HMG-CoA reductase is regulated by environmental salinity and its activity is essential for halotolerance in halophilic fungi

The activity and level of HMG-CoA reductase (HMGR) were addressed in halophilic fungi isolated from solar saltpans. Representative fungi belonging to the orders Dothideales, Eurotiales and Wallemiales have a specific pattern of HMGR regulation, which differs from salt-sensitive and moderately salt-tolerant yeasts. In all of the halophilic fungi studied, HMGR amounts and activities were the lowest at optimal growth salinity and increased under hyposaline and hypersaline conditions. This profile paralleled isoprenylation of cellular proteins in H. werneckii. Inhibition of HMGR in vivo by lovastatin impaired the halotolerant character. HMGR may thus serve as an important molecular marker of halotolerance

Adaptation of extremely halotolerant black yeast Hortaea werneckii to increased osmolarity: a molecular perspective at a glance

Halophilic adaptations have been studied almost exclusively on prokaryotic microorganisms. Discovery of the black yeast Hortaea werneckii as the dominant fungal species in hypersaline waters enabled the introduction of a new model organism to study the mechanisms of salt tolerance in eukaryotes. Its strategies of cellular osmotic adaptations on the physiological and molecular level revealed novel, intricate mechanisms to combat fluctuating salinity. H. werneckii is an extremely halotolerant eukaryotic microorganism and thus a promising source of transgenes for osmotolerance improvement of industrially important yeasts, as well as in crops

Precision of the current methods to measure the alkenone proxy UK'37 and absolute alkenone abundance in sediments : results of an interlaboratory comparison study

Measurements of the UK'37 index and the absolute abundance of alkenones in marine sediments are increasingly used in paleoceanographic research as proxies of past sea surface temperature and haptophyte (mainly coccolith-bearing species) primary productivity, respectively. An important aspect of these studies is to be able to compare reliably data obtained by different laboratories from a wide variety of locations. Hence the intercomparability of data produced by the research community is essential. Here we report results from an anonymous interlaboratory comparison study involving 24 of the leading laboratories that carry out alkenone measurements worldwide. The majority of laboratories produce data that are intercomparable within the considered confidence limits. For the measurement of alkenone concentrations, however, there are systematic biases between laboratories, which might be related to the techniques employed to quantify the components. The maximum difference between any two laboratories for any two single measurements of UK'37 in sediments is estimated, with a probability of 95%, to be <2.18C. In addition, the overall within-laboratory precision for the UK'37 temperature estimates is estimated to be <1.68C (95% probability). Similarly, from the analyses of alkenone concentrations the interlaboratory reproducibility is estimated at 32%, and the repeatability is estimated at 24%. The former is compared to a theoretical estimate of reproducibility and found to be excessively high. Hence there is certainly scope and a demonstrable need to improve reproducibility and repeatability of UK'37 and especially alkenone quantification data across the community of scientists involved in alkenone research

Water-mass control on phytoplankton spatiotemporal variations in the northeastern East China Sea and the western Tsushima Strait revealed by lipid biomarkers

Continental margin ecosystems in the western North Pacific Ocean are subject to strong climate forcing and anthropogenic impacts. To evaluate mechanisms controlling phytoplankton biomass and community structure variations in marginal sea‐open ocean boundary regions, brassicasterol, dinosterol and C37 alkenones were measured in suspended particles in summer and autumn from 2012 to 2013 in the northeastern East China Sea and the western Tsushima Strait (NEECS‐WTS). In summer, the concentrations of brassicasterol (40 ‐ 1535 ng L‐1) and dinosterol (4.2 ‐ 94 ng L‐1) were higher in the southwest of Cheju Island, while C37 alkenones (0 ‐ 30 ng L‐1) were higher in the south of Cheju Island. In autumn, brassicasterol (12 ‐ 106 ng L‐1), dinosterol (2.4 ‐ 21 ng L‐1) and C37 alkenones (0.7 – 7.0 ng L‐1) were higher in the southwest of Cheju Island and the WTS, and higher C37 alkenones also occurred in the Okinawa Trough. Correlation analysis of biomarkers and environmental conditions (temperature, salinity and inorganic nutrient concentrations) clearly demonstrated that phytoplankton biomass and community structure variations can be well elucidated by water masses as indexed by temperature and salinity. High nutrients from the Changjiang River were the main cause of high biomass in summer, while nutrients from subsurface water were likely the key factor regulating phytoplankton biomass in open ocean water stations in autumn. This study indicates that mechanisms controlling phytoplankton biomass in marginal sea‐open ocean boundary regions should be classified by various water masses with different nutrient concentrations, instead of by geography

Precision of the current methods to measure the alkenone proxy U₃₇ K’ and absolute alkenone abundance in sediments: results of an interlaboratory comparison study

Measurements of the U₃₇ K’ index and the absolute abundance of alkenones in marine sediments are increasingly used in paleoceanographic research as proxies of past sea surface temperature and haptophyte (mainly coccolith-bearing species) primary productivity, respectively. An important aspect of these studies is to be able to compare reliably data obtained by different laboratories from a wide variety of locations. Hence the intercomparability of data produced by the research community is essential. Here we report results from an anonymous interlaboratory comparison study involving 24 of the leading laboratories that carry out alkenone measurements worldwide. The majority of laboratories produce data that are intercomparable within the considered confidence limits. For the measurement of alkenone concentrations, however, there are systematic biases between laboratories, which might be related to the techniques employed to quantify the components. The maximum difference between any two laboratories for any two single measurements of U₃₇ K’ in sediments is estimated, with a probability of 95%, to be <2.1°C. In addition, the overall within-laboratory precision for the U₃₇ K’ temperature estimates is estimated to be <1.6°C (95% probability). Similarly, from the analyses of alkenone concentrations the interlaboratory reproducibility is estimated at 32%, and the repeatability is estimated at 24%. The former is compared to a theoretical estimate of reproducibility and found to be excessively high. Hence there is certainly scope and a demonstrable need to improve reproducibility and repeatability of U₃₇ K’ and especially alkenone quantification data across the community of scientists involved in alkenone research

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

Drifting sediment trap measurements were carried out at high temporal frequency in the northwestern Mediterranean Sea in the course of the DYNAPROC 2 campaign, during the transition between late summer to autumn conditions. Molecular biomarkers were analyzed in selected subsets of consecutive samples collected for 6 h at 200 m depth. Fluxes of n-alkanes, long-chain alkenones, sterols and steroid ketones show high variability between consecutive 6-h samples, comparable in range to seasonal variability. n-Alkane export ranges from 1.4 to 29.7 mu g m(-2) d(-1), fluxes of C(37) alkenones varies from 0 to 14.2 mu g m(-2) d(-1). Fluxes of sterols, steroid ketones and C(30) alkane diol respectively range from 31 to 377, 2.2 to 46 and 0.3 to 9.3 mu g m(-2) d(-1). Biomarker flux ranges are coherent with the relatively low primary production and the low export ratio encountered during the study. Molecular characteristics of biomarker composition is consistent with reworked algal and zooplanktonic organic matter. Lipid biomarker composition points to the dominance of haptophytes over dinoflagellates in the exported material, and to a minor contribution of diatoms and eustigmatophytes. The intrusion of coastal water at the study site was recorded by an enhanced imprint of higher plant n-alkanes. Two processes can be responsible for the pulses in biomarker flux: changes in the magnitude of particle flux (dry weight mass flux) and changes in the concentration of biomarkers in the particles. Concurrent variability in fluxes, significant Pearson correlations between fluxes of biomarkers of haptophytes, dinoflagellates, eustigmatophytes, zooplankton activity and higher plants (alkenones, dinosterol, alkyl diols, dehydrocholesterol, steroid ketones, p < 0.01, n=31, suggest that the short term temporal variability of biomarker export fluxes depends primarily on the intensity of particle dry weight flux. Biomarker concentrations vary on a relatively narrower range than biomarker fluxes, indicating that changes in particle composition (due to degradation or change in source apportionment) has a weaker influence on flux variability. Thus, particle aggregation and sinking are key processes to explain the dynamic of biomarker export at a temporal scale of 6 h. None the less, abrupt changes of OC-normalized concentrations of biomarkers, in the time scale of 6 h, indicate that the exported particles composition also show short-time variability. Highest biomarker flux values recorded by the trap samples from 27 to 29 September correspond to highest values of zooplankton biomass integrated between the surface and 200 m. The decrease in primary production after the October wind events is echoed by minima in biomarker flux values. Despite these correspondences, the coupling between primary production and biomarker export is complex

Transport vertical des particules dans l'océan (étude des contaminants organiques et des biomarqueurs du phytoplancton en mer Ligure (NW Méditerranée))

Le transport vertical des particules dans la colonne d eau est un processus majeur de l export de contaminants. Le but de cette thèse à donc été de déterminer les flux de contaminants organiques générés par la sédimentation de particules en mer de Ligure (station DYFAMED), et de caractériser leurs variations grâce à un suivi temporel ainsi qu une approche biogéochimique. Ces flux sont extrêmement variables. Faibles en été, ils augmentent brusquement en hivers suite à la déstratification des couches d eau et à l export vertical de particules de caractère lithique. Au printemps, l augmentation de l empreinte lipidique du phytoplancton indique alors que les particules exportées sont biogènes. Le dépôt de poussières sahariennes à également généré d importants pics de flux en juillet 2002 et novembre 2001. La contamination des particules est ici d origine pétrogénique et son niveau typique de sites Méditerranéens côtiers, bien que la station soit considérée comme site hauturier.PARIS-BIUSJ-Sci.Terre recherche (751052114) / SudocSudocFranceF

Sources, Transport and Deposition of Atmospheric Organic Pollutants in the Mediterranean Sea

International audienceIn this chapter a compilation of existing atmosphericconcentration data and related deposition fluxes of organiccontaminants in the Mediterranean Sea (far from the shoreline) are presented. We have emphasized in compiling anddiscussing available data at open sea and background coastalsites which are most often scarce, but very valuable. Themain objectives of this work were (a) to establish base lineatmospheric concentrations of persistent organic pollutants(POPs) over the open Mediterranean Sea and to assess theirspatial variability and potential sources based on existingdata; (b) to estimate a total atmospheric load of POPs andrelated compounds at open sea based on most recent reporteddata. This literature review reveals that there is still ageneral lack of data on POPs and related contaminants in theatmosphere over the Mediterranean Sea as well as on theirdeposition fluxes, in particular at open sea. This data scarcityis more pronounced for organochlorine pesticides (OCPs) andpolybrominated diphenyl ethers (PBDEs). This situation couldhave been motivated in part by the fact that existing nationaland international regulations and programmes dealing withmarine pollution control and monitoring have relegated theatmospheric pathway to a second tier, if considered at all. The small amount of existing data does not allow identificationof consistent trends. Atmospheric levels of polychlorinateddibenzo-p-dioxins and dibenzofurans (PCDD/Fs) seem to behomogeneous across the Mediterranean Sea, even comparablewith those of big coastal cities, suggesting that even if there arehot spots in the Mediterranean basin the levels found at opensea are mostly driven by the atmospheric circulation patterns.Concentrations of polycyclic aromatic hydrocarbons (PAHs)and polychlorinated biphenyls (PCBs) in the atmosphereover the Mediterranean Sea seem to be within the levels firstmeasured in the 1980s, while a general declining trend wasobserved for hexachlorocyclohexanes (HCHs). Available dataon PBDEs suggest that background costal sites in the EasternMediterranean may be considered as the least polluted areas atpresent. Moreover, coastal sites in the Western Mediterraneanmay present levels comparable to those reported for some ofthe largest urban coastal sites in the Mediterranean Region.The total atmospheric loading of organic contaminants (PAHs+ OCPs + PCBs + PBDEs + PCDD/Fs) to open MediterraneanSea waters is estimated to vary from 2100 to 4360 tonseach year. It is important to note that even if PAHs are thepredominant contaminants inputted to Mediterranean waters,other highly toxic chemicals are also entering the water massesvia the atmosphere forming a complex cocktail of contaminants.Available data show that the Mediterranean waters are notonly a sink for organic contaminants but also a source, with200-1500 tons of organic contaminants (sum of all contaminantgroups) “escaping” each year to the overlying atmosphere.Interestingly, data point to volatilization of toxic contaminantsfrom open sea waters occurring at a higher extent in the EasternMediterranean Basin

Spatial and seasonal variabilities of dissolved hydrocarbons in surface waters from the Northwestern Mediterranean Sea : results from one year intensive sampling

Dissolved aliphatic hydrocarbons (AHs) and polycyclic aromatic hydrocarbons (PAHs) were analysed from surface water collected in continental, harbour and off-shore marine sites from Marseilles coastal area (Northwestern Mediterranean Sea) from February 2011 to February 2012. AH and PAH concentrations were in the range of 0.04-0.53 mu g 1(-1) and 8.1-405 ng 1(-1), respectively. They both displayed seasonal and spatial variations in their concentrations and molecular composition. The lowest AH concentrations were found in summer and the highest PAH concentrations in winter. Both natural and anthropogenic (pyrogenic and petrogenic) hydrocarbon sources were identified. In winter, concentrations and composition patterns highlighted an increase in the signature of unburned and combusted fossil fuels, while they suggested an enhancement of weathering processes in summer months. Hydrocarbon inputs to the dissolved phase seemed to originate mainly from the atmosphere and the Rhone River. Hydrocarbon additional sources were identified only at the harbour site, emphasising the intense shipping traffic and industrial activities occurring in one of the most important Mediterranean harbours. This study underscores the strong dynamics of dissolved hydrocarbons and the uncoupling of the sources, transport and removing processes affecting AHs and PAHs. It also demonstrates the pertinence of taking this dynamics into account for the budget assessments of organic pollutants in coastal environments