Vulnerability of the North Water ecosystem to climate change
Abstract High Arctic ecosystems and Indigenous livelihoods are tightly linked and exposed to climate change, yet assessing their sensitivity requires a long-term perspective. Here, we assess the vulnerability of the North Water polynya, a unique seaice ecosystem that sustains the world’s northernmost Inuit communities and several keystone Arctic species. We reconstruct mid-to-late Holocene changes in sea ice, marine primary production, and little auk colony dynamics through multi-proxy analysis of marine and lake sediment cores. Our results suggest a productive ecosystem by 4400–4200 cal yrs b2k coincident with the arrival of the first humans in Greenland. Climate forcing during the late Holocene, leading to periods of polynya instability and marine productivity decline, is strikingly coeval with the human abandonment of Greenland from c. 2200–1200 cal yrs b2k. Our long-term perspective highlights the future decline of the North Water ecosystem, due to climate warming and changing sea-ice conditions, as an important climate change risk.
(Nature Communications. vol. 12, n° 2041-1723, 01/12/2021)
GEUS, LOCEAN-VOG, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, DGD.REVE, MNHN, HELSUS, ULaval, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, DMI, IGN, UCPH, AWI, UEF, JYU, JYU, METU, IRSTEA, UCPH, GINR
Effects of metals and persistent organic pollutants on the fitness and health of juveniles of the endangered European sturgeon Acipenser sturio exposed to water and sediments of the Garonne and Dordogne rivers
The last remaining population of European sturgeon (Acipenser sturio) lives in the Gironde-Garonne-Dordogne (France) catchment (GGD). Captive young individuals are released into the GGD hydrosystem each year, as part of a restocking programme. This study aims to assess the health status of juveniles A. sturio to current conditions in the GGD hydrosystem, to evaluate their capacity to survive and grow in a moderately anthropized ecosystems. 3-month-old farmed sturgeons were exposed for one month in experimental conditions that mimic the environmental conditions in the Garonne and Dordogne rivers, followed by five months of depuration. After one month of exposure, fish exposed to Dordogne and Garonne waters bioaccumulated higher levels of metals and persistent organic pollutants, displayed a reduced hepato-somatic index, and had depleted levels of lipids and glycogen content in their liver, when compared with the Reference group. However, metabolic and swimming performance, as well as the costs of swimming were not impaired. After the 5 months depuration, a significant decrease of K was observed for all exposure conditions. HSI also decreased with time. The overall health status and adaptive capacity of juvenile A. sturio appeared to be maintained over the experimental 6 months' period. Juveniles of A. sturio seem to have the adaptive capacity to survive and grow in the GGD hydrosystem, after being released as part of a restocking programme.
(Ecotoxicology and Environmental Safety. vol. 225, n° 0147-6513, pp. 112720, 01/12/2021)
LBBM, EDF [E.D.F.], SU, CNRS, OOB, SU, CNRS, LIENSs, INSU - CNRS, ULR, CNRS, UR EABX, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, APEX, PAnTher, Oniris VetAgroBio, INRAE, PAnTher, Oniris VetAgroBio, INRAE
Impact de la pollution lumineuse sur le rythme comportemental de l’huître Crassostrea gigas
(Médecine du sommeil. vol. 18, n° 1769-4493, pp. 196, 01/12/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Stranded in the high tide line: spatial and temporal variability of beached microplastics in a semi-enclosed embayment (Arcachon, France)
Coastal environments are a predominant ultimate destination of marine debris, becoming a key focus of studies assessing microplastic (MP) contamination. Here, we described the visible fraction of MP (from 0.5 to 5 mm) that washed up during the high tide at different sites of a semi-enclosed mesotidal bay and investigated the main abiotic factors driving MP beaching. Three contrasted beaches of the Arcachon Bay (SW France) were monitored on a monthly basis during 2019. Samplings were made along a 100 m longitudinal transect at the high-water strandline (4 quadrats of 0.25m2) and at an intermediate tidal range. Each sampled particle was characterized by morphometric data (e.g. size, shape, color, roughness) and polymer identification was performed by ATR-FTIR technique. Results show that MP concentration was higher on the beach located at the mouth of the bay (36.0 ± 39.2 MP.m-2) than at the back and the outside of the bay (respectively 2.7 ± 4.4 and 1.7 ± 2.4 MP.m-2). This may be related to the strong currents at the entry of the embayment and the beach orientation, exposed to predominant winds. Beached MP were mainly pre-production pellets and fragments as they represented respectively 49% and 39% of all analyzed shapes. Polymers with low density were particularly abundant. Polyethylene represented 69% of all the particles while polypropylene accounted for 17% and polystyrene for 10%. We also observed that MP were mostly washed up when wind, waves and river flow were more intense. Analysis suggest that wind direction and speed are key factors influencing beaching as strong onshore wind enhance this process.
(Science of the Total Environment. vol. 797, n° 0048-9697, pp. 149144, 27/11/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CBMN, UB, ENITAB, INC-CNRS, CNRS
Application of an iterative source localization strategy at a chlorinated solvent site
This study presents an inverse modeling strategy for organic contaminant source localization. The approach infers the hydraulic conductivity field, the dispersivity, and the source zone location. Beginning with initial observed data of contaminant concentration and hydraulic head, the method follows an iterative strategy of adding new observations and revising the source location estimate. Non-linear optimization using the Gauss-Levenberg-Marquardt Algorithm (PEST++) is tested at a real contaminated site. Then a limited number of drilling locations are added, with their positions guided by the Data Worth analysis capabilities of PYEMU. The first phase of PEST++, with PYEMU guidance, followed by addition of monitoring wells provided an initial source location and identified four additional drilling locations. The second phase confirmed the source location, but the estimated hydraulic conductivity field and the Darcy flux were too far from the measured values. The mismatch led to a revised conceptual site model that included two distinct zones, each with a plume emanating from a separate source. A third inverse modelling phase was conducted with the revised site conceptual model. Finally, the source location was compared to results from a Geoprobe@ MiHPT campaign and historical records, confirming both source locations. By merging measurement and modeling in a coupled, iterative framework, two contaminant sources were located through only two drilling campaigns while also reforming the conceptual model of the site. © 2021 The Authors
(Journal of Hydrology X. vol. 13, n° 2589-9155, 26/11/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Toxicité des microplastiques et des nanoplastiques vis-à-vis d'organismes aquatiques le long d'un continuum eau douce-eau de mer
De nombreuses études ont été menées pour évaluer la toxicité des microplastiques (MP), et plus récemment des nanoplastiques (NP) vis-à-vis d’organismes aquatiques. Cependant, certains aspects ont été jusqu'à présent peu étudiés. Ainsi, la majorité des études porte sur les effets des particules plastiques dans le milieu marin tandis que les milieux estuariens et d'eau douce sont relativement peu étudiés malgré leur rôle important dans le transfert des plastiques des continents vers l’océan. De plus, le potentiel transfert des MP et des NP dans les chaînes trophiques aquatiques n’est pas encore bien compris et ses mécanismes sous-jacents restent à élucider. Cela nous a conduit à développer une approche multidisciplinaire pour mieux comprendre les effets de MP et de NP, représentatifs de ceux présents dans les estuaires, sur des espèces clés d'une chaîne alimentaire vivant dans le continuum eau douce-eau de mer. La chaîne alimentaire comprend les algues phytoplanctoniques Desmodesmus subspicatus et Tetraselmis suecica (premier niveau trophique), les mollusques bivalves endobenthiques Corbicula fluminea et Scrobicularia plana (deuxième niveau trophique) et l'anguille européenne Anguilla anguilla (troisième niveau trophique). Les impacts des plastiques sur les espèces aquatiques sont évalués à la fois par voie directe et par voie trophique et sont caractérisés à l'aide d'une approche multi-marqueurs allant des effets au niveau individuel (physiologique, comportemental) au niveau sub-individuel (moléculaire, biochimique). Cette présentation portera sur les résultats des expositions des bivalves aux particules plastiques par voie directe et trophique.
(23/11/2021)
BIOSSE, UCO, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, MMS UCO, UCO, UNAM, GR, UR, INSU - CNRS, CNRS
An overview of the Last Glacial Cycle
This introductory chapter succinctly describes the evolution of the European Ice Sheet configuration during the Last Glacial Period, from the end of Marine Isotopic Stage (MIS) 5e to the onset of MIS 1 (116–14.7 cal ka BP), and defines the millennial-scale changes that have punctuated this time period, that is, the Dansgaard–Oeschger cycles and the different episodes of iceberg discharges, including the Heinrich events. A short description of the impact of these millennial-scale changes on European vegetation and climate is also provided as a prelude to the following chapters.
(pp. 165-169, 19/11/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Abrupt (or millennial or suborbital) climatic variability: Heinrich events/stadials
The causes and consequences of the episodic iceberg-discharge events from the Hudson Strait Ice Stream of the Laurentide Ice Sheet, or Heinrich events (HE), are one of the most explored topics in Pleistocene palaeoclimatology. In this chapter, we summarise three decades of intense research while introducing recent results from both the European and Cordilleran Ice Sheets that could call for a paradigm shift in our understanding of the HE.
(pp. 181-187, 19/11/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Abrupt climatic variability: Dansgaard-Oeschger events
This chapter describes the millennial-scale climatic variability in the atmosphere of Greenland during the Last Glacial Cycle (MIS 5e–MIS 1, 116–14.7 cal ka BP), that is, the Dansgaard–Oeschger (D–O) cycles, and the associated global changes in greenhouse gas atmospheric concentrations, particularly CO2 and CH4, and atmospheric circulation (Ca2+ concentration and d-excess). This chapter highlights the contrasting regional impact of the D–O cycles on the North Atlantic Sea surface temperatures and the vegetation and climate across Europe, as well as the synchronicity between changes in Greenland temperature and the hydrological cycle in the tropics and midlatitudes of the Northern Hemisphere. By contrast, the shape and phasing of millennial-scale events between Greenland and Antarctica differ between the two regions. The mechanisms underlying such a variability are still under debate.
(pp. 175-180, 19/11/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Relation between orbital velocities, pressure and surface elevation in non-linear nearshore water waves
The inability of the linear wave dispersion relation to characterize the dispersive properties of non-linear shoaling and breaking waves in the nearshore has long been recognised. Yet, it remains widely used with linear wave theory to convert between sub-surface pressure, wave orbital velocities and the free surface elevation associated with non-linear nearshore waves. Here, we present a non-linear fully dispersive method for reconstructing the free surface elevation from sub-surface hydrodynamic measurements. This reconstruction requires knowledge of the dispersive properties of the wave field through the dominant wavenumbers magnitude κ , representative in an energy-averaged sense of a mixed sea-state composed of both free and forced components. The present approach is effective starting from intermediate water depths - where non-linear interactions between triads intensify - up to the surf zone, where most wave components are forced and travel approximately at the speed of non-dispersive shallow-water waves. In laboratory conditions, where measurements of κ are available, the non-linear fully dispersive method successfully reconstructs sea-surface energy levels at high frequencies in diverse non-linear and dispersive conditions. In the field, we investigate the potential of a reconstruction that uses a Boussinesq approximation of κ , since such measurements are generally lacking. Overall, the proposed approach offers great potential for collecting more accurate measurements under storm conditions, both in terms of sea-surface energy levels at high frequencies and wave-by-wave statistics ( e.g. wave extrema). Through its control on the efficiency of non-linear energy transfers between triads, the spectral bandwidth is shown to greatly influence non-linear effects in the transfer functions between sub-surface hydrodynamics and the sea-surface elevation.
(Journal of Physical Oceanography, n° 0022-3670, 19/11/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IMB, UB, Bordeaux INP, CNRS, LEGI, CNRS, Fédération OSUG, UGA, Grenoble INP, UGA