Impact of an exceptional winter flood on benthic oxygen and nutrient fluxes in a temperate macrotidal estuary: Potential consequences on summer deoxygenation
Despite 20 years of control on eutrophication, episodes of summer hypoxia still occur in the Loire estuary, impacting water quality and posing a key scientific and management challenge. This work aimed to quantify the contribution of the benthic compartment to hypoxia in the Loire estuary by direct measurement of water-sediment fluxes and an in-depth understanding of the seasonal variations of oxides and phosphorus stocks. During the summer's low-discharge period, results show that the iron oxide-rich deposit is stable under hypoxic conditions, limiting the release of dissolved phosphorus into the overlying water column. The high nitrate content of the water column appears to be an important oxidizer of iron during hypoxic periods, limiting dissolved phosphorus leakage and aggravation of hypoxia. During the exceptional winter flood, significant sediment erosion associated with bubbling phenomena (attributed to methane efflux) created severe fractures in the sediment and stimulated water-sediment exchange. During the following months, these fractures were progressively filled, which decreased the intensity of benthic fluxes. However, due to the high residence time in the water during the summer period, a simple model demonstrated that benthic contributions were sufficient to directly (by direct oxygen consumption) or indirectly (by promoting ammonia oxidation) affect the oxygen stock in the water column during the low-discharge period. Our study demonstrates the importance of the benthic compartment in the occurrence of hypoxia and the obvious lack of knowledge to illustrate and model the biogeochemical functioning of the estuary.
(Frontiers in Marine Science. vol. 10, n° 2296-7745, 16/02/2023)
LPG, UM, UA, INSU - CNRS, CNRS, Nantes univ - UFR ST, Nantes Univ, IPREM, UPPA, INC-CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CHROME, UNIMES, LERMPL, COAST, IFREMER, LPG-ANGERS, LPG, UM, UA, INSU - CNRS, CNRS, Nantes univ - UFR ST
PHANGS–JWST First Results: Interstellar Medium Structure on the Turbulent Jeans Scale in Four Disk Galaxies Observed by JWST and the Atacama Large Millimeter/submillimeter Array
JWST/Mid-Infrared Instrument imaging of the nearby galaxies IC 5332, NGC 628, NGC 1365, and NGC 7496 from PHANGS reveals a richness of gas structures that in each case form a quasi-regular network of interconnected filaments, shells, and voids. We examine whether this multiscale network of structure is consistent with the fragmentation of the gas disk through gravitational instability. We use FilFinder to detect the web of filamentary features in each galaxy and determine their characteristic radial and azimuthal spacings. These spacings are then compared to estimates of the most Toomre-unstable length (a few kiloparsecs), the turbulent Jeans length (a few hundred parsecs), and the disk scale height (tens of parsecs) reconstructed using PHANGS-Atacama Large Millimeter/submillimeter Array observations of the molecular gas as a dynamical tracer. Our analysis of the four galaxies targeted in this work indicates that Jeans-scale structure is pervasive. Future work will be essential for determining how the structure observed in gas disks impacts not only the rate and location of star formation but also how stellar feedback interacts positively or negatively with the surrounding multiphase gas reservoir.
(The Astrophysical Journal Letters. vol. 944, n° 2041-8205, pp. L18, 16/02/2023)
MPIA, OSU, CfA, OSU, RIDI - UPR 9022, IBMC, UNISTRA, CNRS, UNISTRA, INSERM, CNRS, UAB, AlfA, UniCA, LAGRANGE, UNS, INSU - CNRS, UniCA, CNRS, UniCA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LAM, AMU, INSU - CNRS, CNES, CNRS, AIM (UMR7158 / UMR_E_9005 / UM_112), CEA, INSU - CNRS, UPD7, CNRS, UW, CRAL, ENS de Lyon, UCBL, INSU - CNRS, CNRS, ESO, ANU, CALTECH, MPE, NRAO, NRAO, IRAM, CNRS, LERMA (UMR_8112), INSU - CNRS, CNRS, PSL, UCP, SU, CNRS, UC San Diego, UC, JHU
PHANGS–JWST First Results: Destruction of the PAH Molecules in H ii Regions Probed by JWST and MUSE
Polycyclic aromatic hydrocarbons (PAHs) play a critical role in the reprocessing of stellar radiation and balancing the heating and cooling processes in the interstellar medium but appear to be destroyed in H II regions. However, the mechanisms driving their destruction are still not completely understood. Using PHANGS-JWST and PHANGS-MUSE observations, we investigate how the PAH fraction changes in about 1500 H II regions across four nearby star-forming galaxies (NGC 628, NGC 1365, NGC 7496, and IC 5332). We find a strong anticorrelation between the PAH fraction and the ionization parameter (the ratio between the ionizing photon flux and the hydrogen density) of H II regions. This relation becomes steeper for more luminous H II regions. The metallicity of H II regions has only a minor impact on these results in our galaxy sample. We find that the PAH fraction decreases with the Hα equivalent width-a proxy for the age of the H II regions-although this trend is much weaker than the one identified using the ionization parameter. Our results are consistent with a scenario where hydrogen-ionizing UV radiation is the dominant source of PAH destruction in star-forming regions.
Unified Astronomy Thesaurus concepts: Polycyclic aromatic hydrocarbons (1280); H II regions (694); Interstellar dust (836)
(The Astrophysical Journal Letters. vol. 944, n° 2041-8205, pp. L16, 16/02/2023)
MPIA, UC San Diego, UC, OSU, ANU, AlfA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UniCA, LAGRANGE, UNS, INSU - CNRS, UniCA, CNRS, UniCA, LAM, AMU, INSU - CNRS, CNES, CNRS, LERMA, LERMA, ENS-PSL, PSL, INSU - CNRS, CNRS, PSL, SU, CNRS, CY, UW, CRAL, ENS de Lyon, UCBL, INSU - CNRS, CNRS, ESO, CALTECH, MPE, NRAO, NRAO, IRAM, CNRS, LERMA (UMR_8112), INSU - CNRS, CNRS, PSL, UCP, SU, CNRS, JHU, UAB
PHANGS–JWST First Results: The Dust Filament Network of NGC 628 and Its Relation to Star Formation Activity
PHANGS-JWST mid-infrared (MIR) imaging of nearby spiral galaxies has revealed ubiquitous filaments of dust emission in intricate detail. We present a pilot study to systematically map the dust filament network (DFN) at multiple scales between 25 and 400 pc in NGC 628. MIRI images at 7.7, 10, 11.3, and 21 μm of NGC 628 are used to generate maps of the filaments in emission, while PHANGS-HST B-band imaging yields maps of dust attenuation features. We quantify the correspondence between filaments traced by MIR thermal continuum/ polycyclic aromatic hydrocarbon (PAH) emission and filaments detected via extinction/scattering of visible light; the fraction of MIR flux contained in the DFN; and the fraction of H II regions, young star clusters, and associations within the DFN. We examine the dependence of these quantities on the physical scale at which the DFN is extracted. With our highest-resolution DFN maps (25 pc filament width), we find that filaments in emission and attenuation are cospatial in 40% of sight lines, often exhibiting detailed morphological agreement; that ∼30%
(The Astrophysical Journal Letters. vol. 944, n° 2041-8205, pp. L13, 16/02/2023)
JHU, RIDI - UPR 9022, IBMC, UNISTRA, CNRS, UNISTRA, INSERM, CNRS, AlfA, UniCA, LAGRANGE, UNS, INSU - CNRS, UniCA, CNRS, UniCA, LAM, AMU, INSU - CNRS, CNES, CNRS, AIM (UMR7158 / UMR_E_9005 / UM_112), CEA, INSU - CNRS, UPD7, CNRS, UW, ANU, CfA, MPIA, OSU, ESO, UC San Diego, UC, UAB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LERMA, LERMA, ENS-PSL, PSL, INSU - CNRS, CNRS, PSL, SU, CNRS, CY, CRAL, ENS de Lyon, UCBL, INSU - CNRS, CNRS
Bottom evolution patterns driven by hydrodynamic forcing in the Southwest Atlantic Inner Continental Shelf, off Río de la Plata and Patos Lagoon
Sediment transport and depositional processes in the Southwest Atlantic Inner Shelf are strongly influenced by the contribution from Río de la Plata and Patos Lagoon fluvial systems. Understanding the behavior of erosive and depositional processes and bed evolution in the region is of utmost importance to address the impacts of anthropogenic activities, climate change and for navigation security. Therefore, this work aims to improve the understanding of such processes, and their temporal and spatial scales of variability. We employed the SISYPHE morphodynamic model coupled with the TELEMAC-3D hydrodynamic model to simulate the resulting depositional and erosional fluxes and the bottom evolution during a period of 8 years (2005–2012). Results indicate that during this period, depositional fluxes mostly exceeded erosional fluxes in the south of the Patos Lagoon mouth, resulting in predominantly positive bottom evolution. On the other hand, erosional fluxes exceeded depositional fluxes to the north of the Patos Lagoon mouth, resulting in predominantly negative bottom evolution. Widespread positive values of bottom evolution are observed along the northern and southern coasts off the Río de la Plata mouth, indicating a general dominance of sediment deposition over erosion. A wavelet analysis showed that fluvial discharge influences the variability of depositional process on an interannual time scale, whereas the synoptic variability is influenced by wind action. Moreover, positive ENSO periods (El Niño) are related to increased depositional fluxes, and decreased depositional fluxes during the negative phase (La Niña), with pronounced effects off Río de la Plata.
(Continental Shelf Research. vol. 255, n° 0278-4343, pp. 104934, 15/02/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Editorial: Regional coastal deoxygenation and related ecological and biogeochemical modifications in a warming climate
Coastal ecosystems play tremendous roles in socio-economic development, but their functions are degrading due to human activities. One of the most alarming degradations is coastal deoxygenation, driven primarily by the over-enrichment of anthropogenic nutrients and organic matter (eutrophication) in the coastal waters. The coastal deoxygenation has led to the worldwide spread of hypoxic zones (where dissolved oxygen concentration is less than 2 mg/L), with the number of reported hypoxic sites increasing from 45 in the 1960s to around 700 nowadays. Besides being perturbed by human activities locally, coastal waters respond more rapidly than the open ocean to global climate change such as ocean warming. Warmer water temperature reduces oxygen solubility, weakens the mixing of oxygen-rich surface water with oxygen-poor bottom water, and enhances biogeochemical oxygen consumption, exacerbating the coastal deoxygenation situation.
(Frontiers in Marine Science. vol. 10, n° 2296-7745, 06/02/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Non-linear loss of suitable wine regions over Europe in response to increasing global warming
Evaluating the potential climatic suitability for premium wine production is crucial for adaptation planning in Europe. While new wine regions may emerge out of the traditional boundaries, most of the present-day renowned winemaking regions may be threatened by climate change. Here, we analyse the future evolution of the geography of wine production over Europe, through the definition of a novel climatic suitability indicator, which is calculated over the projected grapevine phenological phases to account for their possible contractions under global warming. Our approach consists in coupling six different de-biased downscaled climate projections under two different scenarios of global warming with four phenological models for different grapevine varieties. The resulting suitability indicator is based on fuzzy logic and is calculated over three main components measuring (i) the timing of the fruit physiological maturity, (ii) the risk of water stress and (iii) the risk of pests and diseases. The results demonstrate that the level of global warming largely determines the distribution of future wine regions. For a global temperature increase limited to 2°C above the pre-industrial level, the suitable areas over the traditional regions are reduced by about 4%/°C rise, while for higher levels of global warming, the rate of this loss increases up to 17%/°C. This is compensated by a gradual emergence of new wine regions out of the traditional boundaries. Moreover, we show that reallocating better-suited grapevine varieties to warmer conditions may be a viable adaptation measure to cope with the projected suitability loss over the traditional regions. However, the effectiveness of this strategy appears to decrease as the level of global warming increases. Overall, these findings suggest the existence of a safe limit below 2°C of global warming for the European winemaking sector, while adaptation might become far more challenging beyond this threshold.
(Global Change Biology. vol. 5, n° 1354-1013, pp. 808-826, 01/02/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LOCEAN-VARCLIM, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, UMR EGFV, UB, Bordeaux Sciences Agro, INRAE, CRC, BGS, UB, CNRS, AGROCLIM, INRAE
Inter and intraspecific variability of dieldrin accumulation in Cucurbita fruits: New perspectives for food safety and phytomanagement of contaminated soils
Due to past agricultural practices, it is common to identify arable soils contaminated with persistent and potentially toxic organochlorine pesticides (OCPs). Occurrence of OCPs, including dieldrin, in vegetables can lead to chronic exposure of the consumers. Some market vegetables, particularly the Cucurbitaceae, are known to accumulate high OCP concentrations. Dieldrin concentration in Cucurbita fruits can exceed the Maximal Residue Limit (MRL) resulting in cultivation and sale restrictions for market gardeners. To assess the intra- and interspecific variability of Cucurbitaceae species for low dieldrin concentration in fruits could be a solution. Here, 24 varieties from seven Cucurbitaceae species were cultivated outdoors in large pots, until fruiting, in soils historically contaminated with dieldrin. More than 330 fruits were harvested and analyzed for determining the inter and intraspecific variability of dieldrin accumulation. Significant interspecific differences occurred with mean fruit concentration ranging between 4.2 ± 7.0 and 85.0 ± 19.4 μg dieldrin kg−1 fresh weigh (FW) in watermelons (C. lanatus L.) and cucumbers (C. sativus L.), respectively. Intraspecific differences only occurred for Cucurbita pepo L. with mean concentration ranging between 4.9 ± 1.1 and 70.3 ± 3.6 μg dieldrin kg−1 FW for the varieties Noire maraîchère and Orélia, respectively. For this plant species, the influence of soil concentration, plant exposure time and biomass on fruit dieldrin concentration depended mainly on varieties.
(Science of the Total Environment. vol. 859, n° 0048-9697, pp. 160152, 01/02/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BioGeCo, UB, INRAE, UB, ENSAP Bordeaux, UBM, CNRS
Impact of Sediment Bioturbation on Microphytobenthic Primary Producers: Importance of Macrobenthic Functional Traits
Microphytobenthos (MPB) is one of the most important primary producers in coastal and estuarine ecosystems, where it plays a substantial role in many ecological functions. Although the influence of several environmental factors on MPB biomass and productivity is well documented, the effects of macrofaunal bioturbation remain poorly assessed. The purpose of this study was to experimentally quantify the influence of sediment bioturbation processes (that is, sediment reworking and bioirrigation) on biogeochemical fluxes across the sediment–water interface and MPB biomass and photosynthetic capacities. Two infaunal deposit feeders (the polychaete Hediste diversicolor and the bivalve Scrobicularia plana) exhibiting contrasting bioturbation modes and rates were studied as model organisms. They differently affected MPB biomass and photosynthetic performance. Hence, through an intense bioirrigation activity and the stimulation of nutrient fluxes (NH4+ , NOx, PO42− and dSi) at the sediment surface, H. diversicolor enhanced MPB growth, which seemed to compensate for its direct consumption. Conversely, high sediment reworking rates generated by S. plana, associated with an extensive grazing pressure, drastically limited the development of MPB at the sediment surface. The negative impact of bivalves on MPB biomass increased with increasing density, whereas there was no significant relationship with polychaete density, possibly due to trophic competition. This study demonstrates that macrofaunal bioturbation is a key factor regulating MPB dynamics, with complex interactions that can result in a net either positive or negative effect depending on dominant species functional traits and abundances. This may, in particular, explain the strong spatial and temporal variability of the microbenthic primary productivity in intertidal mudflats.
(Ecosystems, n° 1432-9840, 17/01/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA
Chapter 4 - Introduction to the Last Deglaciation climate
This chapter briefly describes the long-term climate evolution, as well as, the superimposed abrupt climate shifts that have punctuated the Last Deglaciation, that is, the pre-Heinrich Stadial 1 and the Heinrich Stadial 1, the Bølling–Allerød Interstadial and the Younger Dryas Stadial. A short description of the impact of these abrupt changes in the North Atlantic, Greenland and Europe is also provided as a prelude to the following chapters.
(pp. 33-36, 01/01/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS