Showing papers by "Ecolab published in 2015"

A meta-analysis of the effects of nutrient enrichment on litter decomposition in streams

Abstract: The trophic state of many streams is likely to deteriorate in the future due to the continuing increase in human-induced nutrient availability. Therefore, it is of fundamental importance to understand how nutrient enrichment affects plant litter decomposition, a key ecosystem-level process in forest streams. Here, we present a meta-analysis of 99 studies published between 1970 and 2012 that reported the effects of nutrient enrichment on litter decomposition in running waters. When considering the entire database, which consisted of 840 case studies, nutrient enrichment stimulated litter decomposition rate by approximately 50%. The stimulation was higher when the background nutrient concentrations were low and the magnitude of the nutrient enrichment was high, suggesting that oligotrophic streams are most vulnerable to nutrient enrichment. The magnitude of the nutrient-enrichment effect on litter decomposition was higher in the laboratory than in the field experiments, suggesting that laboratory experiments overestimate the effect and their results should be interpreted with caution. Among field experiments, effects of nutrient enrichment were smaller in the correlative than in the manipulative experiments since in the former the effects of nutrient enrichment on litter decomposition were likely confounded by other environmental factors, e.g. pollutants other than nutrients commonly found in streams impacted by human activity. However, primary studies addressing the effect of multiple stressors on litter decomposition are still few and thus it was not possible to consider the interaction between factors in this review. In field manipulative experiments, the effect of nutrient enrichment on litter decomposition depended on the scale at which the nutrients were added: stream reach > streamside channel > litter bag. This may have resulted from a more uniform and continuous exposure of microbes and detritivores to nutrient enrichment at the stream-reach scale. By contrast, nutrient enrichment at the litter-bag scale, often by using diffusing substrates, does not provide uniform controllable nutrient release at either temporal or spatial scales, suggesting that this approach should be abandoned. In field manipulative experiments, the addition of both nitrogen (N) and phosphorus (P) resulted in stronger stimulation of litter decomposition than the addition of N or P alone, suggesting that there might be nutrient co-limitation of decomposition in streams. The magnitude of the nutrient-enrichment effect on litter decomposition was higher for wood than for leaves, and for low-quality than for high-quality leaves. The effect of nutrient enrichment on litter decomposition may also depend on climate. The tendency for larger effect size in colder regions suggests that patterns of biogeography of invertebrate decomposers may be modulating the effect of nutrient enrichment on litter decomposition. Although studies in temperate environments were overrepresented in our database, our meta-analysis suggests that the effect of nutrient enrichment might be strongest in cold oligotrophic streams that depend on low-quality plant litter inputs.

Heavy Metal Stress and Crop Productivity

Abstract: Heavy metal contamination of the environment through anthropogenic activities and/or natural processes is a widespread and serious problem. Heavy metals occur in various forms in soil, which differ greatly with respect to their solubility/bioavailability. The geochemical behavior of heavy metals in soil, their uptake by plants, and effect on crop productivity is affected by various physicochemical properties of soil. Heavy metals mainly accumulate in root cells, due to their blockage by Casparian strips or due to trapping by the cell walls of roots. Excessive heavy metal accumulation in plant tissue impairs either directly or indirectly several biochemical, physiological, and morphological functions in plants and in turns interferes with crop productivity. Heavy metals reduce crop productivity by inducing deleterious effects to various physiological processes in plants including: seed germination, accumulation and remobilization of seed reserves during germination, plant growth, and photosynthesis. At the cellular level, heavy metal toxicity reduces crop productivity by producing reactive oxygen species, disturbing the redox balance and causing oxidative stress. Under heavy metal stress, plants have numerous defense mechanisms to manage heavy metal toxicity and to maintain their productivity, which include reduced heavy metal uptake by plants, sequestration into vacuoles, binding by phytochelatins, and activation of various antioxidants. This chapter presents the effect of heavy metals on physiological reactions in the plants’ crop productivity.

Engineer pioneer plants respond to and affect geomorphic constraints similarly along water-terrestrial interfaces world-wide

Abstract: AIM Within fluvial and coastal ecosystems world-wide, flows of water, wind and sediment generate a shifting landscape mosaic composed of bare substrate and pioneer and mature vegetation successional stages. Pioneer plant species that colonize these ecosystems at the land–water interface have developed specific traits in response to environmental constraints (response traits) and are able to modify habitat conditions by modulating geomorphic processes (effect traits). Changes in the geomorphic environment under the control of engineer plants often feed back to organism traits (feedback traits), and thereby ecosystem functioning, leading to eco-evolutionary dynamics. Here we explain the joint foundations of fluvial and coastal ecosystems according to feedback between plants and the geomorphic environment. LOCATION Dynamic fluvial and coastal ecosystems world-wide. METHOD Drawing from a pre-existing model of ‘fluvial biogeomorphic succession’, we propose a conceptual framework showing that fluvial and coastal ‘biogeomorphic ecosystems’ are functionally similar due to eco-evolutionary feedbacks between plants and geomorphology. RESULTS The relationships between plant traits and their geomorphic environments within different fluvial and coastal biogeomorphic ecosystems are identified and classified within a framework of biogeomorphic functional similarity according to three criteria: (1) pioneer plants develop specific responses to the geomorphic environment; (2) engineer plants modulate the geomorphic environment; (3) geomorphic changes under biotic control within biogeomorphic ecosystems feed back to organisms. MAIN CONCLUSIONS The conceptual framework of functional similarity proposed here will improve our capacity to analyse, compare, manage and restore fluvial and coastal biogeomorphic ecosystems world-wide by using the same protocols based on the three criteria and four phases of the biogeomorphic succession model.

Drought and societal collapse 3200 years ago in the Eastern Mediterranean: a review

Abstract: One of the goals of climate scientists is to understand how climate shifts may have changed the course of history and influenced culture at millennial timescales. Repeatedly, environmental degradation has upset the balance between people, their habitat, and the socioeconomic frameworks in which they live. Among these imbalances, drought, firmly rooted in people's minds as a catalyst of harvest failures and famines, remains a permanent threat because it may trigger or amplify social crises, leading to massive exoduses, conflicts, and political turmoil. The spiral of decline in which the flourishing Eastern Mediterranean civilizations were plunged 3200 years ago, and the ensuing chaos, remains a persistent riddle in Near Eastern history. Scholars tend to believe that this socioeconomic collapse was violent and culturally disruptive. Most of the coastal cities between Pylos and Gaza were destroyed, burned, and often left unoccupied, thereafter, putting an end to the elaborate network of international trade that ensured prosperity in the Aegean and the Eastern Mediterranean. The rural settlements that emerged have mainly persisted through adapted agropastoral activities and limited long-distance trade. At the dusk of this event, regional cultures began to be poorly documented, leading historians to allude to a dark age that lasted for 300 years. Among the roots, tectonic instability and earthquakes, demographic imbalance between social groups, internal collapses, and technological innovations are commonly evoked. However, recent studies have mainly hypothesized about an impact of a centuries-long drought behind the decline. Drought may have hastened the fall of the Old World by sparking famine, invasions, and conflicts, leading to the political, economic, and cultural chaos termed Late Bronze Age collapse'. WIREs Clim Change 2015, 6:369-382. doi: 10.1002/wcc.345 For further resources related to this article, please visit the . Conflict of interest: The authors have declared no conflict of interest for this article.

Role of metal speciation in lead-induced oxidative stress to Vicia faba roots

Abstract: Chemical speciation of metals in soil/solution plays an important role in determining their biogeochemical behavior in soil-plant system. The current study evaluated the influence of applied form of Pb (metal speciation) on its toxicity to metal sensitive Vicia faba L. roots. Lead was applied to young V. faba seedlings alone or chelated by organic ligands (citric acid and ethylenediaminetetraacetic acid). Plants were exposed to all treatments for 1, 4, 8, 12, and 24 h in nutrient solution, and contents of H2O2 and thiobarbituric-acid-reactive substances (TBARS) production were analyzed in V. faba roots. The results showed that Pb toxicity to V. faba roots depended on its applied chemical form and duration of exposure. Lead alone caused two burst of lipid peroxidation and H2O2 induction at 1 h and 12 h. Addition of EDTA dose-dependently inhibited Pb-induced H2O2 and TBARS production, indicating a protective role of this chelator against Pb toxicity during the first 24 h. In contrast, citric acid did not show significant effects on Pb-induced H2O2 and TBARS production, but delayed the induction of these effects. This study suggested that Pb toxicity to V. faba roots varies with Pb speciation in growth medium.

Sediment and nutrient dynamics during storm events in the Enxoé temporary river, southern Portugal

Abstract: In temporary (or intermittent) rivers the first storm event after a dry period is responsible for transferring large amounts of sediment and nutrients into water reservoirs, thereby justifying close monitoring. The objective of this study was to analyse the contribution of storm events to sediment and nutrient transport in the Enxoe temporary river (southern Portugal) using detailed monitoring collected during three hydrological years (September, 2010 to August, 2013), and identify possible sediment and nutrient source areas based on the interpretation of hysteresis in the concentration–discharge relationship. The Enxoe River was monitored for suspended sediment concentration (SSC), total phosphorus (TP), particulate phosphorus (PP), soluble reactive phosphorus (SRP), and nitrate (NO 3 − ). An empirical model was used to describe changes in solute concentrations, and the magnitude and rotational patterns of the hysteretic loops. Twenty-one storm events were registered. SSC, TP, PP, SRP, and NO 3 − concentrations varied between 1.6 and 3790.1, 0.05–11.4, 0–7.6, 0–0.67, and 0–27.84 mg l − 1 , respectively. The highest SSC, TP, and PP concentrations were registered during the first storm event after an extended drought period. Annual sediment yields (13–480 kg ha − 1 y − 1 ) and nitrate (4.4–45.5 kg ha − 1 y − 1 ) were relatively low, while phosphorus losses (0.04–0.96 kg ha − 1 y − 1 ) reached relatively high values during humid years. Sediment and phosphorus transport was influenced by the stream transport capacity and particle availability, whereas nitrate loads were influenced by rainfall, soil hydraulic characteristics, and land management. This work highlights the main processes involved in sediment and nutrients loads in a temporary river during storm events, with a quantification of the relevant elements.

Non‐native species modify the isotopic structure of freshwater fish communities across the globe

Abstract: Multiple anthropogenic pressures including the widespread introductions of non-native species threaten biodiversity and ecosystem functioning notably by modifying the trophic structure of communities. Here, we provided a global evaluation of the impacts of non-native species on the isotopic structure (δ13C and δ15N) of freshwater fish communities. We gathered the stable isotope values (n = 4030) of fish species in 496 fish communities in lentic (lakes, backwaters, reservoirs) and lotic (running waters such as streams, rivers) ecosystems throughout the world and quantified the isotopic structure of communities. Overall, we found that communities containing non-native species had a different isotopic structure than communities without non-native species. However, these differences varied between ecosystem types and the trophic positions of non-native species. In lotic ecosystems, communities containing non-native species had a larger total isotopic niche than communities without non-native species. This was primarily driven by the addition of non-native predators at the top of the food chain that increased δ15N range without modifying the isotopic niche size of native species. In lentic ecosystems, non-native primary consumers increased δ15N range and this was likely driven by an increase of resource availability for species at higher trophic levels, increasing food chain length. The introduction of non-native secondary consumers at the centre of the isotopic niche of recipient communities decreased the core isotopic niche size, the δ13C range of recipient communities and the total isotopic niche of coexisting native species. These results suggested a modified contribution of the basal resources consumed (e.g. multi-chain omnivory) and an increase level of competition with native species. Our results notably imply that, by affecting the isotopic structure of freshwater fish communities at a global scale, non-native species represent an important source of perturbations that should be accounted for when investigating macro-ecological patterns of community structure and biotic interactions.

Forest dynamics and tip-up pools drive pulses of high carbon accumulation rates in a tropical peat dome in Borneo (Southeast Asia)

Abstract: Singapore. National Research Foundation (Singapore-MIT Alliance for Research and Technology)

Fluctuations in the extent of mangroves driven by multi‐decadal changes in North Atlantic waves

Abstract: Aim : The goal of the study was to quantify changes in the extent of mangroves since the mid-twentieth century and to test the hypothesis that these changes are driven by ocean waves. Location : The pristine 300-km-long coast of French Guiana, South America. Methods : We produced time series of mangrove maps using archival remote sensing images. We retrieved significant wave heights (HS), mean wave periods (TM) and mean wave directions (θM) from the European Centre for Medium-Range Weather Forecasts reanalysis products. We used complex empirical orthogonal function (CEOF) decomposition to extract the main mode of mangrove surface area (MS) variability and singular value decomposition (SVD) to test the relationships between MS and HS, TM and θM. Results : The leading mode of variability extracted from the CEOF decomposition of MS captured approximately 78% of the total auto-covariance and revealed multi-decadal fluctuations in MS that were on the order of 10,000 ha. The SVD results indicated that the multi-decadal fluctuation in MS cross-covaried with HS, TM and θM over the North Atlantic sector, particularly in the region immediately off the French Guiana coast that is remotely forced by the North Atlantic Oscillation (NAO) during the winter season. Main conclusions : We provide evidence based on linear statistics that variations in the extent of mangroves are driven by large-scale, low-frequency changes in North Atlantic waves that are related to the NAO. Such a relationship is hypothesized to operate through wave pounding, which alters the mud substrates on which mangroves thrive and which varies with the phase of the NAO. In addition to long-term trends due to anthropogenic climate change, our results stress the importance of studying low-frequency modes of climate variability to understand changes in the extent of mangroves.

Stability as a Phenomenon Emergent from Plasticity–Complexity–Diversity in Eco-physiology

Abstract: The network of plasticity, diversity, complexity, and stability is drawn as a quadruped-scheme. Plasticity is on the top of the scheme and stability is in the center. Plasticity is discussed in some detail. Examples are given of intraspecific plasticity, especially of photosynthesis. Plasticity allows escape from the dilemma of growth or defense of the growth differentiation balance theory (GDB). Analysis by principal component analysis (PCA) of multi-variant traits and their integration explain plastic emergence of phenotypes. Via the phenotypes plasticity can both impede or support diversity by speciation. Diversity, or as we say in the realm of life “biodiversity,” governs spatiotemporal dynamics of competition/facilitation equilibria in stress gradients (stress gradient hypothesis, SGH). Diversity is the basis of complexity. Both, biodiversity and complexity, are challenging and stabilizing in terms of sustaining ecosystems. Via the different connections in the network of the quadruped plasticity, diversity and complexity affect stability. Understanding of the quadruped network offers an outlook on potential applications in environmental management and agro-forest ecology.

Functional trait responses of aquatic macroinvertebrates to simulated drought in a Neotropical bromeliad ecosystem

Abstract: The duration of the dry seasons in south‐eastern Amazonia is expected to increase. Little is known of how freshwater assemblages respond to drought in the humid rainforests and of the extent to which they resist the absence of rainfall before the collapse of the system. We manipulated rainshelters over tank‐forming bromeliads (i.e. the interlocking leaf axils of these plants form wells that collect rainwater) to simulate an exceptionally long dry period (49 days, compared with a 10‐year mean ± SD annual maximum number of 17 ± 5.3 days without rainfall at the study site) and then a rewetting period. By sampling weekly over 3 months, we followed the dynamics of the representation of abundance‐weighted traits in invertebrate assemblages in these treatment plants and in a control group. The functional structure of assemblages was drought resistant until the water volume in the bromeliad pools dropped by 90%, when there was a sudden shift in the functional trait structure due to the loss of most populations except the drought‐resistant culicids. Traits related to life history, body size and preferred food showed significant responses to drought. There was a convergence in the functional traits of species surviving in dry plants, strengthening the idea that environmental filtering, rather than stochasticity, determines the functional trajectory of aquatic assemblages during drought. At the end of the dry period, samples of the detritus potentially containing drought‐resistant eggs/cysts (and eventually live larvae) were taken from the dry plants and rewetted in the laboratory, allowing us to distinguish resistant species from those requiring recolonisation via subsequent oviposition by adults from elsewhere. Patches of water‐filled bromeliads persisting in the area provided the most important pool of colonists, and communities returned to the pre‐disturbance state within 1–2 weeks of rewetting. Our results suggest that the functional trait structure of invertebrate assemblages in bromeliads could remain stable under scenarios of precipitation change that would triple the duration of current dry periods at a local scale. Future experiments should evaluate how environmental factors might alter the tipping point between resistance to drought and a collapse in ecosystem processes.

Silver nanoparticles impact phototrophic biofilm communities to a considerably higher degree than ionic silver

Abstract: Due to the significant increase in nanoparticle production and especially that of silver nanoparticles over the past decade, the toxicity of silver in both ionic (Ag+) and nanoparticulate (AgNPs) form must be studied in detail in order to understand their impact on natural ecosystems. A comparative study of the effect of AgNPs and ionic silver on two independent phototrophic biofilms was conducted in a rotating annular bioreactor (RAB) operating under constant conditions. The concentration of dissolved silver in the inlet solution was progressively increased every 4 days of exposure, from 0.1 to 100 μg L−1. In the course of the 40-day experiment, biofilm samples were collected to determine the evolution of biomass, chlorophyll-a, as well as photosynthetic and heterotrophic enzymatic activities in response to silver addition. Analysis of both dissolved and particulate silver allowed quantification of the distribution coefficient and uptake rate constants. The presence of both AgNPs and Ag+ produced significant changes in the biofilm structure, decreasing the relative percentage of Diatomophyceae and Cyanophyceae and increasing the relative percentage of Chlorophyceae. The accumulation capacity of the phototrophic biofilm with respect to ionic silver and the corresponding distribution coefficients were an order of magnitude higher than those of the phototrophic biofilm with respect to AgNPs. Higher levels of AgNPs decreased the biomass from 8.6 ± 0.2 mg cm−2 for 0–10 μg L−1 AgNPs to 6.0 ± 0.1 mg cm−2 for 100 μg L−1 added AgNPs, whereas ionic silver did not have any toxic effect on the biofilm growth up to 100 μg L−1 of added Ag+. At the same time, AgNPs did not significantly affect the photosynthetic activity of the biofilm surface communities compared to Ag+. It can thus be hypothesized that negatively charged AgNPs may travel through the biofilm water channels, thereby affecting the whole biofilm structure. In contrast, positively charged Ag+ is bound at the cell surfaces and EPS, thus blocking its further flux within the biofilm layers. On the whole, the phototrophic biofilm demonstrated significant capacities to accumulate silver within the surface layers. The main mechanism to avoid the toxic effects is metal complexation with exopolysaccharides and accumulation within cell walls, especially pronounced under Ag+ stress. The significant AgNPs and Ag+ uptake capacities of phototrophic biofilm make it a highly resistant ecosystem in silver-polluted river waters.

Fungal alteration of the elemental composition of leaf litter affects shredder feeding activity

Abstract: 1. Leaf litter from riparian vegetation provides the main source of matter and energy for food webs of small forest streams. Shredding macroinvertebrates mostly feed on this litter when it has been colonised and conditioned by microorganisms, especially by aquatic hyphomycetes. Since shredders feed selectively, they must make foraging decisions based on the physical and chemical characteristics of the food resource, which can change depending on the identity of fungal species. 2. Here, we addressed the effect of changes in fungal assemblage structure on the elemental composi- tion of oak (Quercus robur) leaf litter and how variation in litter quality affects the feeding of a stream shredder. Leaf discs were incubated in microcosms for 2 weeks, inoculated with various fungal assemblages comprised of three species each, and offered to a shredder (Schizopelex festiva, Trichoptera: Sericostomatidae) as food. 3. This shredder ate more leaves with a high mycelial biomass, which depended on fungal assemblage composition. Leaf litter conditioned by different fungal assemblages resulted in different litter N and P concentrations. Mycelial biomass was positively related to litter P concentration, with the lowest and highest P concentrations differing by 40% at most, but not to litter N concentration, even though the lowest and highest N concentrations differed by as much as 35%. The caddisfly larvae ate more leaves with a low C/P ratio. 4. These findings suggest a key role of litter P concentration in eliciting fungal conditioning effects on shredder-mediated litter decomposition.

Role of Water on the Precipitation and Deposition of Asphaltenes in Packed-Bed Microreactors

Abstract: Water naturally comprises some fraction of virtually all petroleum reservoirs worldwide, yet its existence introduces complexity to asphaltene precipitation and deposition mechanisms. This global problem not only impacts upstream conventional and unconventional energy production but also influences downstream chemical refining, the construction industry, and the transportation sector. A transparent packed-bed microreactor (μPBR) with inline analytics was designed to merge two fields of science, oilfield chemistry and microchemical systems, to investigate the role of water on the molecular-to-the-microscale deposition of asphaltenes in quartz porous media. Porosity loss and permeability impairment of the porous media for water mass fractions of <0.001 to 34.5 wt % were investigated. Interestingly, a switch in the mechanism of water (from 0.030 to 3.18 wt %) on the accumulation was discovered. Analyses of porosity–permeability relationships revealed competition between adsorption and desorption followed by ...

Soil genotoxicity assessment—results of an interlaboratory study on the Vicia micronucleus assay in the context of ISO standardization

Abstract: The Vicia micronucleus assay was standardized in an international protocol, ISO 29200, "Assessment of genotoxic effects on higher plants-Vicia faba micronucleus test," for soil or soil materials (e.g., compost, sludge, sediment, waste, and fertilizing materials). The aim of this interlaboratory study on the Vicia micronucleus assay was to investigate the robustness of this in vivo assay in terms of its applicability in different countries where each participant were asked to use their own seeds and reference soil, in agreement with the ISO 29200 standard. The ISO 29200 standard protocol was adopted for this study, and seven laboratories from three countries (France, Italy, and Brazil) participated in the study. Negative and positive controls were correctly evaluated by 100 % of the participants. In the solid-phase test, the micronucleus frequency (number of micronuclei/1,000 cells) varied from 0.0 to 1.8 for the negative control (i.e., Hoagland's solution) and from 5.8 to 85.7 for the positive control (i.e., maleic hydrazide), while these values varied from 0.0 to 1.7 for the negative control and from 14.3 to 97.7 for the positive control in the case of liquid-phase test. The variability in the data obtained does not adversely affect the robustness of the protocol assessed, on the condition that the methodology described in the standard ISO 29200 is strictly respected. Thus, the Vicia micronucleus test (ISO 29200) is appropriate for complementing prokaryotic or in vitro tests cited in legislation related to risk assessment of genotoxicity potential.

Does the non-native European catfish Silurus glanis threaten French river fish populations?

Abstract: The European catfish, Silurus glanis, was widely introduced in western Europe, and it has now established self-sustaining populations in numerous large rivers of western France. Using data collected from surveys conducted by the French National Agency for Water and Aquatic Environment (Onema) from 1989 to 2010 in more than 500 sites throughout the country (10636 electrofishing surveys), we investigated the potential impact of the European catfish on fish communities in French rivers. In the first part of the analysis, we compared trends observed before and after the European catfish was established at given sites (before-after analysis). Species richness, evenness and diversity decreased significantly after the European catfish was established at 1.4%, 1.4% and 5.8% of the sites, respectively. Total fish biomass and density decreased significantly at 6.6% and 2.9% of the sites, respectively. In the second part of the analysis, we compared sites with European catfish against sites lacking European catfish during the same period (with-without analysis). Fish species richness was significantly higher in sites with European catfish. No significant differences in fish diversity, evenness, total fish biomass or density were found between sites with or without European catfish. While our results indicate that the European catfish may in a few cases impact fish communities or populations, it does not appear to be responsible for a countrywide collapse in fish assemblages.