Unraveling organic matter fluxes in Coastal Antarctica using compound-specific analysis of amino acid δ15N

editorial reviewedMarine food webs are complex networks of ecological interactions, but can essentially be summarized using two dimensions, leading to the traditional depiction of food webs as bi-dimensional diagrams. The horizontal dimension of these diagrams encompasses the diversity of producers sustaining the food web. Their vertical structure is dictated by the trophic position of the consumers (e.g. primary consumers, secondary consumers, omnivores, etc.) relative to the food web baseline. Trophic positions provide simple ways to assess organisms’ functional roles and estimate energy flow through ecological communities, while taking into account complex processes such as omnivory. For these reason, they have been a central element to isotope ecologists‘ toolboxes for decades. The most common way of estimating trophic position involves measuring bulk δ15N of consumer tissue and baseline item(s). However, applicability of this time-tested method can be impaired when actual food web baseline are hard or impossible to identify due to temporal mismatch, consumer physiology, or logistical constraints. Coastal Antarctica, with its remoteness, intense seasonality, and extreme conditions, provide a striking example of these limitations, leading to sometimes unrealistic estimations of trophic position. Here, to circumvent this issue, we used compound-specific isotope analysis of amino acid δ15N to estimate trophic positions of 5 key-members of Antarctic zoobenthos: the sea urchin Sterechinus neumayeri, the sea star Odontaster validus, the nemertean worm Parborlasia corrugatus, the scallop Adamussium colbecki, and the anemone Isotealia antarctica. When compared with estimates calculated using the traditional bulk δ15N method, trophic position estimation through amino acid δ15N showed good correspondence for O. validus and P. corrugatus, but not for the other 3 taxa. Our results suggest that use of the traditional bulk method leads to slight underestimation of trophic position for S. neumayeri, strong underestimation for A. colbecki, and considerable overestimation for I. antarctica. Results also suggest that not all investigated seem to depend upon the same food web baseline. Overall, our findings confirm the interest of the more novel amino acid δ15N method to delineate energy fluxes in complex marine ecosystems with multiple primary producers and intricate trophic interactions, such as coastal Antarctica

Using pharmacy dispensing data to predict falls in older individuals

Aims Associations between individual medication use and falling in older individuals are well-documented. However, a comprehensive risk score that takes into account overall medication use and that can be used in daily pharmacy practice is lacking. We, therefore, aimed to determine whether pharmacy dispensing records can be used to predict falls. Methods A retrospective cohort study was conducted using pharmacy dispensing data and self-reported falls among 3454 Dutch individuals aged >= 65 years. Two different methods were used to classify medication exposure for each person: the drug burden index (DBI) for cumulative anticholinergic and sedative medication exposure as well as exposure to fall risk-increasing drugs (FRIDs). Multinomial regression analyses, adjusted for age and sex, were conducted to investigate the association between medication exposure and falling classified as nonfalling, single falling and recurrent falling. The predictive performances of the DBI and FRIDs exposure were estimated by the polytomous discrimination index (PDI). Results There were 521 single fallers (15%) and 485 recurrent fallers (14%). We found significant associations between a DBI >= 1 and single falling (adjusted odds ratio: 1.30 [95% confidence interval {CI}: 1.02-1.66]) and recurrent falling (adjusted odds ratio: 1.60 [95%CI: 1.25-2.04]). The PDI of the DBI model was 0.41 (95%CI: 0.39-0.42) and the PDI of the FRIDs model was 0.45 (95%CI: 0.43-0.47), indicating poor discrimination between fallers and nonfallers. Conclusion The study shows significant associations between medication use and falling. However, the medication-based models were insufficient and other factors should be included to develop a risk score for pharmacy practice

Evaluatie Regeling brede weersverzekering

The agricultural sector has limited opportunities to avoid risks of weather events for open field crops.However, damage caused by extreme weather conditions (such as heavy rain or hail) can have amajor impact on the financial position of the farms and the whole agricultural sector.Before 2002 the Dutch government regularly compensated damage caused by extreme weatherevents. Nowadays the government encourages farmers to participate in a weather insurance schemeby granting a premium subsidy, thus trying to create a commercial market for weather insurances.This report evaluates the premium subsidy. The core questions are first if the subsidy has led to acommercially attractive weather insurance scheme and second if the premium subsidy has reduced thenumber of requests for compensation and the amount. The answer to the first question is no; due to alack of empirical evidence, there is no clear objective answer to the second question

Response of the North Atlantic surface and intermediate ocean structure to climate warming of MIS 11

Investigating past interglacial climates not only help to understand how the climate system operates in general, it also forms a vital basis for climate predictions. We reconstructed vertical stratification changes in temperature and salinity in the North Atlantic for a period some 400 ka ago (MIS11), an interglacial time analogue of a future climate. As inferred from a unique set of biogeochemical, geochemical, and faunal data, the internal upper ocean stratification across MIS 11 shows distinct depth-dependent dynamical changes related to vertical as well as lateral shifts in the upper Atlantic meridional circulation system. Importantly, transient cold events are recognized near the end of the long phase of postglacial warming at surface, subsurface, mid, and deeper water layers. These data demonstrate that MIS 11 coolings over the North Atlantic were initially triggered by freshwater input at the surface and expansion of cold polar waters into the Subpolar Gyre. The cooling signal was then transmitted downwards into mid-water depths. Since the cold events occurred after the main deglacial phase we suggest that their cause might be related to continuous melting of the Greenland ice sheet, a mechanism that might also be relevant for the present and upcoming climate

Exploration speed in captivity predicts foraging tactics and diet in free-living red knots

1. Variation in foraging tactics and diet is usually attributed to differences in morphology, experience and prey availability. Recently, consistent individual differences in behaviour (personality) have been shown to be associated with foraging strategies. Bolder or more exploratory individuals are predicted to have a faster pace‐of‐life and offset the costs of moving more or in risky areas, with higher energetic gains by encountering profitable foraging opportunities and prey. However, the relationship between personality, foraging and diet is poorly understood. 2. We investigated how exploratory behaviour in red knots Calidris canutus is associated with foraging tactics and diet by combining laboratory experiments, field observations and stable isotope analysis. First, we developed a mobile experimental arena to measure exploration speed in controlled settings. We validated the method by repeated testing of individuals over time and contexts. This setup allowed us to measure exploratory personality at the field site, eliminating the need to bring birds into captivity for long periods of time. After releasing birds within days of their capture, we asked whether exploration speed was associated with differences in foraging tactics and diet in the wild. 3. We found that tactile foraging red knots mainly caught hard‐shelled prey that are buried in the sediment, whereas visual foraging knots only captured soft preys located close to or on the surface. We also found that faster explorers showed a higher percentage of visual foraging than slower explorers. By contrast, morphology (bill length and gizzard size) had no significant effect on foraging tactics. Diet analysis based on δ(15)N and δ(13)C stable isotope values of plasma and red blood cells confirmed our field observations with slower explorers mainly consumed hard‐shelled prey while faster explorers consumed more soft than hard‐shelled prey. 4. Our results show that foraging tactics and diet are associated with a personality trait, independent of morphological differences. We discuss how consistent behaviour might develop early in life through positive feedbacks between foraging tactics, prey type and foraging efficiency

Asynchronous responses of aquatic ecosystems to hydroclimatic forcing on the Tibetan Plateau

High-altitude ecosystems react sensitively to hydroclimatic triggers. Here we evaluated the ecological and hydrological changes in a glacier-influenced lake (Hala Hu, China) since the last glacial. Rapid fluctuations of aquatic biomarker concentrations, ratios, and hydrogen isotope values, from 15 to 14,000 and 8 to 5000 years before present, provided evidence for aquatic regime shifts and changes in lake hydrology. In contrast, most negative hydrogen isotope values of terrestrial biomarkers were observed between 9 and 7,000 years before present. This shows that shifts of vapour sources and increased precipitation amounts were not relevant drivers behind ecosystem changes in the studied lake. Instead, receding glaciers and increased meltwater discharge, driven by higher temperatures, caused the pronounced ecological responses. The shifts within phytoplankton communities in the Late Glacial and mid Holocene illustrate the vulnerability of comparable ecosystems to climatic and hydrological changes. This is relevant to assess future ecological responses to global warming

Differential Expression of Proinflammatory Cytokines and Their Inhibitors during the Course of Meningococcal Infections

Circulating concentrations of tumor necrosis factor-α (TNF), interleukin (IL)-1β, IL-6, IL-1 receptor antagonist (IL-1ra), and soluble TNF receptors p55 (sTNFr-55) and p75 (sTNFr-75) and ex vivo production ofTNF, IL-1, IL-6, and IL-1ra using a whole blood culture system were measured during the acute and convalescent stages of meningococcal infection. Circulating TNF and IL-1 were below detection level, whereas IL-6 and IL-1ra, sTNFr-55, and sTNFr-75 were increased at admission. The ex vivo production of proinflammatory cytokines TNF, IL-1, and IL-6 was suppressed at admission and restored gradually during recovery. On the contrary, the production of the antiinflammatory IL-1ra was increased at admission. The elevated concentrations of both IL-1ra and sTNFr early in the course of infection suggest a regulatory role for these antiinflammatory compounds. The observed down-regulation of the ex vivo production of TNF, IL-1, and IL-6 and up-regulation of the production of IL-1 ra in the acute stage may indicate a protective regulation mechanis

Fluorescence Lifetime Imaging Microcopy of Extravasating Cancer Cells in the Mouse Microenvironment

Objective. To determine (i) whether early viral kinetics or other markers during a modified treatment regimen are predictors of treatment outcome and (ii) whether fast responders can be treated for 24 weeks, without compromising the sustained virologic response (SVR) rate. Material and methods. One hundred "difficult-to-treat'' chronic hepatitis C patients (46 previous non-responders/relapsers (any genotype), 54 treatment-naive patients genotypes 1 and 4) were treated with triple antiviral induction therapy: amantadine hydrochloride and ribavirin, combined with 6 weeks interferon alfa-2b induction (weeks 1-2: 18 MU/day, weeks 3-4: 9 MU/day, weeks 5-6: 6 MU/day), thereafter combined with weekly peginterferon alfa-2b. Fast responders (>= 3 log(10) HCV RNA decline at week 4) were randomized to 24 or 48 weeks. Slow responders (= or = 5 IU/mL at week 16 became non-SVR. In previous non-responders/relapsers, the predictive value for SVR was 83% if HCV RNA was = 5 IU/mL at week 8 became non-SVR. Conclusions. With high-dose interferon induction, SVR and non-SVR can be predicted reliably within 16 weeks. Fast responders can be treated for 24 weeks, and SVR is independent of baseline viral load in fast responders

A multiproxy study of past environmental changes in the Sea of Okhotsk during the last 1.5 Ma

Long-chain diols have been detected in a wide range of environments and have been used to reconstruct past environmental changes, however only a few long-term records exist to date. Here we reconstructed past environmental changes in the central Sea of Okhotsk over the last 1.5 million years, covering the Mid-Pleistocene Transition (MPT). Sea surface temperatures (SST) reconstructed using the Long-Chain Diol Index (LDI) reflects glacial/interglacial changes. However, when compared with other organic paleothermometers (Uk′37 and TEXL86) the LDI-SST is lower during interglacials and similar or higher during glacials, possibly suggesting a shift of diol production season during interglacials. The LDI-SST does not change in periodicity around the MPT as observed for the TEXL86, likely due to this seasonal shift. Diatom productivity, as recorded by 1,14-diols and biogenic opal content, increased during the main deglaciations with a succession from Proboscia diatoms to diatoms with a more heavily silicified shell, confirming that primary productivity in the central Sea of Okhotsk is driven by sea-ice progress and retreat. In contrast to the LDI-SST, the 1,14-diols record shows a change in periodicity around the MPT from 41- to 100-kyr cycle, suggesting an influence of orbital parameters on diatom productivity. In the central Sea of Okhotsk, the relative amount of C32 1,15-diol (FC32 1,15), a proxy for riverine input, correlates with sea-level change with more riverine-derived material reaching the core site when the Amur River mouth is closer at lower sea-levels. In agreement, FC32 1,15 shows a change in periodicity during the MPT, with the appearance of a 100-kyr cycle. Our results show that the long chain diols can provide important paleoceanographic information in subpolar environments over long time scales, but that temperature reconstructions can be severely impacted by changes in seasonality