Forest succession suppressed by an introduced plant-fungal symbiosis

Microbial symbionts can affect plant nutrition, defensive chemistry, and biodiversity. Here we test the hypothesis that symbionts alter the speed and direction of plant succession in communities that are shifting from grasslands to forests. A widespread C3 grass introduced to the United States, Lolium arundinaceum (tall fescue), hosts a fungal endophyte that is toxic to herbivores. In replicated experimental grasslands, the presence of the endophyte in tall fescue reduced tree abundance and size, altered tree composition, and slowed plant species turnover. In addition, consumption of tree seedlings by voles (Microtus spp.) was 65% higher in plots with the endophyte at the one grassland site where these data were collected. Despite its negligible contribution to community biomass, a microbial symbiont suppressed tree establishment, posing an important constraint on the natural transition from grasslands to forests.     

Predators influence the tidal distribution of oysters (Crassostrea virginica)

Biotic and abiotic conditions can separately and synergistically influence the abundance and distribution of species and create vertical zonation patterns in marine systems. In Corpus Christi Bay, TX, USA, eastern oysters (Crassostrea virginica) are limited to intertidal habitats, while in adjacent estuaries, oysters not only grow subtidally, but thrive in these areas to the extent they are a viable commercial fishery. The purpose of this study was to assess how predators and abiotic conditions affect oyster mortality and growth at different tidal elevations. Anecdotal evidence suggests that abiotic conditions, primarily hypoxia and salinity, as well as oyster disease, limits oysters to intertidal areas. Yet, in Corpus Christi Bay, oysters are absent from subtidal areas where hypoxia is not known to occur. Infection by Perkinsus marinus (Dermo) is common in the study area, but previous work suggests that infection rates do not increase when oysters are transplanted subtidally. We investigated oyster tidal distributions by transplanting newly settled oysters into intertidal and subtidal areas. Predation on oysters was significantly greater in subtidal as compared to intertidal habitats. When protected from predators using cages, oyster survival significantly increased. Further, oysters in subtidal areas allocated significantly more resources to shell growth than did those in intertidal areas, and oysters are known to grow heavier shells in response to predators. Oyster settlement was not statistically different between inter and subtidal areas, and abiotic conditions measured during the study did not exceed known tolerance limits for oysters. Previous studies have shown that abiotic conditions influence oyster mortality and the success of restored oyster reefs. Our findings indicate that predators can also affect oyster distribution, and their effects should be evaluated when developing plans for oyster management and restoration.     

Evaluation of wetland methyl mercury export as a function of experimental manipulations

Mercury associated with natural enrichment, historic mining, and ore processing is a contaminant of concern in watersheds of the western USA. In this region, water is a highly managed resource and wetlands, known to be important sites of methyl mercury production, are often an integral component of watersheds. This study applied controlled manipulations of four replicated experimental wetland designs with different water and soil mercury concentrations to determine the potential impacts on methyl mercury export. Wetlands were manipulated by drying and wetting, changing hydraulic retention time, and adding sulfate and nitrate to influent waters. In a summer drying and wetting manipulation, an immediate increase in total methyl mercury release was observed with rewetting, however, concentrations decreased quickly. Drying all wetlands over the winter and rewetting in the spring resulted in high net methyl mercury output relative to that observed before drying. Net methyl mercury output was not influenced by changes in hydraulic retention time from 4 to 8 h or to 30 min, or by increasing the nitrate concentration from 0.1 to 10 mg L(-1). The addition of sulfate to the inlet waters of two mesocosms to increase concentrations from approximately 100 to 250 mg L(-1) did not result in a clear effect on methyl mercury output, most likely due to sulfate concentrations being higher than optimal for methyl mercury production. Despite the lack of response to sulfate amendments, the change in sulfate concentration between the inlet and outlet of the mesocosms and temperature were the parameters best correlated with methyl mercury outputs.     

Designing reverse-flow packed bed reactors for stable treatment of volatile organic compounds

Reverse-flow packed bed reactors can be used to treat gaseous pollutants from chemical plants. This article describes the design and operation of a modified reverse-flow reactor (MRFR) which has a recuperator on each end of the reactor and a reaction zone in the middle. The recuperators have low thermal dispersion and the reaction zone has a high thermal dispersion, obtained by placing metal inserts into the bed, parallel with the gas flow. Performance of the MRFR during extended lean and rich conditions is determined with analytical analysis and compares well with numerical simulations of CO oxidation; however, the theory is expected to be useful for any reaction kinetics. A major advantage of this MRFR design is an extended time for the reactor to extinguish during lean conditions. This work also describes MRFR performance with internal reactor cooling, which can be used as a control mechanism to maintain reactor temperature for proper removal of volatile organic compounds.     

Monitoring plastic ingestion by the northern fulmar Fulmarus glacialis in the North Sea

The abundance of plastics in stomachs of northern fulmars from the North Sea is used in the OSPAR Ecological Quality Objective (EcoQO) for marine litter. The preliminary EcoQO defines acceptable ecological quality as the situation where no more than 10% of fulmars exceed a critical level of 0.1 g of plastic in the stomach. During 2003-2007, 95% of 1295 fulmars sampled in the North Sea had plastic in the stomach (on average 35 pieces weighing 0.31 g) and the critical level of 0.1 g of plastic was exceeded by 58% of birds, with regional variations ranging from 48 to 78%. Long term data for the Netherlands since the 1980s show a decrease of industrial, but an increase of user plastics, with shipping and fisheries as the main sources. The EcoQO is now also used as an indicator for Good Environmental Status in the European Marine Strategy Framework Directive.     

Windsor, Ontario exposure assessment study: design and methods validation of personal, indoor, and outdoor air pollution monitoring

The Windsor, Ontario Exposure Assessment Study evaluated the contribution of ambient air pollutants to personal and indoor exposures of adults and asthmatic children living in Windsor, Ontario, Canada. In addition, the role of personal, indoor, and outdoor air pollution exposures upon asthmatic children's respiratory health was assessed. Several active and passive sampling methods were applied, or adapted, for personal, indoor, and outdoor residential monitoring of nitrogen dioxide, volatile organic compounds, particulate matter (PM; PM < or = 2.5 microm [PM2.5] and < or = 10 microm [PM10] in aerodynamic diameter), elemental carbon, ultrafine particles, ozone, air exchange rates, allergens in settled dust, and particulate-associated metals. Participants completed five consecutive days of monitoring during the winter and summer of 2005 and 2006. During 2006, in addition to undertaking the air pollution measurements, asthmatic children completed respiratory health measurements (including peak flow meter tests and exhaled breath condensate) and tracked respiratory symptoms in a diary. Extensive quality assurance and quality control steps were implemented, including the collocation of instruments at the National Air Pollution Surveillance site operated by Environment Canada and at the Michigan Department of Environmental Quality site in Allen Park, Detroit, MI. During field sampling, duplicate and blank samples were also completed and these data are reported. In total, 50 adults and 51 asthmatic children were recruited to participate, resulting in 922 participant days of data. When comparing the methods used in the study with standard reference methods, field blanks were low and bias was acceptable, with most methods being within 20% of reference methods. Duplicates were typically within less than 10% of each other, indicating that study results can be used with confidence. This paper covers study design, recruitment, methodology, time activity diary, surveys, and quality assurance and control results for the different methods used.     

Characterizing long-term hydrologic-response and sediment-transport for the R-5 catchment

Recently there have been several calls to establish long-term data collection networks to monitor near-surface hydrologic response and landscape evolution. The focus of this paper is a long-term dataset from the International Hydrologic Decade (1965-1974). The small upland catchment, known as R-5, located near Chickasha, Olahoma, has been the subject of considerable attention within the event-based hydrologic modeling community for more than 30 yr. Here, for the first time, 8 yr of continuous near-surface hydrologic-response and sediment-transport data are analyzed to show trends in the catchment's long-term behavior. The datasets include precipitation, temperature, solar radiation, soil-water content, infiltration, water discharge, and sediment discharge. Potential and actual evapotranspiration rates were estimated and used to calculate an average annual water balance for the catchment. Findings include, for example, that rainfall intensity rarely exceeds the threshold for Horton-type runoff, soil-water content is both spatially and temporally variable, and the water and sediment discharge rates are positively correlated. The R-5 data provide a unique opportunity to test (and refine) process-based models of continuous hydrologic response and sediment transport at the catchment scale for applications in the emerging fields of hydroecology and hydrogeomorphology.     

Phosphorus and nitrogen sorption to soils in the presence of poultry litter-derived dissolved organic matter

Two environmental aspects associated with land application of poultry litter that have not been comprehensively evaluated are (i) the competition of dissolved organic matter (DOM) and P for soil sorption sites, and (ii) the sorption of dissolved organic nitrogen (DON) relative to inorganic nitrogen species (e.g., NO(3)(-) and NH(4)(+)) and dissolved organic carbon (DOC). The competition between DOM and P for sorption sites has often been assumed to increase the amount of P available for plant growth; however, elevating DOM concentrations may also increase P available for transport to water resources. Batch sorption experiments were conducted to (i) evaluate soil properties governing P sorption to benchmark soils of Southwestern Missouri, (ii) elucidate the impact of poultry litter-derived DOM on P sorption, and (iii) investigate DON retention relative to inorganic N species and DOC. Soils were reacted for 24 h with inorganic P (0-60 mg L(-1)) in the presence and absence of DOM (145 mg C L(-1)) using a background electrolyte solution comparable to DOM extracts (I = 10.8 mmol L(-1); pH 7.7). Soil P sorption was positively correlated with metal oxide (r(2) = 0.70) and clay content (r(2) = 0.79) and negatively correlated with Bray-1 extractable P (r(2) = 0.79). Poultry litter-derived DOM had no significant negative impact on P sorption. Dissolved organic nitrogen was preferentially removed from solution relative to (NO(3)(-)-N + NO(2)(-)-N), NH(4)(+)-N, and DOC. This research indicates that poultry litter-derived DOM is not likely to enhance inorganic P transport which contradicts the assumption that DOM released from organic wastes increases plant-available P when organic amendments and fertilizer P are co-applied. Additionally, this work demonstrates the need to further evaluate the fate and transport of DON in agroecosystem soils receiving poultry litter applications.     

多种聚氧乙烯牛脂胺混合物MON 0818的水生环境危害评估：脉冲暴露后沉积物、温度和恢复能力的影响

我们对一种商业表面活性剂混合物(多种聚氧乙烯牛脂胺)MON 0818进行了一系列毒性测试：1. 测定底栖无脊椎动物和鱼类在沉积物存在的情况下受到的毒性;2.测定大型蚤(Daphnia magna)和4种初级生产者经过24 h的脉冲暴露之后的恢复能力;3.鉴定水体温度上升对于2种冷水鱼类所受到MON 0818毒性的潜在影响。在沉积物存在的情况下,5种生物中有3种在最高10 mg/L的浓度下短期(24 h)死亡率为零。其余2种物种的中位有效浓度则显著高于仅对水体进行测试的结果。15 ℃下北极红点鲑(Salvelinus alpinus)的半数有效浓度统计上低于10 ℃下。绿藻(Rhabdocelis subcapitata)和普通小球藻(Chlorella vulgaris)在经过24 h 1 mg/L的暴露后的恢复期中显示出生长延迟的状况,表明该暴露可能存在潜在影响。尽管如此,2个物种的最大绝对生长速率并未改变,表明其均可恢复。1.5 mg/L下的蝾螈共生藻(Oophila sp.)和100 mg/L下的浮萍(Lemna minor)经过24 h的暴露并未显示显著反应。24 h 5 mg/L暴露之后的恢复期中,大型蚤显示出潜在的死亡率。然而存活个体的生殖终端指标并未受到影响。结果表明在沉积物的存在下MON 0818的快速损耗可以减轻对于被暴露生物的效果,在不小于环境中可能出现的MON 0818浓度情况下,24 h暴露以后的生物的完全恢复是可能的。
精选自Jose L. Rodriguez-Gil, Ryan Prosser, Gregory Hanta, David Poirier, Linda Lissemore, Mark Hanson, Keith R. Solomon. Aquatic hazard assessment of MON 0818, a commercial mixture of alkylamine ethoxylates commonly used in glyphosate-containing herbicide formulations. Part 2: Roles of sediment, temperature, and capacity for recovery following a pulsed exposure. Environmental Toxicology and Chemistry: Volume 36, Issue 2, pages 512–521, July 2017. DOI: 10.1002/etc.3558
详情请见http://onlinelibrary.wiley.com/wol1/doi/10.1002/etc.3558/full