Search

Beach slope is a critical parameter to, e.g., beach safety, wave reflection at the coast and longshore transport rate. However, it is usually considered as a time-invariant and profile-average parameter. Here, we apply a state-of-the-art equilibrium model to hindcast beach slope variability from the time scales of days to years at the high-energy meso-macrotidal sandy beach of Truc Vert, southwest France. We use 9 years of bimonthly beach surveys to compute beach slope time series at different elevations. Results show that beach slope exhibits an equilibrium response with contrasting behaviors along two distinct areas of the beach profile. From 0 to 2 m above mean sea level, which is located under the berm crest, a slope response predominantly at the storm time scale is observed. The beach slope steepens under low energy waves, with the equilibrium model explaining up to 40% of the observed beach slope variability. In contrast, from 2.5 to 4 m above mean sea level, which is above the berm crest, the beach slope steepens under high-energy waves. Within this region of the beach profile, the response time scale increases upwards from seasonal (~2.5 m) to seasonal (~4 m), with the model explaining up to 65% of the observed beach slope variability. Such behaviors are found to be enforced by the berm dynamics developing from the end of the winter to early autumn, providing new perspectives to model and predict beach slope on sandy beaches.

International audience; Droughts affect the interannual variability of global land carbon fluxes and are expected to exert widespread impacts on the carbon cycle given a future climate with more intense and frequent droughts. Evidence indicates that the impacts of droughts on the carbon cycle vary in different seasons, but a quantitative examination of the seasonal differences is lacking. Here we ensemble multiple data streams for greenness indices and carbon fluxes, including those from remote sensing observations, flux tower upscaling, atmospheric inversions, and dynamic global vegetation models (DGVMs), to quantify the seasonal responses of vegetation to extreme droughts in China. We find that summer droughts cause the largest negative responses of leaf area index (LAI, with median standardized anomalies of -0.40), gross primary productivity (GPP, -0.55), and net ecosystem productivity (NEP, -0.74); notably, droughts in autumn largely suppress carbon uptake. The response patterns show a high degree of heterogeneity, and we identify the factors driving these spatial variations using the extreme gradient boosting (XGBoost) machine learning approach. Climate is the dominant driver of spring and autumn GPP responses while LAI predominantly drives summer GPP loss. Looking into the biotic factors, carry-over effects (previous-season vegetation growth affecting current-season growth) contribute substantially to the alleviation of drought stress, in that previous-season greening compensate vegetation loss during droughts. Our results not only quantify the seasonal response differences in carbon fluxes and greenness, but suggest that carbon fluxes respond more sensitively to drought than greenness. Also, we show seasonal differences in the degree to which factors contribute to drought impacts, which highlight that annual-scale drought analyses may mask spring and autumn vegetation response to droughts.

Ticks are a growing concern to human and animal health worldwide and they are leading vectors of arthropod-borne pathogens in the United States. Ticks transmit a wide range of pathogenic microorganisms to humans and animals causing important health and economic impacts. Ticks are pool blood feeders that can attach to the host skin for days to weeks using their saliva to counteract the host defenses. Tick saliva, as in other hematophagous arthropods, contains pharmacological and immunological active compounds, which modulate local and systemic immune responses and induce antibody production. In the present study, we explore differences in the salivary gland extract (SGE) protein content of ticks, Amblyomma americanum, raised in a laboratory colony (CT) versus those found in the field (FT). Western-blot testing showed a set of different immunogenic bands for each antigen. Protein sequencing data from these bands revealed 39 proteins between 10 and 25 kDa from 19 CT and 20 FT. In addition, we measured human IgG antibodies against SGE from CT and FT in healthy individuals residing in Kansas. ELISA revealed that IgG antibody levels were higher when using the SGE from CT as compared to that from FT. Interestingly, antibody levels against both, LT and FT, were high in the warm months (May-June) and decreased in the cold months (September– November). In vitro testing using HUVEC, U937 and SH­SY5Y human cell lines showed higher induction of expression of inflammatory related genes when treating cells with SGE from FT. In conclusion, our results show that the human serum samples reacted more with the CT protein content whereas the FT saliva induced a higher in vitro immune response, causing more inflammation. We hypothesize that differences in the salivary proteins between CT and FT may explain the differential immune responses observed in this study. It is possible that the salivary proteins absent in CT but present in FT are required for tick fitness in nature and possibly have helped to adapt to specific hosts.

International audience; Seasonal variation in the response of riverine microbial communities to an environmentally relevant exposure to glyphosate (about 10 microgl(-1)) was assessed on natural communities collected in spring and summer, using two 14-day microcosm studies. The two experiments showed no major effect of glyphosate on algal biomass (chlorophyll a concentrations), bacterial activity ([(3)H]thymidine incorporation), or bacterial community diversity (16S PCR-TTGE detection). Effects on algal community composition (genus-level taxonomic identification) and eukaryotic community diversity (18S PCR-DGGE on