Living (stained) benthic foraminifera from the Mozambique Channel (eastern Africa): Exploring ecology of deep-sea unicellular meiofauna
Live (Rose-Bengal stained) deep-sea foraminiferal faunas have been studied at four stations between 530–3200-m depth in the Mozambique Channel (eastern Africa) to understand how complex environmental conditions (e.g., organic matter, oxygenation) control their ecological structure (i.e., diversity, density, and microhabitats). Two upper-slope stations, located at 530- and 780-m depth off Madagascar, are bathed by well-oxygenated bottom waters. They are characterized by fine sediments enriched in highly degraded organic matter (low amino-acid bio-availability and reduced chlorophyllic freshness). Mineralization of organic compounds results in relatively moderate oxygen penetration depth (i.e., 15 and 30 mm) in sediment. Interestingly, foraminiferal species richness (S) is exceptionally high at both sites. The highest densities are observed in the 780-m deep station, where peculiar sedimentary facies of organic matter are recorded (OC >2.0% DW). Redox conditions and sedimentary organic matter control the composition and the vertical distribution (i.e. microhabitat) of benthic faunas at both upper-slope sites. Bolivina alata, Bulimina marginata, Haplophragmoides bradyi and Nouria compressa are relevant bio-indicators of enhanced burial of organic matter prevailing at the 780-m deep station (i.e., eutrophic conditions), whereas Uvigerina hispida and Uvigerina semiornata are dominant at the 530-m deep station (i.e., relatively mesotrophic conditions). Two other stations are located on well-ventilated terraces from the deep-sea canyons of Tsiribihina and Zambezi (>3000-m depth). They are characterized by carbonate ooze, which is depleted in degraded organic matter and, where oxygen penetration depth is relatively deep (i.e., > 80 mm). Because of food scarcity, S and densities are relatively low, and agglutinated and organic-walled taxa dominate foraminiferal faunas. Hospitella fulva, a foraminiferal species belonging to Allogromiida, occupies very deep infaunal microhabitat, what disrupts the classical scheme of microhabitat patterns in oligotrophic settings.
(Deep Sea Research Part I: Oceanographic Research Papers. vol. 115, n° 0967-0637, pp. 159-174, 01/09/2016)
GM, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEP, EEP, IFREMER
Loss of connectivity among island-dwelling Peary caribou following sea ice decline
Global warming threatens to reduce population connectivity for terrestrial wildlife through significant and rapid changes to sea ice. Using genetic fingerprinting, we contrasted extant connectivity in island-dwelling Peary caribou in northern Canada with continental-migratory caribou. We next examined if sea-ice contractions in the last decades modulated population connectivity and explored the possible impact of future climate change on long-term connectivity among island caribou. We found a strong correlation between genetic and geodesic distances for both continental and Peary caribou, even after accounting for the possible effect of sea surface. Sea ice has thus been an effective corridor for Peary caribou, promoting inter-island connectivity and population mixing. Using a time series of remote sensing sea-ice data, we show that landscape resistance in the Canadian Arctic Archipelago has increased by approximately 15% since 1979 and may further increase by 20–77% by 2086 under a high-emission scenario (RCP8.5). Under the persistent increase in greenhouse gas concentrations, reduced connectivity may isolate island-dwelling caribou with potentially significant consequences for population viability.
(Biology Letters. vol. 12, n° 1744-9561, pp. 20160235, 01/09/2016)
DMI, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CEN, ULaval, UNIFR, LECA, USMB [Université de Savoie] [Université de Chambéry], CNRS, UGA [2016-2019]
Assessing the toxicity of sediments using the medaka embryo-larval assay and 2 other bioassays
Sediments are sinks for aquatic pollutants, and analyzing toxicity in such complex matrices is still challenging. To evaluate the toxicity of bioavailable pollutants accumulated in sediments from the Bizerte lagoon (Tunisia), a novel assay, the medaka embryo–larval assay by sediment contact, was applied. Japanese medaka (Oryzias latipes) embryos were incubated in direct contact with sediment samples up to hatching. Lethal and sublethal adverse effects were recorded in embryos and larvae up to 20 d postfertilization. Results from medaka embryo–larval assay were compared with cytotoxicity (Microtox®), genotoxicity (SOS chromotest), and pollutant content of sediments. The results highlight differences in the contamination profile and toxicity pattern between the different studied sediments. A significant correlation was shown between medaka embryo–larval assay by sediment contact and SOS chromotest responses and concentrations of most organic pollutants studied. No correlation was shown between pollutant levels and Microtox. According to the number of sediment samples detected as toxic, medaka embryo–larval assay by sediment contact was more sensitive than Microtox, which in turn was more sensitive than the SOS chromotest; and medaka embryo–larval assay by sediment contact allowed sediment toxicity assessment of moderately polluted sediments without pollutant extraction and using an ecologically realistic exposure scenario. Although medaka embryo–larval assay by sediment contact should be tested on a larger sample set, the results show that it is sensitive and convenient enough to monitor the toxicity of natural sediments.
(Environmental Toxicology and Chemistry. vol. 35, n° 0730-7268, pp. 2270-2280, 01/09/2016)
UCAR, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Dynamics of the Upogebia pusilla–Gyge branchialis marine host–parasite system
The influence of burrowing invertebrates on the functioning of soft-bottom ecosystems is tightly dependent on their physiological state, which may itself be strongly affected by parasite infestation. However, the dynamics, prevalence and physiological consequences of parasitism remain poorly known in many species, such as sediment-dwelling crustaceans. During the present study, we investigated the effects of the ectoparasite (bopyrid) isopod Gyge branchialis on the fitness of the gebiidean mud shrimp Upogebia pusilla. A spatial survey conducted in June 2013 at 10 stations scattered across intertidal seagrass meadows of Arcachon Bay (44°40′N, 1°10′W) showed that on average 16 % of mud shrimp were infested by G. branchialis. Moreover, a temporal survey carried out at one of these stations over the year 2014 revealed that prevalence remained relatively high throughout the year, ranging from 10 to 33 %. This interaction has various physiological consequences for U. pusilla. In particular, infested mud shrimp consistently exhibited a significant deficit in total length and individual dry weight as compared with non-infested specimens. Moreover, 89 % of infested males were feminized (i.e., developed female secondary sexual characters), whereas infested females were never ovigerous. Our results demonstrate that G. branchialis strongly impair U. pusilla fitness including its ability to reproduce. Accordingly, through their (1) potential impact on mud shrimp abundances and (2) alteration of their physiological state, high bopyrid infestation could profoundly alter the bioturbation activity of mud shrimp populations and overall their influence on the functioning of soft-bottom ecosystems in Arcachon Bay.
(Marine Biology. vol. 163, n° 0025-3162, 30/08/2016)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Can host density attenuate parasitism?
Bivalve populations display fluctuating densities resulting in different interactions among them and with their environment. Using the edible cockle (Cerastoderma edule) as a model, we investigated two alternative hypotheses concerning the effect of density on individual infection intensity by trematode parasites. Considering that these parasites infect cockles through filtration activity, our first hypothesis was that high host density will have a dilution effect so that infection intensity decreases with host density. Conversely, high cockle density could attract other hosts used by these trematode parasites to complete their life cycle. A 17-year monthly survey of a cockle population in Arcachon Bay, France, showed a negative correlation between the cockle density and the abundance of parasite larvae in juvenile cockles with a significant threshold when adult cockle density reached 400 ind. m−2. This result was confirmed for the four dominating trematode parasites, independently considered. Additionally, a field experiment was performed during 9 months, with cockles maintained in enclosures with two densities (200 and 800 ind. m−2). Individual cockle mean infection was 1.5 times higher at low cockle density, mainly due to one dominant trematode species (Parvatrema minutum). In conclusion and confirming the first advanced hypothesis, for certain environments, negative consequences of bivalve intraspecific competition at high density can be mitigated by lower parasite pressure.
(Journal of the Marine Biological Association of the United Kingdom. vol. 97, n° 0025-3154, pp. 497-505, 16/08/2016)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Permafrost carbon as a missing link to explain CO2 changes during the last deglaciation
The atmospheric concentration of CO2 increased from 190 to 280 ppm between the last glacial maximum 21,000 years ago and the pre-industrial era1, 2. This CO2 rise and its timing have been linked to changes in the Earth’s orbit, ice sheet configuration and volume, and ocean carbon storage2, 3. The ice-core record of δ13CO2 (refs 2,4) in the atmosphere can help to constrain the source of carbon, but previous modelling studies have failed to capture the evolution of δ13CO2 over this period5. Here we show that simulations of the last deglaciation that include a permafrost carbon component can reproduce the ice core records between 21,000 and 10,000 years ago. We suggest that thawing permafrost, due to increasing summer insolation in the northern hemisphere, is the main source of CO2 rise between 17,500 and 15,000 years ago, a period sometimes referred to as the Mystery Interval6. Together with a fresh water release into the North Atlantic, much of the CO2 variability associated with the Bølling-Allerod/Younger Dryas period ~15,000 to ~12,000 years ago can also be explained. In simulations of future warming we find that the permafrost carbon feedback increases global mean temperature by 10–40% relative to simulations without this feedback, with the magnitude of the increase dependent on the evolution of anthropogenic carbon emissions.
(Nature Geoscience. vol. 9, n° 1752-0894, pp. 683–686, 01/08/2016)
UGA [2016-2019], LGGE, INSU - CNRS, CNRS, OSUG, Grenoble INP, INSU - CNRS, IRSTEA, USMB [Université de Savoie] [Université de Chambéry], CNRS, UGA [2016-2019], EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, CLIM, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, VU
The French initiative for scientific cores virtual curating : a user-oriented integrated approach
Managing scientific data is a crucial issue for modern science. This concerns particularly the conservation of high value geological samples: cores. International scientific programs are leading an intense effort to solve this problem and propose detailed high standard work- and dataflows including core handling and curating. However, there is currently no consensual standard for sample and associated metadata management. The national excellence equipment program CLIMCOR aims at developing French facilities for scientific coring (ice, marine and continental). As part of it, we led a reflexion about cores and associated metada curating. Our aim is to conserve all metadata from fieldwork in an integrated cyber-environment which could evolve toward laboratory-acquired data storage. In that aim, our demarche was conducted through a close relationship with field operators and core curators, in order to propose user-oriented solutions.The national core curating initiative currently proposes a single web portal to store field data. For forthcoming samples, we propose a mobile application to capture technical and scientific metadata on the field or in cruise. This application is linked with a unique coring tools library and is adapted to most coring devices, including multiple sections and holes coring operations.Those field data can be uploaded automatically to the national portal, but also referenced through international standards or persistent identifiers (IGSN - SESAR, ORCID) and INSPIRE schema and displayed in international portals (currently, NOAA IMLGS).In this paper, we present the architecture of the integrated system, future perspectives and the approach we adopted to reach our goals.(1) http://climcor-equipex.dt.insu.cnrs.fr/?lang=en
(01/08/2016)
EDYTEM, USMB [Université de Savoie] [Université de Chambéry], CNRS, Fédération OSUG, DTI, INSU - CNRS, CNRS, ISTerre, IFSTTAR, INSU - CNRS, USMB [Université de Savoie] [Université de Chambéry], CNRS, UGA [2016-2019], EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LGGE, INSU - CNRS, CNRS, OSUG, Grenoble INP, INSU - CNRS, IRSTEA, USMB [Université de Savoie] [Université de Chambéry], CNRS, UGA [2016-2019], EMBS, iSTeP, UPMC, CNRS, IRSI, IFREMER, INSU - CNRS
Combined effects of temperature changes and metal contamination at different levels of biological organization in yellow perch
(Aquatic Toxicology. vol. 177, n° 0166-445X, pp. 324-332, 01/08/2016)
UB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, INRS, LECA, USMB [Université de Savoie] [Université de Chambéry], CNRS, UGA [2016-2019], INRS - ETE, INRS, IBIS, ULaval
Sedimentary processes determining the modern carbonate periplatform drift of Little Bahama Bank
This paper presents an analysis of the combined influence of along-slope sediment transport and off-bank sediment export from the Little Bahama Bank (LBB) to the periplatform sediment wedge of the northwestern part of the slope over the last 424 ka. The LBB northwestern slope is divided in (i) a plateau-like structure (margin) at similar to 40 m water depth over at least 4 km parallel to the edge of the LBB; (ii) the uppermost slope with a mean slope angle of similar to 1.15 degrees from 40 to 300 m water depth; (iii) the upper, slope with slope angle of similar to 0.7 from 300 to 650 m water depth, (iv) the middle slope with slope angle of similar to 1.2, from 650 to 800 m water depth, and (v) the lower slope with slope angle of -6 m) that occurred during interglacial periods, the highest sedimentation rates (10-30 cm/ka) and the finest sediment fades were found on the slope. During interglacial periods when RSL < -6 m, LBB was emerged but bank margins were still flooded and correspond to intermediate sedimentation rates (a few to 10 cm/ka) on the slope. Finally, during glacial periods (RSL < -90 m), LBB was emerged (including its margins), sedimentation rates on the slope dropped to a few mm/ka associated to coarser sediment facies. Off-bank-transported sediment is the main sediment supply during sea-level highstands, occurring preferentially during three major periods of LBB flooding over the last 424 ka: marine isotopic stages 1, 5e and 11. During sea level lowstands, shallow carbonate production was very low but could develop over a 4 km-wide plateau-like structure when RSL was above -40 m. The regional Antilles Current affected the sea floor along the northwestern LBB slope and influenced coral mound distribution as well as sediment facies and sequences along the upper and middle slopes (300-800 m). During glacial periods, the stronger influence of the Antilles Current upon the along-slope sedimentation promoted diagenesis via the development of indurated nodules in the upper slope (similar to 400 m water depth). It also encouraged bi-gradational sequences showing a coarsening-up unit followed by a fining-up unit along the middle slope (similar to 800 m water depth) that is thoroughly bioturbated. The characteristics of these contourite sequences were similar to those described in siliciclastic environments, but in contrast were condensed with low sedimentation rates over long (glacial) periods. (C) 2015 Elsevier B.V. All rights reserved.
(Marine Geology. vol. 378, n° 0025-3227, pp. 213-229, 01/08/2016)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, KFUPM, CEREGE, IRD, INRA, AMU, CdF (institution), INSU - CNRS, CNRS, [Total Energies. Anciennement : Total, TotalFina, TotalFinaElf]
Effects of disc asymmetries on astrometric measurements
(Astronomy & Astrophysics - A&A. vol. 592, n° 0004-6361, pp. A39, 01/08/2016)
LESIA (UMR_8109), INSU - CNRS, CNRS, PSL, UPD7, SU, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LUTH (UMR_8102), INSU - CNRS, CNRS, PSL, UPD7, CNRS, SYRTE, INSU - CNRS, CNRS, PSL, SU, CNRS