Leptospira, élevages et écosystèmes : ce que les données de laboratoire nous disent

International audienceL’infection par les leptospires pathogènes en élevage soulève deux questions d’actualité. La première est une question économique relative aux pertes de production qui doivent être réduites pour optimiser la marge financière des éleveurs. La seconde est une question de santé publique relative à la composante zoonotique des leptospires infectant les animaux de production et à l’enregistrement d’un nombre croissant de leptospiroses humaines en lien avec une exposition aux animaux de rente. Ces questions restent ouvertes aujourd’hui en France. Cependant l’analyse des données de laboratoire peut apporter des éléments pertinents pour mieux gérer les infections en élevag

Ocean temperature impact on ice shelf extent in the eastern Antarctic Peninsula

The recent thinning and retreat of Antarctic ice shelves has been attributed to both atmosphere and ocean warming. However, the lack of continuous, multi-year direct observations as well as limitations of climate and ice shelf models prevent a precise assessment on how the ocean forcing affects the fluctuations of a grounded and floating ice cap. Here we show that a +0.3–1.5 °C increase in subsurface ocean temperature (50–400 m) in the northeastern Antarctic Peninsula has driven to major collapse and recession of the regional ice shelf during both the instrumental period and the last 9000 years. Our projections following the representative concentration pathway 8.5 emission scenario from the Fifth Assessment Report of the Intergovernmental Panel on Climate Change reveal a +0.3 °C subsurface ocean temperature warming within the coming decades that will undoubtedly accelerate ice shelf melting, including the southernmost sector of the eastern Antarctic Peninsula.J.E. and C.E. are financially supported by the Spanish Ministerio de Economia y Competitividad (CTM2014–60451-C2–1-P) co-funded by the European Union through FEDER funds. J.-H.K. was supported by the grants funded by the Korea Polar Research Institute (KOPRI, NRF-2015M1A5A1037243 and PE19010). S.S. and J.S.S.D. are supported by the Netherlands Earth System Science Center funded by the Dutch Ministry of Education and Science (OCW). G.S. and D.S. were funded by the EMBRACE project (European Union’s FP7, Grant Number: 282672). We also acknowledge funding from the French ANR CLIMICE, ERC ICEPROXY 203441, ESF PolarClimate, HOLOCLIP 625 and FP7 Past4Future as well as the Netherlands Organisation of Scientific Research (NWO) through a VICI grant to S.S. The HOLOCLIP Project, a joint research project of ESF PolarCLIMATE programme, is funded by national contributions from Italy, France, Germany, Spain, Netherlands, Belgium and the United Kingdom. The research leading to these results has also received support from the European Union’s Seventh Framework programme (FP7/2007–2013) under Grant Agreement No. 243908, “Past4Future, Climate change – Learning from the past climate”

Data report: evaluation of shipboard magnetostratigraphy by alternating field demagnetization of discrete samples, Expedition 361, Site U1475

The paleomagnetic shipboard data of International Ocean Discovery Program Site U1475, with a record reaching back to approximately 7 Ma, allowed for the identification of major magnetic polarity chrons and subchrons back to ~3.5 Ma. However, the natural remanent magnetization (NRM) was very weak, and transitional intervals with unclear polarity were as thick as several meters. The midpoints of these transitional intervals were reported in the shipboard results without decimal places because of the poor data quality. To evaluate and possibly refine the shipboard magnetostratigraphy, subsampling was performed across the polarity transitions. Detailed alternating field (AF) demagnetization experiments were conducted on these discrete samples and were complemented by anhysteretic remanent magnetization acquisition measurements and subsequent demagnetization. AF demagnetization data of NRM were analyzed using anchored principal component analysis (PCA) to obtain the characteristic remanent magnetization. These PCA results generally confirm the smoothed signal across polarity transitions at Site U1475. However, the midpoint depths of the top of the Keana Subchron, the Gauss-Matuyama and Matuyama-Brunhes boundaries, and the base of the Olduvai Subchron were adjusted

Sea ice diatom contributions to Holocene nutrient utilization in East Antarctica

Combined high-resolution Holocene δ30Sidiat and δ13Cdiat paleorecords are presented from theSeasonal Ice Zone, East Antarctica. Both data sets reflect periods of increased nutrient utilization by diatomsduring the Hypsithermal period (circa 7800 to 3500 calendar years (cal years) B.P.), coincident with a higherabundance of open water diatom species (Fragilariopsis kerguelensis), increased biogenic silica productivity(%BSi), and higher regional summer temperatures. The Neoglacial period (after circa 3500 cal years B.P.) isreflected by an increase in sea ice indicative species (Fragilariopsis curta and Fragilariopsis cylindrus,upto50%) along with a decrease in %BSi and δ13Cdiat(< 18‰ to 23‰). However, over this period, δ30Sidiatdata show an increasing trend, to some of the highest values in the Holocene record (average of +0.43‰).Competing hypotheses are discussed to account for the decoupling trend in utilization proxies including ironfertilization, species-dependent fractionation effects, and diatom habitats. Based on mass balance calculations,we highlight that diatom species derived from the semi-enclosed sea ice environment may have a confoundingeffect upon δ30Sidowncorecompositions of the seasonal sea ice zone. A diatom composition, with approximately28% of biogenic silica derived from the sea ice environment (diat-SI) can account for the increased averagecompo sition of δ30Sidiatduring the Neoglacial. These data highlight the significant role sea ice diatoms can playwith relation to their export in sediment records, which has implications on productivity reconstructions fromthe seasonal ice zone

Thalassiosira lentiginosa size variation and associated biogenic silica burial in the Southern Ocean over the last 42 kyrs

International audienceThe diatom Fragilariopsis kerguelensis (O′Meara) Hustedt is thought to be the main carrier of biogenic silica to the Southern Ocean sea-floor, thereby attracting most investigations of diatom biometry. Thalassiosira lentiginosa (Janisch) Fryxell, a large centric diatom which is the second most abundant species in the Southern Ocean, conversely received very little attention to date. We here present the first study on modern sediments to explore the variability of the mean valve area of T. lentiginosa in relation to productivity and modern environmental conditions. Larger T. lentiginosa are observed around the Polar Front Zone with size decreasing both northward and southward as previously observed for F. kerguelensis. Such a pattern neither corresponds to the species productivity changes nor with the iron concentration in surface waters. Conversely, this pattern may be partly due to the low efficiency of Si uptake, internal transport and deposition of silicic acid under conditions which are outside of the species specific temperature range, i.e. at the lower and upper limit of the diatom ecological preferences. We also propose that T. lentiginosa mean valve area variations in four deep-sea cores across the frontal zones in the Atlantic and Indian sectors of the Southern Ocean resulted from changes in sea-surface temperatures and sea-ice presence modulating the species ability to make use nutrient stocks and controlling the length of its growing season, respectively. Our results also indicate that T. lentiginosa exported more biogenic silica to the sea-floor than F. kerguelensis over the last 42 kyrs

Miniaturization of Butler Matrices

International audienc

Circulating serogroups of Leptospira in swine from a 7-year study in France (2011–2017)

International audienceAbstract Background Leptospirosis is a widespread zoonotic disease caused by pathogenic Leptospira and is responsible for significant economic porcine livestock losses. Knowledge of Leptospira serogroups and their distributions is important for evaluation of the relevance of leptospirosis management measures, including use of the prophylactic vaccine that was recently made available in France. A retrospective study was conducted to determine the relationships between different circulating Leptospira serogroups. Pigs from across France presenting clinical signs suggestive of leptospirosis were tested with the microagglutination test (MAT) between 2011 and 2017. We used weighted averages to determine serogroup distributions according to MAT results and considering cross-reactions. Results A total of 19,395 pig sera, mostly from Brittany, were tested, and 22.7% were found to be positive for at least one Leptospira serogroup. Analysis of the 4,346 seropositive results for which the putative infective serogroup could be defined, revealed that two out of ten serogroups were much more frequent than the others: Australis (48.5%) and Icterohaemorrhagiae (38.2%). Other serogroups, including Autumnalis, Panama, Ballum, Tarassovi, Sejroe, Grippotyphosa, Bataviae, and Pomona, were less common. Conclusions Although diagnostic laboratory data cannot be extrapolated to infer the distribution of Leptospira serogroups at the nationwide scale in France, the analysis of such data can provide an overview of the relationship between circulating Leptospira serogroups in space and time. During the last decade, protection against the serogroups Australis and Icterohaemorrhagiae would have prevented most of the clinical porcine leptospirosis cases in the large number of farms that we studied. In the future, epidemiological information related to circulating Leptospira serogroups should be extracted from data with a standardized approach for use in nationwide or international surveillance and prophylactic strategy support

Mapping hotspots of environmental burdens in the framework of cumulative risk assessment in wallonia

Differential exposure to multiple environmental burdens and benefits across populations with varying vulnerability can contribute heavily to health inequalities. Developing environment and health information systems has therefore become a major focus for public health. In this framework, the Scientific Institute of Public Service (ISSeP) works on building an integrated approach of environmental exposure assessment in the Walloon region, Belgium. This study develops an indexbased approach to assess the multiple environmental burdens at regional level and detailed local resolution that can be used in a spatial web tool. Indicators are based on environmental measure of pollutants in ambient air and soil, and on stressors for citizens related to noise and radon. Two methods were combined to identify both zones where pollutions and stressors are cumulating, even below threshold values, and zones where the exceedance of threshold values is frequent. First, a ratio value is calculated for each spatial unit (i.e. statistical sector) by dividing the indicator value by the corresponding threshold values quoted by the WHO or Walloon legal limit values. Other pollution sources (roads, industries, landfills, mine heaps, ...) are estimated by specific GIS processing based on Euclidean distance analysis which vary in relation to pollution effect to population. Secondly, environmental indicators are mapped as proportions of spatial units where the level of potential detrimental environmental factors exceeds the limit values. The spatial tool makes then possible the flexible and weighted combination of the normalized indicators, by computing online the resulting composite indicator. The approach developed in the present study will be compared to other case studies and their aggregation methods by focusing on results and the possible implications on planning interventions by the decision makers

IR Laser Extraction Technique Applied to Oxygen Isotope Analysis of Small Biogenic Silica Samples

International audienc

Sea surface temperature of sediment core GeoB3606-1

Although productivity variations in coastal upwelling areas are mostly attributed to changes in wind strength, productivity dynamics in the Benguela Upwelling System (BUS) is less straightforward due to its complex atmospheric and hydrographic settings. In view of these settings, past productivity variations in the BUS can be better investigated with downcore sediments representing different productivity regimes. In this study, two sediment cores retrieved at ca. 25°–26°S in the BUS and representing different productivity regimes were studied. By using micropaleontological, geochemical and temperature proxies measured on core MD96-2098, recovered at 2910 m water depth in the bathypelagic zone at 26°S off Namibia, variations of filament front location, productivity and temperature in the central BUS over the past 70 kyr were reconstructed. The comparison with newly-generated alkenone-based sea-surface temperature (SST) and previously obtained data at site GeoB3606-1 (~ 25°S; ca. 50 km shoreward from MD96-2098) allowed the recognition of four main phases: (1) upwelling front above the mid slope (70 kyr–44 kyr), (2) seaward displacement of the upwelling front beyond the mid slope (44 kyr–31 kyr), (3) main upwelling front over the hemipelagial (31 kyr–19 kyr), and (4) shoreward contraction of the upwelling filament, and decreased upwelling strength over most of the uppermost bathypelagic (19 kyr–6 kyr). The latitudinal migration of the Southern Hemisphere westerlies and the consequent contractions and expansions of the subpolar gyre played a significant role in millennial and submillennial variability of SST off Namibia. The strength of the southeasterly trade winds, rapid sea-level variations and the equatorward leakage of Antarctic silicate might have acted as amplifiers. Although late Quaternary variations of productivity and upwelling intensity in eastern boundary current systems are thought to be primarily linked to the variability in wind stress, this multi-parameter reconstruction shows that interplaying mechanisms defined the temporal variation pattern of the filament front migrations and the diatom production off Namibia during the past 70 kyr