Wegberm biedt hulp tegen bestuivingscrisis

De achteruitgang van bloemzoekende insecten is een bedrieging voor een scala aan ecologische processen en diensten die deze dieren verzorgen. Wegbermen zijn vaak rijk aan bloeiende kruiden en kunnen daardoor van groot belang zijn voor deze dieren. Maar hoe kunnen deze bermen het beste beheerd worden? Wageningen Universiteit deed een experiment in een grazige berm, waarbij bloembezoek bekeken werd in relatie to vijf maairegime

Biogeochemical cycle in a coccolithophorid bloom

The biogeochemical properties of an extensive bloom of the coccolithophore, Emiliania huxleyi, at the shelf break in the northern Gulf of Biscay was investigated in June 2006. Total Alkalinity (TA) values in the water column showed strong non-conservative behaviour indicative of the impact of calcification, with the highest TA anomalies (up to 26μmol.kg-1) in the high reflectance coccolith patch. Partial pressure of CO2 (pCO2) values ranged from 250 to 338μatm and the area was found to act as a sink for atmospheric CO2.Overall, pCO2@13°C (pCO2 normalized at a constant temperature of 13°C) in the water column was negatively related to TA anomalies in agreement with an overall production of CO2 related to calcification. Hence, the calcifying phase of the E. huxleyi bloom decreased the sink of atmospheric pCO2, but did not reverse the direction of the flux. Rates of pelagic respiration up to 5.5mmol O2.m-3.d-1 suggested a close coupling between primary production and respiration and/or between organic carbon content and respiration. Benthic respiration rates were quite low and varied between 2 and 9mmol O2.m-3.d-1, in agreement with the fact that the study area consists of sandy sediments with low organic matter content. Benthic respiration was well correlated to the chlorophyll a content of the top 1cm of the sediment cores. Evidence was found for dissolution of CaCO3 due to the acidification of superficial sediments in relation to the production of CO2 and the oxidation of H2S in the oxic layers

Estimates of ikaite export from sea ice to the underlying seawater in a sea ice-seawater mesocosm

The precipitation of ikaite and its fate within sea ice is still poorly understood.We quantify temporal inorganic carbon dynamics in sea ice from initial formation to its melt in a sea ice.seawater mesocosm pool from 11 to 29 January 2013. Based on measurements of total alkalinity (TA) and total dissolved inorganic carbon (TCO2), the main processes affecting inorganic carbon dynamics within sea ice were ikaite precipitation and CO2 exchange with the atmosphere. In the underlying seawater, the dissolution of ikaite was the main process affecting inorganic carbon dynamics. Sea ice acted as an active layer, releasing CO2 to the atmosphere during the growth phase, taking up CO2 as it melted and exporting both ikaite and TCO2 into the underlying seawater during the whole experiment. Ikaite precipitation of up to 167 μmolkg-1 within sea ice was estimated, while its export and dissolution into the underlying seawater was responsible for a TA increase of 64.66 μmolkg-1 in the water column. The export of TCO2 from sea ice to the water column increased the underlying seawater TCO2 by 43.5 μmolkg-1, suggesting that almost all of the TCO2 that left the sea ice was exported to the underlying seawater. The export of ikaite from the ice to the underlying seawater was associated with brine rejection during sea ice growth, increased vertical connectivity in sea ice due to the upward percolation of seawater and meltwater flushing during sea ice melt. Based on the change in TA in the water column around the onset of sea ice melt, more than half of the total ikaite precipitated in the ice during sea ice growth was still contained in the ice when the sea ice began to melt. Ikaite crystal dissolution in the water column kept the seawater pCO2 undersaturated with respect to the atmosphere in spite of increased salinity, TA and TCO2 associated with sea ice growth. Results indicate that ikaite export from sea ice and its dissolution in the underlying seawater can potentially hamper the effect of oceanic acidification on the aragonite saturation state (ωaragonite) in fall and in winter in ice-covered areas, at the time when ωaragonite is smallest

Surface Texturization of Breast Implants Impacts Extracellular Matrix and Inflammatory Gene Expression in Asymptomatic Capsules:

Background: Texturing processes have been designed to improve biocompatibility and mechanical anchoring of breast implants. However, a high degree of texturing has been associated with severe abnormalities. In this study, the authors aimed to determine whether implant surface topography could also affect physiology of asymptomatic capsules. Methods: The authors collected topographic measurements from 17 different breast implant devices by interferometry and radiographic microtomography. Morphologic structures were analyzed statistically to obtain a robust breast implant surface classification. The authors obtained three topographic categories of textured implants (i.e., “peak and valleys,” “open cavities,” and “semiopened cavities”) based on the cross-sectional aspects. The authors simultaneously collected 31 Baker grade I capsules, sorted them according to the new classification, established their molecular profile, and examined the tissue organization. Results: Each of the categories showed distinct expression patterns of genes associated with the extracellular matrix (Timp and Mmp members) and inflammatory response (Saa1, Tnsf11, and Il8), despite originating from healthy capsules. In addition, slight variations were observed in the organization of capsular tissues at the histologic level. Conclusions: The authors combined a novel surface implant classification system and gene profiling analysis to show that implant surface topography is a bioactive cue that can trigger gene expression changes in surrounding tissue, even in Baker grade I capsules. The authors’ new classification system avoids confusion regarding the word “texture,” and could be transposed to implant ranges of every manufacturer. This new classification could prove useful in studies on potential links between specific texturizations and the incidence of certain breast-implant associated complications

Melt pond biogeochemistry in central Arctic: first insights from MOSAiC campaign

We undertook a melt pond survey during the international drift campaign MOSAiC Leg 5 (from 22 August to 18 September 2020) to understand variations in climate gases (CO2, CH4, N2O and DMS) and nutrients in melt ponds during the open water and freezing periods, and to study the interactions with atmospheric and ecological parameters (Figure 1a). Inside those melt ponds with a darker color, we found significant quantities of floating organic material within the pond water, along with significant further organic material settled at the bottom of the pond and frozen into the ice (Figure 1b). These floating and sedimented materials were both white and green/brown; the green/brown material was mainly composed of phytoplankton “Melosira arctica”, while the white material was composed of re-mineralized organic matter during degradation (including the remains of krill and other zooplankton). There were strong vertical gradients in physical parameters from the surface to the bottom of the melt pond (within 1 m depth): from +0.2°C to –1.5°C for temperature, from 0 to 29 psu for salinity, and 9.2 to 13.5 mg L–1 for dissolved oxygen (DO). The DO minimum layer (below 9 mg L–1) corresponded with a salinity of 25 psu, which generally occurred at approximately 0.6 m depth, and it increased to over 13 mg L–1 at the atmospheric interface. At the end of Leg 5 (mid-September 2020), these strong gradients disappeared, likely due to the mixing events during the cooling and freezing periods. Prior to and during the freezing period, CO2 flux was measured periodically within the melt pond with a floating chamber system. Because measured in situ CO2 concentration at the melt pond surface (top 10 cm) was low (321 ppm) compared to the atmosphere (approximately 400 ppm), air–to-melt pond CO2 flux was negative (melt pond was acting as a sink for atmospheric CO2) around –3.9 mmol m–2 day–1. Therefore, the melt pond water absorbs significant amounts of CO2 from the atmosphere. We also found extremely low CO2 concentrations (170 ppm) at the freshwater/seawater interface (0.6 m depth) corresponding to the same depth as the DO minimum. Therefore, we expected that if melt pond water is mixed vertically by the wind, cooling, crack formation, and ice movement, the melt pond could become an even stronger sink for atmospheric CO2. Ice cores collected from the bottom of the melt pond were porous at the top 0.50 m, and contain large quantities of organic material similar to that identified floating in the water column This accumulation of material and ongoing degradation processes over the pond bottom ice would contribute significantly to the turnover of carbon, sulphur and nitrogen containing gases cycles within melt pond water and thereby gas exchange process with the atmosphere.MOSAi

Determination of air‐sea ice transfer coefficient for CO2: Significant contribution of gas bubble transport during sea ice growth

Air‐ice CO2 fluxes were measured continuously from the freezing of a young sea‐ice cover until its decay. Cooling seawater was as a sink for atmospheric CO2 but asthe ice crystalsformed,sea ice shifted to a source releasing CO2 to the atmosphere throughout the whole ice growth. Atmospheric warming initiated the decay, re‐shifting sea‐ice to a CO2 sink. Combining these CO2 fluxes with the partial pressure of CO2 within sea ice, we determined gas transfer coefficients for CO2 at air‐ice interface for growth and decay. We hypothesize that this difference originates from the transport of gas bubbles during ice growth, while only diffusion occurs during ice melt. In parallel, we used a 1D biogeochemical model to mimic the observed CO2 fluxes. The formation of gas bubbles was crucial to reproduce fluxes during ice growth where gas bubbles may account for up to 92 % of the upward CO2 fluxes

Diurnal changes in seawater carbonate chemistry speciation at increasing atmospheric carbon dioxide

Natural variability in seawater pH and associated carbonate chemistry parameters is in part driven by biological activities such as photosynthesis and respiration. The amplitude of these variations is expected to increase with increasing seawater carbon dioxide (CO2) concentrations in the future, because of simultaneously decreasing buffer capacity. Here, we address this experimentally during a diurnal cycle in a mesocosm CO2 perturbation study. We show that for about the same amount of dissolved inorganic carbon (DIC) utilized in net community production diel variability in proton (H+) and CO2 concentrations was almost three times higher at CO2 levels of about 675 ± 65 in comparison with levels of 310 ± 30 μatm. With a simple model, adequately simulating our measurements, we visualize carbonate chemistry variability expected for different oceanic regions with relatively low or high net community production. Since enhanced diurnal variability in CO2 and proton concentration may require stronger cellular regulation in phytoplankton to maintain respective gradients, the ability to adjust may differ between communities adapted to low in comparison with high natural variability

Enhanced biological carbon consumption in a high CO2 ocean

The oceans have absorbed nearly half of the fossil-fuel carbon dioxide (CO2) emitted into the atmosphere since pre-industrial times1, causing a measurable reduction in seawater pH and carbonate saturation2. If CO2 emissions continue to rise at current rates, upper-ocean pH will decrease to levels lower than have existed for tens of millions of years and, critically, at a rate of change 100 times greater than at any time over this period3. Recent studies have shown effects of ocean acidification on a variety of marine life forms, in particular calcifying organisms4, 5, 6. Consequences at the community to ecosystem level, in contrast, are largely unknown. Here we show that dissolved inorganic carbon consumption of a natural plankton community maintained in mesocosm enclosures at initial CO2 partial pressures of 350, 700 and 1,050 μatm increases with rising CO2. The community consumed up to 39% more dissolved inorganic carbon at increased CO2 partial pressures compared to present levels, whereas nutrient uptake remained the same. The stoichiometry of carbon to nitrogen drawdown increased from 6.0 at low CO2 to 8.0 at high CO2, thus exceeding the Redfield carbon:nitrogen ratio of 6.6 in today’s ocean7. This excess carbon consumption was associated with higher loss of organic carbon from the upper layer of the stratified mesocosms. If applicable to the natural environment, the observed responses have implications for a variety of marine biological and biogeochemical processes, and underscore the importance of biologically driven feedbacks in the ocean to global change

Non-Gaussian power grid frequency fluctuations characterized by Levy-stable laws and superstatistics

Multiple types of fluctuations impact the collective dynamics of power grids and thus challenge their robust operation. Fluctuations result from processes as different as dynamically changing demands, energy trading and an increasing share of renewable power feed-in. Here we analyse principles underlying the dynamics and statistics of power grid frequency fluctuations. Considering frequency time series for a range of power grids, including grids in North America, Japan and Europe, we find a strong deviation from Gaussianity best described as Lévy-stable and q-Gaussian distributions. We present a coarse framework to analytically characterize the impact of arbitrary noise distributions, as well as a superstatistical approach that systematically interprets heavy tails and skewed distributions. We identify energy trading as a substantial contribution to today’s frequency fluctuations and effective damping of the grid as a controlling factor enabling reduction of fluctuation risks, with enhanced effects for small power grids