Intraspecific facilitation explains the spread of the invasive engineer Spartina anglica in Atlantic salt marshes
Questions Invasiveness depends in part on the ability of exotic species to either exclude native dominants or to fill an empty niche. Comparisons of niches and effects of closely related native and invasive species enable the investigation of this topic. Does Spartina anglica invade European salt marshes through competitive exclusion of the native Spartina maritima or due to the occurrence of an empty ecological niche in highly anoxic conditions? Study Site The Arcachon Bay (France). Methods At three intertidal levels, we quantified competitive response and effect abilities of the two species through a cross-transplantation removal experiment. We also compared the biomass, root/shoot ratio, productivity and environmental conditions (elevation, salinity, redox potential and soil moisture) of salt marsh communities dominated by the exotic Spartina anglica or the native Spartina maritima at three intertidal levels. Results Both established species showed similar biotic resistance to the invasion of the other species, but the exotic showed important intraspecific facilitation for growth. Species had similar niches and total biomass along a gradient of anoxic conditions, but the exotic had a much higher root/shoot ratio and productivity than the native. Owing to its rhizome density, the exotic showed high ability to increase sediment oxygenation, likely to explain its important intraspecific facilitation. Conclusions Our results showed that the invasion success of S. anglica cannot be explained by the competitive exclusion of the native or by its ability to fill an empty niche along a gradient of anoxia. Its behaviour as a self-facilitator invasive engineer very likely explains its rapid spread in the Bay and biotic resistance to the colonization of other congeneric species when established in dense patches. Additionally, we suggest that physical disturbance in marsh communities dominated by the native S. maritima may disrupt its biotic resistance against the invasion of S. anglica.
(Journal of Vegetation Science. vol. 30, n° 1100-9233, pp. 212-223, 01/03/2019)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
A Cool, Nutrient‐Enriched Eastern Equatorial Pacific During the Mid‐Pleistocene Transition
The emergence of high-amplitude, low-frequency glacial-interglacial cycles during the mid-Pleistocene climate transition (MPT; 800–1,200 ka) is associated with global cooling. In the eastern equatorial Pacific, sea surface temperatures cooled, and the upwelling-induced cold tongue expanded significantly during the MPT. Here we use sedimentary records of iron, biogenic silica, and nutrient-nitrogen consumption to evaluate biogeochemical changes hypothesized to accompany the cold tongue expansion. Our results suggest that the eastern equatorial Pacific of the MPT hosted surface waters with higher nitrate contents and biogenic silica production relative to the last 600 ka. Increased production occurred despite low iron supply. We attribute this to enhanced upwelling and nutrient enrichment of thermocline waters, both likely related to the northward migration of Southern Ocean fronts. The return of these fronts to their southward positions after the MPT may be associated with stronger drawdown of nutrients and, potentially, atmospheric CO2 in the Southern Ocean.
(Geophysical Research Letters. vol. 46, n° 0094-8276, pp. 2187-2195, 28/02/2019)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Comparative biomarker responses in Japanese medaka (Oryzias latipes) exposed to benzo[a]pyrene and challenged with betanodavirus at three different life stages
It is now well documented that several contaminants can modulate the fish immune system, leading to disrupted host resistance against pathogens and increased incidence of disease. Since fish are usually co-exposed to chemicals and pathogens in the natural environment, analysis of the immunotoxic effects of pollutants is particularly relevant. The authorities in the European Union have recommended the development of toxicity assays on cell cultures and embryos, as an alternative to testing in vertebrates. This is why in our study, a fish immune challenge assay was developed for the early life stages of Japanese medaka to evaluate and compare the relevance of new biomarkers. Fish were exposed to benzo[a]pyrene (BaP), a model pollutant, for 8days at the embryonic stage, or for 48h at the larvae and juvenile stages, and fish were infected with betanodavirus by bath-challenge of 10TCID/mL. Biometric changes and induction of malformations were observed after embryonic exposure. DNA damage and induction of EROD activity were recorded at the end of all chemical exposures. Viral infection increased the mortality rate significantly and disturbed the behavior of fish after light stimulation. While BaP exposure increased swimming speed, betanodavirus infection slowed swimming activity. In larvae co-exposed to BaP and the virus, the viral titer in the whole body was higher than in fish infected only with the virus. This study highlighted the sensitivity and usefulness of the immune challenge assay on the early life stages of Japanese medaka to evaluate the toxic effects of pollutants.
(Science of the Total Environment. vol. 652, n° 0048-9697, pp. 964-976, 20/02/2019)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ANSES, VIMEP, ANSES
Interactive effects of climate and topography on soil salinity and vegetation zonation in North‐African continental saline depressions
Questions: Complex distal factors such as climate and topography can interact to drive direct proximal ecological gradients and vegetation zonation in geographical and ecological space, in particular salinity and soil moisture in arid climates. We pose the following questions: (a) Does increasing climate aridity alter direct water and salinity gradients along topography gradients in saline depressions in arid climates? (b) Do these effects of increasing climate aridity in turn alter vegetation life-form zonation? (c) Does increasing climate aridity alter community composition along the zonation? Study site: Continental saline depressions of the Mediterranean arid climate of central and southern Tunisia. Methods: We sampled vegetation structure, diversity, and composition and environmental variables at five positions along the topography gradient of continental saline depressions in wet and dry conditions. Results: Climate aridity altered salinity gradients and vegetation structure but not diversity and community composition. Salinity increased with increasing aridity at the lowest positions of the depressions but decreased with increasing aridity at their highest positions. Total vegetation cover and relative abundance of therophytes decreased, whereas relative abundance of chamaephytes increased with increasing climate aridity at the upper habitats. Conclusions: Ecological factors acting at a regional scale can alter the spatial variation of other ecological factors acting at smaller spatial scales, ultimately explaining vegetation zonation in continental saline depressions. Salinity collapses with increasing aridity.
(Journal of Vegetation Science. vol. 30, n° 1100-9233, pp. 312-321, 15/02/2019)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Overtide generation by wind-induced waves in a tidal inlet of SW France
Quarter-diurnal tidal constituents are linked to tidal asymmetries and play a role in the morphodynamic evolution of inlets, estuaries and lagoons. A two-year non-continuous dataset of current velocities and waves was used to improve understanding on the generation of quarter-diurnal harmonics. Data analysis provides evidence for the generation of quarter-diurnal harmonics by wind-induced waves. Data were collected at the entrance to the Arcachon Lagoon, a mixed-energy tidal inlet in Southwest France. Temporal variability of the quarter-diurnal tidal current was identified through wavelet analysis of the main velocity component (alongshore velocity). Quarter-diurnal velocity amplitudes, bottom and wave stresses, and significant wave height suggested a linkage between quarter-diurnal amplification and wave action. Both significant wave height and wave stress were coherent with quarter-diurnal current amplitudes at synoptic frequencies, most markedly in winter months of both years observed. These coherences corroborated the hypothesis that wind-induced waves enhance bottom stresses that can generate and augment quarter-diurnal currents in this region.
(Continental Shelf Research. vol. 174, n° 0278-4343, pp. 66-75, 15/02/2019)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
A dual nanosecond-pulsed laser setup for nanocomposite synthesis—Ag nanoparticles in Al 2 O 3 /VO 2 matrix
(Journal of Applied Physics. vol. 125, n° 0021-8979, pp. 054301, 07/02/2019)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IRCER, IPAM, UNILIM, INC-CNRS, CNRS, IRCER-AXE2, IRCER, IPAM, UNILIM, INC-CNRS, CNRS
Microfluidic technology for plankton research
Plankton produces numerous chemical compounds used in cosmetics and functional foods. They also play a key role in the carbon budget on the Earth. In a context of global change, it becomes important to understand the physiological response of these microorganisms to changing environmental conditions. Their adaptations and the response to specific environmental conditions are often restricted to a few active cells or individuals in large populations. Using analytical capabilities at the subnanoliter scale, microfluidic technology has also demonstrated a high potential in biological assays. Here, we review recent advances in microfluidic technologies to overcome the current challenges in high content analysis both at population and the single cell level.
(Current Opinion in Biotechnology. vol. 55, n° 0958-1669, pp. 134-150, 01/02/2019)
CRPP, UB, INC-CNRS, CNRS, CRPP, INC-CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, MPIDS
Fate of antibiotics present in a primary sludge of WWTP during their co-composting with palm wastes
(Waste Management. vol. 84, n° 0956-053X, pp. 13-19, 01/02/2019)
ENSAT, INP-ENSAT, AgroToulouse, INP-AgroToulouse, Toulouse INP, Comue de Toulouse, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LMFE, UCA, A2E, Toulouse INP, Comue de Toulouse
Distinguishing intraplate from megathrust earthquakes using lacustrine turbidites
Subduction zone seismicity arises from megathrust, crustal, and intraslab earthquakes, and understanding the recurrence patterns of each type is crucial for hazard assessments. Lake sediments can record earthquakes from all three seismogenic sources. Here, we studied the turbidite record of Lo Encañado, an Andean lake located in central Chile. We show that Lo Encañado turbidites can be attributed to (1) subaquatic slope failure by earthquake shaking (coseismic phase), (2) floods or human impact, and (3) postseismic catchment response. All historical events with shaking intensities >VI (modified Mercalli intensity) have triggered coseismic turbidites, but only the intraplate earthquakes triggered subaerial slope failures followed by postseismic turbidites. We argue that this contrasting result is due to different spectra of seismic waves from these earthquake sources: higher-frequency accelerations from intraplate earthquakes are hardly attenuated in rocks around the lake, whereas lower-frequency accelerations from megathrust earthquakes are amplified in soft lake sediments. We tested our findings by comparing acceleration response spectra of recent and historical intraslab and megathrust earthquakes along a longitudinal profile. Results suggest that the location of Andean lakes is ideal to distinguish earthquake sources.
(Geology. vol. 47, n° 0091-7613, pp. 127-130, 01/02/2019)
RCMG, UGent, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Where has the pollution gone? A survey of organic contaminants in Ho Chi Minh city / Saigon River (Vietnam) bed sediments
A wide range of persistent organic chemicals, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), some insecticides, as well as polybrominated diphenyl ethers (PBDEs) and some perfluoroalkyl substances (PFASs) were analyzed in 17 bed sediments collected along the Saigon River and at adjacent canal mouths from upstream to downstream in Ho Chi Minh City (Vietnam). Concentrations were rather low for PAHs, as well as for legacy PCBs and dichloro-diphenyl-trichlorethane and metabolites (DDTs), or below detection limits for several PFASs and all PBDEs measured. Several insecticides (chlorpyrifos-ethyl, and the pyrethroids cypermethrin and λ-cyhalothrin) displayed rather high concentrations at a few sites within the city. There was no distinct upstream – downstream trend for PAHs, (DDTs) or PCBs. Although adjacent canal sediments tended to be more contaminated than Saigon River sediments, the differences were not significant. Emissions are almost certainly substantial for PAHs, and probably also for other contaminants such as PBDEs and some PFASs. During the dry season, contaminants are presumably stored in the city, either in canals or on urban surfaces. Heavy rainfall during the monsoon period carries away contaminated particle flows into the canals and then the Saigon River. The strong tidal influence in the river channel hinders the accumulation of contaminated particles. Contaminated deposits should accordingly be investigated further downstream in depositional environments, such as the mangrove.
(Chemosphere. vol. 217, n° 0045-6535, pp. 261-269, 01/02/2019)
IRSTEA, LEHNA, UCBL, ENTPE, CNRS, GéHCO, UT, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, EPFL, HCMUS, CARE, HCMUT, VNU-HCM, IGE, IRD, Grenoble INP, INSU - CNRS, CNRS, UGA [2016-2019], Fédération OSUG