On the effects of acid pre-treatment on the elemental and isotopic composition of lightly- and heavily-calcified marine invertebrates

Open Access via Springer Compact AgreementPeer reviewedPublisher PD

Spatiotemporal changes in surface sediment characteristics and benthic macrofauna composition off the Rhône River in relation to its hydrological regime

International audienceThe consequences of changes in the water flow of the Rhône River on surface sediment characteristics and benthic macrofauna composition were assessed within 3 distinct areas: (1) the delta front, (2) the prodelta, and (3) the distal zone. Five stations were sampled during or closely after: (1) an oceanic flood (April 2007), (2) a generalized flood (May 2008), (3) a Cevenol flood (December 2008), and (4) a dry period (July 2011). Measurements of sediment characteristics included granulometry (D0.5), bulk descriptors of sedimentary organics (OC, TN and THAA), descriptors of labile components of sedimentary organics (chloropigments, EHAA), and both descriptors of origin (Chl-b/Chl-a, C/N) and lability (Chl-a/(Chl-a+Phaeo-a), EHAA/THAA) of sedimentary organics. Sediment Profile Images were collected during April 2007, May 2008 and July 2011. Temporal changes in both sedimentary organics and benthic macrofauna were more important in the delta front and the prodelta than in the distal zone. Bulk characteristics of sedimentary organics presented decreasing inshore/offshore gradients during both April 2007 and July 2011 but not during May and December 2008. There were significant temporal changes in EHAA/THAA at all stations. Changes in benthic macrofauna composition differed between: (1) the delta front and the prodelta, and (2) the distal zone. In the former area, the dry period was associated with establishing a mature community characterized by high abundances and species richness. The best description of spatiotemporal changes in benthic macrofauna composition by surface sediment characteristics was obtained using D0.5, Chl-b/Chl-a, Chl-a/(Chl-a+Phaeo-a) and EHAA, which supports the role of the quality of sedimentary organics in controlling benthic macrofauna composition

Organic matter remineralization in marine sediments : A Pan-Arctic synthesis

Natural Environment Research Council (GrantNumber(s): NE/J023094/1; Grant recipient(s): Ursula Witte) ArcticNet (GrantNumber(s): Hotspot biodiversity project; Grant recipient(s): Philippe Archambault)Peer reviewedPublisher PD

Origine, qualité et réactivité de la matière organique d'origine continentale dans les sédiments du prodelta du Rhône et sur le plateau adjacent

The Rhône River is the major source of freshwater and terrigenous material to the Mediterranean basin. The Rhône prodelta is characterised by high deposition rates and efficient transformation of sedimentary organics, which is typical for deltaic environments. This raised the question of the fate of these large quantities of organic carbon, delivered by the river to the coastal marine environment, and particularly the impact on benthic microbial community and organic matter recycling efficiency. The multi-disciplinary program " Climate and Human-induced Alterations in Carbon Cycling at the River seA connection " (CHACCRA) was designed to study the fate of nutrients and organic matter delivered by the Rhône River in the prodelta and its adjacent shelf. Sediment cores were collected in the Rhône river mouth and the distal area during four field campaigns (April 2007, May 2008, December 2008 and June 2009). Bulk parameters (grain size, total nitrogen and organic carbon) were analysed to investigate the distribution gradient and location of the flood deposit. In addition, molecular-level proxies (pigments, fatty acids, total and bioavailable amino acids) were used to assess the origin, quality and state of degradation of the organic matter in the sediments. Bacterial community structure was characterised using capillary electrophoresis-single strand conformation polymorphism (CE-SSCP) procedure. This work revealed gradients of origin and quality of organic matter from the river mouth to the open sea. Moreover, the influence of flood events is clearly visible in the nearshore sediments and the biochemical signatures of the deposits are specific to the type of flooding. Finally, the oxic degradation of sedimentary organic matter was assessed experimentally on sediments from the river mouth incubated 40 days at the laboratory. This experiment underlines the high biochemical reactivity of the organic matter labile fraction.Le Rhône est la principale source d'eau douce et de matériels terrigènes vers le bassin méditerranéen. Le prodelta du Rhône est caractérisé par des taux d'accumulation sédimentaire élevés et par une reminéralisation intense de la matière organique sédimentée, ce qui est typique des environnements deltaïques. Une question est soulevée sur le devenir de ces grandes quantités de carbone organique délivrées par le fleuve vers le milieu marin et en particulier leur impact sur les communautés microbiennes benthiques et l'intensité du recyclage de la matière organique. Le programme multi-disciplinaire "Climate and Human-induced Alterations in Carbon Cycling at the River seA connection" (CHACCRA) a été conçu pour étudier le devenir des éléments nutritifs et de la matière organique délivrée par le Rhône sur la marge continentale adjacente. Lors de quatre campagnes de terrain réalisées en avril 2007, mai 2008, décembre 2008 et juin 2009, des carottes de sédiments ont été prélevées à l'embouchure du fleuve et sur le plateau adjacent. La contribution des apports continentaux et leur distribution ont été étudiées à l'aide de paramètres globaux (granulométrie, azote total et carbone organique), tandis que les descripteurs moléculaires (pigments, acides gras, acides aminés totaux et biodisponibles) ont permis de déterminer l'origine, et d'évaluer la qualité ainsi que l'état de dégradation de la matière organique dans les sédiments. La structure de la communauté bactérienne a été caractérisée par la technique de polymorphisme de conformation des simples brins par électrophorèse capillaire (CE-SSCP). Ces travaux mettent en évidence des gradients d'origine et de qualité depuis l'embouchure vers le large. De plus, l'influence des événements de crue est clairement visible dans les sédiments, et les signatures biochimiques des dépôts sont différentes selon le type de crue. Enfin, l'incubation des sédiments a permis d'évaluer la dégradabilité en condition oxique de la matière organique sédimentaire à l'embouchure et de montrer que la fraction labile était très réactive à la dégradation

Subtidal microphytobenthos : effects of inorganic and organic compound supplies on migration, production, and respiration in a tropical coastal environment

Microphytobenthos (MPB) is an important primary producer in coastal ecosystems. In oligotrophic environments, its activity may be controlled by the availability of organic or inorganic compounds but also by its migration behavior. The objective of this study was to determine, in MPB-colonized subtidal sediments, the consequences of short-term enrichments (< 24 h) of organic (alanine, glutamate, and glucose) and inorganic (ammonium, phosphate) compounds on MPB vertical migration and metabolisms, net production (NP), areal gross production (AGP), and community respiration (R). Two contrasting stations located in the southwest lagoon of New Caledonia were investigated: 1 under strong anthropogenic influence and 1 under more oceanic influence. Both stations were dominated by epipelic diatoms. Differences in net primary production were explained by diurnal variation of MPB biomass at the sediment surface, showing the importance of MPB migration in the functioning of these subtidal environments. However, a stimulation or inhibition of MPB migration did not necessarily impact the net primary production of the system; this strongly depends upon the interactions between the autotrophic and heterotrophic compartments, the latter being controlled by the environmental conditions. For the station under low anthropogenic influence, AGP and R were both significantly stimulated by alanine, glucose, and ammonium, and significantly inhibited by phosphate. The similar responses of AGP and R to enrichments suggest that autotrophs and heterotrophs were tightly coupled. Conversely, in the station under strong anthropogenic influence, AGP and R responded differently. Addition of ammonium inhibited AGP without having an impact on R, whereas addition of phosphate inhibited R whilst having no measurable effect on AGP. In this station, the coupling between autotrophs and heterotrophs was weakened, suggesting that the carbon demand of the heterotrophic compartment is probably sustained by the supplies of allochthonous organic matter rather than by exudates from the autotrophic compartment

Origine, qualité et réactivité de la matière organique d'origine continentale dans les sédiments du prodelta du Rhône et sur le plateau adjacent

Le Rhône est la principale source d'eau douce et de matériels terrigènes vers le bassin méditerranéen. Une question est soulevée sur le devenir de ces grandes quantités de carbone organique délivrées par le fleuve vers le milieu marin et en particulier leur impact sur les communautés microbiennes benthiques et l'intensité du recyclage de la matière organique. Lors de quatre campagnes de terrain réalisées en avril 2007, mai 2008, décembre 2008 et juin 2009 dans le cadre de l ARN CHACCRA, des carottes de sédiments ont été prélevées à l embouchure du fleuve et sur le plateau adjacent. La contribution des apports continentaux et leur distribution ont été étudiées à l aide de paramètres globaux (granulométrie, azote total et carbone organique), tandis que les descripteurs moléculaires (pigments, acides gras, acides aminés totaux et biodisponibles) ont permis de déterminer l'origine, et d évaluer la qualité ainsi que l'état de dégradation de la matière organique dans les sédiments. La structure de la communauté bactérienne a été caractérisée par la technique de polymorphisme de conformation des simples brins par électrophorèse capillaire. Ces travaux mettent en évidence des gradients d origine et de qualité depuis l embouchure vers le large. De plus, l influence des événements de crue est clairement visible dans les sédiments, et les signatures biochimiques des dépôts sont différentes selon le type de crue. Enfin, l incubation des sédiments a permis d évaluer la dégradabilité en condition oxique de la matière organique sédimentaire à l embouchure et de montrer que la fraction labile était très réactive à la dégradation.PARIS-BIUSJ-Sci.Terre recherche (751052114) / SudocBANYULS/MER-Observ.Océanol. (660162201) / SudocSudocFranceF

Glacier inputs influence organic matter composition and prokaryotic distribution in a high Arctic fjord (Kongsfjorden, Svalbard)

International audienceWith climate change, the strong seasonality and tight pelagic-benthic coupling in the Arctic is expected to change in the next few decades. It is currently unclear how the benthos will be affected by changes of environmental conditions such as supplies of organic matter (OM) from the water column. In the last decade, Kongsfjorden (79°N), a high Arctic fjord in Svalbard influenced by several glaciers and Atlantic water inflow, has been a site of great interest owing to its high sensitivity to climate change, evidenced by a reduction in ice cover and an increase in melting freshwater. To investigate how spatial and seasonal changes in vertical fluxes can impact the benthic compartment of Kongsfjorden, we studied the organic matter characteristics (in terms of quantity and quality) and prokaryotic distribution in sediments from 3 stations along a transect extending from the glacier into the outer fjord in 4 different seasons (spring, summer, autumn and winter) in 2012–2013. The biochemical parameters used to describe the sedimentary organic matter were organic carbon (OC), total nitrogen, bulk stable isotope ratios, pigments (chorophyll-a and phaeopigments) and biopolymeric carbon (BPC), which is the sum of the main macromolecules, i.e. lipids, proteins and carbohydrates. Prokaryotic abundance and distribution were estimated by 4′,6-diamidino-2-phenylindole (DAPI) staining. This study identifies a well-marked quantitative gradient of biogenic compounds throughout all seasons and also highlights a discrepancy between the quantity and quality of sedimentary organic matter within the fjord. The sediments near the glacier were organic-poor (< 0.3%OC), however the high primary productivity in the water column displayed during spring was reflected in summer sediments, and exhibited higher freshness of material at the inner station compared to the outer basin (means C-chlorophyll-a/OC ~ 5 and 1.5%, respectively). However, sediments at the glacier front were depleted in BPC (~ 0.2–0.3 mg C g− 1 DW) by 4.5 and 9 times compared to sediments from the inner and outer stations. δ13C values in sedimentary organic matter of Kongsfjorden varied between − 23.8 and − 19.3‰ and reflected distinct sources of organic matter between basins. Bacterial total cell numbers in sediments of Kongsfjorden were < 2 × 108 cells ml− 1 and the prokaryotic community structure was strongly influenced by the marked environmental biogenic gradients. Overall, the spatial variability prevailed over the seasonal variability in sediments of Kongsfjorden suggesting that glacier inputs prominently control the functioning of this benthic ecosystem and its communities

Biogeochemistry of fatty acids in a river-dominated Mediterranean ecosystem (Rhône River prodelta, Gulf of Lions, France): Origins and diagenesis

International audienceMajor rivers transfer high loads of continental particulate organic matter to deltaic environments, where the impact on the biogeochemistry and productivity of coastal sediments depends on the sources and lability of these inputs. Our aims are to provide new insights into the reactivity of riverine inputs in coastal environments and to delineate the parameters controlling their fate in these dynamic systems. Sediment cores were collected from a Mediterranean deltaic system (the Rhône prodelta and its adjacent shelf) during a period of moderate river discharge (Spring 2007) and analyzed for their fatty acid composition. Sediment properties were also described using biochemical bulk analyses (organic carbon and lipids), granulometry and profiles of redox potential. Based on the bulk compositional changes and hierarchical clustering of the fatty acid biomarkers, we determined the principal sources of organic matter and their spatial distribution. Fatty acids were primarily of continental origin in the prodelta, shifting to a higher contribution from marine sources in the shelf area. Fatty acids derived from both continental and marine sources were efficiently degraded in the sediments by microbial decay processes in the upper oxic layer. Degradation rate constants calculated from the down-core decreases in concentrations indicate that fatty acid degradation was enhanced in sediments influenced by the Rhône River. The most important parameters affecting fatty acid preservation were the inherent stability of individual molecular components and their physical association with mineral matrices, the source and freshness of the inputs, and the depositional environment (redox condition, accumulation rates)

HYGIENE – CAN A TOOL FROM OUR PAST HELP SAVE THE FUTURE?

Infectious diseases will continue to disrupt modern societies if we do not establish better hygiene literacy to enable a systems approach to hygienical design and planning, wider population access to and uptake of practices, and a strategically better use of cleaning and hygiene as trusted methods to reduce infections. The article introduces the concept of hygiene literacy and outlines how this concept is linked to policies for public health, urban planning, education, research, data collection, and more. Further, it outlines how such a new strategy for Europe could help address infections and epidemics.publishedVersio

HYGIENE – CAN A TOOL FROM OUR PAST HELP SAVE THE FUTURE?

Infectious diseases will continue to disrupt modern societies if we do not establish better hygiene literacy to enable a systems approach to hygienical design and planning, wider population access to and uptake of practices, and a strategically better use of cleaning and hygiene as trusted methods to reduce infections. The article introduces the concept of hygiene literacy and outlines how this concept is linked to policies for public health, urban planning, education, research, data collection, and more. Further, it outlines how such a new strategy for Europe could help address infections and epidemics