On the convergence of quadrature formulas connected with multipoint Padé-type approximants

29 pages, no figures.-- MSC2000 codes: 41A55, 41A21.MR#: MR1408352 (97e:41066)Zbl#: Zbl 0856.41027^aLet $I(F)= \int^1_{- 1} F(x)\omega(x) dx$, where $\omega$ is a complex valued integrable function. We consider quadrature formulas for $I(F)$ which are exact with respect to rational functions with prescribed poles contained in \overline{\bbfC}\backslash [- 1, 1]. Their rate of convergence is studied.The research by the first three authors (P.G.-V., M.J.P., R.O.) was partially supported by the HCM project ROLLS, under Contract CHRX-CT93-0416. Research by the fourth author (G.L.L.) was carried out while on a visit at Universidad de La Laguna. This visit was made possible by a travel grant from CDE-IMU.Publicad

Elevated CO2induces a bloom of microphytobenthos within a shell gravel mesocosm

The geological storage of carbon dioxide (CO2) is expected to be an important component of future global carbon emission mitigation, but there is a need to understand the impacts of a CO2 leak on the marine environment and to develop monitoring protocols for leakage detection. In the present study, sediment cores were exposed to CO2-acidified seawater at one of five pH levels (8.0, 7.5, 7.0, 6.5 and 6.0) for 10 weeks. A bloom of Spirulina sp. and diatoms appeared on sediment surface exposed to pH 7.0 and 7.5 seawater. Quantitative PCR measurements of the abundance of 16S rRNA also indicated an increase within the pH 7.0 and 7.5 treatments after 10 weeks incubation. More detailed analysis of the microbial communities from the pH 7.0, 7.5 and 8.0 treatments confirmed an increase in the relative abundance of Spirulina sp. and Navicula sp. sequences, with changes in the relative abundance of major archaeal and bacterial groups also detected within the pH 7.0 treatment. A decreased flux of silicate from the sediment at this pH was also detected. Monitoring blooms of microphytobenthos may prove useful as an indicator of CO2 leakage within coastal area

Assessment of the environmental, ecosystem, and human activities in coastal Vietnam and Cambodia gathered from satelitte remote sensing

Within the ACCORD (Addressing Challenges of Coastal Communities through Ocean Research for Developing Economies) project, satellite Earth Observations are used for two purposes: 1. To describe basic environmental dynamics around two focus regions, Da Nang Bay in Vietnam and Kep Province in Cambodia. Two aspects of satellite data are examined for this purpose: first, sea surface temperature (SST),); second, water quality data, focussing on chlorophyll a and turbidity. 2. To assess the potential for mapping locations of aquaculture sites around Da Nang Bay, Vietnam, through exploitation of EO data. This second purpose utilises the sea surface radar backscattering coefficient. NOAA’s Pathfinder SST dataset derived from measurements made by AVHRR sensors was used here at 4 km resolution. This dataset offers a long time series, which has gone through rigorous quality control and calibration, and as such is considered a climate-quality dataset. The seasonal cycle as well as the long term dynamics for SST can be observed, showing the monsoon dynamics of the region. No trend in warming over the past two decades is observable from these data. Water quality measurements were investigated using a number of EO-derived products. These products cover different spatial and temporal scales. The first is the ESA Ocean Colour Climate Change Initiative (OC-CCI) – Chlorophyll a dataset. This has a 1 km resolution and is mainly optimised for the open ocean through to moderately turbid coastal waters; the most turbid coastal waters around Da Nang and Kep are frequently masked in this dataset. Larger scale regional seasonality and long term changes in chlorophyll levels are assessed. There is no clear trend through time over the wider regions, however clear spatial dynamics can be observed. The relationship between chlorophyll a and SST over the past two decades was also investigated. Higher levels of chlorophyll a occurred near the coasts at certain times of year, predominantly corresponding to seasonal changes in temperature and increases in river flow during monsoon periods. The coastal and nearshore water quality around Da Nang and Kep was assessed using datasets processed with PML’s Calimnos processor, which includes a blend of algorithms designed for very turbid water and prioritises higher spatial resolution over having the longest time series. The 300 m dataset were derived from Envisat MERIS and Sentinel 3 OLCI, which provide a medium-term time series, although there is a four year gap between the missions so a continuous dataset is not available. These data offer the best balance of resolution and algorithm performance for coastal remote sensing at present. The 60 m water quality dataset was derived from Sentinel 2 MSI, which has been operating since 2015 and hence is a shorter time series. However, the 60 m dataset is especially useful for resolving smaller features, as is demonstrated by highlighting small eddy features and river outflows around both Da Nang bay and Kep. The method for detecting and mapping aquaculture structures, such as finfish cages, shellfish farms and floating houses using freely available Sentinel-1A SAR sensor data was successfully applied to Da Nang bay and nearby rivers. 11 aquaculture sites were identified in the bay and in the rivers, confirmed by comparing with high resolution Google Map satellite images. Comparing static maps across different years shows that this method can be used to monitor temporal changes in detected aquaculture sites

Late winter under ice pelagic microbial communities in the high Arctic Ocean and the impact of short-term exposure to elevated CO2 levels

Polar Oceans are natural CO2 sinks because of the enhanced solubility of CO2 in cold water. The Arctic Ocean is at additional risk of accelerated ocean acidification (OA) because of freshwater inputs from sea ice and rivers, which influence the carbonate system. Winter conditions in the Arctic are of interest because of both cold temperatures and limited CO2 venting to the atmosphere when sea ice is present. Earlier OA experiments on Arctic microbial communities conducted in the absence of ice cover, hinted at shifts in taxa dominance and diversity under lowered pH. The Catlin Arctic Survey provided an opportunity to conduct in situ, under-ice, OA experiments during late Arctic winter. Seawater was collected from under the sea ice off Ellef Ringnes Island, and communities were exposed to three CO2 levels for 6 days. Phylogenetic diversity was greater in the attached fraction compared to the free-living fraction in situ, in the controls and in the treatments. The dominant taxa in all cases were Gammaproteobacteria but acidification had little effect compared to the effects of containment. Phylogenetic net relatedness indices suggested that acidification may have decreased the diversity within some bacterial orders, but overall there was no clear trend. Within the experimental communities, alkalinity best explained the variance among samples and replicates, suggesting subtle changes in the carbonate system need to be considered in such experiments. We conclude that under ice communities have the capacity to respond either by selection or phenotypic plasticity to heightened CO2 levels over the short term

Satellite observations are needed to understand ocean acidification and multi-stressor impacts on fish stocks in a changing Arctic Ocean

This is the final version. Available from Frontiers Media via the DOI in this record. It is widely projected that under future climate scenarios the economic importance of Arctic Ocean fish stocks will increase. The Arctic Ocean is especially vulnerable to ocean acidification and already experiences low pH levels not projected to occur on a global scale until 2100. This paper outlines how ocean acidification must be considered with other potential stressors to accurately predict movement of fish stocks toward, and within, the Arctic and to inform future fish stock management strategies. First, we review the literature on ocean acidification impacts on fish, next we identify the main obstacles that currently preclude ocean acidification from Arctic fish stock projections. Finally, we provide a roadmap to describe how satellite observations can be used to address these gaps: improve knowledge, inform experimental studies, provide regional assessments of vulnerabilities, and implement appropriate management strategies. This roadmap sets out three inter-linked research priorities: (1) Establish organisms and ecosystem physiochemical baselines by increasing the coverage of Arctic physicochemical observations in both space and time; (2) Understand the variability of all stressors in space and time; (3) Map life histories and fish stocks against satellite-derived observations of stressors.European Space AgencyAXA XL Ocean Risk Scholarshi

Arctic Oceanography - Oceanography: Atmosphere-Ocean Exchange, Biogeochemistry & Physics

The Arctic Ocean is, on average, the shallowest of Earth’s oceans. Its vast continental shelf areas, which account for approximately half of the Arctic Ocean’s total area, are heavily influenced by the surrounding land masses through river run-off and coastal erosion. As a main area of deep water formation, the Arctic is one of the main «engines» of global ocean circulation, due to large freshwater inputs, it is also strongly stratified. The Arctic Ocean’s complex oceanographic configuration is tightly linked to the atmosphere, the land, and the cryosphere. The physical dynamics not only drive important climate and global circulation patterns, but also control biogeochemical cycles and ecosystem dynamics. Current changes in Arctic sea-ice thickness and distribution, air and water temperatures, and water column stability are resulting in measurable shifts in the properties and functioning of the ocean and its ecosystems. The Arctic Ocean is forecast to shift to a seasonally ice-free ocean resulting in changes to physical, chemical, and biological processes. These include the exchange of gases across the atmosphere-ocean interface, the wind-driven ciruclation and mixing regimes, light and nutrient availability for primary production, food web dynamics, and export of material to the deep ocean. In anticipation of these changes, extending our knowledge of the present Arctic oceanography and these complex changes has never been more urgent

Observing temporally varying synoptic‐scale total alkalinity and dissolved inorganic carbon in the Arctic Ocean

This is the final version. Available from Wiley via the DOI in this record. Data Availability Statement: The matchup database “OceanSODA-MDB” which was used in the algorithm evaluation is available at https:// data-cersat.ifremer.fr/data/ocean-carbonate/oceansoda-mmdb/ (Land et al., 2023; Land & Piollé, 2022). The python code used to run the analysis can be found at https://doi.org/10.5281/zenodo.10067204 (Green et al., 2023) and was adapted from DOI: https://doi.org/10.5281/zenodo.10069611 (Sims et al., 2022).The long-term absorption by the oceans of atmospheric carbon dioxide is leading to the slow decline of ocean pH, a process termed ocean acidification (OA). The Arctic is a challenging region to gather enough data to examine the changes in carbonate chemistry over sufficient scales. However, algorithms that calculate carbonate chemistry parameters from more frequently measured parameters, such as temperature and salinity, can be used to fill in data gaps. Here, these published algorithms were evaluated against in situ measurements using different data input types (data from satellites or in situ re-analysis climatologies) across the Arctic Ocean. With the lowest uncertainties in the Atlantic influenced Seas (AiS), where re-analysis inputs achieved total alkalinity estimates with Root Mean Squared Deviation (RMSD) of 21 μmol kg−1 and a bias of 2 μmol kg−1 (n = 162) and dissolved inorganic carbon RMSD of 24 μmol kg−1 and bias of −14 μmol kg−1 (n = 262). AiS results using satellite observation inputs show similar bias but larger RMSD, although due to the shorter time span of available satellite observations, more contemporary in situ data would provide further assessment and improvement. Synoptic-scale observations of surface water carbonate conditions in the Arctic are now possible to monitor OA, but targeted in situ data collection is needed to enable the full exploitation of satellite observation-based approaches.European Space AgencyAXA XLJoint Transnational Call on Next Generation Climate Science in Europe for the Ocea

The impact of ocean acidification and warming on the skeletal mechanical properties of the sea urchin Paracentrotus lividus from laboratory and field observations

Increased atmospheric CO2 concentration is leading to changes in the carbonate chemistry and the temperature of the ocean. The impact of these processes on marine organisms will depend on their ability to cope with those changes, particularly the maintenance of calcium carbonate structures. Both a laboratory experiment (long-term exposure to decreased pH and increased temperature) and collections of individuals from natural environments characterized by low pH levels (individuals from intertidal pools and around a CO2 seep) were here coupled to comprehensively study the impact of near-future conditions of pH and temperature on the mechanical properties of the skeleton of the euechinoid sea urchin Paracentrotus lividus. To assess skeletal mechanical properties, we characterized the fracture force, Young's modulus, second moment of area, material nanohardness, and specific Young's modulus of sea urchin test plates. None of these parameters were significantly affected by low pH and/or increased temperature in the laboratory experiment and by low pH only in the individuals chronically exposed to lowered pH from the CO2 seeps. In tidal pools, the fracture force was higher and the Young's modulus lower in ambital plates of individuals from the rock pool characterized by the largest pH variations but also a dominance of calcifying algae, which might explain some of the variation. Thus, decreases of pH to levels expected for 2100 did not directly alter the mechanical properties of the test of P. lividus. Since the maintenance of test integrity is a question of survival for sea urchins and since weakened tests would increase the sea urchins' risk of predation, our findings indicate that the decreasing seawater pH and increasing seawater temperature expected for the end of the century should not represent an immediate threat to sea urchins vulnerability

Ocean acidification and hypoxia alter organic carbon fluxes in marine soft sediments

Anthropogenic stressors can alter the structure and functioning of infaunal communities, which are key drivers of the carbon cycle in marine soft sediments. Nonetheless, the compounded effects of anthropogenic stressors on carbon fluxes in soft benthic systems remain largely unknown. Here, we investigated the cumulative effects of ocean acidification (OA) and hypoxia on the organic carbon fate in marine sediments, through a mesocosm experiment. Isotopically labelled macroalgal detritus (13C) was used as a tracer to assess carbon incorporation in faunal tissue and in sediments under different experimental conditions. In addition, labelled macroalgae (13C), previously exposed to elevated CO2, were also used to assess the organic carbon uptake by fauna and sediments, when both sources and consumers were exposed to elevated CO2. At elevated CO2, infauna increased the uptake of carbon, likely as compensatory response to the higher energetic costs faced under adverse environmental conditions. By contrast, there was no increase in carbon uptake by fauna exposed to both stressors in combination, indicating that even a short‐term hypoxic event may weaken the ability of marine invertebrates to withstand elevated CO2 conditions. In addition, both hypoxia and elevated CO2 increased organic carbon burial in the sediment, potentially affecting sediment biogeochemical processes. Since hypoxia and OA are predicted to increase in the face of climate change, our results suggest that local reduction of hypoxic events may mitigate the impacts of global climate change on marine soft‐sediment systems

Salinity from Space Unlocks Satellite-Based Assessment of Ocean Acidification

Approximately a quarter of the carbon dioxide (CO2) that we emit into the atmosphere is absorbed by the ocean. This oceanic uptake of CO2 leads to a change in marine carbonate chemistry resulting in a decrease of seawater pH and carbonate ion concentration, a process commonly called “Ocean Acidification”. Salinity data are key for assessing the marine carbonate system, and new space-based salinity measurements will enable the development of novel space-based ocean acidification assess- ment. Recent studies have highlighted the need to develop new in situ technology for monitoring ocean acidification, but the potential capabilities of space-based measurements remain largely untapped. Routine measurements from space can provide quasi-synoptic, reproducible data for investigating processes on global scales; they may also be the most efficient way to monitor the ocean surface. As the carbon cycle is dominantly controlled by the balance between the biological and solubility carbon pumps, innovative methods to exploit existing satellite sea surface temperature and ocean color, and new satellite sea surface salinity measurements, are needed and will enable frequent assessment of ocean acidification parameters over large spatial scales