Short scale (6 h) temporal variation of sinking fluxes of planktonic and terrigeneous lipids at 200m in the NW Mediterranean Sea

Drifting sediment trap experiments were carried out at high temporal frequency in the northwestern Mediterranean in the course of the DYNAPROC2 campaign, every 6 h at 200m depth. Molecular biomarkers were analyzed in selected subsets of consecutive samples. Fluxes of n-alkanes, long-chain alkenones, sterols and steroid ketones show high variability between consecutive 6-hsamples, comparable in range to seasonnal variability. n-Alkane export ranges from 1.4 to 29.7 μgm-2 d-1, fluxes of C 37 alkenones varies from 0 to 14.2 μgm-2 d -1. Fluxes of sterols, steroid ketones and C30 alkane diol, respectively range from 31 to 377, 2.2 to 46 and 0.3 to 9.3 μgm -2 d-1. The Biomarker 10 composition is consistent with reworked algal and zooplanktonic organic matter with a remarkable refractory character. After a rain event ensuing the intrusion of coastal water at the study site, the relative signature of higher plant increases and corresponds to higher export fluxes of long-chain odd n-alkanes. Most phytoplanktonic biomarkers show concurrent variability in fluxes. Linear correlations between fluxes of distinct 15 biomarkers and between fluxes of biomarkers and flux of total carbon suggest that the short term temporal variability of export fluxes depends primarily on physical constrains exerted by carrier particle dynamics. Linear correlation of their carbon-normalized concentrations explained a lower part of the variance, indicating that short-term variability in particle composition is a secondary driver of flux timing. At the end of summer strat20 ification, export fluxes account for ca. 1% of the primary productivity. In this studied situation, biomarkers have a long residence time in the water column before they are exported at 200 m. Biomarkers exported at 200m may thus record processes averaged over a larger period than the sampling frequency. For instance, phytoplanktonic biomarker composition of sinking particles fails to reflect the community changes occur25 ring over the 4 weeks of study. At higher time resolution, the diel variability in primary productivity is not recorded by biomarker fluxes either. The coupling between primary productivity and biomarker export shows significant changes on time scales of days and even of 6 h. © Author(s) 2009

Candida tropicalis antifungal cross-resistance is related to different azole target (Erg11p) modifications

ABSTARCT: Candida tropicalis ranks between third and fourth among Candida species most commonly isolated from clinical specimens. Invasive candidiasis and candidemia are treated with amphotericin B or echinocandins as first-line therapy, with extended-spectrum triazoles as acceptable alternatives. Candida tropicalis is usually susceptible to all antifungal agents, although several azole drug-resistant clinical isolates are being reported. However, C. tropicalis resistant to amphotericin B is uncommon, and only a few strains have reliably demonstrated a high level of resistance to this agent. The resistance mechanisms operating in C. tropicalis strains isolated from clinical samples showing resistance to azole drugs alone or with amphotericin B cross-resistance were elucidated. Antifungal drug resistance was related to mutations of the azole target (Erg11p) with or without alterations of the ergosterol biosynthesis pathway. The antifungal drug resistance shown in vitro correlated very well with the results obtained in vivo using the model host Galleria mellonella. Using this panel of strains, the G. mellonella model system was validated as a simple, nonmammalian minihost model that can be used to study in vitro-in vivo correlation of antifungals in C. tropicalis. The development in C. tropicalis of antifungal drug resistance with different mechanisms during antifungal treatment has potential clinical impact and deserves specific prospective studies

Marine ecosystems’ responses to climatic and anthropogenic forcings in the Mediterranean

Corrigendum : https://doi.org/10.1016/j.pocean.2011.08.003International audienceThe semi-enclosed nature of the Mediterranean Sea, together with its smaller inertia due to the relative short residence time of its water masses, make it highly reactive to external forcings, in particular variations of water, energy and matter fluxes at the interfaces. This region, which has been identified as a “hotspot” for climate change, is therefore expected to experience environmental impacts that are considerably greater than those in many other places around the world. These natural pressures interact with the increasing demographic and economic developments occurring heterogeneously in the coastal zone, making the Mediterranean even more sensitive. This review paper aims to provide a review of the state of current functioning and responses of Mediterranean marine biogeochemical cycles and ecosystems with respect to key natural and anthropogenic drivers and to consider the ecosystems’ responses to likely changes in physical, chemical and socio-economical forcings induced by global change and by growing anthropogenic pressure at the regional scale. The current knowledge on and expected changes due to single forcing (hydrodynamics, solar radiation, temperature and acidification, chemical contaminants) and combined forcing (nutrient sources and stoichiometry, extreme events) affecting the biogeochemical fluxes and ecosystem functioning are explored. Expected changes in biodiversity resulting from the combined action of the different forcings are proposed. Finally, modeling capabilities and necessity for modeling are presented. A synthesis of our current knowledge of expected changes is proposed, highlighting relevant questions for the future of the Mediterranean ecosystems that are current research priorities for the scientific community. Finally, we discuss how these priorities can be approached by national and international multi-disciplinary research, which should be implemented on several levels, including observational studies and modeling at different temporal and spatial scales

Marine ecosystems’ responses to climatic and anthropogenic forcings in the Mediterranean

Corrigendum : https://doi.org/10.1016/j.pocean.2011.08.003International audienceThe semi-enclosed nature of the Mediterranean Sea, together with its smaller inertia due to the relative short residence time of its water masses, make it highly reactive to external forcings, in particular variations of water, energy and matter fluxes at the interfaces. This region, which has been identified as a “hotspot” for climate change, is therefore expected to experience environmental impacts that are considerably greater than those in many other places around the world. These natural pressures interact with the increasing demographic and economic developments occurring heterogeneously in the coastal zone, making the Mediterranean even more sensitive. This review paper aims to provide a review of the state of current functioning and responses of Mediterranean marine biogeochemical cycles and ecosystems with respect to key natural and anthropogenic drivers and to consider the ecosystems’ responses to likely changes in physical, chemical and socio-economical forcings induced by global change and by growing anthropogenic pressure at the regional scale. The current knowledge on and expected changes due to single forcing (hydrodynamics, solar radiation, temperature and acidification, chemical contaminants) and combined forcing (nutrient sources and stoichiometry, extreme events) affecting the biogeochemical fluxes and ecosystem functioning are explored. Expected changes in biodiversity resulting from the combined action of the different forcings are proposed. Finally, modeling capabilities and necessity for modeling are presented. A synthesis of our current knowledge of expected changes is proposed, highlighting relevant questions for the future of the Mediterranean ecosystems that are current research priorities for the scientific community. Finally, we discuss how these priorities can be approached by national and international multi-disciplinary research, which should be implemented on several levels, including observational studies and modeling at different temporal and spatial scales