New insights on Cu origin and fate from combined chemical extraction and ᵟ⁶⁵Cu isotopic composition: Application to Cu transfers in a Mediterranean vineyard catchment

Repeated use of Cu based fungicides (Bordeaux mixture: Ca(OH)2+CuSO4) to control vine downy hasled to signi!cant increase of Cu in vineyard soils. In Mediterranean catchments, brief and intense flood events can multiply stream discharge by up to 10 and are responsible for important soil leaching and therefore for high "uxes of Cu exported at the outlet of the catchment. In order to assess the origin and fate of Cu measured in the Baillaury catchment (South of France, combined sequential extraction (SCE) and isotopic Cu compositions (δ65Cu) approaches are proposed in this study

Origin and fate of copper in a small Mediterranean vineyard catchment: New insights from combined chemical extraction and δ65Cu isotopic composition

For centuries, many Mediterranean catchments were covered with vineyards in which copper was widely applied to protect grapevines against fungus. In the Mediterranean-type flow regime, brief and intense flood events increase the stream water discharge by up to 10 times and cause soil leaching and storm runoff. Because vineyards are primarily cultivated on steep slopes, high Cu fluxes are discharged by surface water runoff into the rivers. The purpose of this work was to investigate the riverine behavior and transport of anthropogenic Cu by coupling a sequential chemical extraction (SCE) procedure, used to determine Cu partitioning between residual and non-residual fractions, with δ65Cu isotopic measurements in each fraction. In the Baillaury catchment, France, we sampled soils (cultivated and abandoned), river bed sediments (BS), suspended particulate matter (SPM), and river water during the flash flood event of February 2009. Copper partitioning using SCE show that most of Cu in abandoned vineyard soil was in the residual phase (>60%) whereas in cultivated soil, BS and SPM, Cu was mostly (>25%) in non-residual fractions, mainly adsorbed onto iron oxide fractions. A small fraction of Cu was associated with organic matter (5 to 10%). Calculated enrichment factors (EF) are higher than 2 and the anthropogenic contribution was estimated between 50 to 85%. Values for δ65Cu in bulk samples were similar to bedrock therefore; δ65Cu on SCE fractions of superficial soils and SPM allowed for discrimination between Cu origin and distribution. Copper in residual fractions was of natural mineral origin (δ65Cu close to local bedrock, +0.07‰). Copper in water soluble fraction of SPM (δ65Cu = +0.26‰) was similar to dissolved river Cu (δ65Cu = +0.31‰). Copper from fungicide treatment (δ65Cu = −0.35‰) was bound to organic matter (δ65Cu = −0.20‰) without or with slight isotopic fractioning. A preferential adsorption of 65Cu onto iron oxides (δ65Cu = +0.5‰) is shown

Variability of chromophoric dissolved organic matter in three freshwater-influenced systems along central-southern Chile

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Interplay between the NADP-Linked Thioredoxin and Glutathione Systems in Arabidopsis Auxin Signaling[C][W]

NADP-linked thioredoxin and glutathione systems are key reduction pathways in living organisms. Based on a genetic approach, this study shows that these pathways interfere with auxin transport and metabolism, defining a link between redox regulation and auxin signaling

Dissolved organic matter released by two marine heterotrophic bacterial strains and its bioavailability for natural prokaryotic communities

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A seasonal survey of the food web in the Lapalme Lagoon (northwestern Mediterranean) assessed by carbon and nitrogen stable isotope analysis

International audienceWe used carbon and nitrogen stable isotope analysis to describe the food web of the Lapalme Lagoon, one of the best preserved coastal lagoons along the French Mediterranean coast. Three surveys, corresponding to contrasting situations both in terms of continental inputs and of connection between the lagoon and the open sea, were conducted in June and September 2004 and in February 2005. There were significant spatiotemporal changes in the isotopic ratios of both primary producers and consumers. Temporal changes were mostly linked to important C-13-depleted continental inputs caused by the long period of heavy rainfall before the June survey. Conversely, isotopic ratios were rather similar in September and February despite the opening of the connection of the lagoon with the sea between these two surveys. The interpretation of the results in terms of the structure of the trophic network differed between the June period and the two other ones. In September 2004 and February 2005, the food web was mostly based on SOM and lagoon POM pools with only a few consumers departing from this general trend. In June 2004, a significant proportion of consumers were conversely C-13-depleted probably due to the assimilation of significant amounts of continental inputs by grazers and filter-feeders. This stresses the necessity of carrying out seasonal surveys to get a sound idea of the structure of the food web in highly variable ecosystems such as coastal lagoons. Spatial changes in isotopic ratios were likely linked to: (1) the salinity/confinement gradient with a trend toward lower delta C-13 and delta N-15 values (i.e., higher continental influence) in the inner part of the main lagoon; and (2) the high delta N-15 values of primary producers and discretely motile consumers in a semi-confined site located downstream a vineyard receiving large amounts of fertilizers. We hypothesised that these inputs are quickly N-15-enriched through denitrification and ammonia volatilisation processes and then contribute to the N-15-enrichment of salt marsh plants and seagrass at this site. This interpretation is supported by the fact that such a 15 N-enrichment of primary producers only occurred in February (i.e., after the dispersion of the fertilizers). Conversely, discretely motile consumers were 15 N-enriched all year round, which suggests that they were mostly exploiting the detritic pool derived from 1 5 N-enriched salt marsh plants

New insights on Cu origin and fate from combined chemical extraction and ᵟ⁶⁵Cu isotopic composition: Application to Cu transfers in a Mediterranean vineyard catchment

International audienceRepeated use of Cu based fungicides (Bordeaux mixture: Ca(OH)2+CuSO4) to control vine downy hasled to signi!cant increase of Cu in vineyard soils. In Mediterranean catchments, brief and intense flood events can multiply stream discharge by up to 10 and are responsible for important soil leaching and therefore for high "uxes of Cu exported at the outlet of the catchment. In order to assess the origin and fate of Cu measured in the Baillaury catchment (South of France, combined sequential extraction (SCE) and isotopic Cu compositions (δ65Cu) approaches are proposed in this study

Light-driven increase in C yield is linked to maintenance in the proteorhodopsin-containing photobacterium angustum S14

International audienceProteorhodopsin-containing prokaryotes (PCPs) are photoheterotrophic microorganisms containing transmembrane light-driven proton pumps called proteorhodopsins (PRs). Due to the prevalence of these organisms in the upper water column of the World’s Ocean, and their potential for ATP generation, PCPs have been suggested to significantly influence energy and matter flows in the biosphere. So far, evidence for the significance of PCP light-driven metabolism has been obtained by comparing growth in batch culture, under light versus dark conditions, and it appears that responses to light are in the majority of the cases linked to unfavorable conditions. We studied light responses to carbon yields of the PCP Photobacterium angustum S14 using chemostat conditions and light-dark cycles. We observed significant effects of light-dark cycles as well as significant differences between samples after 12 h illumination versus 12 h darkness only under higher substrate levels leading to higher cell counts (c.a. 5-10 • 108 cells • ml-1) and lower pH. Responses of yield to changes in growth rate were used to estimate Pirt’s maintenance coefficient and to assign for the first time a metric for these so-called unfavorable conditions that might be useful to evaluate energetic budgets and the potential for light-driven metabolism by PCPs. It appears that light responses by Photobacterium angustum S14 are linked to energetic balance rather than to substrate concentration

Changes in bacterial community metabolism and composition during the degradation of dissolved organic matter from the jellyfish Aurelia aurita in a Mediterranean coastal lagoon

International audienceSpatial increases and temporal shifts in outbreaks of gelatinous plankton have been observed over the past several decades in many estuarine and coastal ecosystems. The effects of these blooms on marine ecosystem functioning and particularly on the dynamics of the heterotrophic bacteria are still unclear. The response of the bacterial community from a Mediterranean coastal lagoon to the addition of dissolved organic matter (DOM) from the jellyfish Aurelia aurita, corresponding to an enrichment of dissolved organic carbon (DOC) by 1.4, was assessed for 22 days in microcosms (8 l). The high bioavailability of this material led to (i) a rapid mineralization of the DOC and dissolved organic nitrogen from the jellyfish and (ii) the accumulation of high concentrations of ammonium and orthophosphate in the water column. DOM from jellyfish greatly stimulated heterotrophic prokaryotic production and respiration rates during the first 2 days; then, these activities showed a continuous decay until reaching those measured in the control microcosms (lagoon water only) at the end of the experiment. Bacterial growth efficiency remained below 20 %, indicating that most of the DOM was respired and a minor part was channeled to biomass production. Changes in bacterial diversity were assessed by tag pyrosequencing of partial bacterial 16S rRNA genes, DNA fingerprints, and a cultivation approach. While bacterial diversity in control microcosms showed little changes during the experiment, the addition of DOM from the jellyfish induced a rapid growth of Pseudoalteromonas and Vibrio species that were isolated. After 9 days, the bacterial community was dominated by Bacteroidetes, which appeared more adapted to metabolize high-molecular-weight DOM. At the end of the experiment, the bacterial community shifted toward a higher proportion of Alphaproteobacteria. Resilience of the bacterial community after the addition of DOM from the jellyfish was higher for metabolic functions than diversity, suggesting that jellyfish blooms can induce durable changes in the bacterial community structure in coastal lagoons

When riverine dissolved organic matter (DOM) meets labile DOM in coastal waters: changes in bacterial community activity and composition

International audienceHeterotrophic bacterial communities in marine environments are exposed to a heterogeneous mixture of dissolved organic compounds with different bioreactivity that may control both their activity and composition. The coastal environment is an example of a mixing area where recalcitrant allochthonous organic matter from rivers can encounter labile organic matter from marine phytoplanktonic blooms. The objective of this study was to explore the effects of mixed qualities of dissolved organic matter (DOM) on bacterial community activity (BCA) and bacterial community composition (BCC) and to test for a priming effect when DOM sources are added in combination. Coastal marine bacterial communities were incubated separately with a mixture of amino acids and with natural riverine DOM or with both sources together for 42 days. Addition of amino acids alone or in combination with riverine DOM led to a similar stimulation of BCA compared to control condition, whereas addition of riverine DOM alone did not modify BCA compared to the control. On the contrary, BCC analyzed by 16S rRNA gene pyrosequencing was not affected by the addition of amino acids alone, but changed dramatically with riverine DOM alone or in combination with amino acids. Our results show that changes in BCA and BCC can be driven by different types of DOM, but that these changes are not necessarily coupled. Moreover, the addition of labile DOM did not modify the microbial decomposition of riverine DOM, nor the BCC, suggesting that a priming effect did not occur under these experimental conditions