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Dezerald, O.; Talaga, S.; Leroy, C.; Carrias, J.-F.; Corbara, B.; Dejean, A.; Céréghino, R. |
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Title |
Environmental determinants of macroinvertebrate diversity in small water bodies: Insights from tank-bromeliads |
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Journal Article |
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2014 |
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Hydrobiologia |
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Hydrobiologia |
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723 |
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1 |
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77-86 |
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Freshwater biodiversity; Linear mixed effect modelling; Microcosms; Phytotelmata; Ponds |
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The interlocking leaves of tank-forming bromeliads (Bromeliaceae) collect rainwater and detritus, thus creating a freshwater habitat for specialized organisms. Their abundance and the possibility of quantifying communities with accuracy give us unparalleled insight into how changes in local to regional environments influence community diversity in small water bodies. We sampled 365 bromeliads (365 invertebrate communities) along a southeastern to northwestern range in French Guiana. Geographic locality determined the species pool for bromeliad invertebrates, and local environments determined the abundance patterns through the selection of traits that are best adapted to the bromeliad habitats. Patterns in community structure mostly emerged from patterns of predator species occurrence and abundance across local-regional environments, while the set of detritivores remained constant. Water volume had a strong positive correlation with invertebrate diversity, making it a biologically relevant measure of the pools' carrying capacity. The significant effects of incoming detritus and incident light show that changes in local environments (e.g., the conversion of forest to cropping systems) strongly influence freshwater communities. Because changes in local environments do not affect detritivores and predators equally, one may expect functional shifts as sets of invertebrates with particular traits are replaced or complemented by other sets with different traits. © 2013 Springer Science+Business Media Dordrecht. |
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CNRS, EcoLab (UMR-CNRS 5245), 118 Route de Narbonne, 31062 Toulouse, France |
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00188158 (Issn) |
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EcoFoG @ webmaster @ |
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517 |
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Dezerald, O.; Leroy, C.; Corbara, B.; Dejean, A.; Talaga, S.; Céréghino, R. |
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Environmental drivers of invertebrate population dynamics in Neotropical tank bromeliads |
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2017 |
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Freshwater Biology |
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Freshw Biol |
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62 |
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2 |
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229-242 |
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food webs; freshwater invertebrates; growth rate; life history; rainforest |
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Tank bromeliads form a conspicuous, yet neglected freshwater habitat in Neotropical forests. Recent studies driven by interests in medical entomology, fundamental aspects of bromeliad ecology and experimental research on food webs have, however, prompted increasing interest in bromeliad aquatic ecosystems. As yet, there is nothing in the literature about the life histories and environmental drivers of invertebrate population dynamics in tank bromeliads.
Based on fortnightly samples taken over one year, size frequency plots and individual dry masses allowed us to establish the life cycles and growth rates of the dominant aquatic invertebrates in a common bromeliad species of French Guiana. Linear mixed-effect models and Mantel tests were used to predict changes in density, biomass, and growth rates in relation to temperature, rainfall, humidity and detrital resources.
Annual variations in invertebrate densities and biomasses could be described according to three types of distribution: unimodal, bimodal or almost constant. Despite seasonal variations, precipitation, temperature, relative humidity and detritus concentration accounted significantly for changes in density and biomass, but we found no significant responses in growth rates of most invertebrate species. Species rather displayed non-seasonal life cycles with overlapping cohorts throughout the year. There was also a trend for delayed abundance peaks among congeneric species sharing similar functional traits, suggesting temporal partitioning of available resources.
Beyond novel knowledge, quantitative information on life histories is important to predict food-web dynamics under the influence of external forcing and self-organisation. Our results suggest that changes in species distribution that will affect population dynamics through biotic interactions in space and/or time could have greater effects on food webs and ecosystem functioning than changes in environmental factors per se. |
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1365-2427 |
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716 |
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Dezerald, O.; Leroy, C.; Corbara, B.; Carrias, J.-F.; Pélozuelo, L.; Dejean, A.; Céréghino, R. |
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Title |
Food-Web Structure in Relation to Environmental Gradients and Predator-Prey Ratios in Tank-Bromeliad Ecosystems |
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2013 |
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PLoS ONE |
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PLoS ONE |
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8 |
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8 |
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e71735 |
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Little is known of how linkage patterns between species change along environmental gradients. The small, spatially discrete food webs inhabiting tank-bromeliads provide an excellent opportunity to analyse patterns of community diversity and food-web topology (connectance, linkage density, nestedness) in relation to key environmental variables (habitat size, detrital resource, incident radiation) and predators:prey ratios. We sampled 365 bromeliads in a wide range of understorey environments in French Guiana and used gut contents of invertebrates to draw the corresponding 365 connectance webs. At the bromeliad scale, habitat size (water volume) determined the number of species that constitute food-web nodes, the proportion of predators, and food-web topology. The number of species as well as the proportion of predators within bromeliads declined from open to forested habitats, where the volume of water collected by bromeliads was generally lower because of rainfall interception by the canopy. A core group of microorganisms and generalist detritivores remained relatively constant across environments. This suggests that (i) a highly-connected core ensures food-web stability and key ecosystem functions across environments, and (ii) larger deviations in food-web structures can be expected following disturbance if detritivores share traits that determine responses to environmental changes. While linkage density and nestedness were lower in bromeliads in the forest than in open areas, experiments are needed to confirm a trend for lower food-web stability in the understorey of primary forests. © 2013 Dézerald et al. |
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EcoLab, Laboratoire Ecologie Fonctionnelle et Environnement, CNRS UMR 5245, Toulouse, France |
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19326203 (Issn) |
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Export Date: 30 August 2013; Source: Scopus; Art. No.: e71735; Coden: Polnc; doi: 10.1371/journal.pone.0071735; Language of Original Document: English; Correspondence Address: Dézerald, O.; EcoFoG, Ecologie des Forêts de Guyane, CNRS UMR 8172, Kourou, France; email: olivier.dezerald@gmail.com |
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499 |
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Dezerald, O.; Céréghino, R.; Corbara, B.; Dejean, A.; Leroy, C. |
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Title |
Temperature: Diet Interactions Affect Survival through Foraging Behavior in a Bromeliad-Dwelling Predator |
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2015 |
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Biotropica |
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Biotropica |
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47 |
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5 |
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569-578 |
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Toxorhynchites haemorrhoidalis; Biocontrol agent; Development; French Guiana; Selective feeding behavior; Tank bromeliad |
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Temperature, food quantity and quality play important roles in insect growth and survival, influencing population dynamics as well as interactions with other community members. However, the interaction between temperature and diet and its ecological consequences have been poorly documented. Toxorhynchites are well-known biocontrol agents for container-inhabiting mosquito larvae. We found that Toxorhynchites haemorrhoidalis larvae (Diptera: Culicidae) inhabiting water-filled rosettes of tank bromeliads catch and eat prey of both aquatic (mosquito larvae) and terrestrial origin (ants), using distinct predatory methods. They carried out frontal attacks on ants, but ambushed mosquito larvae. In choice tests, T. haemorrhoidalis favored terrestrial prey. Temperature had a significant effect on predator development and survival through its interaction with diet, but did not alter the preference for ants. T. haemorrhoidalis larvae emerged quickly when fed only mosquito larvae, whereas all individuals died before pupation when fed only ants. We conclude that behavioral factors (i.e., attraction to ants that disturb the surface of the water) overtake physiological factors (i.e., the adverse outcome of elevated temperature and an ant-based diet) in determining a predator's response to temperature:diet interactions. Finally, because T. haemorrhoidalis larvae preferentially feed on terrestrial insects in tank bromeliads, mosquito larvae may indirectly benefit from predation release. © 2015 Association for Tropical Biology and Conservation Inc. |
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UMR AMAP (botAnique et Modelisation de l'Architecture des Plantes et des vegetations), IRD, Boulevard de la Lironde, TA A-51/PS2, Montpellier Cedex 5, France |
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Export Date: 17 September 2015 |
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EcoFoG @ webmaster @ |
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624 |
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Dezerald, O.; Céréghino, R.; Corbara, B.; Dejean, A.; Leroy, C. |
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Functional trait responses of aquatic macroinvertebrates to simulated drought in a Neotropical bromeliad ecosystem |
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Journal Article |
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2015 |
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Freshwater Biology |
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Freshwater Biology |
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60 |
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9 |
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1917-1929 |
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Food webs; Precipitations; Rainforests; Resistance/resilience; Tipping point |
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The duration of the dry seasons in south-eastern Amazonia is expected to increase. Little is known of how freshwater assemblages respond to drought in the humid rainforests and of the extent to which they resist the absence of rainfall before the collapse of the system. We manipulated rainshelters over tank-forming bromeliads (i.e. the interlocking leaf axils of these plants form wells that collect rainwater) to simulate an exceptionally long dry period (49 days, compared with a 10-year mean ± SD annual maximum number of 17 ± 5.3 days without rainfall at the study site) and then a rewetting period. By sampling weekly over 3 months, we followed the dynamics of the representation of abundance-weighted traits in invertebrate assemblages in these treatment plants and in a control group. The functional structure of assemblages was drought resistant until the water volume in the bromeliad pools dropped by 90%, when there was a sudden shift in the functional trait structure due to the loss of most populations except the drought-resistant culicids. Traits related to life history, body size and preferred food showed significant responses to drought. There was a convergence in the functional traits of species surviving in dry plants, strengthening the idea that environmental filtering, rather than stochasticity, determines the functional trajectory of aquatic assemblages during drought. At the end of the dry period, samples of the detritus potentially containing drought-resistant eggs/cysts (and eventually live larvae) were taken from the dry plants and rewetted in the laboratory, allowing us to distinguish resistant species from those requiring recolonisation via subsequent oviposition by adults from elsewhere. Patches of water-filled bromeliads persisting in the area provided the most important pool of colonists, and communities returned to the pre-disturbance state within 1-2 weeks of rewetting. Our results suggest that the functional trait structure of invertebrate assemblages in bromeliads could remain stable under scenarios of precipitation change that would triple the duration of current dry periods at a local scale. Future experiments should evaluate how environmental factors might alter the tipping point between resistance to drought and a collapse in ecosystem processes. © 2015 John Wiley & Sons Ltd. |
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IRD, UMR AMAP (botAnique et Modélisation de l'Architecture des Plantes et des vegetations), Boulevard de la Lironde, TA A-51/PS2, Montpellier Cedex 5, France |
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Export Date: 27 August 2015 |
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616 |
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Dezecache, Camille; Faure, Emmanuel; Gond, Valéry; Salles, Jean-Michel; Vieilledent, Ghislain; Herault, Bruno |
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Gold-rush in a forested El Dorado: deforestation leakages and the need for regional cooperation |
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2017 |
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Environmental Research Letters |
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12 |
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3 |
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034013 |
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Tropical forests of the Guiana Shield are the most affected by gold-mining in South America, experiencing an exponential increase in deforestation since the early 2000’s. Using yearly deforestation data encompassing Guyana, Suriname, French Guiana and the Brazilian State of Amapá, we demonstrated a strong relationship between deforestation due to gold-mining and gold-prices at the regional scale. In order to assess additional drivers of deforestation due to gold-mining, we focused on the national scale and highlighted the heterogeneity of the response to gold-prices under different political contexts. Deforestation due to gold-mining over the Guiana Shield occurs mainly in Guyana and Suriname. On the contrary, past and current repressive policies in Amapá and French Guiana likely contribute to the decorrelation of deforestation and gold prices. In this work, we finally present a case study focusing on French Guiana and Suriname, two neighbouring countries with very different levels of law enforcement against illegal gold-mining. We developed a modelling framework to estimate potential deforestation leakages from French Guiana to Suriname in the border areas. Based on our assumptions, we estimated a decrease in deforestation due to gold-mining of approx. 4300 hectares in French Guiana and an increase of approx. 12 100 hectares in Suriname in response to the active military repression of illegal gold-mining launched in French Guiana. Gold-mining in the Guiana Shield provides challenging questions regarding REDD+ implementation. These questions are discussed at the end of this study and are important to policy makers who need to provide sustainable alternative employment to local populations in order to ensure the effectiveness of environmental policies. |
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1748-9326 |
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EcoFoG @ webmaster @ |
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738 |
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Dezecache, C.; Salles, J.-M.; Herault, B. |
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Questioning emissions-based approaches for the definition of REDD+ deforestation baselines in high forest cover/low deforestation countries |
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2018 |
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Carbon Balance Manage. |
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13 |
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21 |
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Baseline; Deforestation; Guiana Shield; HFLD countries; Redd+; Reference level; Spatial modelling |
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Background: REDD+ is being questioned by the particular status of High Forest/Low Deforestation countries. Indeed, the formulation of reference levels is made difficult by the confrontation of low historical deforestation records with the forest transition theory on the one hand. On the other hand, those countries might formulate incredibly high deforestation scenarios to ensure large payments even in case of inaction. Results: Using a wide range of scenarios within the Guiana Shield, from methods involving basic assumptions made from past deforestation, to explicit modelling of deforestation using relevant socio-economic variables at the regional scale, we show that the most common methodologies predict huge increases in deforestation, unlikely to happen given the existing socio-economic situation. More importantly, it is unlikely that funds provided under most of these scenarios could compensate for the total cost of avoided deforestation in the region, including social and economic costs. Conclusion: This study suggests that a useful and efficient international mechanism should really focus on removing the underlying political and socio-economic forces of deforestation rather than on hypothetical result-based payments estimated from very questionable reference levels. |
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BioMed Central Ltd. |
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17500680 (Issn) |
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EcoFoG @ webmaster @ |
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837 |
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Devault, D.A.; Lévi, Y.; Karolak, S. |
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Applying sewage epidemiology approach to estimate illicit drug consumption in a tropical context: Bias related to sewage temperature and pH |
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2017 |
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Science of the Total Environment |
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Science of the Total Environment |
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584-585 |
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252-258 |
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Cannabis; Degradation; H2s; Half-life; Illicit drugs; Wastewater |
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Illicit drug consumption can be estimated from drug target residue (DTR) in wastewater, with the reliability of results being partly linked to DTR stability in the sewage network. However, wastewater temperature and pH drive the stability of molecules and, in this context, tropical conditions must be studied to specify the impact of residence time in the sewage network on DTR degradation. Warmth enhances biotic and abiotic processes such as degradation, leading to a decrease in oxygen content, and consequently, early diagenesis conditions in wastewater. In this study, we conduct laboratory studies under acidic pH and high temperature (30 °C) conditions to determine the degradation half-lives of cocaine (COC), tetrahydrocannabinol, and heroine targets, allowing COC/benzoylecgonine (BZE) ratio variations to be predicted in sewage networks. A rapid COC degradation is observed, as already reported in the literature but without a short-term significant difference between 20 °C and 30 °C. Acidic pH seems to prevent degradation. Thus, theoretically, the use of COC as DTR is only reliable in acidic conditions, with the decrease in COC concentration being 6% at 8 h, but over 40% in other conditions. By contrast, the use of BZE as DTR to estimate COC consumption, which is performed in practice, can be undertaken with the same back-calculation equation as used in temperate countries. However, 11-nor-delta-9-carboxytetrahydrocannabinol stability is more influenced by high temperature: concentration levels after 24 h are 20% lower at 30 °C than at 20 °C, corresponding to a 20% and 40% decrease, respectively. Based on a mean residence time of 8 h, underestimated cannabis consumption is close to 15% in tropical contexts, which is double that of temperate areas. © 2017 Elsevier B.V. |
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Public Health and Environnement Laboratory, UMR 8079 Ecologie Systématique Evolution, Univ. Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, Orsay, France |
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Export Date: 8 March 2017 |
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EcoFoG @ webmaster @ |
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741 |
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Devault, D.A.; Beilvert, B.; Winterton, P. |
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Ship breaking or scuttling? A review of environmental, economic and forensic issues for decision support |
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2017 |
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Environmental Science and Pollution Research |
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Environ. Sci. Pollut. Res. |
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24 |
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33 |
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25741-25774 |
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Artificial reef; Diving; Ship recycling; Ship Recycling Facilities; Shipbreaking; Tourism; Working conditions; Wrecks; artificial reef; coastal erosion; coastal zone management; cost-benefit analysis; decision support system; developing world; economic impact; environmental economics; environmental impact assessment; environmental issue; facility location; health and safety; invasive species; profitability; recycling; shipping; tourism; working conditions; wreck; analysis; decision support system; economics; international cooperation; pollution; prevention and control; procedures; recycling; ship; statistics and numerical data; Decision Support Techniques; Environmental Pollution; Internationality; Recycling; Ships |
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In a globalized world, the world trade fleet plays a pivotal role in limiting transport costs. But, the management of obsolete ships is an acute problem, with most Ship Recycling Facilities (SRF) situated in developing countries. They are renowned for their controversial work and safety conditions and their environmental impact. Paradoxically, dismantlement is paid for by the shipowners in accordance with international conventions therefore it is more profitable for them to sell off ships destined for scrapping. Scuttling, the alternative to scrapping, is assessed in the present review to compare the cost/benefit ratios of the two approaches. Although scrapping provides employment and raw materials – but with environmental, health and safety costs – scuttling provides fisheries and diving tourism opportunities but needs appropriate management to avoid organic and metal pollution, introduction of invasive species and exacerbation of coastal erosion. It is also limited by appropriate bottom depth, ship type and number. The present review inventories the environmental, health, safety, economic, and forensic aspects of each alternative. © 2016, Springer-Verlag Berlin Heidelberg. |
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Département Langues et Gestion, Université Toulouse III – Paul Sabatier, 118 route de Narbonne, Toulouse cedex 09, 31062, France |
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Springer Verlag |
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EcoFoG @ webmaster @ |
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869 |
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Dessert, C.; Clergue, C.; Rousteau, A.; Crispi, O.; Benedetti, M.F. |
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Atmospheric contribution to cations cycling in highly weathered catchment, Guadeloupe (Lesser Antilles) |
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2020 |
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Chemical Geology |
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Chem. Geol. |
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531 |
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119354 |
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Atmospheric deposit; Cation-nutrient recycling; Critical Zone; Saharan dust; Sr and Nd isotopes; Atmospheric chemistry; Biogeochemistry; Catchments; Deposits; Dust; Ecosystems; Forestry; Isotopes; Lakes; Positive ions; Rain; Recycling; Runoff; Soil moisture; Soil surveys; Tropics; Vegetation; Volcanoes; Weathering; Atmospheric deposits; Critical zones; Nutrient recycling; Saharan dust; Sr and Nd isotopes; Nutrients; catchment; cation; dust; isotopic composition; neodymium isotope; regolith; strontium isotope; trace element; water chemistry; water quality; Guadeloupe; Leeward Islands [Lesser Antilles]; Sahara |
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Abstract |
The important fertilizing role of atmospheric dust, and particularly African dust, in tropical rainforests is increasingly recognized but still poorly quantified. To better evaluate dust input into the Caribbean basin, we sampled critical zone compartments of a small forested volcanic catchment in Guadeloupe (soils, parent rock, atmospheric dust, plants, soil solutions, stream and rain waters). The aims of this study are to track sources of cation nutrients (Ca, Mg, K, Sr) developed on highly weathered soil in the rainforest of Guadeloupe, to quantify plant recycling of these nutrients, and to identify constraints on regolith development and its associated nutrient pool. In the Quiock Creek catchment, a large isotopic range of 87Sr/86Sr and eNd values was observed despite the small scale of observation. Sr isotopic composition of the dissolved load varied from 0.7084 in rainfall to 0.7110 in soil solution, whereas it ranges between 0.7068 and 0.7153 for soil samples and between 0.7096 and 0.7102 for plants. The Nd isotopic composition varied between -8.39 in near-surface soil samples to 2.71 in deeper soil. All samples had an intermediate signature between that of the bedrock endmember (87Sr/86Sr = 0.7038; eNd = 4.8) and the atmospheric endmember (sea salt: 87Sr/86Sr = 0.7092 and Saharan dust: 87Sr/86Sr = 0.7187, eNd=-11.5). The regolith was built on pyroclastic deposits, but, because of extreme leaching, the regolith has lost its original bedrock signature and inherited an exogenous atmospheric signature. Our results show that only the chemical weathering of the fresh near-surface minerals can provide nutrients to the ecosystem (first 30 cm). However, this dust weathering is too low to sustain the tropical forest ecosystem on its own. The cationic mass balance at the catchment scale, as well as the Sr isotopic signature, show that cation and Sr fluxes are of atmospheric origin only and that original bedrock no longer participates in nutrient cycles. The vegetation reflects the 87Sr/86Sr of the dissolved pool of atmospheric Sr. At the soil-plant scale, the cation-nutrient fluxes provided by vegetation (litter fall + leaf excretion) are major compared to input and output fluxes. The annual Ca, K, Sr and Mg fluxes within the vegetation are, respectively, 31, 28, 20 and 3 times greater than the exported fluxes at the outlet of the basin. The residence time of nutrients in the vegetation is 16 years for K and close to 45 years for Sr, Ca and Mg. These results emphasize the highly efficient vegetative turnover that dominates the nutrient cycle in the Quiock Creek catchment. This first characterization of biogeochemical cycles in the Guadeloupean rainforest suggests that the forest community of Quiock Creek is sustained by a small near-surface nutrient pool disconnected from the deep volcanic bedrock. We also demonstrated that, even with efficient nutrient recycling, Saharan dust plays a significant role in maintaining ecosystem productivity in Guadeloupe over long-time scales. |
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Laboratoire de biologie et de physiologie végétales, UMR EcoFoG, CNRS, Cirad, INRA, Université des Antilles, Université de Guyane, Pointe-à-Pitre, 97159, France |
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Elsevier B.V. |
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00092541 (Issn) |
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Export Date: 18 November 2019; Correspondence Address: Dessert, C.; Université de Paris, Institut de physique du globe de Paris, CNRSFrance; email: dessert@ipgp.fr |
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EcoFoG @ webmaster @ |
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895 |
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