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Abstract: Terrigenous organic matter (TOM) transfer from a watershed to a lake plays a key role in contaminants fate and greenhouse gazes emission in these aquatic ecosystems. In this study, we linked physiographic and vegetation characteristics of a watershed with TOM nature deposited in lake sediments. TOM was characterized using lignin biomarkers as indicators of TOM sources and state of degradation. Geographical information system (GIS) also allowed us to integrate and describe the landscape morpho-edaphic characteristics of a defined drainage basin. Combining these tools we found a significant and positive relationship (R 2 =0.65, p <0.002) between mean slope of the watershed and the terrigenous fraction estimated by Λ8 in recent sediments. The mean slope also correlated with the composition of TOM in recent sediments as P/(V+S) and 3,5Bd/V ratios significantly decreased with the steepness of the watersheds (R 2 =0.57, p <0.021 and R 2 =0.71, p <0.004, respectively). More precisely, areas with slopes comprised between 4° and 10° have a major influence on TOM inputs to lakes. The vegetation composition of each watershed influenced the composition of recent sediments of the sampled lakes. The increasing presence of angiosperm trees in the watershed influenced the export of TOM to the lake as Λ8 increased significantly with the presence of this type of vegetation (R 2 =0.44, p <0.019). A similar relationship was also observed with S/V ratios, an indicator of angiosperm sources for TOM. The type of vegetation also greatly influenced the degradation state of OM. In this study, we were able to determine that low-sloped areas (0–2°) act as buffer zones for lignin inputs and by extension for TOM loading to sediments. The relative contribution of TOM from the soil organic horizons also increased in steeper watersheds. This study has significant implications in our understanding of the fate of TOM in lacustrine ecosystems. [Copyright &y& Elsevier]

The δ15N trophic enrichment in littoral food webs is not well known despite the importance of macroinvertebrates in lacustrine energy fluxes. We wanted to assess the influence of functional feeding group (grazer, collector, shredder, predator, predator–hematophagous, predator–sucker) and spatiotemporal variables (year, month, station of sampling) on littoral macroinvertebrate δ15N signatures. For 2 years, during the plant growth period phytophilous littoral macroinvertebrates were sampled in Lake St. Pierre, a large fluvial lake of the St. Lawrence River, Québec, Canada. The δ15N analyses showed that station was the most important factor for explaining δ15N variation, followed by sampling month and functional feeding group. The organisms sampled in the stations of the south shore, which experienced greater macrophyte abundance, slower currents, and stronger NO3 depletion exhibited higher δ15N values than those sampled on the north shore. Grazer-to-predator δ15N enrichment valued 1.6‰, which is inferior to the 3.4‰ generally admitted in food-web research. Shredders exhibited the lowest δ15N values and predators–hematophagous the highest. δ15N signature of invertebrates increased 3‰ through the summer between May and September. Only samples collected within a short period should be pooled to avoid an error value equivalent to one trophic level (1.6) enrichment. Furthermore, it is recommended not to pool macroinvertebrate samples collected at stations with differing watershed land uses. [ABSTRACT FROM AUTHOR]

This research aimed to better understand the gap between journalists and scientists in the context of the media coverage of an environmental issue in Québec (Canada). Through in-depth interviews with journalists and scientists, we were able to identify different sources of frustration felt by both protagonists, notably the question of the scientists' revision of the journalists' text, the journalists' lack of accuracy, and the problem of different time frames in the media and the scientific worlds. This study also offered insights for bridging the gaps. [ABSTRACT FROM AUTHOR]

This study presents the role of specific terrigenous organic compounds as important vectors of mercury (Hg) transported from watersheds to lakes of the Canadian boreal forest. In order to differentiate the autochthonous from the allochthonous organic matter (OM), lignin derived biomarker signatures [Lambda, S/V, C/V, P/(V + S), 3,5-Bd/V and (Ad/Al)v] were used. Since lignin is exclusively produced by terrigenous plants, this approach can give a non equivocal picture of the watershed inputs to the lakes. Moreover, it allows a characterization of the source of OM and its state of degradation. The water column of six lakes from the Canadian Shield was sampled monthly between June and September 2005. Lake total dissolved Hg concentrations and Lambda were positively correlated, meaning that Hg and ligneous inputs are linked (dissolved OM r2 = 0.62, p < 0.0001; particulate OM r2 = 0.76, p < 0.0001). Ratios of P/(V + S) and 3,5-Bd/V from both dissolved OM and particulate OM of the water column suggest an inverse relationship between the progressive state of pedogenesis and maturation of the OM in soil before entering the lake, and the Hg concentrations in the water column. No relation was found between Hg levels in the lakes and the watershed flora composition—angiosperm versus gymnosperm or woody versus non-woody compounds. This study has significant implications for watershed management of ecosystems since limiting fresh terrestrial OM inputs should reduce Hg inputs to the aquatic systems. This is particularly the case for large-scale land-use impacts, such as deforestation, agriculture and urbanization, associated to large quantities of soil OM being transferred to aquatic systems. [ABSTRACT FROM AUTHOR]

Lake St. Pierre (LSP), constituted of a 120 km2 stretching of the St. Lawrence River (Southern Québec), hosts the largest freshwater fishery industry in Canada. The lake drains, through its main tributaries, an important area of agrarian land and was subjected to intense industrial activities in the past century. In this paper, we present (1) an estimation of the seasonal aquatic mercury (Hg) inputs to LSP from the St-Lawrence River and two major tributaries; (2) a reconstruction, by the analysis of sediment cores, of the historic inputs of Hg into LSP and in a large riparian wetland, Bay St. François. Our results indicate that the aquatic Hg inputs to LSP (290 kg Hg between April 2003 and April 2004) are moderately elevated with most of the inputs occurring from the St. Lawrence River, either in spring or early winter, during high flow episodes. The sediment profiles suggest a recent decrease in Hg inputs, likely attributable to improvements of industrial practices. The observed perturbation of the surface sediments give evidence of an active hydrodynamic regime, suggesting that LSP could only act as a transitory system for suspended sediment and Hg, with seasonal accumulation and recurrent re-suspension resulting from changes in the hydrodynamic regime. Finally, we observed positive MeHg fluxes from the sediment to the water at different seasons in Bay St. François. However, Hg levels in fish like walleyes of LSP are reported to be low, which could be explained by faster fish growth rates following in part intense fishing pressure in LSP. [ABSTRACT FROM AUTHOR]

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Information exchanges, debates, and negotiations through community social networks are essential to ensure the sustainability of the development process initiated in participatory research. The authors analyze the structural properties and robustness of a discussion network about mercury issues in a community in the Brazilian Amazon involved in a participatory research aimed at reducing exposure to the pollutant. Most of the villagers are connected in a large network and are separated from other individuals by few intermediaries. The structure of the discussion network displays resilience to the random elimination of villagers but shows vulnerability to the removal of one villager who has been a long-term collaborator of the project. Although the network exhibits a structure likely to favor an efficient flow of information, results show that specific actions should be taken to stimulate the emergence of a pool of opinion leaders and increase the redundancy of discussion channels. [ABSTRACT FROM AUTHOR]

Although high levels of fish consumption and bioindicators of mercury exposure have been reported for traditional populations in the Amazon, little is known about their actual daily intake of Hg. Using an ecosystem approach, calculate daily mercury intake in adult fish-eaters, examine the relations between mercury intake and bioindicators of exposure and the factors that influence these relations. A cross-sectional dietary survey on fish and fruit consumption frequency was carried out with 256 persons from six villages of the Tapajós River. Fish portion per meal was determined. Mercury concentration was determined for 1123 local fish specimens. Daily mercury intake (μg/kg/day) was determined for men and women from each village using the average fish-mercury concentration for the fish caught in their fishing zone, the average quantity of fish per meal, fish-species frequency consumption and participants’ body weight. Fish-mercury averaged 0.33 μg/g±0.33. Daily mercury intake varied between 0 and 11.8 μg/kg/day (mean 0.92 μg/kg/day±0.89) and varied by gender and village. Mean blood- and hair-mercury were 58.7±36.1 μg/l and 17.9±11.5 μg/g, respectively. There was a strong and positive relation between blood-mercury and daily mercury intake, with an inverse relation for fruit intake and schooling; significant variations were observed with immigrant status, and among villages. Hair-mercury was directly associated with daily mercury intake and inversely related to schooling and fruit consumption. Fruit consumption modified the relation between daily mercury intake and blood-mercury levels: for the same daily mercury intake, persons eating more fruit had lower blood-mercury concentrations (ANCOVA Interaction term: F=10.9, P<0.0001). The median difference of the ratio of blood-mercury to daily mercury intake between low and high fruit consumers was 26, representing a 26.3% reduction. These findings reveal high levels of daily mercury intake. Rigorous studies for developing risk-based reference doses in the Amazon should be undertaken to orient viable risk-management strategies to reduce exposure, while maintaining fish diet.Journal of Exposure Science and Environmental Epidemiology (2008) 18, 76–87; doi:10.1038/sj.jes.7500599; published online 5 September 2007 [ABSTRACT FROM AUTHOR]

In order to evaluate the role of photochemistry in the carbon dioxide (CO2) generation from a 10-year-old boreal reservoir, the photomineralization of dissolved organic matter (DOM) was assessed and compared to a boreal river as well as to boreal and temperate lakes during July and August, 2003. Sterile water samples were irradiated by sunlight over the whole photoperiod and subsequently analyzed for CO2. Mean energy-normalized apparent photochemical yield of CO2 (an index of DOM photoreactivity normalized for the energy absorbed by samples) was significantly higher in the reservoir (27.7 ± 13.0 mg CO2·m−3·kJ−1) and the boreal river (35.8 ± 2.3 mg CO2·m−3·kJ−1) than in the boreal lakes (15.5 ± 5.1 mg CO2·m−3·kJ−1). The DOM photoreactivity of the temperate lakes (20.9 ± 8.1 mg CO2·m−3·kJ−1) was not statistically different from any type of boreal water bodies. There was no significant difference in either the integrated photoproduction of CO2 (273–433 mg CO2·m−2·d−1) or the potential photochemical contribution to CO2 diffusive fluxes (56–92%) among these water bodies. DOM photoreactivity was significantly affected by the cumulative hydrological residence time (CHRT) when considering the whole data set. However, when considering only the boreal water bodies, iron (Fe) and manganese (Mn) also intervened. The fact that DOM photoreactivity was related to CHRT as well as to Fe and Mn concentrations, which are respectively permanent and long-lasting features of the reservoir, suggests that the photoproduction of CO2 is not likely to decrease over time. This process may therefore play a substantial role in the long-term CO2 emissions from boreal reservoirs during the summer, its potential contribution to CO2 diffusive fluxes being estimated at 56 ± 29 %. [ABSTRACT FROM AUTHOR]

In this paper, we synthesize available information on the links between changes in ecosystem loading of inorganic mercury (Hg) and levels of methylmercury (MeHg) in fish. Although it is widely hypothesized that increased Hg load to aquatic ecosystems leads to increases in MeHg in fish, there is limited quantitative data to test this hypothesis. Here we examine the available evidence from a range of sources: studies of ecosystems contaminated by industrial discharges, observations of fish MeHg responses to changes in atmospheric load, studies over space and environmental gradients, and experimental manipulations. A summary of the current understanding of the main processes involved in the transport and transformation from Hg load to MeHg in fish is provided. The role of Hg loading is discussed in context with other factors affecting Hg cycling and bioaccumulation in relation to timing and magnitude of response in fish MeHg. The main conclusion drawn is that changes in Hg loading (increase or decrease) will yield a response in fish MeHg but that the timing and magnitude of the response will vary depending of ecosystem-specific variables and the form of the Hg loaded. [ABSTRACT FROM AUTHOR]

Lake sediments are a potential source of mercury (Hg) for aquatic biota. Here, we investigated the predictive power of (a) key parameters for lake catchment morphometry and (b) organic matter composition of sediments in an effort to account for observed variations of total (THg) and methyl (MeHg) mercury concentrations in lake sediments. Using regression models we demonstrate that the morphometric parameters lake depth as well as inclination of catchment soils and lake bottoms can significantly predict variations of THg concentrations, but not MeHg, at profundal lake sediments. Although THg and MeHg concentrations in sediments could not be predicted by specific organic matter sources, as elucidated by atomic C/N ratios, our data suggest that wetland-derived total organic carbon (TOC) contained less THg concentrations than TOC derived from mostly forested watersheds. However, TOC concentrations could significantly predict MeHg concentrations and the proportion of methylated Hg at all sediment stations. Finally, from an ecotoxicological point of view, we propose that concentrations of TOC at surface lake sediments, rather than parameters of catchment morphometry, may predict dietary sources of MeHg for benthic consumers and consequently perhaps for organisms at higher trophic levels. [ABSTRACT FROM AUTHOR]

In the province of Québec, Canada, a policy for protecting shores recommends the presence of 3 m wide riparian buffer strips (RBS) along field crops to minimize agro-chemical leaching to surface waters. Fast-growing woody crops like Salix miyabeana ‘SX64’ could generate revenues from energy dedicated biomass production within the RBS land area withdrawn from grain production. To determine the potential biomass productivity, experimental RBS were established on two sites — Saint-Roch-de-l’Achigan (SR) and Boisbriand (BB) — with three treatments set up in triplicata composed of mixed herbaceous vegetation (CX), low (3X: 3 rows) and high (5X: 5 rows) density plantations of willows. Growth (stem number, diameter and height) was measured annually from 2011 to 2014; and yield (Mg dw·ha −1 ) was measured in 2014. Growth and yield significantly differ between sites (SR < BB). In the 3 m wide strips, 23-24 Mg dw stems·ha −1 ·year −1 yield in compacted sandy loam soil at SR resembles typical field productions but the 56–89 Mg dw stems·ha −1 ·year −1 in a humisol at BB is larger compared to field plantations. In the light of the present research, we conclude that considerable biomass productivity may be produced in RBS. This result should be considered along with harvesting, transformation or market opportunities to help farmers assess the viability of this practice on their farm. [ABSTRACT FROM AUTHOR]

To evaluate the effect of reservoir flooding on carbon cycling over time, we studied sedimentary environments in three natural lakes that existed prior to impoundment and that have been incorporated in the larger lentic system of a 70-yr-old boreal reservoir in Quebec. Elemental and biomarker analyses were determined in all core intervals and three soil profiles to characterize source inputs of organic matter to sediments. Following impoundment, a twoto threefold increase in lignin concentrations (5 to 10-25 mg [10 g dry wt]-1) associated with similar decreases in selected terrigenous biomarker ratios (cinnamyl phenols : vanillyl phenols, C:V, 1.0-2.0 to 0.2-0.5; 3,5-dihydroxybenzoic acid : vanillyl phenols, 3,5-Bd :V, 0.2-0.5 to 0.1-0.2; and p-hydroxyl phenols : sum of vanillyl and syringyl phenols, P : [V+S], 0.3-0.7 to 0.1-0.4) illustrate the effect of soil erosion and subsequent translocation of surface soil organic matter (SOM) to sedimentary deposits. Using a mixing model based on mass-normalized biomarker yields in identified surface and mineral soil end-members, we show that although the proportion of mineral-derived SOM predominates in the receiving sedimentary systems during preflooding conditions (97-99% of allochthonous inputs), translocated surface SOM increased in postflooding sediments to comprise up to 5-30% of the total allochthonous organic matter inputs. Using a similar quantitative mixing model based on elemental C and N contents in the autochthonous and the mixed allochthonous end-members, we estimated that concomitant to the redistribution of eroded soil organic matter, reservoir flooding induces a 1.5- to 2-fold increase in the fraction of autochthonous organic matter transferred to sedimentary environments of the reservoir. Results presented here suggest that reservoir flooding induces a change of state in lake systems that may perdure over time scales of decades to centuries. [ABSTRACT FROM AUTHOR]

Abstract: Over a century, subsistence agriculture has been practiced in the Brazilian Amazon, using slash-and-burn as a traditional land clearing technique. However, fire clearing leads to nutrient losses, and the increasing demographic pressure reduces the duration of the fallow period, threatening the system sustainability. The chop-and-mulch land clearing method, combined or not with legume-enriched fallow, is a promising alternative technique as the retention of organic residues upon land clearance of fallow could promote soil fertility. The aim of this study is to assess the effect of fire-free land preparation on soil physicochemical properties by comparing the effects of traditional slash-and-burn with (i) chop-and mulch with enriched fallow in croplands and (ii) chop-and-mulch without enriched fallow in pastures. The chop-and-mulch of a legume-enriched fallow conserved soil bulk density, and significantly increased nutrient concentrations and organic matter content compared to the burnt cropland and the control forest. In the pastures, the use of chop-and-mulch of a non-enriched fallow had less impact on soil physical and chemical properties, excepted on water retention capacity and total P stock. Land clearing of fallows by chop-and-mulch, especially when enriched with legumes could significantly improve agriculture sustainability in the region and reduce the pressure on primary forests. [Copyright &y& Elsevier]

Background: Research on changing dietary practices is rare in lower and middle income countries, and understanding the impact of global economic processes on population health and nutrition is important, especially of rural communities. We analyzed the diet of 22 families in Brasília Legal, a riverside community in the Tapajós River region of the Brazilian Amazon, using nonparametric tests to compare dietary surveys taken in 1999 and 2010.Results: Data from the two surveys show that food obtained through commercial supply chains became more frequent in household diets, corresponding to significant increases in daily consumption of food items rich in energy, protein, and sugar. At the same time, there was a decline in traditional Amazonian food intake.Conclusions: Comparing these results with household socio-economic characteristics and drawing on open-ended interviews, we consider the multiple influences that economic development processes may have had on local diets. The introduction of new income sources and employment opportunities, infrastructural and transportation expansion, as well as environmental change appear to have influenced the observed dietary shifts. Such shifts are likely to have important implications for the nutritional status of communities in the Amazon, highlighting concerning trade-offs between current development trajectories and human health. Public policies and health education programs must urgently consider the interactions between sustainable development priorities in order to address emerging health risks in this rapidly changing region. [ABSTRACT FROM AUTHOR]

Phosphate (PO 4 3− ) has been shown to increase glyphosate uptake by willow, a plant species known for its phytoremediation potential. However, it remains unclear if this stimulation of glyphosate uptake can result in an elevated glyphosate toxicity to plants (which could prevent the use of willows in glyphosate-remediation programs). Consequently, we studied the effects of PO 4 3− on glyphosate uptake and toxicity in a fast growing willow cultivar ( Salix miyabeana SX64). Plants were grown in hydroponic solution with a combination of glyphosate (0, 0.001, 0.065 and 1 mg l −1 ) and PO 4 3− (0, 200 and 400 mg l −1 ). We demonstrated that PO 4 3− fertilization greatly increased glyphosate uptake by roots and its translocation to leaves, which resulted in increased shikimate concentration in leaves. In addition to its deleterious effects in photosynthesis, glyphosate induced oxidative stress through hydrogen peroxide accumulation. Although it has increased glyphosate accumulation, PO 4 3− fertilization attenuated the herbicide’s deleterious effects by increasing the activity of antioxidant systems and alleviating glyphosate-induced oxidative stress. Our results indicate that in addition to the glyphosate uptake, PO 4 3− is involved in glyphosate toxicity in willow by preventing glyphosate induced oxidative stress. [ABSTRACT FROM AUTHOR]

This review examines the phytotoxicity of glyphosate and its metabolite aminomethylphosphonic acid, as well as the herbicidal effects of glyphosate, presenting their interconnected consequences on various plant physiological processes.It is generally claimed that glyphosate kills undesired plants by affecting the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) enzyme, disturbing the shikimate pathway. However, the mechanisms leading to plant death may also be related to secondary or indirect effects of glyphosate on plant physiology. Moreover, some plants can metabolize glyphosate to aminomethylphosphonic acid (AMPA) or be exposed to AMPA from different environmental matrices. AMPA is a recognized phytotoxin, and its co-occurrence with glyphosate could modify the effects of glyphosate on plant physiology. The present review provides an overall picture of alterations of plant physiology caused by environmental exposure to glyphosate and its metabolite AMPA, and summarizes their effects on several physiological processes. It particularly focuses on photosynthesis, from photochemical events to C assimilation and translocation, as well as oxidative stress. The effects of glyphosate and AMPA on several plant physiological processes have been linked, with the aim of better understanding their phytotoxicity and glyphosate herbicidal effects. [ABSTRACT FROM AUTHOR]

We examined if smallholders that immigrated to the Amazon over the last 40 years (highway-era families) and households with historical ties to the region (rubber-era families) adopt different livelihood activities and land-use/land-cover (LULC) patterns, in four communities along the Tapajós River in the Brazilian Amazon. Using quantitative data, we characterized three portfolios of livelihood activities, each associated to different LULC. Both rubber-era and highway-era families practice a wide range of activities from all portfolios; however, families that have been in the region for several generations tend to adopt traditional activities (e.g., fishing, non-timber forest product gathering and sales), while recently settled families tend to practice agrarian activities more intensively (e.g., cattle ranching, sale of non-native crops). We then draw on qualitative data to examine some of the underlying reasons for these differences. While recognizing that livelihoods are complex systems with many influential factors, we reflect on some of the overlooked drivers of livelihood and LULC choices such as knowledge, visions of development, and the immaterial value and symbolic meaning of resources. We also reflect on how they shape intended land management choices and relate to household settlement histories. The implications for regional resource-use planning and future research are mentioned. [ABSTRACT FROM AUTHOR]