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The forest effects on the isotopic composition of rainfall in the northwestern Amazon Basin
No full textIn the Amazon basin, intense precipitation recycling across the forest significantly modifies the isotopic composition of rainfall (delta O-18, delta D). In the tropical hydrologic cycle, such an effect can be identified through deuterium excess (dxs), yet it remains unclear what environmental factors control dxs, increasing the uncertainty of dxs-based paleoclimate reconstructions. Here we present a 4-year record of the isotopic composition of rainfall, monitored in the northwestern Amazon basin. We analyze the isotopic variations as a function of the air mass history, based on atmospheric back trajectory analyses, satellite observations of precipitation upstream, leaf area index, and simulated moisture recycling along the transport pathway. We show that the precipitation recycling in the forest exerts a significant control on the isotopic composition of precipitation in the northwestern Amazon basin, especially on dxs during the dry season (r = 0.71). Applying these observations to existing speleothem and pollen paleorecords, we conclude that winter precipitation increased after the mid-Holocene, as the expansion of the forest allowed for more moisture recycling. Therefore, forest effects should be considered when interpreting paleorecords of past precipitation changes
Ecotoxicity of polyethylene nanoplastics from the North Atlantic oceanic gyre on freshwater and marine organisms (microalgae and filter-feeding bivalves)
No full textEach year, 5 to 10 million tons of plastic waste is dumped in the oceans via freshwaters and accumulated in huge oceanic gyres. Under the effect of several abiotic factors, macro plastic wastes (or plastic wastes with macro sizes) are fractionated into microplastics (MP) and finally reach the nanometric size (nanoplastic NP). To reveal potential toxic impacts of these NPs, two microalgae, Scenedemus subspicatus (freshwater green algae), and Thalassiosira weissiflogii (marine diatom) were exposed for up to 48 h at 1, 10, 100, 1000, and 10,000 mu g/L to reference polyethylene NPs (PER) or NPs made from polyethylene collected in the North Atlantic gyre (PEN, 7th continent expedition in 2015). Freshwater filter-feeding bivalves, Corbicula fluminea, were exposed to 1000 mu g/L of PER and PEN for 48 h to study a possible modification of their filtration or digestion capacity. The results show that PER and PEN do not influence the cell growth of T. weissiflogii, but the PEN exposure causes growth inhibition of S. subspicatus for all exposure concentrations tested. This growth inhibition is enhanced for a higher concentration of PER or PEN (10,000 mu g/L) in S. subspicatus. The marine diatom T. weissiflogii appears to be less impacted by plastic pollution than the green algae S. subspicatus for the exposure time. Exposure to NPs does not lead to any alteration of bivalve filtration; however, fecal and pseudo-fecal production increased after PEN exposure, suggesting the implementation of rejection mechanisms for inedible particles
A global analysis of the morphology of linear erosion features
No full textConcentrated flow erosion poses a serious threat to agriculture across the world as it scours soils into linear features that can be wide and large, which dramatically decreases land productivity and accessibility, and causes serious downslope and downstream impacts. Despite the widespread occurrence of concentrated flow erosion features across the globe, variations in their sizes have received limited attention. Their morphometric characteristics inform on the amount of fertile soil material eroded and transported to lower parts of landscapes and to river networks. The main objective of this study was to elucidate the impacts of climate (tropical, sub-tropical and temperate), soil texture (clayey, loamy, silty and sandy) and land use (cropland, forest, grassland and urban) on the morphology (length: L, width: W, depth: D, W:D ratio) of linear erosion features (rills and gullies). A total of 769 linear features from 53 published studies across the world were used in the current analysis. The average length was 458.2 m for gullies and 114.7 m for rills. Width averaged 9.5 m for gullies and 1.0 m for rills and W:D was respectively 4.0 and 6.7, which corresponded in all cases to significant difference at P < 0.05. Oceania exhibited the longest (1201 m on average) but shallowest (0.88 m) gullies. Asia had the widest (21.9 m) and Africa the deepest (6.3 m) gullies. In contrast, Europe exhibited shorter gullies (304 m) and rills (56 m) and of low width (5.0 and 0.6 m respectively). Besides, there was a trend for rills to decrease in L, W and D with the increase in mean annual precipitation and for rills' W to increase with increasing mean annual temperature (r = 0.32). The length of the features also increased from forest to settlement through grassland and cropland, and with increasing altitude above sea level (r = 0.47 for gullies and r = 0.26 for rills). As soil clay content increased, the depth of rills increased (r = 0.19) and their W:D decreased (r = - 0.14). These quantitative results may contribute to erosion modelling and to the spatial assessment of land susceptibility to concentrated flow erosion, which is a prerequisite for the protection and rehabilitation of ecosystems
Artemisinin and its derivatives target mitochondrial c-type cytochromes in yeast and human cells
No full textArtemisinin and its derivatives kill malaria parasites and inhibit the proliferation of cancer cells. In both processes, heme was shown to play a key role in artemisinin bioactivation. We found that artemisinin and clinical artemisinin derivatives are able to compensate for a mutation in the yeast Bcsl protein, a key chaperon involved in biogenesis of the mitochondrial respiratory complex III. The equivalent Bcsl variant causes an encephalopathy in human by affecting complex III assembly. We show that artemisinin derivatives decrease the content of mitochondrial cytochromes and disturb the maturation of the complex III cytochrome cl. This last effect is likely responsible for the compensation by decreasing the detrimental over-accumulation of the inactive pre-complex III observed in the bcs1 mutant. We further show that a fluorescent dihydroartemisinin probe rapidly accumulates in the mitochondrial network and targets cytochromes c and c1 in yeast, human cells and isolated mitochondria. in vitro this probe interacts with purified cytochrome c only under reducing conditions and we detect cytochrome c-dihydroartemisinin covalent adducts by mass spectrometry analyses. We propose that reduced mitochondrial c-type cytochromes act as both targets and mediators of artemisinin bioactivation in yeast and human cells
Association dynamics of tuna and purse seine bycatch species with drifting fish aggregating devices (FADs) in the tropical eastern Atlantic Ocean
No full textSeveral pelagic fish species are known to regularly associate with floating objects in the open ocean, including commercially valuable species. The tuna purse seine industry takes advantage of this associative behavior and has been increasingly deploying free-drifting man-made floating objects, also known as fish aggregating devices (FADs). Using passive acoustic telemetry, this study describes the associative dynamics of the main targeted tropical tuna species (Thunnus albacores, T. obelus and Katsuwonus pelamis), as well as three major bycatch species, silky shark (Carcharhinus falciformis), rainbow runner (Elagatis bipinmdata) and oceanic triggerfish (Canthidermis maculata). Short-term excursions away from the FADs were frequently performed by all tuna species as well by silky sharks. These excursions were characterized by a marked diel pattern, mainly occurring during nighttime. Rainbow runners and oceanic triggerfish were much more present at the FADs and rarely performed excursions. Average continuous residence times (CRTs) ranged from 6 days, for silky shark, up to 25 days for bigeye tuna. Similar to silky shark, average CRTs for skipjack tuna and oceanic triggerfish were less than 10 days. For yellowfin tuna and rainbow runner, CRTs averaged 19 and 16 days, respectively. Bigeye and yellowfin tuna remained associated to a single drifting FAD for a record of 55 days and 607 km traveled
Fluvial and oceanographic influences on suspended sediment dispersal in the Magdalena River Estuary
No full textThe Magdalena River is the main contributor of fresh water and sediment to the Caribbean Sea. Hydrological inputs from the Magdalena River are 10,287 and 4068 m(3) s(-1) at high and low flows, respectively. Sediment delivery from the Magdalena River is among the largest in the world, with 142 x 10(6) t yr(-1) of transported suspended matter. We used MODIS images to develop a regional model and assess the spatial and temporal variability of suspended sediment concentration at the mouth of the Magdalena River, map the extent of the turbidity plume using its morphometric properties, and identify the main fluvial and oceanographic factors associated with plume variability. We analyzed monthly average suspended sediment concentration data for the period 2003-2017. MODIS images were calibrated with in situ measurements of suspended sediment concentrations in surface waters of the study area. A finite mixing model was used to identify turbidity thresholds and define areas within the plume. Calculated suspended sediment concentrations indicate high turbidity in the Magdalena River mouth (178.6 +/- 78.7 mg L-1), values that are of the same order of magnitude as those measured in the Yangtze, Huang He and Amazon River mouths. Calculated plume areas (diffuse, solid and mixing) and their shapes suggest that the Magdalena River plume has a limited area, related to conditions such as wind speed and direction, streamflow, and sediment transport. Calculated areas and shapes demonstrate the ability to generate a near-field area, which indicates the presence of a clear convergence front. The data also emphasize the importance of sediment transport from the Magdalena River to the Caribbean Sea. Such fluvial transport is important in the biogeochemistry of estuarine systems, especially in turbid estuaries, where there is marked variability in the distribution of sediment in surface waters
Sexual health needs of female sex workers in Cote d'Ivoire : a mixed-methods study to prepare the future implementation of pre-exposure prophylaxis (PrEP) for HIV prevention
No full textObjective To describe sexual and reproductive health (SRH) needs of female sex workers (FSWs) to inform the future implementation of pre-exposure prophylaxis (PrEP) for HIV prevention in this population. Design and setting The ANRS 12361 PrEP-CI cross-sectional and mixed-methods study was designed and implemented with two community-based organisations in Cote d'Ivoire. Participants A convenience sample of 1000 FSWs aged >= 18, not known as HIV-positive, completed a standardised questionnaire assessing sociodemographic characteristics, sexual practices, use of community health services and a priori acceptability of PrEP. Twenty-two indepth interviews and eight focus group discussions were also conducted to document FSWs' risky practices and sexual behaviours, experiences with violence and discrimination, attitudes regarding HIV and sexually transmitted infections (STIs), and barriers to SRH services. Results Although 87% described consistent condom use with clients, more than 22% declared accepting condomless sexual intercourse for a large sum of money. Furthermore, condom use with their steady partner and knowledge of their partner's HIV status were low despite their acknowledged concurrent sexual partnerships. While inconsistent condom use exposed FSWs to STIs and undesired pregnancies, the prevalence of contraceptive strategies other than condoms was low (39%) due to fear of contraception causing sterility. FSWs faced obstacles to accessing SRH care and preferred advice from their peers or self-medication. Conclusions Despite adoption of preventive behaviour in most cases, FSWs are still highly exposed to HIV. Furthermore, FSWs seem to face several barriers to accessing SRH. Implementing PrEP among FSWs in West Africa, such as in Cote d'Ivoire, constitutes an opportunity to consider the regular follow-up of HIV-negative FSWs. PrEP initiation should not condition access to SRH services; conversely, SRH services could be a way to attract FSWs into HIV prevention. Our results highlight the importance of developing a people-focused approach that integrates all SRH needs when transitioning from PrEP efficacy trials to implementation
Impact of contrasted weather conditions on CDOM absorption/fluorescence and biogeochemistry in the eastern lagoon of New Caledonia
No full textNew Caledonia (Southwest Pacific), like all tropical Pacific Island countries, is impacted by weather events, climate change, and local anthropogenic forcing. Strong erosion of particles and dissolved organic matter (DOM) from ultramafic rocks, associated with trace metals dissemination (i.e., nickel, manganese and cobalt), potentially affects lagoon waters and coral reefs surrounding the main island. The CALIOPE (CALedonian Inherent Optical PropErties) cruises were performed along the Eastern Lagoon of New Caledonia (ELNC) (400 km, 13 transects from Bay to open ocean, 51 stations) during contrasted meteorological conditions: a dry period (October 2011), a windy situation (March 2014), and a strong rainy event (March 2016). CDOM absorption and fluorescence (FDOM), particulate absorption, backscattering, suspended particulate matter (SPM), total chlorophyll a (TChla), nutrients (NOx), pigment and phytoplankton composition were measured. Among the four CDOM fluorophores, the humic-like component (lambda(Ex)/lambda(Em): 235/460 nm), assimilated to a photoproduct of terrestrial organic matter, had relatively low fluorescence compared to protein-like fluorophores. As CDOM absorption, particulate absorption, backscattering, SPM, total chlorophyll a (TChla) and nutrient (NOx) concentrations, this humic-like material generally showed the highest values during rainfall events, the latter inducing an increase in riverine terrigeneous inputs and change toward higher phytoplankton size classes. The tyrosine 1-like (lambda(Ex)/lambda(Em): 220, 275/304 nm) and tryptophan-like fluorophores (lambda(Ex)/lambda(Em): 230, 300/352 nm) were strongly influenced by wind displaying a 7-fold and 3-fold increase, respectively in windy situation compared to calm conditions. These increases could be related to enhancements of autochthonous biological activities (highest mean concentrations of Synechococcus spp., phycoerythrin, pico- and nano-eukaryotes, heterotrophic bacteria and nanoplankton observed in wind condition) through the inputs of organic and mineral materials issued from the wind-induced sediment resuspension, atmospheric deposition and water mass mixing. By contrast, the tyrosine 2-like fluorophore (lambda(Ex)/lambda(Em): 245, 275/304 nm) substantially increased during rain events and presented the lowest values in wind conditions. These strong increases may be linked to the stimulation of planktonic activities due to riverine inputs. Therefore, this study emphasizes the significant differential influence of weather conditions (calm/wind/rain) on biogeochemistry and CDOM/FDOM distributions in the ELNC
Broader geographical distribution of Toscana virus in the Mediterranean region suggests the existence of larger varieties of sand fly vectors
No full textToscana virus (TOSV) is endemic in the Mediterranean basin, where it is transmitted by sand flies. TOSV can infect humans and cause febrile illness as well as neuroinvasive infections affecting the central and peripheral nervous systems. Although TOSV is a significant human pathogen, it remains neglected and there are consequently many gaps of knowledge. Recent seroepidemiology studies and case reports showed that TOSV's geographic distribution is much wider than was assumed a decade ago. The apparent extension of the TOSV circulation area raises the question of the sandfly species that are able to transmit the virus in natural conditions. Phlebotomus (Ph.) perniciosus and Ph. perfiliewi were historically identified as competent species. Recent results suggest that other species of sand flies could be competent for TOSV maintenance and transmission. Here we organize current knowledge in entomology, epidemiology, and virology supporting the possible existence of additional phlebotomine species such as Ph. longicuspis, Ph. sergenti, Ph. tobbi, Ph. neglectus, and Sergentomyia minuta in TOSV maintenance. We also highlight some of the knowledge gaps to be addressed in future studies