as a region of disaster and conflict, as well as of opportunity and cooperation. Disaster diplomacy is one approach for examining how dealing with disasters might or might not affect conflict and cooperation, yet little work on Arctic disaster diplomacy has been completed, especially regarding specific bilateral relations. This paper contributes to filling in this gap by focusing on the post-USSR era to provide the first examination of the prospects and relevance of Norway-Russia disaster-related interaction for the Svalbard archipelago. As a discussion paper focusing on one case study, Norway-Russia disaster diplomacy is analysed in the context of S…

Data from: How to fight multiple enemies: target-specific chemical defences in an aposematic moth

2017

Animals have evolved different defensive strategies to survive predation, among which chemical defences are particularly widespread and diverse. Here we investigate the function of chemical defence diversity, hypothesising that such diversity has evolved as a response to multiple enemies. The aposematic wood tiger moth (Arctia plantaginis) displays conspicuous hindwing colouration and secretes two distinct defensive fluids, from their thoracic glands and abdomen. We presented fluids from lab-reared moths to two biologically relevant predators, birds and ants, and measured their reaction in controlled bioassays (no information on colour was provided). We found that defensive fluids are targe…

Data from: Mechanisms of reciprocity and diversity in social networks: a modelling and comparative approach

2018

Three mechanisms have been proposed to underlie reciprocation of social behaviors in gregarious animals: ‘calculated reciprocity’, ‘emotional bookkeeping’ and ‘symmetry-based reciprocity’. Among these explanations, emotional book-keeping has received the broadest support from experimental and observational studies. On the other hand, three individual-based models have shown that reciprocation may emerge via ‘symmetry-based reciprocity’, ‘emotional bookkeeping’, or a combination of both mechanisms. Here we use these three models to assess their relative fit with empirical data on reciprocation and social network structure across different groups and species of macaques. We collected grooming…

Data from: De novo synthesis of chemical defences in an aposematic moth

2019

Many animals protect themselves from predation with chemicals, both self-made or sequestered from their diet. The potential drivers of the diversity of these chemicals have been long studied, but our knowledge them, and their acquisition mode, is heavily based on specialist herbivores that sequester their defences. The wood tiger moth (Arctia plantaginis, Linnaeus, 1758) is a well-studied aposematic species, but the nature of its chemical defences has not been fully described. Here we report the presence of two methoxypyrazines, 2-sec-butyl-3-methoxypyrazine and 2-isobutyl-3-methoxypyrazine, in the moths’ defensive secretions. By raising larvae on an artificial diet, we confirm, for the fir…

Data from: Grazing decreases N partitioning among coexisting plant species

2018

1. Herbivores play a key role in shaping ecosystem structure and functions by influencing plant and microbial community composition and nutrient cycling. 2. This study investigated the long-term effects of herbivores on plant resource acquisition. We explored differences in the natural δ15N signatures in plant, microbial and soil N pools, and examined mycorrhizal colonization in two tundra sites that have been either lightly or heavily grazed by reindeer for more than 50 years. The study examined changes in nutrient acquisition in five common tundra plants with contrasting traits and mycorrhiza status; the mycorrhizal dwarf shrubs, Betula nana, Vaccinium myrtillus and Empetrum hermaphroditu…