Anoxic Treatments Research Articles

Oxygen and dissolved organic carbon control release of N, P and Fe from the sediments of a shallow, polymictic lake

We examined potential causes of nutrient release from the sediments of a shallow polymictic reservoir that, unlike many other shallow lakes, had not received large amounts of nutrient loading. It was hypothesised that the sediments released greater amounts of nutrients under anoxic rather than oxic conditions and that nitrogen (N) and phosphorus (P) release was limited by the availability of different types of organic substrate. Sediment incubation experiments under oxic and anoxic conditions were conducted in summer and in winter. One anoxic incubation experiment with the addition of different types of dissolved organic substrate (glucose, acetate, formate and propionate) was carried out. Concentrations of nitrite and nitrate (NOx −-N), ammonium (NH4 +-N), soluble reactive P (srP) and iron (Fe(II)) were monitored in the supernatant of the incubation chambers over 28 days. Thermal stratification was monitored in situ for 17 months and sediment composition was analysed. NOx −-N concentration increased by 5.67 ± 0.33 mg N l−1 in anoxic conditions but was much lower in oxic treatments. Release of srP was low in anoxic and oxic treatments (0.004 ± 0.001 mg P l−1) but was stimulated by 0.027 ± 0.015 mg P l−1 under additions of formate. Fe(II) release was mostly stimulated by glucose additions (25.59 ± 4.28 mg Fe l−1). P release was much lower than observed in eutrophic lakes. P release does not appear to be as a result of the reduction of Fe minerals and concurrent dissolution of orthophosphate, often reported as the most prevalent pathway for P release from anaerobic lake sediments. Iron and P flux from lake sediments can be independent from each other and can be controlled by dissolved organic C. Further, the study confirms the role of oxygen availability in controlling nutrient release from the sediments.

Arundo donax L. response to low oxygen stress

Production of nonfood species is promoted to marginal, degraded lands abandoned by mainstream agricultural, where extremes in water availability (droughts and floods) have increased frequency and intensity and account for severe reductions in yields. A metabolic analysis of anoxic and hypoxic stress response was performed in a time-course experiment on Arundo donax L., a perennial rhizomatous grass identified as a leading candidate crop for lignocellulosic feedstock in the Mediterranean environment, due to its positive energy balance, and low ecological/agro-management demands. Tolerance to oxygen deprivation was determined after reoxygenation. Giant reed displayed time-dependent reduction in absolute growth and alterations in the derived physiological attributes under low oxygen stress. Our results show that although giant reed's responses to anoxic and hypoxic treatments share a common energy crisis related to the anaerobic metabolism, they differ in terms of ADH activity and related gene response. In leaves and roots tissues, the expression of this anaerobic gene was strongly enhanced under anoxia, whereas the ADH expression under submergence condition was relatively low. The activity profiles of ADH were not completely reflected in the expression patterns in either tissue. A high basal activity of the enzyme was recorded in both leaves and roots in normoxic tissues. In leaves, the treatments did not significantly affect ADH activity, remaining relatively stables at low levels during the time-course experiment. A different pattern of ADH was observed in roots, with a stronger, albeit transient, induction in both oxygen deficiency treatments.

Anoxic stress and rapid cold hardening enhance cold tolerance of the migratory locust

Anoxia and rapid cold hardening (RCH) can increase the cold tolerance of many animals. However, mechanisms underlying these two kinds of stresses remain unclear. In this study, we aimed to explore the relationship of acclimation to cold stress with acclimation to anoxic stress in the migratory locust, Locusta migratoria. RCH at 0°C for 3h promoted the survival of cold stress-exposed locusts. Anoxic hypercapnia (CO2 anoxic treatment) for 40min exerted an effect similar to that of RCH. Anoxic hypercapnia within 1h can all promote the cold hardiness of locusts. We investigated the transcript levels of six heat shock protein (Hsp) genes, namely, Hsp20.5, Hsp20.6, Hsp20.7, Hsp40, Hsp70, and Hsp90. Four genes, namely, Hsp90, Hsp40, Hsp20.5, and Hsp20.7, showed differential responses to RCH and anoxic hypercapnia treatments. Under cold stress, locusts exposed to the two regimens showed different responses for Hsp90, Hsp20.5, and Hsp20.7. However, the varied responses disappeared after recovery from cold stress. Compared with the control group, the transcript levels of six Hsp genes were generally downregulated in locusts subjected to anoxic hypercapnia or/and RCH. These results indicate that anoxic stress and RCH have different mechanisms of regulating the transcription of Hsp family members even if the two treatments exerted similar effects on cold tolerance of the migratory locust. However, Hsps may not play a major role in the promotion of cold hardiness by the two treatments.

Real-time evaluation of the efficacy of anoxic treatment for Cultural Heritage objects

The paper describes an analytical approach that allows to forecast the end time of the oxygen dilution process during the preparation phase of anoxic treatments for the eradication of biological attacks to objects of art. The described methodology allows also to verify during the process if the dilution procedure is progressing correctly.

Effects of NH4–N concentrations and gradient redox level on growth and allied biochemical parameters of Elodea nuttallii (Planch.)

Aquatic plants frequently encounter multiple stresses under natural conditions. Nuttall's water weed, Elodea nuttallii (Planch.) is a submerged aquatic macrophyte which has flexible ability to use different nutrient sources from various environments. However, recently the growth of E. nuttallii has been declining in waters of Japan and in the Chesapeake Bay, a large estuary in the United States. In the present experiment, we studied growth and survival capabilities of the plant under a gradient of redox conditions; from highly oxic (+400 to +440mV) to extremely reduced (−180 to −120mV) conditions. Reduced environment was prepared by adding glucose to growth medium and nitrogen gas bubbling, while the oxic environment was brought about by atmospheric air bubbling. In comparison to the oxic environment, growth rate and carbon–nitrogen content of the plants were significantly affected negatively at hypoxic and anoxic conditions. In hypoxic and anoxic environments, indole acetic acid (IAA), tissue nitrogen and chlorophyll levels were down-regulated, whereas hydrogen peroxide (H2O2), indole acetic acid oxidase (IAAO) and peroxidase (POD) levels were up-regulated. It was also found that high NH4–N concentrations (10–40ppm) affect the growth rate and biochemical parameters of the plant; however, in hypoxic and anoxic treatments the effects were more severe. We conclude that E. nuttallii is poorly tolerant to hypoxia/anoxia. Moreover, oxygen stress combined with high ammonium concentration act as important factors influencing distribution and abundance of this species.

The physiological response of the marine platyhelminth Macrostomum lignano to different environmental oxygen concentrations

The respiration rate of meiofauna is difficult to measure, and the response to variations in the environmental oxygen concentration has so far been mainly addressed through behavioral investigation. We investigated the effect of different oxygen concentrations on the physiology of the marine platyhelminth Macrostomum lignano. Respiration was measured using batches of 20 animals in a glass microtiter plate equipped with optical oxygen sensor spots. At higher oxygen saturations (>12 kPa), the animals showed a clear oxyconforming behavior. However, below this value, the flatworms kept respiration rates constant at 0.064±0.001 nmol O2 l(-1) h(-1) individual(-1) down to 3 kPa PO2, and this rate was increased by 30% in animals that were reoxygenated after enduring a period of 1.5 h in anoxia. Physiological changes related to tissue oxygenation were assessed using live imaging techniques with different fluorophores in animals maintained in normoxic (21 kPa), hyperoxic (40 kPa) or near-anoxic (~0 kPa) conditions and subjected to anoxia-reoxygenation. The pH-sensitive dyes Ageladine-A and BCECF both indicated that pHi under near-anoxia increases by about 0.07-0.10 units. Mitochondrial membrane potential, Δψm, was higher in anoxic and hyperoxic than in normoxic conditions (JC1 dye data). Staining with ROS-sensitive dyes - DHE for detection of superoxide anion (O2•(-)) formation and C-H DFFDA for other ROS species aside from O2•(-) (H2O2, HOO• and ONOO) - showed increased ROS formation following anoxia-reoxygenation treatment. Animals exposed to hyperoxic, normoxic and anoxic treatments displayed no significant differences in O2•(-) formation, whereas mitochondrial ROS formation as detected by C-H2DFFDA was higher after hyperoxic exposure and lowest under near-anoxia conditions compared with the normoxic control group. Macrostomum lignano seems to be a species that is tolerant of a wide range of oxygen concentrations (being able to maintain aerobic metabolism from extremely low PO2 up to hyperoxic conditions), which is an essential prerequisite for successfully dealing with the drastic environmental oxygen variations that occur within intertidal sediments.

저산소 농도 살충 챔버 시스템 시제작 및 박물관 해충 살충 성능 평가

박물관에서 문화재 해충의 살충을 위해 사용되어 온 메틸브로마이드는 오존층 파괴물질로써 2015년 사용이 금지됨에 따라 대체법으로써 아르곤이나 질소를 사용한 저산소 농도 살충법이 도입되었다. 국립민속박물관에서는 국내 최초로 저산소 농도 살충법의 적용이 가능한 저산소 농도 살충 챔버 시스템을 시제작하여 설치하였다. 저산소 농도 살충 챔버 시스템은 챔버 내부 용량이 <TEX>$0.5m^3$</TEX>이며, 아르곤, 질소, 이산소탄소의 사용이 가능하다. 이 시스템은 산소 농도 0.01~20%, 온도 <TEX>$10{\sim}50^{\circ}C$</TEX>, 습도 30~80%를 자동적으로 제어가 가능하며, 산소 농도 제어는 설정값 이상으로 상승할 때마다 가습 가스와 건조 가스를 혼합하여 주입하는 방법을 채택하였다. 시운전을 위해 30일 동안 가동 결과, 산소 농도, 온도 및 습도가 일정하게 유지되었다. 그리고 권연벌레 애벌레와 성충, 애알락수시렁이 애벌레 대해 아르곤 가스를 사용하여 산소 농도 0.01%, 온도 <TEX>$25^{\circ}C$</TEX> 및 습도 50% 환경에서 살충 성능을 평가한 결과, 권연벌레 성충은 3~5일, 애벌레는 7일, 애알락수시렁이 애벌레는 3일이 소요되어, 시제작된 저산소 농도 살충 챔버 시스템의 살충 성능을 확인할 수 있었다. 평가 결과로부터 저산소 농도 살충 챔버 시스템은 박물관에서 메틸브로마이드 대체법인 저산소 농도 살충법의 기술을 개발하는데 충분히 활용이 가능함을 확인하였다. Anoxic treatments using argon and nitrogen gas in controlled atmospheres have been used as a alternative to methyl bromide for insect disinfection in museums. Anoxic chamber system was manufactured and installed at The National Folk Museum of Korea for the first time in Korea. The internal capacity of anoxic chamber is 0.5m3 in which is able to use argon, nitrogen and carbon dioxide gas. This system is equipped with oxygen concentration, temperature and ralative humidity control devices and automatically controlled oxygen concentration from 0.01 to 20%, temperature from 10 to <TEX>$50^{\circ}C$</TEX> and relative humidity 30 to 80%. To control the oxygen concentration, anoxic chamber system is adopted semi-dynamic method which supplies mixture of humidified gas and dry gas whenever oxygen concentration in chamber becomes higher than setting value. It has kept regularly oxygen concentration, temperature and relative humidity for 20 days using argon gas. To evaluate the disinfection of cigarette beetle larvae and adults and varied carpet beetle larvae, the anoxic chamber system maintained 0.01% of oxygen concentration, <TEX>$25^{\circ}C$</TEX> in temperature and 50% in relative humidity for 30 days. Cigarette beetle larvae were killed in 7 days and adults in 3~5 days. And varied carpet beetle larvae were killed in 3 days. It reaches the conclusion form the evaluation this anoxic chamber system can be used to develop anoxic treatment as an alternative of methyl bromide for insect disinfection of infested cultural properties in museums.

Enhanced iron oxidation to improve AMD treatment

Fe(II) and acidity are the most commonly encountered contaminants in acid mine drainage (AMD). Passive treatment for AMD involves addition of alkalinity, aerobic processes that result in oxidation of Fe(II) to Fe(III) oxides, and anoxic treatments in which sulfate is reduced to sulfide with consequent precipitation of Fe(II) sulfides. Alkalinity is usually provided by dissolution of limestone in passive treatments or by addition of lime or caustic in active systems. This paper focuses on the chemistry of AMD treatment, the mechanisms and the rates of oxidation of Fe(II) to produce Fe(III) oxides and strategies that can be used to manipulate the treatment chemistry in order to control the rate of oxidation and the quality of the residual Fe(III) oxides.

Reactive oxygen species-driven transcription in Arabidopsis under oxygen deprivation.

Reactive oxygen species (ROS) play an important role as triggers of gene expression during biotic and abiotic stresses, among which is low oxygen (O(2)). Previous studies have shown that ROS regulation under low O(2) is driven by a RHO-like GTPase that allows tight control of hydrogen peroxide (H(2)O(2)) production. H(2)O(2) is thought to regulate the expression of heat shock proteins, in a mechanism that is common to both O(2) deprivation and to heat stress. In this work, we used publicly available Arabidopsis (Arabidopsis thaliana) microarray datasets related to ROS and O(2) deprivation to define transcriptome convergence pattern. Our results show that although Arabidopsis response to anoxic and hypoxic treatments share a common core of genes related to the anaerobic metabolism, they differ in terms of ROS-related gene response. We propose that H(2)O(2) production under O(2) deprivation is a trait present in a very early phase of anoxia, and that ROS are needed for the regulation of a set of genes belonging to the heat shock protein and ROS-mediated groups. This mechanism, likely not regulated via the N-end rule pathway for O(2) sensing, is probably mediated by a NADPH oxidase and it is involved in plant tolerance to the stress.

砂质潮间带自由生活海洋线虫对缺氧的响应——微型受控生态系研究

The community structure and vertical distribution of the nematode fauna in relation to oxygen deficiency,and their ability for recovery after re-establishment of normal oxygen conditions,were investigated in laboratory microcosms.Perspex cores of sediment(i.d 2.9cm) were collected to a depth of 5 cm from the sandy beach in the Huiquan Bay,Qingdao(China) in November 2009,and incubated in laboratory microcosms.The vertical distribution of nematodes was examined in response to sediment inversion in these cores with the presence of an air-flushed silicone tube introducing oxygen to the sediment layer(laboratory microcosm Ⅰ).Three cores were directly filled with fresh sea water and continuously aerated.This was the control treatment.In three other cores,the sediment was first turned upside down,imposing anoxic conditions on the original surface sediment(referred to as the upside down treatment).Following an incubation of 1 week,peak densities of nematodes were recorded in the surface sediment in cores with oxygenation.This suggests that oxidized sediments provided favorable conditions for nematodes and indicated that these nematodes may migrate in the sediment as a response to low oxygen conditions.Observations on the species level suggested that vertical migrations of nematodes are in some cases species-specific.Pseudosteineria sp1 and Rhynchonema sp1 might avoid low oxygen condition by migrating into the oxidized sediment,while Thalassironus sp1 could survive the reduced oxygen conditions and was found in high density in the bottom sediments with low oxygen.In laboratory microcosm Ⅱ,community structure of nematodes was examined in response to anoxic conditions without the presence of an air-flushed silicone tube introducing oxygen to the sediment layer.Surface(0—2 cm) sediments were collected on March 2010 from the studied site at low tide and these layers of sediment were incubated in perspex jars(i.d.11.5 cm;height 8.5 cm).All jars were directly filled with fresh sea water and sealed tightly.The controls were flushed with air and the anoxic treatments were not flushed throughout the incubation.All treatments were incubated for 14 days.In another treatment,four jars were made anoxic for 14 days and subsequently reoxygenated with air for 10 days to examine the nematodes ability for recovery when normal oxygen conditions were re-established.The final densities of nematodes and of the dominant species were assessed.After anoxic incubation,nematode density and biodiversity was reduced and community structure changed.Survival in anoxic conditions was species-specific.Pseudosteineria sp1 was sensitive to anoxic conditions and might emerge into the water column and colonize sediments after re-establishment of normal oxygen conditions.Daptonema sp3 was quite sensitive while Daptonema sp1,both adults and juveniles,was more tolerant to anoxic conditions,with its density increasing in anoxic conditions and becoming the most dominant species.Nematode density and biodiversity increased after reoxygenation of anoxic sediment.The densities and reproduction of Neochromadora sp1 and Spilophorella sp1 increased quickly after oxygen restoration in anoxic incubations.This suggests that these 2 species might act as opportunistic species.However,nematode community structure was not restored and such restoration may need a longer time.

Controlled atmospheres against insect pests in museums: a review and some considerations

Controlled atmospheres using nitrogen represent a safe and effective method for both objects and human health. The use of this technique against pests in museums has received an increasing amount of interest during the last twenty years. This paper looks at the researches into anoxic treatments that use nitrogen from the late &amp;lsquo;80s until now. At the moment, the recommended protocol suggests an oxygen percentage below 1% for at least three weeks. Considering that the major practical problems of controlled atmospheres are connected to treatment time and low oxygen percentage, it is very important to develop more flexible protocols that consider higher oxygen percentages or shorter treatment times, exploiting temperature and/or relative humidity. At oxygen percentage higher than those commonly used, temperature and relative humidity are very critical to insects&amp;rsquo; development and success. Preliminary data (unpublished) show that it is possible to adapt the application of the controlled atmospheres to different situations, taking advantage of favorable conditions already present in the considered situation and at the same time to use the other parameters at more favorable levels.

Microbial Mineralization of Dichloroethene and Vinyl Chloride under Hypoxic Conditions

Mineralization of 14C‐radiolabled vinyl chloride ([1,2‐14C] VC) and cis‐dichloroethene ([1,2‐14C] cis‐DCE) under hypoxic (initial dissolved oxygen (DO) concentrations about 0.1 mg/L) and nominally anoxic (DO minimum detection limit = 0.01 mg/L) was examined in chloroethene‐exposed sediments from two groundwater and two surface water sites. The results show significant VC and dichloroethene (DCE) mineralization under hypoxic conditions. All the sample treatments exhibited pseudo‐first‐order kinetics for DCE and VC mineralization over an extended range of substrate concentrations. First‐order rates for VC mineralization were approximately 1 to 2 orders of magnitude higher in hypoxic groundwater sediment treatments and at least three times higher in hypoxic surface water sediment treatments than in the respective anoxic treatments. For VC, oxygen‐linked processes accounted for 65 to 85% of mineralization at DO concentrations below 0.1 mg/L, and 14CO2 was the only degradation product observed in VC treatments under hypoxic conditions. Because the lower detection limit for DO concentrations measured in the field is typically 0.1 to 0.5 mg/L, these results indicate that oxygen‐linked VC and DCE biodegradation can be significant under field conditions that appear anoxic. Furthermore, because rates of VC mineralization exceeded rates of DCE mineralization under hypoxic conditions, DCE accumulation without concomitant accumulation of VC may not be evidence of a DCE degradative “stall” in chloroethene plumes. Significantly, mineralization of VC above the level that could reasonably be attributed to residual DO contamination was also observed in several nominally anoxic (DO minimum detection limit = 0.01 mg/L) microcosm treatments.

Arsenic in an alkaline AMD treatment sludge: Characterization and stability under prolonged anoxic conditions

Lime treatment of acid mine drainage (AMD) generates large volumes of neutralization sludge that are often stored under water covers. The sludge consists mainly of calcite, gypsum and a widespread ferrihydrite-like Fe phase with several associated species of metal(loid) contaminants. The long-term stability of metal(loid)s in this chemically ill-defined material remains unknown. In this study, the stability and speciation of As in AMD sludge subjected to prolonged anoxic conditions is determined. The total As concentration in the sludge is 300 mg kg{sup -1}. In the laboratory, three distinct water cover treatments were imposed on the sludge to induce different redox conditions (100%N{sub 2}, 100%N{sub 2} + glucose, 95%N{sub 2}:5%H{sub 2}). These treatments were compared against a control of oxidized, water-saturated sludge. Electron micro-probe (EMP) analysis and spatially resolved synchrotron X-ray fluorescence (SXRF) results indicate that As is dominantly associated with Fe in the sludge. In all treatments and throughout the experiment, measured concentrations of dissolved As were less than 5 {micro}g L{sup -1}. Dissolved Mn concentration in the N{sub 2} + glucose treatment increased significantly compared to other treatments. Manganese and As K-edge X-ray absorption near edge structure spectroscopy (XANES) analyses showed that Mn was the redox-active element in themore » solid-phase, while As was stable. Arsenic(V) was still the dominant species in all water-covered sludges after 9 months of anoxic treatments. In contrast, Mn(IV) in the original sludge was partially reduced into Mn(II) in all water-covered sludges. The effect was most pronounced in the N{sub 2} + glucose treatment, suggesting microbial reduction. Micro-scale SXRF and XANES analysis of the treated sludge showed that Mn(II) accumulated in areas already enriched in Fe and As. Overall, the study shows that AMD sludges remain stable under prolonged anoxic conditions. External sources of chemical reductants or soluble C were needed to induce lower redox state in the systems, and even under these imposed treatments, only weakly reducing conditions (Mn threshold) developed. The results suggest that As(V) in AMD sludge will remain stable under prolonged anoxic conditions as long as Mn(IV) is present and organic matter accumulation is negligible.« less

Metabolic responses of novel cellulolytic and saccharolytic agricultural soil Bacteria to oxygen

Cellulose is the most abundant biopolymer in terrestrial ecosystems and is degraded by microbial communities in soils. However, relatively little is known about the diversity and function of soil prokaryotes that might participate in the overall degradation of this biopolymer. The active cellulolytic and saccharolytic Bacteria in an agricultural soil were evaluated by 16S rRNA (13)C-based stable isotope probing. Cellulose, cellobiose and glucose were mineralized under oxic conditions in soil slurries to carbon dioxide. Under anoxic conditions, these substrates were converted primarily to acetate, butyrate, carbon dioxide, hydrogen and traces of propionate and iso-butyrate; the production of these fermentation end-products was concomitant with the apparent reduction of iron(III). [(13)C]-cellulose was mainly degraded under oxic conditions by novel family-level taxa of the Bacteroidetes and Chloroflexi, and a known family-level taxon of Planctomycetes, whereas degradation under anoxic conditions was facilitated by the Kineosporiaceae (Actinobacteria) and cluster III Clostridiaceae and novel clusters within Bacteroidetes. Active aerobic sub-communities in oxic [(13)C]-cellobiose and [(13)C]-glucose treatments were dominated by Intrasporangiaceae and Micrococcaceae (Actinobacteria) whereas active cluster I Clostridiaceae (Firmicutes) were prevalent in anoxic treatments. A very large number (i.e. 28) of the detected taxa did not closely affiliate with known families, and active Archaea were not detected in any of the treatments. These collective findings suggest that: (i) a large uncultured diversity of soil Bacteria was involved in the utilization of cellulose and products of its hydrolysis, (ii) the active saccharolytic community differed phylogenetically from the active cellulolytic community, (iii) oxygen availability impacted differentially on the activity of taxa and (iv) different redox guilds (e.g. fermenters and iron reducers) compete or interact during cellulose degradation in aerated soils.

Selection of indicator bacteria based on screening of 16S rDNA metagenomic library from a two-stage anoxic–oxic bioreactor system degrading azo dyes

Dye degradation has gained attention of late due to indiscriminate disposal from user industries. Enhancing efficiency of biological treatment provides a cheaper alternative vis-à-vis other advanced technologies. Dye molecules are metabolized biologically via anoxic and oxic treatments. In this study, bacterial community surviving on dye effluent working in anoxic–oxic bioreactor was analyzed using 16S rDNA approach. Azo-dye decolorizing and degrading bacterial community was enriched in lab-scale two-stage anoxic–oxic bioreactor. 16S rDNA metagenomic libraries of enriched population were constructed, screened and phylogenetically analyzed separately. Removal of ∼35% COD with complete decolorization was observed in anoxic bioreactor. Process was carried out by uncultured gamma proteobacterium constituting 48% of the total population and 12% clones having homology to Klebsiella. Aromatic amines generated during partial treatment under anoxic bioreactor were treated by aerobic population having 72% unculturable unidentified bacterium and rest of the population consisting of Thauera sp., Pseudoxanthomonas sp., Desulfomicrobium sp., Ottowia sp., Acidovorax sp., and Bacteriodetes bacterium sp.

Lake sediment treatment with aluminum, iron, calcium and nitrate additives to reduce phosphorus release

Treatment of lake sediments with salts is a promising approach for preventing phosphorus release from sediments. Five 35-d treatments of undisturbed sediment cores in the East Lake, Wuhan, China were applied under anoxic conditions: nothing added (control), Al2(SO4)3 added, FeCl3 added, CaCl2 added, and NaNO3 added. To identify changes in the P binding sites in the sediment caused by the treatments, different P binding forms were extracted from the sediment before and after the treatments. We found that the mean P release rates for anoxic treatments with Al2(SO4)3, FeCl3, CaCl2 and NaNO3 were −0.6, 0.03, 0.6 and 2.6 mg/(m2·d), respectively, while the P release rate with no additives was 7.3 mg/(m2·d). In suboxic conditions, the concentration of total phosphorus (TPaverage 657 mg/kg) in sediment was much lower than that of untreated sediment (TPaverage 688 mg/kg) and treatments with salts (TP(Al2(SO4)3) 793 mg/kg, TP(FeCl3) 781 mg/kg, TP(NaNO3) 802 mg/kg, TP(CaCl2) 747 mg/kg). We also found that adding CaCl2 prevented P release because of apatite formation and because PCa (Ca bound P) increased at the sediment surface. Addition of Fe3+ and NO3− to the sediment increased the amounts of PFe, Mn (Redox-sensitive P, mostly Fe and Mn compounds), since iron oxide has the ability to combine P. Addition of Al2(SO4)3 increased the fraction of PAl, Fe (P bound to metal oxides (Al, Fe)) and decreased the P and Fe in the water above the anoxic sediment, showing the greater ability of Al in binding P. The results showed that Al2(SO4)3, FeCl3, CaCl2 and NaNO3 all had an effect in controlling phosphorus release. The effect was related to the forms of phosphorus existing in the sediment before treatment and the forms resulting after adding the four reagents. The combination of Al3+ or Fe3+ with NO3− promises to be a reasonable chemical treatment for increasing the P retention capacity of sediments in eutrophic lakes. If chemical treatment is combined with bioremediation, the aim of environmental repair may be achieved.

Remote monitoring of electroencephalogram, electrocardiogram, and behavior during controlled atmosphere stunning in broilers: Implications for welfare

This study examined the welfare implications of euthanizing broilers with 3 gas mixtures relevant to the commercial application of controlled atmosphere stunning (CAS). Birds were implanted/equipped with electrodes to measure brain activity (electroencephalogram, EEG) and heart rate. These signals were recorded using a purpose-built telemetry-logging system, small enough to be worn by each bird in a spandex backpack. The birds were euthanized in a scaled-down CAS apparatus consisting of a conveyor belt passing through 2 compartments. Three gas environments were applied (8 birds per treatment): 1) anoxia (N(2) with <2% residual O(2), in both compartments), 2) hypercapnic anoxia (N(2) with 30% CO(2) and <2% residual O(2), in both compartments), and 3) a 2-phase approach with a hypercapnic hyperoxygenated anesthetic phase (40% CO(2), 30% O(2), and 30% N(2), in the first compartment, 80 s) followed by a second euthanasia phase (80% CO(2) in air, in the second compartment). All 3 CAS approaches effectively achieved nonrecovery states, and time to loss of consciousness for each bird was determined by visual determination of isoelectric EEG and by calculation of the correlation dimension of the EEG. Hypercapnic anoxia resulted in rapid unconsciousness and death; both anoxic treatments were associated with early onset prolonged wing flapping and sustained tonic convulsions as displayed in the electrophysiological recordings. These responses were seen in the period when consciousness remained a possibility. Hypercapnic hyperoxygenation (the 2-phase approach) was associated with respiratory disruption, but this treatment eliminated initial clonic convulsions in the stunning process, and tonic convulsions were not seen. These results suggest that the presence of O(2) in the first stage of CAS is associated with an absence of potentially distressing behavioral responses. The respiratory discomfort associated with hypercapnic hyperoxygenation is an issue. We propose that this may be compensated by a more gradual induction to unconsciousness, which eliminates the impact of other potentially negative experiences.

Lotus tenuis tolerates the interactive effects of salinity and waterlogging by 'excluding' Na+ and Cl- from the xylem

Salinity and waterlogging interact to reduce growth of poorly adapted species by, amongst other processes, increasing the rate of Na(+) and Cl(-) transport to shoots. Xylem concentrations of these ions were measured in sap collected using xylem-feeding spittlebugs (Philaenus spumarius) from Lotus tenuis and Lotus corniculatus in saline (NaCl) and anoxic (stagnant) treatments. In aerated NaCl solution (200 mM), L. corniculatus had 50% higher Cl(-) concentrations in the xylem and shoot compared with L. tenuis, whereas concentrations of Na(+) and K(+) did not differ between the species. In stagnant-plus-NaCl solution, xylem Cl(-) and Na(+) concentrations of L. corniculatus increased to twice those of L. tenuis. These differences in xylem ion concentrations, which were not caused by variation in transpiration between the two species, contributed to lower net accumulation of Na(+) and Cl(-) in shoots of L. tenuis, indicating that ion transport mechanisms in roots of L. tenuis were contributing to better 'exclusion' of Cl(-) and Na(+) from shoots, compared with L. corniculatus. Root porosity was also higher in L. tenuis, due to constitutive aerenchyma, than in L. corniculatus, suggesting that enhanced root aeration contributed to the maintenance of Na(+) and Cl(-) 'exclusion' in L. tenuis exposed to stagnant-plus-NaCl treatment. Lotus tenuis also had greater dry mass than L. corniculatus after 56 d in NaCl or stagnant-plus-NaCl treatment. Thus, Cl(-) 'exclusion' is a key trait contributing to salt tolerance of L. tenuis, and 'exclusion' of both Cl(-) and Na(+) from the xylem enables L. tenuis to tolerate, better than L. corniculatus, the interactive stresses of salinity and waterlogging.

The effect of artificial defaunation on bacterial assemblages of intertidal sediments

The use of the artificial defaunation of sediments is widespread among studies examining the disturbance and recovery of benthic macrofaunal communities. Standard methods of defaunation include driving the sediment to anoxia, freezing and sieving. In this study we performed a field experiment to test the assumption that the bacterial assemblages are unaffected by these methods of defaunation. Same-sized patches of sediment were defaunated by covering sediment with plastic sheeting (weighted by concrete blocks), freezing or sieving (1-mm mesh). Macrofaunal counts of sediment cores, taken to determine the effectiveness of each defaunation method, indicated that although none of the treatments removed 100% of macrofauna, all resulted in reduced macrofaunal presence, with the sieved treatment being the most effective. Bacterial samples were taken over the course of a month to determine both the initial and long-term effects of defaunation on bacterial community structure. Numerical effects were determined via epifluorescence microscopy, whereas differences in community composition were followed using PCR and denaturing gradient gel electrophoresis (DGGE). The anoxic treatments resulted in significant numerical changes in both active and total cell counts over time, while the frozen and sieved treatments caused less apparent changes. All of the treatments initially changed the composition of the community; however, anoxic and sieved treatments resulted in subtle changes while the frozen treatment produced more notable and variable changes within the community. The composition of the bacterial community in all of the treatment plots trended towards recovery, or convergence towards that of ambient sediments, by the t = 25-day sampling period.

Short anoxic treatments to enhance trans-resveratrol content in grapes and wine

In a search for a method to improve the (endogenous) trans-resveratrol content in post harvested grapes, several short anoxic treatments with dry nitrogen have been assayed. A significant enhancement of the trans-resveratrol content was obtained, especially for treatments under 24 h; moreover, with shorter treatments (e.g. 6 or 15 h) the induced higher content of trans-resveratrol was maintained during several days with no appreciable anoxic damage of the grapes. These results allowed the design of an anoxic treatment protocol for wine grapes prior to the vinification process that led to a trans-resveratrol enriched wine.