Daily Uptake Research Articles

Pectin–chitosan physical hydrogels as potential drug delivery vehicles

Pectin–chitosan hydrogels are intriguing and relatively new type of physically crosslinked hydrogels. Here we present for the first time a study exploring the suitability of pectin–chitosan hydrogels to serve as drug carriers and the mechanism controlling the release patterns. Using drug release assays, we demonstrated sustained release of three model drugs (mesalamine, curcumin and progesterone) over a period of 24h in physiological conditions. Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) experiments were used to characterize the interactions between the investigated drugs and the polymers. These experiments, as well as swelling analysis, support the claim that the magnitude of interactions strongly affect the release rates. These new pectin–chitosan thermoreversible hydrogels may improve the life style of many patients by reducing the daily uptake of chronic medicines.

Irrigation water consumption modelling of a soilless cucumber crop under specific greenhouse conditions in a humid tropical climate

ABSTRACT: The irrigation water consumption of a soilless cucumber crop under greenhouse conditions in a humid tropical climate has been evaluated in this paper in order to improve the irrigation water and fertilizers management in these specific conditions. For this purpose, a field experiment was conducted. Two trials were carried out during the years 2011 and 2014 in an experimental farm located in Vinces (Ecuador). In each trial, the complete growing cycle of a cucumber crop grown under a greenhouse was evaluated. Crop development was monitored and a good fit to a sigmoidal Gompertz type growth function was reported. The daily water uptake of the crop was measured and related to the most relevant indoor climate variables. Two different combination methods, namely the Penman-Monteith equation and the Baille equation, were applied. However, the results obtained with these combination methods were not satisfactory due to the poor correlation between the climatic variables, especially the incoming radiation, and the crop's water uptake (WU). On contrary, a good correlation was reported between the crop's water uptake and the leaf area index (LAI), especially in the initial crop stages. However, when the crop is fully developed, the WU stabilizes and becomes independent from the LAI. A preliminary model to simulate the water uptake of the crop was adjusted using the data obtained in the first experiment and then validated with the data of the second experiment.

Chemotherapy: some potential risks under antineoplastic drugs handling

There is a large number of healthcare workers who may be exposed to anticancer drugs in different healthcare settings in Russia. Contamination of working environment, throughout the hospital medication system from hospital pharmacy to medical waste facilities, is found in a number of studies. Monitoring of the environmental contamination with these drugs was performed by different methods in various countries. Daily uptake of the anticancer drugs by the personnel exposed for many years may be realized in reproductive impairments and increased cancer risk. The female healthcare workers who handle antineoplastic drugs showed a greater risk of birth defects in offspring, spontaneous abortions, breast cancer and a number of other cancer site revealed by epidemiological methods. Data on the cancer incidence of pharmacists and laboratory workers potentially exposed to the cytostatic drugs are provided. In Russia, the monitoring of occupational cytostatic exposure is required as it would not be correct to apply data obtained in other countries to the Russian conditions. The data for biological and epidemiological monitoring are considered as the background for effective prevention of adverse health effects in healthcare personnel exposed to antineoplastic drugs.

Novel Molecular Spectroscopic Multimethod Approach for Monitoring Water Absorption/Desorption Kinetics of CAD/CAM Poly(Methyl Methacrylate) Prosthodontics.

Water absorbed to poly(methyl methacrylate) (PMMA)-based CAD/CAM (computer-assisted design/computer-assisted manufacturing) prosthodontics can alter their properties including hardness and stability. In the present contribution, water absorption and desorption kinetics under defined experimental conditions were monitored employing several supplementary and advanced Fourier transform infrared (FT-IR) spectroscopic techniques in combination with multivariate analysis (MVA). In this synergistic vibrational spectroscopic multimethod approach, first a novel near-infrared (NIR) diffuse fiber optic probe reflection spectroscopic method was established for time-resolved analysis of water uptake within seven days under controlled conditions. Near-infrared water absorbance spectra in a wavenumber range between 5288-5100 cm-1 (combination band) and 5424-5352 cm-1 (second overtone) were used establishing corresponding calibration and validation models to quantify the amount of water in the milligram range. Therefore, 14 well-defined samples exposed to prior optimized experimental conditions were taken into consideration. The average daily water uptake conducting reference analysis was calculated as 22 mg/day for one week. Additionally, in this study for the first time NIR two-dimensional correlation spectroscopy (2D-COS) was conducted to monitor and interpret the spectral dynamics of water absorption on the prosthodontics in a wavenumber range of 5100-5300 cm-1. For sensitive time-resolved recording of water desorption, a recently developed high-temperature, high-pressure FT-IR reaction cell with water-free ultra-dry in situ and operando operation was applied. The reaction cell, as well as the sample holder, was fully made of quartz glass, with no hot metal or ceramic parts in the vicinity of the high temperature zone. Applying a temperature gradient in the range of 25-150 ℃, mid-infrared (MIR) 2D-COS was successfully conducted to get insights into the dynamic behavior of O-H (1400-1800 cm-1) absorption bands with increasing temperature over time and the release of CO2 (2450 cm-1) from the polymers. In addition, an ATR FT-IR imaging setup was optimized in order to investigate the surface homogeneity of the PMMA-based resins with a spatial resolution to 2 µm. From this vibrational spectroscopic multimethod approach and the collection of several analytical data, conclusions were drawn as to which degree the surface structure and/or its porosity have an impact onto the amount of water absorption.

Bioaccumulation of heavy metals by shrimp (Litopenaeus schmitti): A dose–response approach for coastal resources management

We reveal a dose–response relationship for bioaccumulation of Zn, Cu and Cr in shrimp Litopenaeus schmitti from Sepetiba Bay, Rio de Janeiro, Brazil. Our model estimates the current risk (AD50 was 70% of the legal limit) and the daily metal uptake rate for each metal. It can also evaluate the relative reliability of predictions for tissue concentrations reaching the legal limits for human consumption (approximately 1year) and predictions related to asymptotic length, arising from (i) direct regression of the metal concentration (MeC) versus total length (TL) and age (duration of exposure), and (ii) correlation of the incorporation rate (IR=MeC/TL) with age. Metal incorporation rates (IR), i.e. a kinetic proxy for absorption during growth up to attainment of asymptotic length, decrease with age, reflecting a slow-down in metal absorption. This pattern mitigates the high initial concentrations observed for juveniles.

Biological monitoring of urinary 1-hydroxypyrene by PAHs exposure among primary school students in Shiraz, Iran

This research aimed to estimate PAHs exposure in primary school students and determine its association with other PAHs-related factors. In total, 120 male primary school students (9-12years old) were randomly selected from urban and suburban areas in Shiraz. The parents were required to complete a questionnaire including information about second-hand smoke exposure, residential traffic density, daily diet, and walking or being driven to school. High-performance liquid chromatography with fluorescence detector was also used to analyze urinary 1-OHP. t test, ANOVA (with Ducan's post hoc test), and multiple regression analysis were used to analyze the relationship between quantitative and qualitative variables and urinary 1-OHP concentration. The range and geometric mean of the creatinine-corrected 1-OHP levels were 120-6950 and 1460ng/g creatinine, respectively. Besides, 1-OHP levels were higher among the children with smoker parents compared to those having non-smoker parents. The results also revealed a correlation between the duration of exposure to second-hand tobacco smoke and 1-OHP concentration. This correlation was also observed for daily uptake of smoked or grilled foods. However, traffic congestion did not have any significant effects on 1-OHP levels. PAHs are commonly present in Iranian diet. As a result, the weekly intake of dietary PAHs was the most effective predictor of PAHs exposure in the study population. Due to adverse health effects of PAHs on humans, especially children, more extensive studies are required to identify the sources that contribute to environmental PAHs exposure.

In-situ measured primary productivity of ice algae in Arctic sea ice floes using a new incubation method

Recent changes in climate and environmental conditions have had great negative effects such as decreasing sea ice thickness and the extent of Arctic sea ice floes that support ice-related organisms. However, limited field observations hinder the understanding of the impacts of the current changes in the previously ice-covered regions on sea ice algae and other ice-related ecosystems. Our main objective in this study was to measure recent primary production of ice algae and their relative contribution to total primary production (ice plus pelagic primary production). In-situ primary productivity experiments with a new incubation system for ice algae were conducted in 3 sea ice cores at 2 different ice camps in the northern Chukchi Sea, 2014, using a 13C and 15N isotope tracer technique. A new incubation system was tested for conducting primary productivity experiments on ice algae that has several advantages over previous incubation methods, enabling stable carbon and nitrogen uptake experiments on ice algae under more natural environmental conditions. The vertical C-shaped distributions of the ice algal chl-a, with elevated concentrations at the top and bottom of the sea ice were observed in all cores, which is unusual for Arctic sea ice. The mean chl-a concentration (0.05 ± 0.03 mg chl-a m−3) and the daily carbon uptake rates (ranging from 0.55 to 2.23 mg C m−2 d−1) for the ice algae were much lower in this study than in previous studies in the Arctic Ocean. This is likely because of the late sampling periods and thus the substantial melting occurring. Ice algae contributed 1.5–5.7% of the total particulate organic carbon (POC) contents of the combined euphotic water columns and sea ice floes. In comparison, ice algae contributed 4.8–8.6% to the total primary production which is greater than previously reported in the Arctic Ocean. If all of the ice-associated productions were included, the contributions of the sea ice floes to the total primary production would be greater in the Arctic Ocean and their importance would be greater in the arctic marine ecosystems.

Contamination with ergot bodies (Claviceps purpurea sensu lato) of two horse pastures in Northern Germany.

Because the occurrence of Claviceps in European pastures may have been overlooked to cause serious health problem for grazing animals, we documented the degree of Claviceps contamination in two horse pastures and estimated whether the horses could have ingested a critical quantity of alkaloids. We counted the Claviceps sclerotia and determined alkaloid levels using high performance liquid chromatography with fluorescence detection. Depending on the location, the number of sclerotia varied from 0.09 to 0.19 per square meter (central area) and from 0.23 to 55.8 per square meter (border strips). Alkaloid levels in individual sclerotia also varied in different genera of grasses, ranging from 0.98±0.17μg/kg in Agrostis sp. to 25.82±9.73μg/kg in Dactylis sp., equivalent to 0.98μg/kg and 7.26mg/kg. Sclerotia from Dactylis contained high levels of ergosine (0.209%±0.100%) and ergocristine (0.374%±0.070%). Depending on the localization in pastures, alkaloid levels in forage (dry matter, DM) ranged from 16.1 to 45.4μg/kg in central areas and from 23.9 to 722μg/kg in border strips. The amount of alkaloids that a horse could have ingested depended on its daily DM uptake, which was higher in the central areas (5.85kg/day) than in the border strips (2.73 or 0.78kg/day). In the central areas, this amount of alkaloids ranged from 94.2 to 265.9μg/day; and in the border strips, from 65.3 (in 2.73kg DM/day) to as much as 563.8μg/day (in 0.78kg DM/day). All these amounts are higher than the European averages for alkaloids ingested by horses via feedstuffs.

Nitric oxide-fixation by non-symbiotic haemoglobin proteins in Arabidopsis thaliana under N-limited conditions.

Nitric oxide (NO) is an important signalling molecule that is involved in many different physiological processes in plants. Here, we report about a NO-fixing mechanism in Arabidopsis, which allows the fixation of atmospheric NO into nitrogen metabolism. We fumigated Arabidopsis plants cultivated in soil or as hydroponic cultures during the whole growing period with up to 3 ppmv of NO gas. Transcriptomic, proteomic and metabolomic analyses were used to identify non-symbiotic haemoglobin proteins as key components of the NO-fixing process. Overexpressing non-symbiotic haemoglobin 1 or 2 genes resulted in fourfold higher nitrate levels in these plants compared with NO-treated wild-type. Correspondingly, rosettes size and weight, vegetative shoot thickness and seed yield were 25, 40, 30, and 50% higher, respectively, than in wild-type plants. Fumigation with 250 ppbv 15 NO confirmed the importance of non-symbiotic haemoglobin 1 and 2 for the NO-fixation pathway, and we calculated a daily uptake for non-symbiotic haemoglobin 2 overexpressing plants of 250 mg N/kg dry weight. This mechanism is probably important under conditions with limited N supply via the soil. Moreover, the plant-based NO uptake lowers the concentration of insanitary atmospheric NOx, and in this context, NO-fixation can be beneficial to air quality.

Estimating the environmental footprint of barley with improved nitrogen uptake efficiency—a Swedish scenario study

Abstract Plant breeding is a powerful tool for improving nitrogen (N) uptake efficiency and thus reducing the environmental impact relating to crop production. This study evaluated the environmental impact of current barley production systems in two Swedish agricultural areas (South and East) compared with scenarios with improved N uptake efficiency at two levels, in which the fraction of mineral N available for daily crop uptake was increased by 50 and 100%. Life cycle assessment (LCA) methodology was used to quantify energy use, global warming potential (GWP) and acidification and eutrophication potentials along the production chain for spring barley with differing N uptake efficiency, but similar N application rate. The functional unit, to which all energy use and emissions were related, was 1 Mg barley grain. Energy use, GWP and acidification proved to be higher for the East production system, mainly due to lower yield, while eutrophication was higher for South. The two impacts most affected by improved N uptake efficiency were eutrophication and GWP, with GWP decreasing due to a combination of higher yield, soil carbon sequestration and lower indirect emissions of N 2 O due to lower N leaching. Accounting for land savings due to increased yield, reducing the pressure to transform land elsewhere, would further lower the carbon footprint. Potential eutrophication per Mg grain was reduced by 15% in the production system with the highest N uptake efficiency in southern Sweden. Crops with improved N uptake efficiency can thus be an important complementary measure for reducing N losses to water, provided that the N application rate does not increase. However, incentives for farmers to maintain or even lower the N application rate might be required. Using simulation modelling is a promising approach for assessment of expected effects of improved crop varieties when no long-term experimental data are available. However, advanced crop models are required to better reflect the effect of plant breeding on e.g. expected yield. Future model development should involve expertise in plant breeding, plant physiology and dynamic crop and soil modelling.

Field Investigation and Numerical Analysis of Residential Building Damaged by Expansive Soil Movement Caused by Tree Root Drying

Trees have long been known to cause damages to pavements and buildings as a result of soil desiccation by tree roots. This paper presents a case study of a residential house damaged by expansive soil movement caused by tree root drying. Daily transpiration and water uptake of a large Eucalypt tree, located 7 m from the northwest corner of the house, was monitored by using a sap flow meter. A numerical analysis was conducted to estimate the soil suction distribution and soil movement under influence of the tree. The measured soil suction profiles indicated that the large Eucalypt tree on the site had influenced the soil moisture condition to a depth of approximately 3.5 m, i.e., 1.5 m below the level of underpins. The case study revealed that the damage was most likely caused by tree root drying, and the differential foundation movements that had occurred after installation of underpins could be attributed to relatively shallow depth of underpins.

Dominant controls of transpiration along a hillslope transect inferred from ecohydrological measurements and thermodynamic limits

Abstract. We combine ecohydrological observations of sap flow and soil moisture with thermodynamically constrained estimates of atmospheric evaporative demand to infer the dominant controls of forest transpiration in complex terrain. We hypothesize that daily variations in transpiration are dominated by variations in atmospheric demand, while site-specific controls, including limiting soil moisture, act on longer timescales. We test these hypotheses with data of a measurement setup consisting of five sites along a valley cross section in Luxembourg. Both hillslopes are covered by forest dominated by European beech (Fagus sylvatica L.). Two independent measurements are used to estimate stand transpiration: (i) sap flow and (ii) diurnal variations in soil moisture, which were used to estimate the daily root water uptake. Atmospheric evaporative demand is estimated through thermodynamically constrained evaporation, which only requires absorbed solar radiation and temperature as input data without any empirical parameters. Both transpiration estimates are strongly correlated to atmospheric demand at the daily timescale. We find that neither vapor pressure deficit nor wind speed add to the explained variance, supporting the idea that they are dependent variables on land–atmosphere exchange and the surface energy budget. Estimated stand transpiration was in a similar range at the north-facing and the south-facing hillslopes despite the different aspect and the largely different stand composition. We identified an inverse relationship between sap flux density and the site-average sapwood area per tree as estimated by the site forest inventories. This suggests that tree hydraulic adaptation can compensate for heterogeneous conditions. However, during dry summer periods differences in topographic factors and stand structure can cause spatially variable transpiration rates. We conclude that absorption of solar radiation at the surface forms a dominant control for turbulent heat and mass exchange and that vegetation across the hillslope adjusts to this constraint at the tree and stand level. These findings should help to improve the description of land-surface–atmosphere exchange at regional scales.

Rhus vernicifluaStokes attenuates cholestatic liver cirrhosis-induced interstitial fibrosis via Smad3 down-regulation and Smad7 up-regulation

Cholestatic liver cirrhosis (CLC) eventually proceeds to end-stage liver failure by mediating overwhelming deposition of collagen, which is produced by activated interstitial myofibroblasts. Although the beneficial effects of Rhus verniciflua Stokes (RVS) on various diseases are well-known, its therapeutic effect and possible underlying mechanism on interstitial fibrosis associated with CLC are not elucidated. This study was designed to assess the protective effects of RVS and its possible underlying mechanisms in rat models of CLC established by bile duct ligation (BDL). We demonstrated that BDL markedly elevated the serological parameters such as aspartate aminotransferase, alanine transaminase, total bilirubin, and direct bilirubin, all of which were significantly attenuated by the daily uptake of RVS (2 mg/kg/day) for 28 days (14 days before and after operation) via intragastric route. We observed that BDL drastically induced the deterioration of liver histoarchitecture and excessive deposition of extracellular matrix (ECM), both of which were significantly attenuated by RVS. In addition, we revealed that RVS inhibited BDL-induced proliferation and activation of interstitial myofibroblasts, a highly suggestive cell type for ECM production, as shown by immunohistochemical and semi-quantitative detection of α-smooth muscle actin and vimentin. Finally, we demonstrated that the anti-fibrotic effect of RVS was associated with the inactivation of Smad3, the key downstream target of a major fibrogenic cytokine, i.e., transforming growth factor β (TGF-β). Simultaneously, we also found that RVS reciprocally increased the expression of Smad7, a negative regulatory protein of the TGF-β/Smad3 pathway. Taken together, these results suggested that RVS has a therapeutic effect on CLC, and these effects are, at least partly, due to the inhibition of liver fibrosis by the downregulation of Smad3 and upregulation of Smad7.

Potential Yield of Contrasting Soybean Maturity Groups in Southern Uruguayan Conditions

Soybean potential yield (Glycine max (L.) Merr.) is determined by temperature, radiation, photoperiod and genotype in every location. The variability of potential yields is strongly associated with changes in available solar radiation through years. Selection of management practices that lead to maintaining high yields are: genotype, sowing date and row spacing. Sowing date enables coupling solar radiation offer with the crop stages were yield is defined. Furthermore, potential yield for every environment depends on genotype. Selection of the maturity group (MG) defines the initiation of the reproductive period, which conditions the nod number, the maximum leaf area index (LAI) and the environmental conditions during grain filling. Additionally, growth habit of each genotype is also related to potential yield. Early sowing date allows the expression of the greatest differences among MG. A crop growth simulation study showed that the average potential productivity of early maturing cultivars (MG from III to V) achieved higher yields than later maturing cultivars (MG from V to VII) at early sowing date conditions in Uruguayan latitudes. Later maturing cultivars localize their critical period when daily radiation curve declines (late January - February) and consequently the growth rate during reproductive stage is not maximized. The objective of this study was to determine the potential crop growth and yield of different MG in two ambient crated by early and mid sowing date, at southern Uruguayan latitudes. The experiment was carried out during summer 2014-2015. Contrasting MG -from III to VII-were tested on two sowing dates: 15/10 and 15/11. Different growing variables were measured during the growing season: evolution of the intercepted solar radiation, biomass (B), soil water content, number of pods per square meter and crop yield. Results showed that early maturing cultivars expressed higher yields in both sowing dates. The yield on mid-October sowing date ranged from 5400 to 6300 kg ha-1 for early maturing cultivars and 4600 to 5600 kg ha-1 for later maturing cultivars. For mid November sowing date the yields ranged from 4600 to 5200 kg ha-1 for early maturing cultivars and 3800 to 5500 kg ha-1 for later maturing cultivars. However, evolution of LAI and B was similar among MG. The main difference showed was accumulated biomass at initial reproductive stage. Daily water uptake did not differ among MG; nevertheless, total water uptake responded positively to the increase of the crop cycle length. The highest potential yield for season 2014-2015 was reached with early maturing cultivars. Results showed that yields could be maximized with management practices as supplementary irrigation and the use of short MG sowed in October. The use of these practices lead to obtain over 6000 kg ha-1 crop yield combined with high water productivity.

Daily macronutrient uptake patterns in relation to plant age in hydroponic lettuce

ABSTRACTA greenhouse experiment was conducted to study and quantify the daily uptake rate of nitrate, ammonium, phosphoric acid, potassium, calcium, magnesium, and sulfate (NO3−, NH4+, H2PO4−, K+, Ca2+, Mg2+ and SO42−) and to characterize the uptake daily pattern at different plant ages in a lettuce crop. The uptake rates per gram of plant fresh weight were calculated at 2-hour intervals through sampling the nutrient solution and analyzing it by NO3−/NH4+ conductivity and inductively coupled plasma atomic emission spectrometry (ICP-AES). The uptake rate of nitrogen, phosphorus and potassium (N, P and K) per unit mass of plant decreased with plant age following a reduction in plant relative growth rate. No significant differences were found in the absorption of Ca, Mg and sulfur (S) between the different weeks of growth. The daily absorption patterns showed no preference for the absorption of any of the ions during the daytime. A significant reduction in the absorption peaks of all the ions with increasing plant age was observed.

Assessing the risk to green sturgeon from application of imidacloprid to control burrowing shrimp in Willapa Bay, Washington-Part I: exposure characterization.

Willapa Bay and Grays Harbor (WA, USA) comprise the largest region of commercial oyster cultivation on the Pacific Coast. The activities of 2 species of burrowing shrimp impair growth and survival of oysters reared on the intertidal mudflats. To maintain viable harvests, the oyster growers have proposed controlling the shrimp by applying the insecticide imidacloprid onto harvested beds. Green sturgeon (listed in the Endangered Species Act) forage on burrowing shrimp and could be exposed to imidacloprid in the sediment porewater and through consumed prey. Studies were conducted to evaluate the likelihood that green sturgeon would be exposed to imidacloprid and to characterize the subsequent environmental exposure. Comparisons between treated and untreated control beds following test application of the insecticide suggested that green sturgeon fed opportunistically on imidacloprid-impaired shrimp. The highest interpolated imidacloprid residue concentrations in field samples following chemical application were 27.8 µg kg(-1) and 31.4 µg kg(-1) in porewater and shrimp, respectively. Results from modeled branchial and dietary uptake, based on conservative assumptions, indicated that the porewater exposure route had the greatest contribution to systemic absorption of imidacloprid. The highest average daily uptake from porewater (177.9 µg kg(-1) body wt) was 9.5-fold greater than total dietary uptake (18.8 µg kg(-1) body wt). Concentrations and durations of exposure would be lower than the levels expected to elicit direct acute or chronic toxic effects.

Potential overestimation in primary and new productions of phytoplankton from a short time incubation method

A short (4–5 hour) incubation method for a 13C-15N dual isotope tracer technique has been widely applied for the measurements of daily primary and new productions of phytoplankton. However, there has been no research conducted to determine if there are any differences in the estimated daily productions between short incubation periods and 24 hour incubations. Based on hourly uptake rates estimated from a 4 hour incubation at a coastal site in the East/Japan Sea, the daily carbon and nitrogen uptake rates of total phytoplankton were approximately 60% overestimated compared to those derived from a 24 hour incubation. Especially for large phytoplankton, the daily carbon uptake rates based on the 4 hour incubation were greatly overestimated (> 200%). In contrast, the daily rates of small phytoplankton were not significantly different between the two different incubations. This is mainly because the daily carbon and nitrogen uptake rates of large phytoplankton were significantly correlated with light intensity. Consequently, the contributions of small phytoplankton were underestimated whereas large phytoplankton contributions were overestimated in daily carbon and nitrogen uptake rates based on a 4 hour incubation. Further investigations into these potential overestimations in daily carbon and nitrogen uptake rates of phytoplankton, especially for large size cells, will be needed to be carried out in order to obtain better estimations of annual primary and new productions.

Effects of episodic flooding on the net ecosystem CO2 exchange of a supratidal wetland in the Yellow River Delta

AbstractEpisodic flooding due to intense rainfall events is characteristic in many wetlands, which may modify wetland‐atmosphere exchange of CO2. However, the degree to which episodic flooding affects net ecosystem CO2 exchange (NEE) is poorly documented in supratidal wetlands of coastal zone, where rainfall‐driven episodic flooding often occurs. To address this issue, the ecosystem CO2 fluxes were continuously measured using the eddy covariance technique for 4 years (2010–2013) in a supratidal wetland in the Yellow River Delta. Our results showed that over the growing season, the daily average uptake in the supratidal wetland was −1.4, −1.3, −1.0, and −1.3 g C m−2 d−1 for 2010, 2011, 2012, and 2013, respectively. On the annual scale, the supratidal wetland functioned as a strong sink for atmospheric CO2, with the annual NEE of −223, −164, and −247 g C m−2 yr−1 for 2011, 2012, and 2013, respectively. The mean diurnal pattern of NEE exhibited a smaller range of variation before episodic flooding than after it. Episodic flooding reduced the average daytime net CO2 uptake and the maximum rates of photosynthesis. In addition, flooding clearly suppressed the nighttime CO2 release from the wetland but increased its temperature sensitivity. Therefore, effects of episodic flooding on the direction and magnitude of NEE should be considered when predicting the ecosystem responses to future climate change in supratidal wetlands.

Regional productivity of phytoplankton in the Western Arctic Ocean during summer in 2010

Phytoplankton production measurements were conducted in the northeast Chukchi Sea and western Canada Basin in the summer season, from 20 July to 10 August 2010, using a 13C–15N dual tracer technique. The daily carbon uptake rate in the northeast Chukchi Sea in 2010 was extremely low, with a mean of 29.8mgCm−2d−1 (SD=17.6mgCm−2d−1). Regional and temporal differences caused the low production rate compared to previous studies in the northeast Chukchi Sea. In the western Canada Basin, the mean daily carbon uptake rate from this study was 20.6mgCm−2d−1, which was influenced by the dominance of small phytoplankton resulting in a low carbon uptake rate in the region. The regionally high nitrate uptake rates compared to ammonium uptake rates in the western Canada Basin can be caused by warm-core eddies, which supply high levels of nitrate to the euphotic zone. Warm-core eddies in the Canada Basin substantially enhanced local phytoplankton production and the contribution of large phytoplankton. Therefore, the effects of physical forcing events (such as “an” eddy) on the primary production need to be examined further to better understand changes of primary production under ongoing environmental changes in the Arctic Ocean.

Nitrate content in a collection of higher mushrooms.

Data of mushroom nitrate content from scientific studies is limited. There have been two such recent investigations (mainly regarding certain cultivated species). To obtain comparable analytical data, we analyzed 134 samples of 54 taxa gathered and prepared by our department. The mushroom species were evaluated according to their nutritional types: saprotrophic, mycorrhizal and wood-decaying groups. Low and relatively invariable contents were found in the mycorrhizal (216.5 mg kg(-1) dry matter (DM) and wood-decaying groups (228.6 mg kg(-1) DM), but in the saprotrophic group we observed a wide variability (151.4-12 715 mg kg(-1) DM). A considerable nitrate content was found in samples of seven 'accumulator' species (Clitocybe nebularis, C. odora, Lepista nuda, L. personata, L. irina, Macrolepiota rachodes and M. procera). The toxicological relevance of daily uptake of acceptable nitrate content via mushrooms only is not presumable, but the 'accumulator' saprotrophic species can be 'contributors' to our nitrate intake in foods.