An assessment of reef coral calcification over the late Cenozoic
Shallow-water reef-building corals have an extensive geological record and many aspects of their evolution, biodiversity, and biogeography are known in great details. In contrast, the adaptive potential and risk of extinction of coral reefs in response to excessive warming and ocean acidification remains largely undocumented. It is well established that anthropogenic CO2 emissions cause global warming and ocean acidification (lowering of pH), which increasingly impede the biomineralization process in many marine calcareous biota. The “light-enhanced” calcification machinery of the shallow-water reef corals is particularly threatened by this development through the combined effect of a lowering of the supersaturation of seawater with CaCO3 (aragonite) and an expulsion of the symbiotic zooxanthellae (bleaching). The bleaching is of prime importance, because it interrupts the supply of DIC and metabolites required for pH upregulation within the calcification fluid. The degree of calcification in scleractinian reef corals may therefore represent a suitable tracer to assess the state of the ocean carbonate system and the photosynthetic performance of the zooxanthellae during past episodes of natural environmental change. This study presents the first comprehensive set of calcification data from corals covering the early Miocene to early Pleistocene interval (20.8 to 1.2 million years, Ma). Various screening procedures ensured that the studied coral skeletons are pristine and suited to yield meaningful stable isotope data (δ¹⁸O, δ¹³C) and calcification records. δ¹⁸O and δ¹³C values document growth environments consistent with current tropical and subtropical settings. To assess fossil calcification rates, we use a reference dataset of recent corals from the Indo-Pacific (Porites) and an independent validation dataset from the Western Atlantic-Caribbean (Orbicella). Almost all fossil corals document very low annual rates of upward growth (“extension rate”) relative to present, and lower skeletal bulk density than predicted by established modern relationships. To allow for a quantitative assessment of coral calcification performance, we use a new approach that we term the calcification anomaly. It is insensitive to sea-surface temperature and well-suited for comparative assessments of calcification performance between reef sites and over time. Based on this approach, the majority of fossil corals in our dataset displays hypo-calcification, while a few show optimal calcification and none display hyper-calcification. Compared to present-day growth conditions, the fossil calcification data show that (1) skeletogenesis responded in a fully compatible way to known environmental stresses (e.g. turbid water, elevated salinity, eutrophy), and that (2) the calcification performance within the reef window (i.e. oligotrophic clear-water settings) remained below that of modern z-corals. Since fossil coral δ¹³C values are compatible with those of modern reef corals, we infer that the light-enhanced calcification system of symbiotic scleractinian corals was fully established by the beginning of the Neogene and that lower-than-present calcification performance was the likely response to a chronically low pH and/or low carbonate saturation state of the global ocean. If so, the present-day saturation state appears to be rather an exception than the norm and probably not a suitable starting point for predicting future calcification trends. In addition, using trends from the geological past does not include anthropogenic side-effects such as eutrophication and pollution.
(Earth-Science Reviews. vol. 204, n° 0012-8252, pp. 103154, 01/05/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, HNHP, MNHN, UPVD, CNRS
Organic contaminants sorbed to microplastics affect marine medaka fish early life stages development
The role of polyethylene microplastics 4-6 mu m size (MPs) in the toxicity of environmental compounds to fish early life stages (ELS) was investigated. Marine medaka Oryzias melastigma embryos and larvae were exposed to suspended MPs spiked with three model contaminants: benzo(a)pyrene (MP-BaP), perfluorooctanesulfonic acid (MP-PFOS) and benzophenone-3 (MP-BP3) for 12 days. There was no evidence of MPs ingestion but MPs agglomerated on the surface of the chorion. Fish ELS exposed to virgin MPs did not show toxic effects. Exposure to MP-PFOS decreased embryonic survival and prevented hatching. Larvae exposed to MP-BaP or MP-BP3 exhibited reduced growth, increased developmental anomalies and abnormal behavior. Compared to equivalent water-borne concentrations, BaP and PFOS appeared to be more embryotoxic when spiked on MPs than when alone in seawater. These results suggest a relevant pollutant transfer by direct contact of MPs to fish ELS that should be included in the ecotoxicological risk assessment of MPs.
(Marine Pollution Bulletin. vol. 154, n° 0025-326X, pp. 111059, 01/05/2020)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LRHLR, HGS, IFREMER, GABI, INRAE, UMR MARBEC, IRD, IFREMER, UM, CNRS
Microplastic Contamination of Sediment and Water Column in the Seine River Estuary
Nowadays, microplastic (MPs) pollution is well documented in marine ecosystems since the first publication alarming about marine plastic pollution in 1972 [Carpenter, E.J., Smith, K.L.: Plastics on the Sargasso sea surface. Science 175, 1240–1241 (1972)]. Similarly, continental contamination is more and more investigated. More recently, interest for estuarine systems is growing. Estuaries are considered as a suspected predominant pathway for microplastic pollution from continent to oceans. The specific conditions of estuaries, like salinity gradient, tides and hydrodynamics, could affect the repartition, settling and transfer of microplastics to marine systems.
(pp. 4-9, 24/04/2020)
LEESU, ENPC, UPEC UP12, GERS-LEE, LERN, COAST, IFREMER, RDT, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Insights on Ecotoxicological Effects of Microplastics in Marine Ecosystems: The EPHEMARE Project
The Ephemare project was supported in the period 2015–2018 by JPI Oceans, as one of 4 sister projects in the joint action on ecological aspects of microplastics. Ephemare investigated several issues concerning the ecotoxicological effects of microplastics (MPs) in marine organisms. Ephemare included 16 European Institutions from 10 Countries and was organized into seven, highly complementary Work Packages (WPs) with the aim to elucidate adsorption and release of chemicals to/from MPs, coupled with MP ingestion rates, translocation in different tissues, trophic transfer and egestion, potential toxicological effects and mechanisms of action, as well as real distributions of MPs in marine organisms from several European areas.
(pp. 12-19, 24/04/2020)
UNIVPM, UAlg, UM, CNRS, IRD, IFREMER, UMR MARBEC, IRD, IFREMER, UM, CNRS, GU, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GABI, INRAE, IAS, CNR, CIIMAR, UiO, UCC
Biological Clocks and Rhythms in Polar Organisms
Biological clocks are universal to all living organisms on Earth. Their ubiquity is testament to their importance to life: from cells to organs and from the simplest cyanobacteria to plants and primates, they are central to orchestrating life on this planet. Biological clocks are usually set by the 'beat' of the day-night cycle, so what happens in polar regions during the Polar Night or Polar Day when there are periods of 24 hours of darkness or light? How would a biological clock function without a time-keeper? This chapter details evidence that biological clocks are central to structuring daily and seasonal activities in organisms at high latitudes. Importantly, despite a strongly reduced or absent day night cycles, biological clocks in the Polar Night still appear to be regulated by background illumination. Here we explore evidence for highly cyclic activity, from behaviour patterns to clock gene expression, in copepods, krill and bivalves. The ultimate goal will be to understand the role of endogenous clocks in driving important daily and seasonal life cycle functions and to determine scope for plasticity in a rapidly changing environment.
(pp. 217-240, 09/04/2020)
CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Environmentally relevant mixture of S-metolachlor and its two metabolites affects thyroid metabolism in zebrafish embryos
(Aquatic Toxicology. vol. 221, n° 0166-445X, pp. 105444, 01/04/2020)
UB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CNRS
Facies associations, detrital clay grain coats and mineralogical characterization of the Gironde estuary tidal bars: A modern analogue for deeply buried estuarine sandstone reservoirs
Estuarine tidal bar sandstones are complex reservoir geobodies commonly exploited by the oil and gas industry. In order to better predict the reservoir potential of these geobodies, this study provides a modern-day reservoir analogue, describing tidal bars in the inner and outer Gironde estuary from the microscopic to the macroscopic scale.The originality of this work lies in the multi-scale study of modern estuarine tidal bars based on numerous piston cores extracted in a high-energy environment. This work demonstrates that these tidal bars are composite sedimentary bodies made up of individual reservoir sand units separated by thick muddy layers. Their vertical facies associations and internal architectures are controlled by local hydrodynamic variations and seasonal river influxes. Detrital clay grain coats are notably characterized using a portable and handheld mineral spectrometer from the base to the top of the tidal bars. X-ray diffraction and electron microscopes reveal that these coats are mainly composed of di-octahedral smectite, illite, chlorite and kaolinite associated with other components such as diatoms or pyrite. The best reservoir geobodies are those with the minimum clay permeability barriers at the macro and mesoscale. An optimum coated grain content and clay fraction volume is also needed for generating authigenic clay coatings and inhibiting quartz overgrowth. These conditions are met within the tidal sand bars of the outer estuary funnel that are expected to be the best reservoir geobodies in deeply buried sandstones.
(Marine and Petroleum Geology. vol. 114, n° 0264-8172, pp. 104225 (IF 3,538), 01/04/2020)
GEOPS, INSU - CNRS, CNRS, EGID, IC2MP [Poitiers], UP, INC-CNRS, CNRS, HydrASA, IC2MP [Poitiers], UP, INC-CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Modeling mud and sand transfers between a macrotidal estuary and the continental shelf: influence of the sediment-transport parameterization
Coastal environments are directly influenced by terrigenous inputs coming from rivers through estuaries. Quantifying the amount of nutrients and contaminants transported by sediments from continental areas to the sea is crucial for marine resources protection. However, the complexity of estuarine dynamics makes it difficult to quantify sediment fluxes from field measurements alone and requires numerical modeling. Thus, using a realistic 3D hydrodynamic and sediment transport model, this study aims at evaluating the influence of model empirical parameters on sediment fluxes and estimating uncertainties on mud and sand transfers at a macrotidal estuary mouth. A sensitivity analysis, considering changes in sediment transport parameters, revealed that the system is not only sensitive to settling and erosion parameterizations, but also to the spin‐up period and the sediment sliding process. Both estuarine circulation and tidal pumping induce a residual up‐estuary transport, which is balanced by seaward export during spring tides. Although more fine sediments are exported within the surface turbid plume during high river discharge, the net mud transport is directed up‐estuary due to increased baroclinic circulation. Besides, model results highlighted a strong seasonal variability in sediment fluxes with a short and high import during high river flow and a long and weak export during low river flow. Uncertainties associated with the simulated fluxes were about 93% for mud and 51% for non‐cohesive classes, based on the best performing parameter sets for surface suspended sediment concentrations. These results can be reliably extrapolated to similar macrotidal estuarine systems.Plain language summaryEstuaries are transitional zones between terrestrial and marine environments (freshwater vs saltwater). Because of their potential to transport nutrients and contaminants, quantifying the amount of sediment particles (mud and sand) exchanged at this interfacial area is essential for marine resources protection. Here, we use a realistic numerical model of sediment transport applied to an estuary and its adjacent continental shelf. Some parameters in the model are not well‐known and require calibration. This study aims at evaluating the impact of various model calibrations on simulated sediment exchanges at the estuary mouth. We found that the simulated sediment behavior is very sensitive to the selected model parameters. The quantity and direction of simulated exchanges are influenced by the parameterization of sediment erosion and settling (i.e. the rate at which particles are suspended and settle out). The dominant physical processes driving these exchanges are strongly influenced by river flow and tide amplitude. Sediment transfers are very intense and directed upstream during a short period in winter and compensated by weak export seaward during a long period in summer. Besides, uncertainties associated with simulated sediment exchanges are about 93% for mud and 51% for sands, which can reliably be applied to similar estuarine systems.
(Journal of Geophysical Research. Oceans. vol. 125, n° 2169-9275, pp. e2019JC015643 (37p.), 01/04/2020)
DYNECO, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Experimental ingestion of fluorescent microplastics by pacific oysters, Crassostrea gigas, and their effects on the behaviour and development at early stages
(Chemosphere, n° 0045-6535, pp. 126793, 01/04/2020)
LIENSs, INSU - CNRS, ULR, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Controls of local geology and cross-shore/longshore processes on embayed beach shoreline variability
10 Shoreline variability along the 3.6-km long Narrabeen Beach embayment in SE Australia is 11 investigated over a 5-year period. We apply the one-line shoreline change model LX-Shore, 12 which couples longshore and cross-shore processes and can handle complex shoreline 13 planforms, non-erodible emerged headlands and submerged rocky features. The model 14 skilfully reproduces the three dominant modes of shoreline variability, which are by 15 decreasing order of variance: cross-shore migration, rotation, and a third mode possibly 16 related to breathing. Model results confirm previous observations that longshore processes 17 primarily contribute to the rotation and third modes on the timescales of months to seasons, 18 while cross-shore processes control the shoreline migration on shorter timescales from hours 19 (storms) to months. Additional simulations simplifying progressively the bathymetry show 20 how the inherent geology strongly modulates the spatial modes of shoreline variability. The 21 offshore central rocky outcrop is found to limit the rotation. In contrast, the submerged rocky 22 platforms that extend from the headlands enhance the shoreline rotation mode and increase 23 alongshore variability of the cross-shore migration mode, owing to increased alongshore 24 variability in wave exposure. Offshore wave transformation across large-scale submerged 25 rocky features and headland shape are therefore critical to contemporary shoreline dynamics. 26 2
(Marine Geology. vol. 422, n° 0025-3227, pp. 106118, 01/04/2020)
MEDyC, URCA, URCA, CNRS, BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS