Radiation transfer and heat budget during the ice season in Lake Pääjärvi, Finland

Lake Pääjärvi, a boreal Finnish lake, was investigated in winter for weather conditions, structure and thickness of ice and snow, solar radiation, and under-ice current and temperature. Heat budget of Lake Pääjärvi in January–March was governed by terrestrial radiation losses of 20–35 W m^?2 recompensed by ice growth of 0.5–1.0 cm day^?1. In April, snow melted, albedo decreased from 0.8 to <0.1, and the mean ice melt rate was 1.5 cm day^?1. Internal melting and surface melting were about equal. The mean turbulent heat loss was small. The heat flux from the water to ice was about 5 W m^?2 in winter, increasing to 12 W m^?2 in the melting season. The light attenuation coefficient was 1.1 m^?1 for the congelation ice (black ice) in winter, compared with 1.5 m^?1 for the lake water, and it was up to 3 m^?1 for candled congelation ice in spring, and about 10 m^?1 for superimposed ice (white ice) and snow. Gas bubbles were the main factor that reduced the transparency of ice. The radiation penetrating the ice heated the water body causing convective currents and horizontal heat transfer. This increased the temperature of the water body to about 3°C before the ice break-up. After the snow had melted, the euphotic depth (the depth of 1% surface irradiance) was estimated as 2.0 m, only two-thirds that in summer.     

Functional characteristics of a fruticose type of lichen, Stereocaulon foliolosum Nyl. in response to light and water stress

Stereocaulon foliolosum a fruticose type of lichen under its natural habitat is subjected to low temperature, high light conditions and frequent moisture stress due its rocky substratum. To understand as to how this lichen copes up with these stresses, we studied the reflectance properties, light utilization capacity and the desiccation tolerance under laboratory conditions. S. foliolosum showed light saturation point for photosynthesis at 390 μmol CO₂ m^?2 s^?1 and the light compensation point for photosynthesis at 64 μmol CO₂ m^?2 s^?1. Our experiments show that S. foliolosum has a low absorptivity (30–35 %) towards the incident light. The maximum rates of net photosynthesis and apparent electron transport observed were 1.9 μmol CO₂ m^?2 s^?1 and 45 μmol e^? m^?2 s^?1, respectively. The lichen recovers immediately after photoinhibition under low light conditions. S. foliolosum on subjecting to desiccation results in the decrease of light absorptivity and the reflectance properties associated with water status of the thalli show a change. During desiccation, a simultaneous decrease in photosynthesis, dark respiration and quenching in the fluorescence properties was observed. However, all the observed changes show a rapid recovery on rewetting the lichen. Our study shows that desiccation does not have a severe or long-term impact on S. foliolosum and the lichen is also well adapted to confront high light intensities.     

Microbiological Explorations in the Northern Part of the Barents Sea in Early Winter

The total number of microorganisms and rates of microbial processes of the carbon cycle were determined in snow, sea ice, water, and seafloor sediments of the northern part of the Barents Sea from September to October, 1998. The explorations were carried out in two areas: along the transection from Franz Josef Land to Victoria Island and along the continental slope region covered with solid ice at latitude 81°–82° N and longitude 37°–39° E. At the time of study, the ice cover was represented by thick one-year old ice (up to 1.2 m), perennial ice (up to 1.85 m), and pack ice. The number of bacteria in the snow cover, sea ice, and seawater was 12 to 14, 50 to 110, and 10 to 240 × 10³ cells/ml, respectively. Rates of dark CO₂ assimilation, glucose utilization, and methane oxidation by bacteria were determined. The highest rate of microbial processes was found in samples of the lowermost newly formed sea ice. The lowest level of activity for all processes was observed in melted snow water. A direct relation was shown between the concentration of C_org, the bacterial biomass, and the values of ¹³C_org in mixtures of melted snow and ice. The number of microorganisms and rates of microbial processes in seafloor sediments measured at the stations on the continental slope are comparable to those in the central part of the Barents Sea and the northern part of the Kara Sea.     

Growth and phosphorus removal by <Emphasis Type="Italic">Synechococcus elongatus</Emphasis> co-immobilized in alginate beads with <Emphasis Type="Italic">Azospirillum brasilense</Emphasis>

This study examined the co-immobilization of the cyanobacterium Synechococcus elongatus with the plant growth-promoting bacterium Azospirillum brasilense in alginate beads and its potential application for the removal of phosphorus from aquaculture wastewater. Co-immobilization of both microorganisms significantly increased the cell density of S. elongatus (2852.5?×?10⁴ cells mL^?1) compared with that of immobilization of cyanobacteria alone (1325.2?×?10⁴ cells mL^?1). Chlorophyll a content was similar in co-immobilized (11.1?±?3.5 pg cell^?1) and immobilized S. elongatus (14.5?±?4.9 pg cell^?1). Azospirillum brasilense showed continuous growth until day 2, after which its cell concentration declined until the end of the assay. Co-immobilized S. elongatus removed more phosphorus (44.8 %) than immobilized cyanobacteria cells alone (32.0 %). In conclusion, phosphate removal was greater with free cells of S. elongatus but overlapped with the values that were obtained with the treatment of co-immobilization of cells. Our results demonstrate that A. brasilense enhances the growth of S. elongatus and improves its removal of phosphorus when they are co-immobilized in alginate beads compared with only immobilization of cyanobacteria cells alone.     

Bacteria recovered from a high-altitude,tropical glacier in Venezuelan Andes

Glacial-ice microorganisms are intensively studied world-wide for a number of reasons, including their psychrophilic lifestyle, their usefulness in biotechnology procedures and their relationship with the search of life outside our planet. However, because of the difficulties for accessing and working at altitudes of >5.000 m above sea level, tropical glaciers have received much less attention than their arctic and antarctic counterparts. In the present work we isolated and characterized a total of forty-five pure isolates originating from direct plating of melted ice collected at the base of a rapidly-retreating, small glacier located at around 4.900 m.a.s.l. in Mount Humboldt (Sierra Nevada National Park, Mérida State, Venezuela). Initial examination of melted ice showed the presence of abundant- (>10⁶ cells ml^?1), morphologically diverse- and active bacterial cells, many of which were very small (“dwarf cells”). The majority of the isolates were psychrophilic or psychrotolerant and many produced and excreted cold-active extracellular enzymes (proteases and amylases). The antibiotic tests showed an elevated percentage of isolates resistant to high doses (100 μg/ml) of different antibiotics including ampicillin, penicillin, nalidixic acid, streptomycin, chloramphenicol, kanamycin and tetracycline. Multiresistance was also observed, with 22.22 % of the strains simultaneously resistant up to five of the antibiotics tested. Metal resistance against Ni⁺⁺, Zn⁺⁺ and Cu⁺⁺ was also detected. In accordance with these results, plasmids of low and high molecular weight were detected in 47 % of the isolates. Twenty-two partial 16S rDNA sequences analyzed allowed grouping the isolates within five different phyla/classes: Alpha-, Beta- and Gamma-proteobacteria, Actinobacteria and Flavobacteria. This is the first report concerning South American Andean glacial ice microorganisms.     

High Atmospheric Nitrate Inputs and Nitrogen Turnover in Semi-arid Urban Catchments

The influx of atmospheric nitrogen to soils and surfaces in arid environments is of growing concern due to increased N emissions and N usage associated with urbanization. Atmospheric nitrogen inputs to the critical zone can occur as wet (rain or snow) or dry (dust or aerosols) deposition, and can lead to eutrophication, soil acidification, and groundwater contamination through leaching of excess nitrate. The objective of this research was to use the δ¹⁵N, δ¹⁸O, and Δ¹⁷O values of atmospheric nitrate (NO₃ ^?) (precipitation and aerosols) and NO₃ ^? in runoff to assess the importance of N deposition and turnover in semi-arid urban watersheds. Data show that the fractions of atmospheric NO₃ ^? exported from all the urban catchments, throughout the study period, were substantially higher than in nearly all other ecosystems studied with mean atmospheric contributions of 38% (min 0% and max 82%). These results suggest that catchment and stream channel imperviousness enhance atmospheric NO₃ ^? export due to inefficient N cycling and retention. In contrast, catchment and stream channel perviousness allow for enhanced N processing and therefore reduced atmospheric NO₃ ^? export. Overall high fractions of atmospheric NO₃ ^? were primarily attributed to slow N turn over in arid/semi-arid ecosystems. A relatively high fraction of nitrification NO₃ ^? (~30%) was found in runoff from a nearly completely impervious watershed (91%). This was attributed to nitrification of atmospheric NH₄ ⁺ in dry-deposited dust, suggesting that N nitrifiers have adapted to urban micro niches. Gross nitrification rates based on NO₃ ^? Δ¹⁷O values ranged from a low 3.04 ± 2 kg NO₃-N km^?2 day^?1 in highly impervious catchments to a high of 10.15 ± 1 kg NO₃-N km^?2 day^?1 in the low density urban catchment. These low gross nitrification rates were attributed to low soil C:N ratios that control gross autotrophic nitrification by regulating gross NH₄ ⁺ production rates.     

Rhizosphere effects on ion concentrations near different root zones of Norway spruce (Picea abies (L.) Karst.) and root types of Douglas-fir (Pseudotsuga menziesii L.) seedlings

In many temperate ecosystems, rates of atmospheric nitrogen deposition remain high over winter despite decreased agricultural activity over this season. The extent to which this nitrogen is accessible for plant growth over the following growing season may depend strongly on uptake by plants and soil microorganisms from late fall through early spring, when the majority of aboveground plant tissue has senesced. We added Ca(¹⁵NO₃)₂ (5 atom %¹⁵N) at a rate of 2 g m^?2 of N (corresponding to 100 mg ¹⁵N m^?2) to the surface of plots in a temperate old field during either late fall, winter, spring melt or early spring. We quantified the recovery of excess ¹⁵N in the soil microbial biomass and soil extracts following spring melt and in aboveground plant tissue at the peak of the plant growing season. Nitrate additions had no significant effect on total aboveground plant biomass, relative species abundance or percent tissue nitrogen. However, mean excess ¹⁵N in aboveground plant tissue varied significantly among treatments, with values of 8.1, 2.6, 0.3 and 7.3 mg m^?2 for late fall, winter, spring melt and early spring addition plots, respectively. Corresponding values of excess ¹⁵N were 3.1, 1.4 and 0.2 mg m^?2 in microbial biomass, and 0.17, 0.07 and 0.03 mg m^?2 in soil extracts, for late fall, winter and spring melt addition plots, respectively. Overall, these results indicate that nitrogen retention from late fall through early spring may depend highly on plant uptake in this system, and that only a small fraction of the nitrogen that accumulates in the winter snow pack may be available to plants.     

Ecosystem respiration derived from 222Rn measurements on Rishiri Island, Japan

We evaluated the nighttime CO₂ flux (ecosystem respiration) on Rishiri Island, located at the northern tip of Hokkaido, Japan, from 2009 to 2011, by using the relationship between atmospheric ²²²Rn and CO₂ concentrations. The annual mean CO₂ flux was 1.8 μmol m^?2 s^?1, with a maximum monthly mean in July (4.6 ± 2.6 μmol m^?2 s^?1) and a broad minimum from December to March (0.33 ± 0.29 μmol m^?2 s^?1). The annual mean was comparable to fluxes at the JapanFlux sites in northern Japan. During the season of snow cover (mid-December to early April), the CO₂ flux was low (0.45 ± 0.43 μmol m^?2 s^?1). Total annual respiration was estimated at 679 ± 174 g cm^?2, about 8 % of which occurred during the season of snow cover.     

Snow cover manipulation in agricultural fields: as an option for mitigating greenhouse gas emissions

Short-term N₂O emission occurs in relation to snowmelt within seasonally frozen soil. To understand the effects of changing winter climates on the N₂O flux, snow cover manipulation experiments are useful. In Japan, snow cover manipulation is practiced by farmers to improve agricultural yield and is executed either by applying a broadcast of blackish agent onto the snow cover, which leads to faster snow-melting thereby extending the crop-growing season, or by snow cover removal/re-accumulation, leading to an enhanced soil frost depth for weed management. Implementation of these practices involves using an amount of fossil fuel, in addition to influencing soil-derived N₂O emissions, therefore, the load factors of snow cover management practices per unit area of agricultural field were estimated in this study. Field data including micrometeorological conditions, ground surface flux of N₂O, and amount of fossil fuel consumed during machinery operation for management practices, were obtained at two sites in Hokkaido over 2 years (2008–2010). Fuel consumption for the field spreading was found to be unexpectedly small (0.017 Mg CO₂ eq ha^?1). It was therefore suggested that acceleration of snowmelt may have the potential to reduce net greenhouse gas emissions if the agent used is a low-degradable C-rich material, such as charcoal. For soil frost control, the fossil fuel consumption during a set of snow cover removal/re-accumulation (estimated as 0.052 Mg CO₂ eq ha^?1) is discussed, together with the relationship between possible mechanisms causing stimulation of N₂O production in frozen soil and inherent large differences in N₂O flux among sites.     

Environmental variables controlling soil respiration on diurnal, seasonal and annual time-scales in a mixed mountain forest in Switzerland

Studies on soil respiration in mountain forests are rather scarce compared to their broad distribution. Therefore, we investigated daily, seasonal and annual soil respiration rates in a mixed forest (Lägeren), located at about 700 m in the Swiss Jura mountains, during 2 years (2006 and 2007). Soil respiration (SR) was measured continuously with high temporal resolution (half-hourly) at one single point (SR_automated) and periodically with high spatial resolution (SR_manual) at 16 plots within the study site. Both, SR_automated and SR_manual showed a similar seasonal cycle. SR strongly depended on soil temperature in 2007 (R ² = 0.82–0.92), but less so in 2006 (R ² = 0.56–0.76) when SR was water limited during a summer drought. Including soil moisture improved the fit of the 2006 model significantly (R ² = 0.78–0.97). Total annual SR for the study site was estimated as 869 g C m^?2 year^?1 for 2006 and as 907 g C m^?2 year^?1 for 2007 (uncertainty <10% at the 95% confidence interval, determined by bootstrapping). Selected environmental conditions were assessed in more detail: (1) Rapid, but contrasting changes of SR were found after summer rainfall. Depending on soil moisture at pre-rain conditions, summer rain could either cause a pulse of CO₂ from the soil or an abrupt decrease of SR_automated due to water logging of soil pores. (2) Two contrasting winter seasons resulted in SR being about 60–70% (31.2–44.6 g C m^?2) higher during a mild winter (2007) compared to a harsh winter (2006). (3) Analysing SR for selected periods on a diurnal scale revealed a counter-clockwise hysteresis with soil surface temperatures. This indication of a time-lagged response of SR to temperature was further supported by a very strong relationship (R ² = 0.86–0.90) of SR to soil temperature with a time-lag of 2–4 h.     

An in vitro analysis of intestinal ammonia handling in fasted and fed freshwater rainbow trout (Oncorhynchus mykiss)

Ammonia transport and metabolism were investigated in the intestinal tract of freshwater rainbow trout which had been either fasted for 7 days, or fasted then fed a satiating meal of commercial trout pellets. In vivo, total ammonia concentrations (T _amm) in the chyme were approximately 1 mmol L^?1 across the entire intestine at 24 h after the meal. Highest chyme pH and P _NH3 values occurred in the posterior intestine. In vitro gut sac experiments examined ammonia handling with mucosal (Jm_amm) and serosal (Js_amm) fluxes under conditions of fasting and feeding, with either background (control ≤0.013 mmol L^?1) or high luminal ammonia concentrations (HLA = 1 mmol L^?1), the latter mimicking those seen in chyme in vivo. Feeding status (fasted or fed) appeared to influence ammonia handling by each individual section. The anterior intestine exhibited the greatest Jm_amm and Js_amm values under fasted control conditions, but these differences tended to disappear under typical post-feeding conditions when total endogenous ammonia production (Jt_amm = Js_amm ? Jm_amm, signs considered) was greatly elevated in all intestinal sections. Under fasted conditions, glutamate dehydrogenase (GDH) and glutaminase (GLN) activities were equal across all sections, but the ammonia-trapping enzyme glutamine synthetase (GS) exhibited highest activity in the posterior intestine, in contradiction to previous literature. Feeding clearly stimulated the total rate of endogenous ammonia production (Jt_amm), even in the absence of a high luminal ammonia load. This was accompanied by an increase in GDH activity of the anterior intestine, which was also the site of the largest Jt_amm. In all sections, during HLA exposure, either alone or in combination with feeding, there were much larger increases in endogenous Jt_amm, most of which was effluxed to the serosal solution. This is interpreted as a response to avoid potential cytotoxicity due to overburdened detoxification mechanisms in the face of elevated mucosal ammonia. Thus T _amm of the intestinal tissue remained relatively constant regardless of feeding status and exposure to HLA. Ammonia production by the gut may explain up to 18 % of whole-body ammonia excretion in vivo under fasting conditions, and 47 % after feeding, of which more than half originates from endogenous production rather than from absorption from the lumen.     

Sulfur and molybdenum fractionation in marine and riverine alluvium paddy soils

Intermittently submergence and drainage status of paddy fields can cause alterations in morphological and chemical characteristics of soils. We conducted a sequential fractionation study to provide an insight into solubility of Sulfur (S) and Molybdenum (Mo) in flooded alluvial paddy soils. The samples (0–15 and 15–30 cm) were taken from marine and riverine alluvial soils in Kedah and Kelantan areas, respectively, and were sequentially extracted with NaHCO₃, NaOH, HCl, and HClO₄–HNO₃. Total S in upper and lower layers of Kedah and Kelantan ranged between 273 and 1121 mg kg^?1, and 177 to 1509 mg kg^?1, respectively. In upper layers and subsoil of Kedah, average total Mo were 0.34 and 0.27 mg kg^?1, respectively. Average total Mo in Kelantan were 0.25 mg kg^?1 (surface layer) and 0.28 mg kg^?1 (subsoil). Cation exchange capacity (CEC) was positively correlated with plant available amounts of Mo in upper layers of Kedah area. Also, total and medium-term plant-available S was correlated with total carbon (C) at lower layers of Kelantan soil series. But in surface layers of Kelantan soil series, CEC was strongly correlated with total and medium-term plant-available S. Our results indicates that the influence of flooding conditions on soil S and Mo contents in paddy fields may cause long-term changes in S and Mo chemical reactivities.     

Salinity improves chilling resistance in Suaeda salsa

Suaeda salsa L., a C3 euhalophytic herb, is native to saline soils, demonstrates high resistance to salinity stress. The effect of chilling stress on S. salsa under high salinity, particularly the change in unsaturated fatty acid content within membrane lipids, has not been investigated. After a 12 h chilling treatment (4 °C) performed under low irradiance (100 μmol m^?2 s^?1), the chlorophyll contents, maximal photochemical efficiency of photosystem II (F _v/F _m) and actual PSII efficiency (ΦPSII) were determined. These measurements were significantly decreased in S. salsa leaves in the absence of salt treatment yet there were no significant changes with a 200 mM NaCl treatment. Chlorophyll contents, F _v/F _m and ΦPSII in S. salsa under 200 mM NaCl were higher than those without salt treatment. The unsaturated fatty acid content and the double bond index (DBI) of major membrane lipids of monogalactosyldiacylglycerols, digalactosyldiacylglycerols (DGDG), sulphoquinovosyldiacylglycerols and phosphatidylglycerols (PG) significantly increased following the chilling treatment (4 °C) (with 12 h of low irradiance and 200 mM of NaCl). The DBI of DGDG and PG was decreased in the absence of the salt treatment. These results suggest that in the euhalophyte S. salsa, a 200 mM NaCl treatment increases chilling tolerance under conditions of low irradiance (100 μmol m^?2 s^?1).     

Molecular cloning and characterization of two novel fructose-specific transporters from the osmotolerant and fructophilic yeast Candida magnoliae JH110

Sugar transport is very critical in developing an efficient and rapid conversion process of a mixture of sugars by engineered microorganisms. By using expressed sequence tag data generated for the fructophilic yeast Candida magnoliae JH110, we identified two fructose-specific transporters, CmFSY1 and CmFFZ1, which show high homology with known fructose transporters of other yeasts. The CmFSY1 and CmFFZ1 genes harbor no introns and encode proteins of 574 and 582 amino acids, respectively. Heterologous expression of the two fructose-specific transporter genes in a Saccharomyces cerevisiae, which is unable to utilize hexoses, revealed that both transporters are functionally expressed and specifically transport fructose. These results were further corroborated by kinetic analysis of the fructose transport that showed that CmFsy1p is a high-affinity fructose–proton symporter with low capacity (K _M?=?0.13?±?0.01 mM, V _max?=?2.1?±?0.3 mmol h^?1 [gdw]^?1) and that CmFfz1p is a low-affinity fructose-specific facilitator with high capacity (K _M?=?105?±?12 mM, V _max?=?8.6?±?0.7 mmol h^?1 [gdw]^?1). These fructose-specific transporters can be used for improving fructose transport in engineered microorganisms for the production of biofuels and chemicals from fructose-containing feedstock.     

Winter CO2 fluxes in a sub-alpine grassland in relation to snow cover, radiation and temperature

Carbon dioxide (CO₂) emissions were measured over a period of 3 years at the sub-alpine Swiss CARBOMONT site Rigi Seebodenalp. Here we show, that winter respiration contributes larger than expected to the annual CO₂ budget at this high altitude, rich in belowground organic carbon grassland (7–15% C by mass). Furthermore the contribution of winter emissions to the annual CO₂ budget is highly dependent on the definition of “winter” itself. Cumulative winter respiration determined over a 6 month period from 15th of October until 15th of April contributed 23.3 ± 2.4 and 6.0 ± 0.3% to the annual respiration during the years under observation, respectively. The insulation effect of snow and a lowering of the freezing point caused by high concentrations of soil organic solutes prevented the soil from freezing. These conditions favored higher soil temperatures resulting in relatively high respiratory losses. The duration of snow cover and micrometeorological conditions determining the photosynthetic activity of the vegetation during snow-free periods influenced the size and the variability of the winter CO₂ fluxes. Seasonal values are strongly influenced by the days at the end and the beginning of the defined winter period, caused by large variations in length of periods with air temperatures below freezing. Losses of CO₂ from the snow-covered soil were highest in winter 2003/2004. These high losses were partially explained by higher temperatures in the topsoil, caused by higher air temperatures just before snowfall. Thus, losses are not a consequence of higher soil temperatures registered during the summer heat wave 2003. However, water stress in summer 2003 might have caused an increment in dead organic matter in the soil providing additional substrate for microbial respiration in the following winter. Although considerable day-to-day fluctuations in snow effluxes were recorded, no conclusive and generally valid relationship could be found between CO₂ losses from the snow pack and snow depth, rate of snow melt, wind speed or air pressure. This suggests that time lags and hysteresis effects may be more important for understanding winter respiration than concurrent environmental conditions in most ecosystems of comparable type.     

Production and optimization of poly-γ-glutamic acid by Bacillus subtilis BL53 isolated from the Amazonian environment

The aims of this research were to screen and characterize a new microbial source of γ-PGA, to optimize aspects of culture conditions and medium composition using central composite design and response surface methodologies. The influence of bioreactor stirring rates on the production of γ-PGA was also investigated and the oxygen volumetric mass transfer coefficients (k _La) were established. The most productive strain was identified by 16S rDNA analysis as Bacillus subtilis, and its γ-PGA production in rotatory shaker was threefold increased under optimized conditions (37 °C, pH 6.9, and 1.22 mM Zn²⁺), compared to conventional medium. In bioreactor, the γ-PGA production was further increased, reaching 17 g l^?1, 70 % higher than shaker cultures. γ-PGA production showed high dependency on oxygen transfer. At k _La of 210 h^?1, the cultivation time could be reduced to 48 h, about 50 % of the time required for operations at k _La 55 h^?1.     

H<Subscript>2</Subscript>S biotreatment with sulfide-oxidizing heterotrophic bacteria

Many industrial activities produce H₂S, which is toxic at high levels and odorous at even very low levels. Chemolithotrophic sulfur-oxidizing bacteria are often used in its remediation. Recently, we have reported that many heterotrophic bacteria can use sulfide:quinone oxidoreductase and persulfide dioxygenase to oxidize H₂S to thiosulfate and sulfite. These bacteria may also potentially be used in H₂S biotreatment. Here we report how various heterotrophic bacteria with these enzymes were cultured with organic compounds and the cells were able to rapidly oxidize H₂S to zero-valence sulfur and thiosulfate, causing no apparent acidification. Some also converted the produced thiosulfate to tetrathionate. The rates of sulfide oxidation by some of the tested bacteria in suspension, ranging from 8 to 50 µmol min^?1 g^?1 of cell dry weight at pH 7.4, sufficient for H₂S biotreatment. The immobilized bacteria removed H₂S as efficiently as the bacteria in suspension, and the inclusion of Fe₃O₄ nanoparticles during immobilization resulted in increased efficiency for sulfide removal, in part due to chemical oxidation H₂S by Fe₃O₄. Thus, heterotrophic bacteria may be used for H₂S biotreatment under aerobic conditions.     

Seasonal variability of methane in the rivers and lagoons of Ivory Coast (West Africa)

We report a data-set of dissolved methane (CH₄) in three rivers (Comoé, Bia and Tanoé) and five lagoons (Grand-Lahou, Ebrié, Potou, Aby and Tendo) of Ivory Coast (West Africa), during the four main climatic seasons (high dry season, high rainy season, low dry season and low rainy season). The surface waters of the three rivers were over-saturated in CH₄ with respect to atmospheric equilibrium (2221–38719%), and the seasonal variability of CH₄ seemed to be largely controlled by dilution during the flooding period. The strong correlation of CH₄ concentrations with the partial pressure of CO₂ (pCO₂) and dissolved silicate (DSi) confirm the dominance of a continental sources (from soils) for both CO₂ and CH₄ in these rivers. Diffusive air–water CH₄ fluxes ranged between 25 and 1187 μmol m^?2 day^?1, and annual integrated values were 288 ± 107, 155 ± 38, and 241 ± 91 μmol m^?2 day^?1 in the Comoé, Bia and Tanoé rivers, respectively. In the five lagoons, surface waters were also over-saturated in CH₄ (ranging from 1496 to 51843%). Diffusive air–water CH₄ fluxes ranged between 20 and 2403 μmol m^?2 day^?1, and annual integrated values were 78 ± 34, 338 ± 217, 227 ± 79, 330 ± 153 and 326 ± 181 μmol m^?2 day^?1 in the Grand-Lahou, Ebrié, Potou, Aby and Tendo lagoons, respectively. The largest CH₄ over-saturations were observed in the Tendo and Aby lagoons that are permanently stratified systems (unlike the other three lagoons), leading to anoxic bottom waters favorable for a large CH₄ production. In addition, these two stratified lagoons showed low pCO₂ values due to high primary production, which suggests an efficient transfer of organic matter across the pycnocline. As a result, the stratified Tendo and Aby lagoons were respectively, a low source of CO₂ to the atmosphere and a sink of atmospheric CO₂ while the other three well-mixed lagoons were strong sources of CO₂ to the atmosphere but less over-saturated in CH₄.     

Effect of salinity on growth, ion accumulation and the roles of ions in osmotic adjustment of two populations of Suaeda salsa

The effect of salinity on growth, ion accumulation and the roles of ions in osmotic adjustment of two populations of Suaeda salsa were investigated. Seeds were collected from an intertidal zone or a saline inland zone in the Yellow River Delta in Shandong province, China. Seedlings were exposed to 10, 100, 200, 400 or 600 mM NaCl for 18 days in a greenhouse. NO₃ ^? concentration in the soil where S. salsa grows in an intertidal zone was much lower than that for the second population, but leaf NO₃ ^? concentration was the same in the two populations under field conditions. When plants were cultured in a greenhouse under natural light conditions, S. salsa from the intertidal zone showed fewer main stem branches and lower relative shoot growth compared to S. salsa from saline inland. Leaf Cl^? concentration of saline inland S. salsa was significantly higher than that of S. salsa from the intertidal zone, while the opposite was true for the concentration of NO₃ ^? in leaves of plants. For S. salsa from the intertidal zone NO₃ ^? contributed more than Cl^? to the osmotic potential, whereas S. salsa from the saline inland exhibited a reverse relationship under saline conditions, indicating that NO₃ ^? plays an important osmotic role in S. salsa from the intertidal zone in high salinity. In conclusion, S. salsa from the intertidal zone may employ superior control of ion uptake and content than S. salsa from the saline inland zone. The two populations of Suaeda salsa presented different ability in chloride exclusion and nitrate accumulation. These characteristics may affect the distributions of S. salsa in natural highly saline environments.     

Mycotoxigenic fungi and mycotoxins associated with stored maize from different regions of Lesotho

Samples of stored maize from villages located in five different agroecological zones (southern lowlands, northern lowlands, Senqu river valley, foothills and mountains) of Lesotho were collected in 2009/10 and 2010/11 and assessed for contamination with toxigenic fungi. The water activity of all samples collected during the two seasons was <0.70. The total fungal populations of the maize from different regions in the two seasons was not significantly different (p?>?0.05). Fusarium verticillioides, F. proliferatum and F. subglutinans predominated in different regions in both seasons based on molecular analyses. In the 2009/10 season, the isolates of these species all produced FB₁, while in the 2010/11 season, very few produced FB₁. A. flavus isolates (2009/10) were recovered from mountains and Senqu river valley samples while the 2010/11 isolates were predominantly from the foothills and northern lowlands. The mountain isolates of Aspergillus section Flavi produced the highest levels of AFB₁ (20 mg kg^?1). Aspergillus parasiticus was only isolated from the foothills, Senqu river valley and southern lowlands samples, and the AFB₁ levels produced ranged from ‘none detected’ to 3.5 mg kg^?1. The Aspergillus ochraceous isolates were least frequently encountered in both seasons. In the 2009/10 season, the isolates from the northern lowlands produced ochratoxin A (OTA) in culture. No isolates of A. niger from different regions in both seasons produced any OTA. Multi-mycotoxin analyses of the maize samples were done for a range of mycotoxins. At least one sample from each region in both seasons was FB₁-positive. FB₁ levels for 2010/11 samples (7–936 μg kg^?1) were higher than in the 2009/10 season (2–3 μg kg^?1). In both seasons, the mountains registered the highest levels of FB₁. Deoxynivalenol (DON) was recovered from all the samples analysed, with the highest mean contamination of 1,469 μg kg^?1 in samples from the northern lowlands. Moniliformin (MON) was detected from all agroecological zones in the two seasons (5–320 μg kg^?1 in 2009/10; 15–1,205 μg kg^?1 in 2010/11). Emerging toxins such as fusaproliferin (FUS) and beauvericin (BEA) were also detected. OTA was not detected in any of the samples analysed. Only one 2009/10 sample in the Senqu river valley was positive for AFB₁. This is the first report on toxigenic fungi and multi-mycotoxin contamination of maize samples from subsistence farmers’ stores in different agroecological zones of Lesotho.