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The release of inorganic and organic contaminants from municipal solid waste incinerator (MSWI) bottom ash is controlled to a large extent by the release of dissolved organic carbon (DOC), and in particular by the reactive humic (HA) and fulvic acids (FA) subfractions of DOC. The properties of organic matter contributing to the release of DOC, HA and FA are, therefore, important for environmental risk assessment. In this study we have quantitatively measured the carbon speciation, and its relation with the leaching of Cu, in three fresh and carbonated MSWI bottom ash samples. Results show that up to only 25% of loss on ignition (LOI) consists of organic carbon (OC), while about 17% of OC in the three samples consists of HA and FA. Up to 50% of DOC in MSWI bottom ash leachates was identified as fulvic acid (FA). This value is substantially higher than previously estimated for these MSWI bottom ash samples and is consistent with the higher recovery of the new method that was applied. The results of this study imply that methods focusing on specific carbon fractions are more appropriate for assessment of environmentally relevant organic carbon species than the measurement of LOI.

We have studied the availability and leaching of polycyclic aromatic hydrocarbons (PAHs) from two contaminated materials, a tar-containing asphalt granulate (Σ16 US-EPA PAHs 3412 mg/kg) and gasworks soil (ΣPAHs 900 mg/kg), by comparing results from three typical types of leaching tests: a column, sequential batch, and two different availability tests. The sequential batch test was found to largely resemble the column test. However, the leaching of particularly the larger PAHs (>5 aromatic rings) was found to be enhanced in the batch test by up to an order of magnitude, probably due to their association with large DOC (dissolved organic carbon) molecules generated by the vigorous mixing. The release of PAHs in the two availability tests, in which the leaching is facilitated by either a high concentration of DOC or Tenax resin, was similar, although the latter test was easier to perform and yielded more repeatable results. The availability was much higher than the amount leached in the column and sequential batch tests. However, biodegradation had apparently occurred in the column test and the total amount of PAHs released by either leaching or biodegradation, 9% and 26% for asphalt granulate and gasworks soil, respectively, did equal the amount leached in the availability tests. Therefore, the availability was found to provide a relevant measure of the PAH fraction that can be released from the solid phase. These results stress the importance of using the available instead of the total amount of contaminant in the risk analysis of solid materials in utilization or disposal.

Peatlands cover only 3% of the Earth's land surface but boreal and subarctic peatlands store about 15–30% of the world's soil carbon (C) as peat. Despite their potential for large positive feedbacks to the climate system through sequestration and emission of greenhouse gases, peatlands are not explicitly included in global climate models and therefore in predictions of future climate change. In April 2007 a symposium was held in Wageningen, the Netherlands, to advance our understanding of peatland C cycling. This paper synthesizes the main findings of the symposium, focusing on (i) small-scale processes, (ii) C fluxes at the landscape scale, and (iii) peatlands in the context of climate change. The main drivers controlling C fluxes are largely scale dependent and most are related to some aspects of hydrology. Despite high spatial and annual variability in Net Ecosystem Exchange (NEE), the differences in cumulative annual NEE are more a function of broad scale geographic location and physical setting than internal factors, suggesting the existence of strong feedbacks. In contrast, trace gas emissions seem mainly controlled by local factors. Key uncertainties remain concerning the existence of perturbation thresholds, the relative strengths of the CO2 and CH4 feedback, the links among peatland surface climate, hydrology, ecosystem structure and function, and trace gas biogeochemistry as well as the similarity of process rates across peatland types and climatic zones. Progress on these research areas can only be realized by stronger co-operation between disciplines that address different spatial and temporal scales.

The estuarine mixing zone of the Tana River (northern Kenya) and an extensive deltaic area just south of the estuary were sampled in April 2004 with the aim of identifying the distribution, sources, and processing of particulate and dissolved organic carbon (POC, DOC) and inorganic carbon (DIC). C4 inputs from the catchment contributed similar to 50% to the POC pool in the Tana River and estuary, and in the mangrove creek water column and intertidal sediments. The delta C-13 values of DOC, however, were typically much more negative than that of POC, indicating a substantially higher contribution by C3 and/or mangrove-derived carbon in the DOC pool. The undersaturation of O-2, high pCO(2), and the nonconservative nature of DIC and delta C-13(DIC) suggest a strongly heterotrophic water column, particularly in the freshwater part of the Tana and in the tidal creeks in the delta, where high additional inputs of organic matter were observed. However, some of these sites showed delta O-18(DO) signatures lower than the atmospheric equilibrium (i.e., +24.2%(0)) indicative of significant O-2 production by photosynthesis. Therefore, the heterotrophic signature in the water column is likely the result of a strong interaction with the large intertidal areas, whereby respiratory activity in sediments and in the overlying water column during tidal inundation leave a marked signature on the water column. This is confirmed by the covariation between salinity-normalized total alkalinity and DIC, whose slope indicates an important role for anaerobic diagenetic processes. If our data are representative for other large river systems in the region, current estimates are likely to underestimate suspended matter and both inorganic and organic C fluxes to the Indian Ocean from tropical east Africa. ispartof: Limnology and oceanography vol:52 issue:1 pages:46-59 status: published

The marine sponges Dysidea avara and Chondrosia reniformis (globular forms) were cultured in the laboratory on a diet of viable Phaeodactylum tricornutum cells and dissolved nutrients (algae and fish powders). Our growth data were combined with literature data for Pseudosuberites andrewsi (a globular sponge) and for the encrusting sponges Oscarella lobularis, Hemimycale columella, and Crambe crambe. The suitability of three growth models-linear, exponential, and radial accretive-for describing the growth of globular and encrusting sponges was assessed. Radial accretive growth was determined to be the best model to describe growth of both encrusting and globular sponges. Average growth rates of 0.051+/-0.016 and 0.019+/-0.003 mm/day (calculated as the increase of the radius of the sponge per day) were obtained experimentally for D. avara and C. reniformis, respectively.

The objective of this study was to determine the effects of UV-B radiation on charophycean algae under natural conditions, since charophytes enhance water transparency in freshwater systems and levels of UV-B radiation have increased by ozone depletion. Potential and actual UV-B effects were studied by combining a glasshouse experiment in which plants were exposed to various levels of UV-B radiation and field measurements in two freshwater systems dominated by charophytes in the Netherlands. The glasshouse experiment showed that charophytes were sensitive to UV-B radiation. UV-B radiation negatively affected growth, while it increased levels of DNA damage in Chara aspera. Moreover, the charophytes did not seem to develop UV-B screens to protect against UV-B radiation since no increase in UV-B absorbing compounds was found. At field conditions, both spectroradiometrical measurements and DNA dosimeters showed that UV-B radiation was attenuated quickly in both freshwater systems, indicating that UV-B does not reach the submerged charophyte vegetation. However, specific conditions, like fluctuating water tables, may result in UV-B exposure to charophytes for certain periods annually. © New Phytologist (2005).

1. The effect of light intensity on the decomposition of poplar (Populus nigra) leaves and growth of the shredders, Asellus aquaticus and Gammarus pulex, was studied in a laboratory experiment. The response was studied along a gradient of six light intensities of 0, 5, 23, 54, 97 and 156 ¿mol m -2 s-1. It was hypothesised that an increase in light intensity would increase growth of shredders, because of an increase of algae (i.e. food quality) in the leaf-biofilm. 2. Light intensity affected both leaf-biofilm quality and consumer behaviour and affected several aspects of the decomposition-consumer interaction. In the absence of invertebrates, leaf mass loss was lower in the dark, while light intensity had no significant effect on mass loss of poplar leaf in the presence of invertebrates. Light intensity affected algal biomass, density and composition, and had a significant positive effect on the growth of both shredders. 3. Our results suggest that algae can be an important component of the nutritional value of the leaf-biofilm for benthic invertebrates, directly as an additional food source and indirectly through a link with bacteria and/or fungi. 4. The River Continuum Concept mainly emphasises allochthonous inputs to headwater streams and autochthonous production further downstream. Our results suggest that light, by its effect on the biofilms on leaf surfaces, might be a more important factor in headwaters than is usually assumed.

International audience; It has long been recognised that there are strong interactions and feedbacks between climate, upper ocean biogeochemistry and marine food webs, and also that food web structure and phytoplankton community distribution are important determinants of variability in carbon production and export from the euphotic zone. Numerical models provide a vital tool to explore these interactions, given their capability to investigate multiple connected components of the system and the sensitivity to multiple drivers, including potential future conditions. A major driver for ecosystem model development is the demand for quantitative tools to support ecosystem-based management initiatives. The purpose of this paper is to review approaches to the modelling of marine ecosystems with a focus on the North Atlantic Ocean and its adjacent shelf seas, and to highlight the challenges they face and suggest ways forward. We consider the state of the art in simulating oceans and shelf sea physics, planktonic and higher trophic level ecosystems, and look towards building an integrative approach with these existing tools. We note how the different approaches have evolved historically and that many of the previous obstacles to harmonisation may no longer be present. We illustrate this with examples from the on-going and planned modelling effort in the Integrative Modelling Work Package of the EURO-BASIN programme.

In aquatic ecosystems, predation is affected both by turbulence and visibility, but the combined effects are poorly known. Both factors are changing in lakes in the Northern Hemisphere; the average levels of turbulence are predicted to increase due to increasing wind activities, while water transparency is decreasing, e.g., due to variations in precipitation, and sediment resuspension. We explored experimentally how turbulence influenced the effects of planktivorous fish and invertebrate predators on zooplankton when it was combined with low visibility caused by high levels of water color. The study was conducted as a factorial design in 24 outdoor ponds, using the natural zooplankton community as a prey population. Perch and roach were used as vertebrate predators and Chaoborus flavicans larvae as invertebrate predators. In addition to calm conditions, the turbulent dissipation rate used in the experiments was 10−6 m2 s−3, and the water color was 140 mg Pt L−1. The results demonstrated that in a system dominated by invertebrates, predation pressure on cladocerans increased considerably under intermediate turbulence. Under calm conditions, chaoborids caused only a minor reduction in the crustacean biomass. The effect of fish predation on cladocerans was slightly reduced by turbulence, while predation on cyclopoids was strongly enhanced. Surprisingly, under turbulent conditions fish reduced cyclopoid biomass, whereas in calm water it increased in the presence of fish. We thus concluded that turbulence affects fish selectivity. The results suggested that in dystrophic invertebrate-dominated lakes, turbulence may severely affect the abundance of cladocerans. In fish-dominated dystrophic lakes, on the other hand, turbulence-induced changes in planktivory may considerably affect copepods instead of cladocerans. In lakes inhabited by both invertebrates and fish, the response of top-down regulation to turbulence resembles that in fish-dominated systems, due to intraguild predation. The changes in planktivorous predation induced by abiotic factors may possibly cascade to primary producers.

Liquid water has been known to occur beneath the Antarctic ice sheet for more than 40 years, but only recently have these subglacial aqueous environments been recognized as microbial ecosystems that may influence biogeochemical transformations on a global scale. Here we present the first geomicrobiological description of water and surficial sediments obtained from direct sampling of a subglacial Antarctic lake. Subglacial Lake Whillans (SLW) lies beneath approximately 800 m of ice on the lower portion of the Whillans Ice Stream (WIS) in West Antarctica and is part of an extensive and evolving subglacial drainage network. The water column of SLW contained metabolically active microorganisms and was derived primarily from glacial ice melt with solute sources from lithogenic weathering and a minor seawater component. Heterotrophic and autotrophic production data together with small subunit ribosomal RNA gene sequencing and biogeochemical data indicate that SLW is a chemosynthetically driven ecosystem inhabited by a diverse assemblage of bacteria and archaea. Our results confirm that aquatic environments beneath the Antarctic ice sheet support viable microbial ecosystems, corroborating previous reports suggesting that they contain globally relevant pools of carbon and microbes that can mobilize elements from the lithosphere and influence Southern Ocean geochemical and biological systems.

We tested the hypothesis that in the euphotic zone of oligotrophic oceanic waters, the growth-limiting nutrients for bacterioplankton vary over a diel cycle due to competition with phyto- plankton, leading to distinct diel patterns in bacterioplankton. During a cruise across the subtropical Atlantic Ocean, a distinct diel periodicity in bacterioplankton was detectable, with highest bacterial abundance in the early morning and declining over the day. A peak in the frequency of dividing cells (FDC, 20 to 25% of the total bacterial community) was recorded at midnight; FDC rates were consis- tently low during the day and cell volume increased over the day until the early night period. No diel variations in these parameters were detectable in the layers below the deep chlorophyll maximum (DCM). Bio-assay experiments with freshly collected, N+P amended water were started in the early morning. No significant bacterial growth was detectable in the early morning while, in the bio-assays that started at noon, significant bacterial growth was detectable in the N+P treatments. P amendment alone also caused an increase in bacterial abundance although to a lesser extent. Thus, we have evi- dence that the bacterioplankton in the euphotic layer of the subtropical Atlantic are not limited by the availability of N+P in the morning (most likely limited in C) but at noon when they are competing with phytoplankton for the inorganic N+P sources. Based on the concomitantly measured decline in inorganic N+P in the bio-assays, we estimated the C:N:P ratio of newly produced bacteria. The mean atomic C:N:P ratio for the bacteria in the N+P amended bio-assay experiments started in the early morning was C:N:P = 15:13:1 while the corresponding ratio for bacteria in the bio-assays started at noon was C:N:P = 118:11:1. This diel variation in the C:N:P ratio was caused by the 1 order of mag- nitude higher bacterial C production at noon as compared to the early morning. Thus, excess uptake of N+P occurs during the morning and luxury C uptake during noon. This plasticity in the C:N:P ratio of bacterioplankton might be a strategy to overcome, at least partly, periods of shortage in a specific nutrient species in the oligotrophic subtropical Atlantic.

High-frequency, long-term and multisolute measurements are required to assess the impact of human pressures on water quality due to (i) the high temporal and spatial variability of climate and human activity and (ii) the fact that chemical solutes combine short- and long-term dynamics. Such data series are scarce. This study, based on an original and unpublished time series from the Kervidy-Naizin headwater catchment (Brittany, France), aims to determine solute transfer processes and dynamics that characterise this strongly human-impacted catchment. The Kervidy-Naizin catchment is a temperate, intensive agricultural catchment, hydrologically controlled by shallow groundwater. Over 10 yr, five solutes (nitrate, sulphate, chloride, and dissolved organic and inorganic carbon) were monitored daily at the catchment outlet and roughly every four months in the shallow groundwater. The concentrations of all five solutes showed seasonal variations but the patterns of the variations differed from one solute to another. Nitrate and chloride exhibit rather smooth variations. In contrast, sulphate as well as organic and inorganic carbon is dominated by flood flushes. The observed nitrate and chloride patterns are typical of an intensive agricultural catchment hydrologically controlled by shallow groundwater. Nitrate and chloride originating mainly from organic fertilisers accumulated over several years in the shallow groundwater. They are seasonally exported when upland groundwater connects with the stream during the wet season. Conversely, sulphate as well as organic and inorganic carbon patterns are not specific to agricultural catchments. These solutes do not come from fertilisers and do not accumulate in soil or shallow groundwater; instead, they are biogeochemically produced in the catchment. The results allowed development of a generic classification system based on the specific temporal patterns and source locations of each solute. It also considers the stocking period and the dominant process that limits transport to the stream, i.e. the connectivity of the stocking compartment. This mechanistic classification can be applied to any chemical solute to help assess its origin, storage or production location and transfer mechanism in similar catchments.

There is growing evidence of the importance of extramatrical mycelium (EMM) of mycorrhizal fungi in carbon (C) cycling in ecosystems. However, our understanding has until recently been mainly based on laboratory experiments, and knowledge of such basic parameters as variations in mycelial production, standing biomass and turnover as well as the regulatory mechanisms behind such variations in forest soils is limited. Presently, the production of EMM by ectomycorrhizal (EM) fungi has been estimated at ~140 different forest sites to be up to several hundreds of kg per ha per year, but the published data are biased towards Picea abies in Scandinavia. Little is known about the standing biomass and turnover of EMM in other systems, and its influence on the C stored or lost from soils. Here, focussing on ectomycorrhizas, we discuss the factors that regulate the production and turnover of EMM and its role in soil C dynamics, identifying important gaps in this knowledge. C availability seems to be the key factor determining EMM production and possibly its standing biomass in forests but direct effects of mineral nutrient availability on the EMM can be important. There is great uncertainty about the rate of turnover of EMM. There is increasing evidence that residues of EM fungi play a major role in the formation of stable N and C in SOM, which highlights the need to include mycorrhizal effects in models of global soil C stores. Skupno št. avtorjev: 14. Bibliografija: str. 21-27.

International audience; Fish play a key role in the trophic dynamics of lakes. With climate warming, complex changes in fish assemblage structure may be expected owing to direct effects of temperature and indirect effects operating through eutrophication, water level changes, stratification and salinisation. We reviewed published and new long-term (10-100 years) fish data series from 24 European lakes (area: 0.04-5,648 km(2); mean depth: 1-177 m; a north-south gradient from Sweden to Spain). Along with an annual temperature increase of about 0.15-0.3A degrees C per decade profound changes have occurred in either fish assemblage composition, body size and/or age structure during recent decades and a shift towards higher dominance of eurythermal species. These shifts have occurred despite a reduction in nutrient loading in many of the lakes that should have benefited the larger-sized individuals and the fish species typically inhabiting cold-water, low-nutrient lakes. The cold-stenothermic Arctic charr has been particularly affected and its abundance has decreased in the majority of the lakes where its presence was recorded. The harvest of cool-stenothermal brown trout has decreased substantially in two southern lakes. Vendace, whitefish and smelt show a different response depending on lake depth and latitude. Perch has apparently been stimulated in the north, with stronger year classes in warm years, but its abundance has declined in the southern Lake Maggiore, Italy. Where introduced, roach seems to take advantage of the higher temperature after years of low population densities. Eurythermal species such as common bream, pike-perch and/or shad are apparently on the increase in several of the lakes. The response of fish to the warming has been surprisingly strong and fast in recent decades, making them ideal sentinels for detecting and documenting climate-induced modifications of freshwater ecosystems.

The Law of the Minimum was originally formulated by Justus von Liebig, as one of the 50 interlinked laws concerned with agriculture. The original writings of J. von Liebig often were misinterpreted by his successors. Brandt (1899) took this one law out of its context and proposed that limitation by nitrogen is a dominant factor in plankton ecology, far beyond its original application to agriculture. This was opposed by Nathansohn (1908) who suggested instead a dynamic balance of growth and loss terms. Towards validating, or eventually falsifying Brandt's hypothesis, Atkins, Harvey, Cooper and others developed the chemical methods necessary for re-defining ocean nutrient cycling and growth limitation. The major exception to these modern perspectives was the Antarctic Paradox of high nutrients and low chlorophyll which inspired Gran, Atkins, Harvey and Cooper to pioneer the concept of iron limitation. An exhaustive overview is given of efforts to define Fe in seawater and its controlling effect on in situ plankton growth, for the 1920–1984 period. Somewhat parallel work in the laboratory on single species of algae in chelation-controlled media has provided much insight, but is sketched only briefly. Martin and contemporaries developed the chemical methods necessary for defining the ocean chemistry of Fe and its role for in situ growth. These developments are sketched for the 1982–1991 period. Once again the Law of the Minimum and associated bold hypotheses served, albeit briefly, to bring a nutrient element in the forefront of research. This, and the recent awareness of CO2 as rate limiting factor, underline the conclusion that advances in sciences often hinge on advances in technology, confirming Kuhn (1962). In this case the new analytical techniques developed by Atkins, Harvey, Cooper, Martin and their associates have proven revolutionary for plankton ecology. Some observations in plankton ecology may be reminiscent of the agricultural Law of the Minimum, but this would not warrant its direct application, beyond its original context and agriculture, to plankton ecology. Rather the net rate of increase of phytoplankton is the dynamic balance of multiple growth and loss terms, together also determining the biomass at given time and space.

As a result of ubiquitous excretion by micro-organisms, extracellular polymeric substances are reported in high concentrations in marine systems. The majority of this material is exopolysaccharide (EPS). Despite previous studies showing that EPS can affect carbon as well as trace metal cycling, little is known about the effect on Fe - a critical nutrient limiting primary productivity in up to 40% of the ocean. Here, we have characterised an EPS purified from bacteria isolated from the pelagic Southern Ocean (Pseudoalteromonas sp.) and investigated its role in Fe chemical speciation, solubility, as well as bioavailability for two keystone Southern Ocean phytoplankton strains. This EPS has an average molecular weight of 4.6 MDa, exhibiting mainly -OH. COO- and -NH2 functional groups. An asymmetrical flow field-flow fractionation coupled online with UV-spectrophotometer, differential refractive index, and multiangle laser light scattering (aFIFFF-UV-DRI-MALS) demonstrates that this EPS is polydisperse with three, not well resolved, size populations having molar masses in the range from 0.57 to 15.8 MDa. Fe was exclusively associated with the medium size fraction of this EPS and was the most abundant trace metal with 2.2 nM Fe per nM EPS. Only a third of this Fe was chemically labile, and the strength of Fe-EPS complexes increased with equilibration time. 1 nM EPS is efficient to retain Fe in solution, mainly in the colloidal phase (0.02-0.2 mu m). Fe bound to the EPS was highly bioavailable (25% as much as for inorganic Fe). Due to combined effect of EPS on Fe solubility and bioavailability, it can increase the residence time of bioavailable Fe in the euphotic zone, therefore possibly sustaining and controlling primary productivity in sensitive oceanic regions, such as the Southern Ocean. (C) 2010 Elsevier B.V. All rights reserved.

The terrestrial carbon (C) cycle has received increasing interest over the past few decades, however, there is still a lack of understanding of the fate of newly assimilated C allocated within plants and to the soil, stored within ecosystems and lost to the atmosphere. Stable carbon isotope studies can give novel insights into these issues. In this review we provide an overview of an emerging picture of plant-soil-atmosphere C fluxes, as based on C isotope studies, and identify processes determining related C isotope signatures. The first part of the review focuses on isotopic fractionation processes within plants during and after photosynthesis. The second major part elaborates on plant-internal and plant-rhizosphere C allocation patterns at different time scales (diel, seasonal, interannual), including the speed of C transfer and time lags in the coupling of assimilation and respiration, as well as the magnitude and controls of plant-soil C allocation and respiratory fluxes. Plant responses to changing environmental conditions, the functional relationship between the physiological and phenological status of plants and C transfer, and interactions between C, water and nutrient dynamics are discussed. The role of the C counterflow from the rhizosphere to the aboveground parts of the plants, e.g. via CO2 dissolved in the xylem water or as xylem-transported sugars, is highlighted. The third part is centered around belowground C turnover, focusing especially on above- and belowground litter inputs, soil organic matter formation and turnover, production and loss of dissolved organic C, soil respiration and CO2 fixation by soil microbes. Furthermore, plant controls on microbial communities and activity via exudates and litter production as well as microbial community effects on C mineralization are reviewed. A further part of the paper is dedicated to physical interactions between soil CO2 and the soil matrix, such as CO2 diffusion and dissolution processes within the soil profile. Finally, we highlight state-of-the-art stable isotope methodologies and their latest developments. From the presented evidence we conclude that there exists a tight coupling of physical, chemical and biological processes involved in C cycling and C isotope fluxes in the plant-soil-atmosphere system. Generally, research using information from C isotopes allows an integrated view of the different processes involved. However, complex interactions among the range of processes complicate or currently impede the interpretation of isotopic signals in CO2 or organic compounds at the plant and ecosystem level. This review tries to identify present knowledge gaps in correctly interpreting carbon stable isotope signals in the plant-soil-atmosphere system and how future research approaches could contribute to closing these gaps.

The biogeochemistry of carbon and nutrients (N, P) in the surface layer of the ocean strongly depends on the interaction between C, N and P at the cell level and at the population level where interaction between primary producers (phytoplankton) and remineralizers (heterotrophic bacteria) impact the overall stock and dynamics of organic carbon. To understand these interactions in the surface layer of the Mediterranean Sea, we implemented, using Eco3M, a multi-element, steady state, mechanistic model. This cell-based model intend to represent the growth of phytoplankton and heterotrophic bacteria under various amount of nutrients. As a results, it displays the expected biogeochemical characteristics of the system and give us insight on the expected interaction between phytoplankton and heterotrophic bacteria both in term of competition for inorganic nutrients and in term of commensalism for organic carbon. In this study, we found a good quantitative agreement between model results and literrature data for stocks and fluxes of the western Mediterranean basin. In addition, for phytoplankton we show how the uncoupling between carbon production and growth could impact the overall DOC dynamic and based on these results, we proposed a new explanantion for the observed DOC accumulation in the surface layer of the Mediterranean Sea.

The abundance and activity of the major members of the heterotrophic microbial community – from viruses to ciliates – were studied along a longitudinal transect across the Mediterranean Sea in the summer of 2008. The Mediterranean Sea is characterized by a west to-east gradient of deepening of DCM (deep chlorophyll maximum) and increasing oligotrophy reflected in gradients of biomass and production. However, within this well documented longitudinal trend, hydrological mesoscale features exist and likely influence microbial dynamics. Here we present data from a W-E transect of 17 stations during the period of summer stratification. Along the transect the production and fate of organic matter was investigated at three selected sites each one located in the centre of an anticyclonic eddy: in the Algero-Provencal Basin (St. A), the Ionian Basin (St. B), and the Levantine Basin (St. C). The 3 geographically distant eddies showed low values of the different heterotrophic compartments of the microbial food web, and except for viruses in site C, all integrated (0–150 m) stocks were higher in reference stations located in the same basin outside the eddies. During our study the 3 eddies showed equilibrium between GPP (Gross Primary Production) and DCR (Dark Community Respiration). Integrated PPp (Particulate Primary Production) values at A, B and C varied from ~140 to ~190 mg C m−2.

We present a new synthesis, based on a suite of complementary approaches, of the primary production and carbon sink in forests of the 25 member states of the European Union (EU-25) during 1990-2005. Upscaled terrestrial observations and model-based approaches agree within 25% on the mean net primary production (NPP) of forests, i.e. 520 +/- 75 g C m-2 yr-1 over a forest area of 1.32 x 106 km2 to 1.55 x 106 km2 (EU-25). New estimates of the mean long-term carbon forest sink (net biome production, NBP) of EU-25 forests amounts 75 +/- 20 g C m-2 yr-1. The ratio of NBP to NPP is 0.15 +/- 0.05. Estimates of the fate of the carbon inputs via NPP in wood harvests, forest fires, losses to lakes and rivers and heterotrophic respiration remain uncertain, which explains the considerable uncertainty of NBP. Inventory-based assessments and assumptions suggest that 29 +/- 15% of the NBP (i.e., 22 g C m-2 yr-1) is sequestered in the forest soil, but large uncertainty remains concerning the drivers and future of the soil organic carbon. The remaining 71 +/- 15% of the NBP (i.e., 53 g C m-2 yr-1) is realized as woody biomass increments. In the EU-25, the relatively large forest NBP is thought to be the result of a sustained difference between NPP, which increased during the past decades, and carbon losses primarily by harvest and heterotrophic respiration, which increased less over the same period.

The aim of this study was to investigate temporal trends and controlling factors of As and V in running waters throughout Sweden. For this purpose, data on stream water chemistry from 62 streams of varying catchment size and characteristics, included in the Swedish environmental monitoring programmes were evaluated. The geochemical software Visual MINTEQ was used to model the speciation and trend analyses were performed on total concentrations of As and Vas well as modelled fractions (dissolved species as well as arsenate and vanadate adsorbed to ferrihydrite). The trend analyses showed increasing total concentrations of As and V in southern Sweden. Concentrations of As and V correlated significantly to Fe concentrations in 59 and 60 of the 62 streams respectively, indicating that Fe is an important determining factor for As and V concentrations in Swedish streams. This was confirmed by the geochemical modelling that indicated that the adsorbed fraction is the dominant form of As and V and that the concentrations of As and V in Swedish streams are thus highly determined by concentrations of colloidal or particulate Fe. It is therefore suggested that the increasing trends of As and V are to a large extent due to increasing concentrations of colloidal Fe, which is stabilised by increasing concentrations of DOC. Further the geochemical modelling indicates that the dissolved fraction of As and V generally is small, with the exception of a few streams with high pH and/or phosphate concentrations. QC 20110215

This study assessed cardiovascular disease risk factors in three groups of human subjects aged 20–34 [young, 20 male (M)/33 female (F)], 60–74 (aged, 29M/29F), and > 90 years (nonagenarian, 47M/50F). Components of the metabolic syndrome, cardiovascular disease, and markers of inflammation and oxidative stress were assessed. Nonagenarians weighed less than the two other groups (P

The objectives of this study were to investigate formation of trihalomethane (THM) species in waters treated by different methods and to determine effectiveness of using various methods for controlling disinfection by-product (DBP) precursors in drinking water. Experiments were carried out using batch experimental set-ups. Combinations of pre-ozonation, post-ozonation, enhanced coagulation, rapid sand filtration, activated carbon filtration and UV radiation were performed. Finished waters were analyzed for dissolved organic carbon (DOC), biodegradable dissolved organic carbon (BDOC), ultraviolet absorbance at 254 nm (UV 254 ), total trihalomethane formation potential (TTHMFP), bromide and bromate. The results indicated that using the sequence of pre-ozonation/enhanced coagulation/activated carbon filter is the most effective method for reducing THM precursors. It was also concluded that the formation of THM species primarily related to the characteristics of finished water before chlorination.

[1] The bacterial response to dust pulses was investigated in the Mediterranean Sea through a combined field and experimental study. During the stratification period, characterized by a nutrient-starved mixed layer isolated from the depth, a Saharan dust event (2.6 gm(-2)) induced a 1.5-fold increase in bacterial abundance (BA) and a 2-fold increase in bacterial respiration (BR). Experimental dust additions (equivalent to fluxes of 5 and 20 g m(-2)) to bacteria natural assemblages also stimulated BA (between 2- and 4-fold increases) and BR (between 1.5- and 3-fold increases). Pooling the in situ and experimental data, linear relationships were obtained between dust concentration and BA (r(2) = 0.86; p < 0.01) and BR (r(2) = 0.89; p < 0.001). The dust-induced bacterial bloom resulted in a C mineralization of 0.5 g m(-2), which may represent up to 70% of bioavailable DOC annually exported to the depth in the Mediterranean. These results demonstrate that heterotrophic bacteria may play a much larger role in the connections between dust and the ocean carbon cycle than previously recognized and highlight the need for a more accurate understanding of how dust pulses may affect C export in the oligotrophic ocean.

Two sediment cores retrieved at the northern slope of Sakhalin Island, Sea of Okhotsk, were analyzed for biogenic opal, organic carbon, carbonate, sulfur, major element concentrations, mineral contents, and dissolved substances including nutrients, sulfate, methane, major cations, humic substances, and total alkalinity. Down-core trends in mineral abundance suggest that plagioclase feldspars and other reactive silicate phases (olivine, pyroxene, volcanic ash) are transformed into smectite in the methanogenic sediment sections. The element ratios Na/Al, Mg/Al, and Ca/Al in the solid phase decrease with sediment depth indicating a loss of mobile cations with depth and producing a significant down-core increase in the chemical index of alteration. Pore waters separated from the sediment cores are highly enriched in dissolved magnesium, total alkalinity, humic substances, and boron. The high contents of dissolved organic carbon in the deeper methanogenic sediment sections (50–150 mg dm-3) may promote the dissolution of silicate phases through complexation of Al3+ and other structure-building cations. A non-steady state transport-reaction model was developed and applied to evaluate the down-core trends observed in the solid and dissolved phases. Dissolved Mg and total alkalinity were used to track the in-situ rates of marine silicate weathering since thermodynamic equilibrium calculations showed that these tracers are not affected by ion exchange processes with sediment surfaces. The modeling showed that silicate weathering is limited to the deeper methanogenic sediment section whereas reverse weathering was the dominant process in the overlying surface sediments. Depth-integrated rates of marine silicate weathering in methanogenic sediments derived from the model (81.4–99.2 mmol CO2 m-2 year-1) are lower than the marine weathering rates calculated from the solid phase data (198–245 mmol CO2 m-2 year-1) suggesting a decrease in marine weathering over time. The production of CO2 through reverse weathering in surface sediments (4.22–15.0 mmol CO2 m-2 year-1) is about one order of magnitude smaller than the weathering-induced CO2 consumption in the underlying sediments. The evaluation of pore water data from other continental margin sites shows that silicate weathering is a common process in methanogenic sediments. The global rate of CO2 consumption through marine silicate weathering estimated here as 5–20 Tmol CO2 year-1 is as high as the global rate of continental silicate weathering.

Seasonal increases in the ultraviolet (UV) transparency of the surface waters of an oligotrophic lake in Pennsylvania suggest that clear-water phase (CWP) events similar to those previously observed for visible light also exist for the potentially damaging UV wavelengths. Seasonal increases in zooplankton grazers indicate that they play a role in these changes in UV that is similar to the role that zooplankton play in CWP events involving longer-wavelength visible, or photosynthetically active radiation (PAR, 400¿700 nm). The potential role of zooplankton and incident UV in generating UV CWP events was investigated with a set of in situ microcosm experiments that manipulated UV and zooplankton, and followed changes in particulate and dissolved absorbance in the UV (320 nm) and PAR wavelength ranges over an 8-d period in April. Nutrients were also manipulated independently to examine the potential role of nutrient regeneration by zooplankton grazing in altering water transparency. Photobleaching by incident solar UV led to a strong and significant decrease in dissolved UV and PAR absorbance. The presence of zooplankton grazers also significantly decreased dissolved UV absorbance but increased dissolved PAR absorbance. Neither zooplankton nor UV had any significant effects on UV or PAR absorbance by particulates. In contrast, nutrient additions significantly increased dissolved absorbance in both the UV and PAR wavelength ranges, indicating that regeneration of nutrients by zooplankton offsets decreases in UV absorbance and enhances increases in PAR absorbance due to grazing. While photobleaching by UV radiation is likely to make a consistent strong contribution to UV CWP events in lakes, the net effects of zooplankton on UV transparency in a given lake will depend upon multiple factors including zooplankton density and a balance between the edibility and extent of nutrient limitation of the phytoplankton.

International audience; Soil CO2 and N2O concentrations were simulated with a model predicting C and N transport in the vadose zone during a 7-mo field experiment, after maize (Zea mays L.) harvesting and incorporation of maize residues into the soil. The gas transport model was based on the dusty gas theory and combined with the PASTIS model. During the experiment, soil atmosphere (CO2 and N2O), soil solution (NO3 − and dissolved organic carbon [DOC]), soil water content and temperature, and potential denitrifying and aerobic respiratory activities were measured in a 2.50-m-thick soil profile. Soil gas concentrations were correctly simulated even though the model did not simulate all the biological processes that produced N2O. Nitrous oxide concentration peaks after rain were slightly overestimated, as the WFPS (water-filled pore space) was not estimated accurately enough to predict local anoxic conditions. To model CO2 concentrations, account had to be taken of DOC adsorption onto soil mineral particles and of zymogenous biomass death during the period when the ground was frozen. The model satisfactorily simulated NO3 − concentrations in the top soil profile, notably during major rainfall events, and maize residue dry matter loss during the experiment. The modeling of biological processes needs to be improved to provide a better simulation of C and N transport in the vadose zone. In particular, the use of WFPS was not sufficient to predict anoxic periods; simulations should improve if soil aggregate structure is also taken into account.

Estee artículo contiene 14 páginas, 6 figuras., Sponges are the oldest known extant animal-microbe symbiosis. These ubiquitous benthic animals play an important role in marine ecosystems in the cycling of dissolved organic matter (DOM), the largest source of organic matter on Earth. The conventional view on DOM cycling through microbial processing has been challenged by the interaction between this efficient filter-feeding host and its diverse and abundant microbiome. Here we quantify, for the first time, the role of host cells and microbial symbionts in sponge heterotrophy. We combined stable isotope probing and nanoscale secondary ion mass spectrometry to compare the processing of different sources of DOM (glucose, amino acids, algal-produced) and particulate organic matter (POM) by a high-microbial abundance (HMA) and low-microbial abundance (LMA) sponge with single-cell resolution. Contrary to common notion, we found that both microbial symbionts and host choanocyte (i.e. filter) cells and were active in DOM uptake. Although all DOM sources were assimilated by both sponges, higher microbial biomass in the HMA sponge corresponded to an increased capacity to process a greater variety of dissolved compounds. Nevertheless, in situ feeding data demonstrated that DOM was the primary carbon source for both the LMA and HMA sponge, accounting for ~90% of their heterotrophic diets. Microbes accounted for the majority (65–87%) of DOM assimilated by the HMA sponge (and ~60% of its total heterotrophic diet) but, This work was funded by the DFG CRC1182-TP B1 “Origin and Function of Metaorganisms” to UH, the Spanish Government grant (RTI2018–094187-B100) and “Generalitat de Catalunya” research group grant (2017SGR1011) to MR and RC, the Netherlands Organization for Scientific Research (NWO-VIDI 864.13.007) to DvO, the European Research Council under the European Union’s Horizon 2020 research and innovation programme (Starting Grant 715513) to JMG, and the Swiss Science Foundation Grant (200021_179092) to AM., With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

Finnish-lake and fish-status surveys indicated that 4900 small headwater lakes suffered from acidic deposition and 1600–3200 roach (Rutilus rutilus) and perch (Perca fluviatilis) populations were affected or extinct by the end of 1980s. Since the late 1980s, successful sulphur emission reductions in Europe have induced a chemical recovery of acidified lakes. This resulted in decreases in sulphate and labile aluminium concentrations and increases in pH and alkalinity during the 1990s. The first signs of recovery in affected perch populations were observed in the early 1990s. New strong year-classes appeared and the population structure returned to normal. Little if any recovery of the affected populations of the more acid-sensitive species, roach, was recorded. This may have been due to still critical water quality conditions for successful reproduction of sensitive roach and/or organic acid episodes in the 2000s, suppressing the recovery of buffering capacity.

Headwater catchments are the fundamental units that connect the land to the ocean. Hydrological flow and biogeochemical processes are intricately coupled, yet their respective sciences have progressed without much integration. Reaction kinetic theories that prescribe rate dependence on environmental variables (e.g., temperature and water content) have advanced substantially, mostly in well-mixed reactors, columns, and warming experiments without considering the characteristics of hydrological flow at the catchment scale. These theories have shown significant divergence from observations in natural systems. On the other hand, hydrological theories, including transit time theory, have progressed substantially yet have not been incorporated into understanding reactions at the catchment scale. Here we advocate for the development of integrated hydro-biogeochemical theories across gradients of climate, vegetation, and geology conditions. The lack of such theories presents barriers for understanding mechanisms and forecasting the future of the Critical Zone under human- and climate-induced perturbations. Although integration has started and co-located measurements are well under way, tremendous challenges remain. In particular, even in this era of "big data," we are still limited by data and will need to (1) intensify measurements beyond river channels and characterize the vertical connectivity and broadly the shallow and deep subsurface; (2) expand to older water dating beyond the time scales reflected in stable water isotopes; (3) combine the use of reactive solutes, nonreactive tracers, and isotopes; and (4) augment measurements in environments that are undergoing rapid changes. To develop integrated theories, it is essential to (1) engage models at all stages to develop model-informed data collection strategies and to maximize data usage; (2) adopt a "simple but not simplistic," or fit-for-purpose approach to include essential processes in process-based models; (3) blend the use of process-based and data-driven models in the framework of "theory-guided data science." Within the framework of hypothesis testing, model-data fusion can advance integrated theories that mechanistically link catchments' internal structures and external drivers to their functioning. It can not only advance the field of hydro-biogeochemistry, but also enable hind- and fore-casting and serve the society at large. Broadly, future education will need to cultivate thinkers at the intersections of traditional disciplines with hollistic approaches for understanding interacting processes in complex earth systems. This article is categorized under: Science of Water > Methods, Wiley Interdisciplinary Reviews. Water, 8 (1), ISSN:2049-1948