Éditeur(s) : HAL CCSD Royal Society, The
Résumé : There is broad consensus that the diversity of functional traits within species assemblages drives several ecological processes. It is also widely recognized that rare species are the first to become extinct following human-induced disturbances. Surprisingly, however, the functional importance of rare species is still poorly understood, particularly in tropical species-rich assemblages where the majority of species are rare, and the rate of species extinction can be high. Here, we investigated the consequences of local and regional extinctions on the functional structure of species assemblages. We used three extensive datasets (stream fish from the Brazilian Amazon, rainforest trees from French Guiana, and birds from the Australian Wet Tropics) and built an integrative measure of species rarity versus commonness, combining local abundance, geographical range, and habitat breadth. Using different scenarios of species loss, we found a disproportionate impact of rare species extinction for the three groups, with significant reductions in levels of functional richness, specialization, and originality of assemblages, which may severely undermine the integrity of ecological processes. The whole breadth of functional abilities within species assemblages, which is disproportionately supported by rare species, is certainly critical in maintaining ecosystems particularly under the ongoing rapid environmental transitions.
ISSN: 0962-8452

hal-01532639
https://hal.archives-ouvertes.fr/hal-01532639
DOI : 10.1098/rspb.2016.0084
PRODINRA : 384617

Éditeur(s) : HAL CCSD European Geosciences Union
Résumé : International audience
The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is < 2000 mm yr(-1) (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall < 2000 mm yr(-1).
ISSN: 1726-4170

hal-01557759
https://hal.univ-lorraine.fr/hal-01557759
https://hal.univ-lorraine.fr/hal-01557759/document
https://hal.univ-lorraine.fr/hal-01557759/file/bg-13-2537-2016.pdf
DOI : 10.5194/bg-13-2537-2016

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Although coral reefs support the largest concentrations of marine biodiversity worldwide, the extent to which the global system of marine-protected areas (MPAs) represents individual species and the breadth of evolutionary history across the Tree of Life has never been quantified. Here we show that only 5.7% of scleractinian coral species and 21.7% of labrid fish species reach the minimum protection target of 10% of their geographic ranges within MPAs. We also estimate that the current global MPA system secures only 1.7% of the Tree of Life for corals, and 17.6% for fishes. Regionally, the Atlantic and Eastern Pacific show the greatest deficit of protection for corals while for fishes this deficit is located primarily in the Western Indian Ocean and in the Central Pacific. Our results call for a global coordinated expansion of current conservation efforts to fully secure the Tree of Life on coral reefs.
ISSN: 2041-1723

hal-01282920
https://hal-univ-perp.archives-ouvertes.fr/hal-01282920
https://hal-univ-perp.archives-ouvertes.fr/hal-01282920/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01282920/file/ncomms10359.pdf
DOI : 10.1038/ncomms10359

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Biofouling increases the operational and economic costs associated with pearl production. As currentprocedures for reducing oyster biofouling can be detrimental to survival and growth and may pollute thesurrounding environment developing alternative, biologically-mediated, methods could potentially in-crease both production and ecological sustainability. With this in mind, the present study investigatednatural cleaning of black-lipped pearl oysters, Pinctada margaritifera, by butterflyfishes (Chaetodon). Thefeeding behaviour of six butterflyfish species was examined at Rangiroa Atoll, French Polynesia: Chae-todon auriga, Chaetodon citrinellus, Chaetodon ephippium, Chaetodon lunulatus, Chaetodon trifascialis andChaetodon ulietensis. All species cleaned the surface of pearl oysters by removing epibionts (from 16% to40% of total biomass), although dietary variation may explain different cleaning efficiencies. Generalistomnivores (C. auriga, C. citrinellus, C. ephippium and C. ulietensis) were the most efficient cleaners (%cleaning range: 26e40% of total biomass). Within this group, C. ephippium removed the most biomass(average of 41%) targeting algae and anemones. However, C. auriga targeted the most diverse range ofepibionts, removing significant amounts of algae, sponges, tunicates, and anemones. These resultssuggest that foraging by butterflyfishes can substantially reduce biofouling on economically-importanttropical bivalves.
ISSN: 0272-7714

hal-01434152
https://hal-univ-perp.archives-ouvertes.fr/hal-01434152
DOI : 10.1016/j.ecss.2016.04.001

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The nucleation and growth processes of spherulitic alkali feldspar have been investigated in this study through X-ray microtomography and electron backscatter diffraction (EBSD) data. Here we present the first data on Shape Preferred Orientation (SPO) and Crystal Preferred Orientation (CPO) of alkali feldspar within spherulites. The analysis of synchrotron X-ray microtomography and EBSD datasets allowed us to study the morphometric characteristics of spherulites in trachytic melts in quantitative fashion, highlighting the three-dimensional shape, preferred orientation, branching of lamellae and crystal twinning, providing insights about the nucleation mechanism involved in the crystallization of the spherulites. The nucleation starts with a heterogeneous nucleus (pre-existing crystal or bubble) and subsequently it evolves forming “bow tie” morphologies, reaching radially spherulitic shapes in few hours. Since each lamella within spherulite is also twinned, these synthetic spherulites cannot be considered as single nuclei but crystal aggregates originated by heterogeneous nucleation. A twin boundary may have a lower energy than general crystal–crystal boundaries and many of the twinned grains show evidence of strong local bending which, combined with twin plane, creates local sites for heterogeneous nucleation.This study shows that the growth rates of the lamellae (10− 6–10− 7 cm/s) in spherulites are either similar or slightly higher than that for single crystals by up to one order of magnitude. Furthermore, the highest volumetric growth rates (10− 11–10− 12 cm3/s) show that the alkali feldspar within spherulites can grow fast reaching a volumetric size of ~ 10 μm3 in 1 s.
ISSN: 0024-4937

hal-01172356
https://hal.archives-ouvertes.fr/hal-01172356
DOI : 10.1016/j.lithos.2014.12.003

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Low-level exposure to polychlorinated biphenyl-153 (PCB-153) and dichlorodiphenyldichloroethylene (p-p'-DDE) can impair fetal growth; however, the exposure-response relationship and effect modifiers of such association are not well established. This study is an extension of an earlier European meta-analysis. Our aim was to explore exposure-response relationship between PCB-153 and p-p'-DDE and birth outcomes; to evaluate whether any no exposure-effect level and susceptible subgroups exist; and to assess the role of maternal gestational weight gain (GWG). We used a pooled dataset of 9377 mother-child pairs enrolled in 14 study populations from 11 European birth cohorts. General additive models were used to evaluate the shape of the relationships between organochlorine compounds and birth outcomes. We observed an inverse linear exposure-response relationship between prenatal exposure to PCB-153 and birth weight [decline of 194g (95% CI -314, -74) per 1μg/L increase in PCB-153]. We showed effects on birth weight over the entire exposure range, including at low levels. This reduction seems to be stronger among children of mothers who were non-Caucasian or had smoked during pregnancy. The most susceptible subgroup was girls whose mothers smoked during pregnancy. After adjusting for absolute GWG or estimated fat mass, a reduction in birth weight was still observed. This study suggests that the association between low-level exposure to PCB-153 and birth weight exists and follows an inverse linear exposure-response relationship with effects even at low levels, and that maternal smoking and ethnicity modify this association.
ISSN: 0160-4120

hal-01118572
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01118572
PUBMED : 25314142
DOI : 10.1016/j.envint.2014.09.013

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
As climate change continues to impact socio-ecological systems, tools that assist conservation managers to understand vulnerability and target adaptations are essential. Quantitative assessments of vulnerability are rare because available frameworks are complex and lack guidance for dealing with data limitations and integrating across scales and disciplines. This paper describes a semi-quantitative method for assessing vulnerability to climate change that integrates socio-ecological factors to address management objectives and support decision-making. The method applies a framework first adopted by the Intergovernmental Panel on Climate Change and uses a structured 10-step process. The scores for each framework element are normalized and multiplied to produce a vulnerability score and then the assessed components are ranked from high to low vulnerability. Sensitivity analyses determine which indicators most influence the analysis and the resultant decision-making process so data quality for these indicators can be reviewed to increase robustness. Prioritisation of components for conservation considers other economic, social and cultural values with vulnerability rankings to target actions that reduce vulnerability to climate change by decreasing exposure or sensitivity and/or increasing adaptive capacity. This framework provides practical decision-support and has been applied to marine ecosystems and fisheries, with two case applications provided as examples: (1) food security in Pacific Island nations under climate-driven fish declines, and (2) fisheries in the Gulf of Carpentaria, northern Australia. The step-wise process outlined here is broadly applicable and can be undertaken with minimal resources using existing data, thereby having great potential to inform adaptive natural resource management in diverse locations.
ISSN: 0308-597X

hal-01380403
https://hal-univ-perp.archives-ouvertes.fr/hal-01380403
DOI : 10.1016/j.marpol.2016.09.024

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Background : Biological communities are normally composed of a few abundant and many rare species. This pattern is particularly prominent in microbial communities, in which most constituent taxa are usually extremely rare. Although abundant and rare subcommunities may present intrinsic characteristics that could be crucial for understanding community dynamics and ecosystem functioning, microbiologists normally do not differentiate between them. Here, we investigate abundant and rare subcommunities of marine microbial eukaryotes, a crucial group of organisms that remains among the least-explored biodiversity components of the biosphere. We surveyed surface waters of six separate coastal locations in Europe, independently considering the picoplankton, nanoplankton, and microplankton/mesoplankton organismal size fractions.Results : Deep Illumina sequencing of the 18S rRNA indicated that the abundant regional community was mostly structured by organismal size fraction, whereas the rare regional community was mainly structured by geographic origin. However, some abundant and rare taxa presented similar biogeography, pointing to spatiotemporal structure in the rare microeukaryote biosphere. Abundant and rare subcommunities presented regular proportions across samples, indicating similar species-abundance distributions despite taxonomic compositional variation. Several taxa were abundant in one location and rare in other locations, suggesting large oscillations in abundance. The substantial amount of metabolically active lineages found in the rare biosphere suggests that this subcommunity constitutes a diversity reservoir that can respond rapidly to environmental change.Conclusions : We propose that marine planktonic microeukaryote assemblages incorporate dynamic and metabolically active abundant and rare subcommunities, with contrasting structuring patterns but fairly regular proportions, across space and time.
ISSN: 0960-9822

hal-01149637
http://hal.upmc.fr/hal-01149637
http://hal.upmc.fr/hal-01149637/document
http://hal.upmc.fr/hal-01149637/file/Logares_et_al_CurrentBiol_accepted.pdf
DOI : 10.1016/j.cub.2014.02.050

Éditeur(s) : HAL CCSD Ecological Society of America
Résumé : Reliable assessment of fish origin is of critical importance for exploited species, since nursery areas must be identified and protected to maintain recruitment to the adult stock. During the last two decades, otolith chemical signatures (or "fingerprints") have been increasingly used as tools to discriminate between coastal habitats. However, correct assessment of fish origin from otolith fingerprints depends on various environmental and methodological parameters, including the choice of the statistical method used to assign fish to unknown origin. Among the available methods of classification, Linear Discriminant Analysis (LDA) is the most frequently used, although it assumes data are multivariate normal with homogeneous within-group dispersions, conditions that are not always met by otolith chemical data, even after transformation. Other less constrained classification methods are available, but there is a current lack of comparative analysis in applications to otolith microchemistry. Here, we assessed stock identification accuracy for four classification methods (LDA, Quadratic Discriminant Analysis [QDA], Random Forests [RF], and Artificial Neural Networks [ANN]), through the use of three distinct data sets. In each case, all possible combinations of chemical elements were examined to identify the elements to be used for optimal accuracy in fish assignment to their actual origin. Our study shows that accuracy differs according to the model and the number of elements considered. Best combinations did not include all the elements measured, and it was not possible to define an ad hoc multielement combination for accurate site discrimination. Among all the models tested, RF and ANN performed best, especially for complex data sets (e. g., with numerous fish species and/or chemical elements involved). However, for these data, RF was less time-consuming and more interpretable than ANN, and far more efficient and less demanding in terms of assumptions than LDA or QDA. Therefore, when LDA and QDA assumptions cannot be reached, the use of machine learning methods, such as RF, should be preferred for stock assessment and nursery identification based on otolith microchemistry, especially when data set include multispecific otolith signatures and/or many chemical elements.
ISSN: 1051-0761

hal-00644549
https://hal.archives-ouvertes.fr/hal-00644549
DOI : 10.1890/09-1887.1

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Seabirds concentrate nutrients from large marine areas on their nesting islands playing an important ecological role in nutrient transfer between marine and terrestrial ecosystems. Here we investigate the role of guano on corals reefs across scales by analyzing the stable nitrogen isotopic (delta N-15) values of the scleractinian coral Pocillopora damicornis on fringing reefs around two Pacific remote islets with large seabird colonies. Marine stations closest to the seabird colonies had higher nitrate + nitrite concentrations compared to more distant stations. Coral and zooxanthellae delta N-15 values were also higher at these sites, suggesting that guano-derived nitrogen is assimilated into corals and contributes to their nitrogen requirements. The spatial extent of guano influence was however restricted to a local scale. Our results demonstrate that seabird-derived nutrients not only spread across the terrestrial ecosystem, but also affect components of the adjacent marine ecosystem. Further studies are now needed to assess if this nutrient input has a positive or negative effect for corals. Such studies on remote islets also open fresh perspectives to understand how nutrients affect coral reefs isolated from other anthropogenic stressors.
ISSN: 2045-2322

hal-01681575
https://hal.archives-ouvertes.fr/hal-01681575
DOI : 10.1038/s41598-017-03781-y

Éditeur(s) : Pergamon-elsevier Science Ltd
Résumé : In the present work, a biophysical dispersal model is used to understand the role of the physical environment in determining reef fish larval dispersal patterns in the South-West Lagoon of New Caledonia. We focus on a reef fish species, the humbug damselfish Dascyllus aruanus, to investigate seasonal variability of simulated larval retention at the scale of a reef patch and at the scale of the lagoon, and to explore links between larval retention and wind variability. The model shows that retention exhibits considerable temporal variability and periodically reaches values much larger than anticipated. Non-zero larval settlement occurs over a large part of the lagoon. Nevertheless, settlement values decrease quickly away from the natal reef and mean dispersal distances are of order 25-35 km. Cross-correlation analyses indicate that weather conditions characterized by strong south east trade winds lead to low retention rates at both local (reef) and regional (lagoon) scales. By contrast, subtropical weather conditions characterized by weak winds result in high retention rates. These results suggest that large-scale weather regimes can be used as proxies for larval retention of the humbug damselfish in the South-West Lagoon of New Caledonia. Nevertheless, relatively small mean dispersal distances suggest that meta-population dynamics occur on relatively small spatial scales.
Progress In Oceanography (0079-6611) (Pergamon-elsevier Science Ltd), 2014-03 , Vol. 122 , P. 105-115

Droits : 2013 Elsevier Ltd. All rights reserved.
http://archimer.ifremer.fr/doc/00170/28115/26326.pdf
DOI:10.1016/j.pocean.2013.12.006
http://archimer.ifremer.fr/doc/00170/28115/

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Different marine habitats are characterised by different soundscapes. How or which differences may be representative of the habitat characteristics and/or community structure remains however to be explored. A growing project in passive acoustics is to find a way to use soundscapes to have information on the habitat and on its changes. In this study we have successfully tested the potential of two acoustic indices, i.e. the average sound pressure level and the acoustic complexity index based on the frequency spectrum. Inside and outside marine protected areas of Moorea Island (French Polynesia), sound pressure level was positively correlated with the characteristics of the substratum and acoustic complexity was positively correlated with fish diversity. It clearly shows soundscape can be used to evaluate the acoustic features of marine protected areas, which presented a significantly higher ambient sound pressure level and were more acoustically complex than non-protected areas. This study further emphasizes the importance of acoustics as a tool in the monitoring of marine environments and in the elaboration and management of future conservation plans. Coral reef ecosystems are among the most biologically diverse and complex marine ecosystems worldwide. In addition to their biological and ecological importance, coral reefs support major economic and physical functions (e.g. food production, tourism, biotechnology development and coastal protection) that are essential for many countries 1. Unfortunately, coral reefs are severely threatened: 20% of coral reefs can no longer be defined as such, another 25% are currently endangered and another 25% will be endangered by 2050 2. The frequency and severity of natural perturbations (e.g. cyclone, outbreaks of predators, particularly the crown-of-thorns starfish [COTS] Acanthaster planci) and anthropogenic perturbations (e.g. ocean acidification, pesticides, rising seawater temperatures) on coral reefs have greatly increased worldwide in the last three decades, and, as a consequence, reef communities (fish, coral and benthic invertebrates) have suffered unprecedented levels of decline 3,4
ISSN: 2045-2322

hal-01370610
https://hal-uvsq.archives-ouvertes.fr/hal-01370610
https://hal-uvsq.archives-ouvertes.fr/hal-01370610/document
https://hal-uvsq.archives-ouvertes.fr/hal-01370610/file/2016%20Sci.Rep.pdf
DOI : 10.1038/srep33326

Éditeur(s) : EDP Sciences
Résumé : The present paper aims at identifying and assessing indicators of the effects of Marine Protected Areas (MPAs) in coral reef regions, based on a bibliography review in ecology, economics and social sciences. First the various effects Studied within each of these domains and the variables used to measure them were censused. Potential ecological indicators were assessed through their link with the question used (here termed "relevance") and their "effectiveness" which encompasses the issues of precision, accuracy and statistical power. Relevance and effectiveness were respectively measured by the frequency of use of each indicator and the proportion of significant results in the reviewed articles. For social and economic effects, the approach was not possible due to the low number of references: we thus discussed the issue of finding appropriate indicators for those fields. Results indicate: 1- the unbalance in literature between disciplines: 2- the need for protocols and methodologies which include controls in order to assess MPA effects: 3- an important proportion of ecological indicators with low effectiveness: 4- the large number of ecological effects still not studied or not demonstrated at present.
Cet article vise à identifier des indicateurs de l'effet des aires marines protégées (AMP) en milieu corallien, sur la base d'une synthèse bibliographique dans les domaines écologiques, économiques et sociaux, et principalement en milieu corallien. Nous recensons d'abord les différents effets attendus des AMP pour chacun des domaines, et les variables retenues pour les étudier. Les indicateurs écologiques potentiels sont évalués au travers de leur lien avec l'effet étudié (ici appelé "pertinence") et de leur "efficacité" qui regroupe les notions de précision, justesse et puissance statistique. Pertinence et efficacité sont respectivement mesurées par la fréquence d'utilisation et la proportion de résultats significatifs trouvés dans les articles recensés. Pour les aspects économiques et sociaux, le faible nombre de références ne permet pas une approche comparable à celle utilisée pour les indicateurs écologiques, et nous discutons donc de la question de l'identification d'indicateurs, et suggérons quelques pistes de recherche. Les principales conclusions de ce travail sont: i) le décalage entre les nombres de publications entre disciplines; ii) la nécessité de protocoles et méthodologies incluant des situations de contrôle pour évaluer les effets des MPA; iii) la faible efficacité de nombreux indicateurs écologiques; et iv) le nombre élevé d'effets peu ou pas étudiés ou démontrés à l'heure actuelle.
Aquatic Living Resources (0990-7440) (EDP Sciences), 2005 , Vol. 18 , N. 1 , P. 15-33

Droits : EDP Sciences, IFREMER, IRD 2005
http://archimer.ifremer.fr/doc/2005/publication-409.pdf
DOI:10.1051/alr:2005011
http://archimer.ifremer.fr/doc/00000/409/

Éditeur(s) : HAL CCSD Consejo Superior de Investigaciones Científicas
Résumé : International audience
The temporal variation in carbon and nitrogen isotopic compositions (noted as δ 13 C and δ 15 N) was investigated in the convict surgeonfish (Acanthurus triostegus) at Moorea (French Polynesia). Over a period of 24 days, juveniles were reared in aquaria and subjected to two different feeding treatments: granules or algae. The dynamics of δ 13 C and δ 15 N in two muscles (the adductor mandibulae complex and the epaxial musculature) having different functions were compared. At the end of experiments, a steady-state isotopic system in each muscle tissue was not reached. Especially for the algal treatment, we found different patterns of variation in isotopic compositions over time between the two muscles. The turnovers of δ 13 C showed opposite trends for each muscle but differences are mitigated by starvation and by the metamorphosis. Our study highlighted that the metabolism of coral reef fish may be subjected to catabolism or anabolism of non-protein precursors at settlement, inducing variation in isotopic compositions that are not linked to diet change. Comparación de la dinámica de variación isotópica en dos músculos de un pez de arrecife de coral durante la fase de asentamiento Resumen: La variación temporal en la composiciones isotópicas del carbono y nitrógeno (δ 13 C y δ 15 N) fue investigada en el pez cirujano Acanthurus triostegus en Moorea (Polinesia Francesa). Durante un período de 24 días, peces juveniles se mantuvieron en acuarios y se sometieron a dos tratamientos de alimentación: gránulos o algas. Se compararon las dinámicas de cambio δ 13 C y δ 15 N en dos músculos con diferentes funciones (complejo aductor mandibular y musculatura epiaxial). Al final de los experimentos, no se alcanzó un sistema isotópico de estado estacionario en ningún tejido. Especialmente para el tratamiento de algas, encontramos distintos patrones de variación en composiciones isotópicas en el tiempo entre los dos músculos. Las variaciones en δ 13 C mostraron tendencias opuestas para cada músculo, pero las diferencias fueron mitigadas por la inanición y la metamorfosis. Nuestro estudio destaca que el metabolismo de los peces de arrecife puede ser sometido a catabolismo o anabolismo por los precursores no proteicos durante el asentamiento, induciendo variación en las composi-ciones isotópicas que no están vinculados al cambio de dieta.
ISSN: 0214-8358

Droits : http://creativecommons.org/licenses/by-nc/
hal-01212253
https://hal-univ-perp.archives-ouvertes.fr/hal-01212253
https://hal-univ-perp.archives-ouvertes.fr/hal-01212253/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01212253/file/1598-3145-1-PB.pdf
DOI : 10.3989/scimar.04225.31A

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The Demerara plateau, located offshore French Guiana and Suriname, is part of a passive transform continental margin particularly prone to develop slope instabilities, probably in relation to the presence of a free distal border along its steep continental slope. Slope failure occurred at different periods (Cretaceous to Neogene) and shows an overall retrogressive evolution through time. Upslope these failure headscarp, an enigmatic regional Mio-Pliocene unconformity has been discovered through the interpretation of new academic and industrial datasets. The aim of this work is to describe and understand the origin of this surface. Our analysis shows that this unconformity is made of a series of valleys that cross-cut sedimentary strata. Each one of these valleys has a short lateral extent and is closed along two perpendicular directions, which suggests that it could correspond to a highly meandering system, or to some sub-circular depressions. The infill of these features is equivalent to the regional stratigraphic strata found outside the structures, but in a subdued position. This seems to imply that the structures have originated by a local loss of sediments at their base or by sliding processes. Furthermore, these depressions intersect each other through time, while migrating progressively downslope.We discuss a series of hypotheses that try to explain the onset and evolution of these depressions forming the Mio-Pliocene unconformity (Canyons? Slope failures? Contourite moats? Hydrate pockmarks?). Having established that these structures are depressions formed by collapse, and have many similarities with structures recently described in the literature as pockmarks associated with gas hydrate dissolution, we favor this hypothesis.We propose that these hydrate pockmarks form with a mass failure that was triggered by fluid-overpressure development at the base of the hydrate stability zone.
ISSN: 0025-3227

hal-01365920
https://hal.archives-ouvertes.fr/hal-01365920
DOI : 10.1016/j.margeo.2015.04.001

Éditeur(s) : Oxford Univ Press
Résumé : Biological reference points are important tools for fisheries management. Reference points are not static, butmay change when a population's environment or the population itself changes. Fisheries-induced evolution is one mechanism that can alter population characteristics, leading to "shifting" reference points by modifying the underlying biological processes or by changing the perception of a fishery system. The former causes changes in "true" reference points, whereas the latter is caused by changes in the yardsticks used to quantify a system's status. Unaccounted shifts of either kind imply that reference points gradually lose their intended meaning. This can lead to increased precaution, which is safe, but potentially costly. Shifts can also occur in more perilous directions, such that actual risks are greater than anticipated. Our qualitative analysis suggests that all commonly used reference points are susceptible to shifting through fisheries-induced evolution, including the limit and "precautionary" reference points for spawning-stock biomass, B-lim and B-pa, and the target reference point for fishing mortality, F-0.1. Our findings call for increased awareness of fisheries-induced changes and highlight the value of always basing reference points on adequately updated information, to capture all changes in the biological processes that drive fish population dynamics.
Ices Journal Of Marine Science (1054-3139) (Oxford Univ Press), 2013-07 , Vol. 70 , N. 4 , P. 707-721

Droits : 2013 International Council for the Exploration of the Sea. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com
http://archimer.ifremer.fr/doc/00151/26228/24302.pdf
DOI:10.1093/icesjms/fst077
http://archimer.ifremer.fr/doc/00151/26228/

Éditeur(s) : HAL CCSD Wiley-Blackwell
Résumé : International audience
Although protists are critical components of marine ecosystems, they are still poorly characterized. Here we analysed the taxonomic diversity of planktonic and benthic protist communities collected in six distant European coastal sites. Environmental deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) from three size fractions (pico-, nano- and micro/mesoplankton), as well as from dissolved DNA and surface sediments were used as templates for tag pyrosequencing of the V4 region of the 18S ribosomal DNA. Beta-diversity analyses split the protist community structure into three main clusters: picoplankton-nanoplankton-dissolved DNA, micro/mesoplankton and sediments. Within each cluster, protist communities from the same site and time clustered together, while communities from the same site but different seasons were unrelated. Both DNA and RNA-based surveys provided similar relative abundances for most class-level taxonomic groups. Yet, particular groups were overrepresented in one of the two templates, such as marine alveolates (MALV)-I and MALV-II that were much more abundant in DNA surveys. Overall, the groups displaying the highest relative contribution were Dinophyceae, Diatomea, Ciliophora and Acantharia. Also, well represented were Mamiellophyceae, Cryptomonadales, marine alveolates and marine stramenopiles in the picoplankton, and Monadofilosa and basal Fungi in sediments. Our extensive and systematic sequencing of geographically separated sites provides the most comprehensive molecular description of coastal marine protist diversity to date.
ISSN: 1462-2912

hal-01191731
http://hal.upmc.fr/hal-01191731
http://hal.upmc.fr/hal-01191731/document
http://hal.upmc.fr/hal-01191731/file/Massana_2015_Marine_protist.pdf
DOI : 10.1111/1462-2920.12955

Éditeur(s) : HAL CCSD American Association for the Advancement of Science
Résumé : International audience
Sediments cored along the southwestern Iberian margin during Integrated Ocean Drilling Program Expedition 339 provide constraints on Mediterranean Outflow Water (MOW) circulation patterns from the Pliocene epoch to the present day. After the Strait of Gibraltar opened (5.33 million years ago), a limited volume of MOW entered the Atlantic. Depositional hiatuses indicate erosion by bottom currents related to higher volumes of MOW circulating into the North Atlantic, beginning in the late Pliocene. The hiatuses coincide with regional tectonic events and changes in global thermohaline circulation (THC). This suggests that MOW influenced Atlantic Meridional Overturning Circulation (AMOC), THC, and climatic shifts by contributing a component of warm, saline water to northern latitudes while in turn being influenced by plate tectonics.
ISSN: 0036-8075

hal-01054316
https://hal.archives-ouvertes.fr/hal-01054316
DOI : 10.1126/science.1251306

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
As environmental sounds are used by larval fish and crustaceans to locate and orientate towards habitat during settlement, variations in the acoustic signature produced by habitats could provide valuable information about habitat quality, helping larvae to differentiate between potential settlement sites. However, very little is known about how acoustic signatures differ between proximate habitats. This study described within-and between-site differences in the sound spectra of five contiguous habitats at Moorea Island, French Polynesia: the inner reef crest, the barrier reef, the fringing reef, a pass and a coastal mangrove forest. Habitats with coral (inner, barrier and fringing reefs) were characterized by a similar sound spectrum with average intensities ranging from 70 to 78 dB re 1μPa.Hz-1. The
ISSN: 1932-6203

hal-01211705
https://hal-univ-perp.archives-ouvertes.fr/hal-01211705
https://hal-univ-perp.archives-ouvertes.fr/hal-01211705/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01211705/file/journal.pone.0135733.pdf
DOI : 10.1371/journal.pone.0135733

Éditeur(s) : HAL CCSD Coastal Education and Research Foundation, Inc.
Résumé : International audience
Morphodynamics of sandy, macrotidal, embayed beaches is complex because of the numerous physical processes interacting at the same location over a wide range of temporal scales. As most of these processes are controlled by beach morphology, dynamic feedbacks are generally observed between hydro- and morphodynamics. Investigating short-term processes is essential in order to improve long term morphological prediction. A key question is to understand how beach slope reacts to forcing conditions, in particular the response time of the beach profile, how long the transient state lasts. This study deals with the spatial and temporal responses of beach morphology to varying incident conditions. Here we report main observations, preliminary results and on-going investigations on the DYNATREZ1 field campaign, which was conducted in the framework of the National Observation Service Dynalit. Beach profiles are shown to adapt rapidly to forcing conditions, within two days, with more intense variations observed in the high tide swash zone. The presence of infragravity waves and their dissipation on the beach is highlighted. It is likely that the very large variability in beach slope observed over a single neapspring cycle is responsible for the accordingly large variability in wave skewness, asymmetry and breaking processes, and thus in sediment fluxes and morphological changes.
ICS 2016 Sydney
Sydney, Australia

hal-01254465
https://hal.archives-ouvertes.fr/hal-01254465
DOI : 10.2112/SI75-075.1