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Trophic structure of a nektobenthic community exploited by a multispecific bottom trawling fishery in Northeastern Brazil
No full textWe used complementary stable isotope (SIA) and stomach content (SCA) analyses to investigate feeding relationships among species of the nektobenthic communities and the potential ecological effects of the bottom trawling of a coastal ecosystem in northeastern Brazil. Carbon (delta C-13) and nitrogen (delta N-15) compositions were determined for five basal sources and 28 consumers, from zooplankton to shrimp and fish species. Fishes and basal sources showed a broad range of delta N-15 (fishes: 6.49-14.94 parts per thousand; sources: 2.58-6.79 parts per thousand) and delta C-13 values (fishes: -23.86 to -13.71 parts per thousand; sources: -24.32 to -13.53 parts per thousand), while shrimps and crabs exhibited similar nitrogen and carbon ratios. Six trophic consumer groups were determined among zooplankton, crustaceans and fishes by SIA, with trophic pathways associated mostly with benthic sources. SCA results indicated a preference for benthic invertebrates, mainly worms, crabs and shrimps, as prey for the fish fauna, highlighting their importance in the food web. In overall, differences between SCA and the SIA approaches were observed, except for groups composed mainly for shrimps and some species of high delta N-15 values, mostly piscivorous and zoobenthivores. Given the absence of regulation for bottom trawling activities in the area, the cumulative effects of trawling on population parameters, species composition, potentially decreasing the abundance of benthic preys (e.g., shrimps, worms and crabs) may lead to changes in the trophic structure potentially affect the food web and the sustainability of the fishery
Increased Amazon Basin wet-season precipitation and river discharge since the early 1990s driven by tropical Pacific variability
No full textThe Amazon Basin, the largest watershed on Earth, experienced a significant increase in wet-season precipitation and high-season river discharge from the early 1990s to early 2010s. Some studies have linked the increased Amazon Basin hydrologic cycle to decadal trends of increased Pacific trade winds, eastern Pacific sea surface temperature (SST) cooling, and associated strengthening of the Pacific Walker circulation. However, it has been difficult to disentangle the role of Pacific decadal variability from the impacts of greenhouse gases and other external climate drivers over the same period. Here, we separate the contributions of external forcings from those of Pacific decadal variability by comparing two large ensembles of climate model experiments with identical radiative forcing agents but imposing different tropical Pacific wind stress. One ensemble constrains tropical Pacific wind stress to its long-term climatology, suppressing tropical Pacific decadal variability; the other ensemble imposes the observed tropical Pacific wind stress anomalies, simulating realistic tropical Pacific decadal variability. Comparing the Amazon Basin hydroclimate response in the two ensembles allows us to distinguish the contributions of external forcings common to both simulations from those related to Pacific trade wind variability. For the 1992-2012 trend, the experiments with observed tropical Pacific wind stress anomalies simulate strengthening of the Walker circulation between the Pacific and South America and sharpening of the Pacific-Atlantic interbasin SST contrast, driving increased Amazon Basin wet-season precipitation and high-season discharge. In contrast, these circulation and hydrologic intensification trends are absent in the simulations with climatological tropical Pacific wind stress. This work underscores the importance of Pacific decadal variability in driving hydrological cycle changes and modulating the hydroclimate impacts of global warming over the Amazon Basin
Modeling the response of soil moisture to climate variability in the Mediterranean region
No full textFuture climate scenarios for the Mediterranean region indicate a possible decrease in annual precipitation associated with an intensification of extreme rainfall events in the coming years. A major challenge in this region is to evaluate the impacts of changing precipitation patterns on extreme hydrological events such as droughts and floods. For this, it is important to understand the impact of climate change on soil moisture since it is a proxy for agricultural droughts, and the antecedent soil moisture condition plays a key role on runoff generation. This study focuses on 10 sites, located in southern France, with available soil moisture, temperature, and precipitation observations for a 10-year time period. Soil moisture is simulated at each site at the hourly time step using a model of soil water content. The sensitivity of the simulated soil moisture to different changes in precipitation and temperature is evaluated by simulating the soil moisture response to temperature and precipitation scenarios generated using a delta change method for temperature and a stochastic model (the Neyman-Scott rectangular pulse model) for precipitation. Results show that soil moisture is more impacted by changes in precipitation intermittence than precipitation intensity and temperature. Overall, increased temperature and precipitation intensity associated with more intermittent precipitation leads to decreased soil moisture and an increase in the annual number of days with dry soil moisture conditions. In particular, a temperature increase of +4 degrees C combined with a decrease of annual rainfall between 10 % and 20 %, corresponding to the current available climate scenarios for the Mediterranean, lead to a lengthening of the drought period from June to October with an average of +28 d of soil moisture drought per year
Timorese archaeobotany : an anthracological pilot study at the late Holocene Lepu-Kina rockshelter, Atauro Island, East Timor
No full textThis paper details an anthracological pilot study for the Lepu-Kina rockshelter site (AT-7), located on Atauro Island, East Timor and considers the implications of the preliminary results for the archaeology of the region. Archaeological wood charcoal analysis can reveal aspects of fuel selection, human landscape modifications and management of vegetal resources. The difficulties inherent in tropical archaeobotany have, however, constrained anthracological research in Island Southeast Asia. This study is therefore principally an attempt to assess the potential for future anthracological investigations to address archaeological questions related to vegetation resource uses and horticultural practices in Island Southeast Asia. Results reveal that the occupants of the Lepu-Kina rockshelter 2500 years ago had access to abundant semi-evergreen tropical forests and savannah. The presence of Artocarpus, identified as either breadnut or breadfruit (A. cf. altilis/camansi) is also recorded. These results confirm that a more expansive anthracological investigation of the Lepu-Kina rockshelter, accompanied by a local or regional reference collection and wood anatomy resource, has significant potential to expand on these initial observations
Long term high frequency sediment observatory in an alpine catchment : the Arc-Isere rivers, France
No full textWe present a dataset on to the Arc-Isere long-term environmental research observatory, which is part of the Rhone Basin Long Term Environmental Research Observatory. This alpine catchment located in the French Alps is characterized by high Suspended Particulate Matter (SPM) in anthropogenized valleys. Suspended Sediment Concentrations (SSC) naturally observed in the river are very high, ranging from a few tens of milligrams per litre at low flow to tens of grams per litre during major natural hydrological events (floods, debris flows) or river dam hydraulic flushes. One research objective related to this site is to better understanding the SSC dynamics along the river using a system of nested catchments (Arvan, Arc, and Isere) in order to assess both temporal and spatial dynamics. The data allow the quantification of fine sediment yields and also the evaluation of possible morphological changes due to fine sediment deposition or resuspension. Additionally, the observatory database support studies on contaminants (either dissolved or particulate contaminants). Our monitoring includes six stations with high frequency (2-30 min) streamflow, SSC measurement using turbidity sensors, and associated automatic sampling. Discharge is measured via water level measurements and a rating curve. The oldest station (Grenoble-campus) started recording discharge and concentration data from April 2006 while others stations were built between 2009 and 2011. Data are available in an online data website called 'Base de Donnees des Observatoires en Hydrologie' (Hydrological observatory database, ) with a DOI reference for the dataset. The hydrological and sediment transport time series are stored, managed and made available to a wide community with unfettered access in order to be used at their full extent. This database is used as a data exchange tool for both scientists and operational end-users and there is an associated online tool to compute integrated fluxes
L&8217;épidémie de choléra en Haïti : histoire d'un fiasco des Nations Unies et de la persévérance d&8217;un (collectif) chercheur français : tribune à partir de la lecture de "Choléra ; Haïti 2010-2018, histoire d&8217;un désastre" par Renaud Piarroux, Cnrs - 2019
No full textAlors que la pandémie de Covid-19 fait des ravages dans le monde, il est certainement utile de prendre un peu de recul épidémiologique. La lecture de l'ouvrage de Renaud Piarroux concernant son expérience de lutte contre l’épidémie de choléra en Haïti entre 2010 et 2018 est riche d’enseignements. Il montre le fiasco et les errances du système des Nations Unies et de certains de ses cadres mais aussi la vision étriquée des diplomates et des responsables de la santé mondiale française. Mais l'ouvrage est aussi précieux pour comprendre le fonctionnement académique de la santé publique mondiale, à l'image du désastre contemporain covidien : une santé publique biomédicale, orientée vers certaines maladies en particulier, sans vision interdisciplinaire et avec son lot de dérives, d'abus et de clientélisme scientifique. Les étudiant.es et les jeunes chercheur.es devraient pouvoir se saisir de cette analyse pour faire évoluer la situation...en espérant qu'on leur donne de la place
Comparison of nematode communities in anecic earthworm casts and adjacent soil reveal a land use-independent trophic group signature
No full textBy ingesting soil and organic matter in different soil horizons and depositing casts on soil surface, anecic earthworms have large influence on soil ecological processes. However, we still have a limited understanding of the consequences of earthworm casting activity on nematode communities, and the role played by the land use in this relationship. Therefore, the main objective of this study was to compare the effect of the anecic earthworm Amynthas adexilis (Thai, 1984) on the structure of nematode communities, in a woodland and meadow presenting different soil organic C content in northern Vietnam. Nematode population and physico-chemical properties of casts produced by the anecic earthworm A. adexilis and adjacent soil presenting no recent earthworm activity (0-10 cm deep) were characterized. A. adexilis incorporated organic matter into its casts compared to the adjacent bulk top soil horizon, reflected by a significant increase of the organic carbon and nitrogen contents (1.4 times more in the meadow and 1.8 times more in the woodland). Earthworm casts contained 2.6 and 1.7 times more nematodes than the adjacent top soil, in meadow and woodland, respectively. The effect of earthworm casting activity on nematode community structure was similar in both land uses. Compared to the soil, casts were significantly enriched in all trophic groups (between 1.9 and 11.6 times more in casts in the meadow, and between 1.6 and 23.7 times more in casts in the woodland, depending on the trophic group), except for obligate plant feeders that were under-represented (1.4 times less in casts for both land uses). The plant parasitic index decreased in the casts compared to the soil, indicating an environment less favourable for plant parasitic nematodes
L'écologie des mondes = Ecology of our worlds
No full textPuisées dans les trésors de la littérature mondiale, les citations qui composent cet ouvrage laissent entendre les voix de poètes, de philosophes, de romanciers et d'artistes comme autant de témoignages sur la diversité et la complexité des liens qui, depuis la nuit des temps, unissent les humains à la Nature. De splendides illustrations, elles aussi issues de toutes les cultures et civilisations de l'humanité, viennent en contrepoint de ces paroles, publiées ici en français, en anglais, mais aussi dans leur langue d'origine. En ces temps de bouleversement du climat et de menaces fortes sur la biodiversité, chaque lecteur, d'où qu'il vienne, pourra avec ce recueil porter un autre regard sur l'environnement qui l'entoure et y trouver force et inspiration pour nouer des relations plus harmonieuses et responsables avec la Nature
Reanalysing the 2007-19 glaciological mass-balance series of Mera Glacier, Nepal, Central Himalaya, using geodetic mass balance
No full textThe 2007-19 glaciological mass-balance series of Mera Glacier in the Everest Region, East Nepal, is reanalysed using the geodetic mass balance assessed by differencing two DEMs obtained from Pleiades stereo-images acquired in November 2012 and in October 2018. The glaciological glacier-wide annual mass balance of Mera Glacier has to be systematically decreased by 0.11 m w.e. a(-1) to match the geodetic mass balance. We attribute part of the positive bias of the glaciological mass balance to an over-estimation of the accumulation above 5520 m a.s.l., likely due to a measurement network unable to capture its spatial variability. Over the period 2007-19, Mera Glacier has lost mass at a rate of -0.41 +/- 0.20 m w.e. a(-1), in general agreement with regional averages for the central Himalaya. We observe a succession of negative mass-balance years since 2013
Southern Ocean in-situ temperature trends over 25 years emerge from interannual variability
No full textDespite playing a major role in global ocean heat storage, the Southern Ocean remains the most sparsely measured region of the global ocean. Here, a unique 25-year temperature time-series of the upper 800m, repeated several times a year across the Southern Ocean, allows us to document the long-term change within water-masses and how it compares to the interannual variability. Three regions stand out as having strong trends that dominate over interannual variability: warming of the subantarctic waters (0.290.09 degrees C per decade); cooling of the near-surface subpolar waters (-0.07 +/- 0.04 degrees C per decade); and warming of the subsurface subpolar deep waters (0.04 +/- 0.01 degrees C per decade). Although this subsurface warming of subpolar deep waters is small, it is the most robust long-term trend of our section, being in a region with weak interannual variability. This robust warming is associated with a large shoaling of the maximum temperature core in the subpolar deep water (39 +/- 09m per decade), which has been significantly underestimated by a factor of 3 to 10 in past studies. We find temperature changes of comparable magnitude to those reported in Amundsen-Bellingshausen Seas, which calls for a reconsideration of current ocean changes with important consequences for our understanding of future Antarctic ice-sheet mass loss. The Southern Ocean takes up the most heat and carbon, yet because of its remote and harsh location, it remains relatively sparsely measured. Here the authors use a 25 year temperature series which shows a clear, long term trend in subsurface warming that emerges from interannual variability