DON Concentrations Research Articles

Deoxynivalenol Induces Drp-1-Mediated Mitochondrial Dysfunction via Elevating Oxidative Stress.

Mitochondrial dysfunction is often linked to neurotoxicity and neurological diseases and stems from oxidative stress, yet effective therapies are lacking. Deoxynivalenol (DON or vomitoxin) is one of the most common and hazardous type-B trichothecene mycotoxins, which contaminates crops used for food and animal feed. Despite the abundance of preliminary reports, comprehensive investigations are scarce to explore the relationship between these fungal metabolites and neurodegenerative disorders. The present study aimed to elucidate the precise role of DON in mitochondrial dynamics and cell death in neuronal cells. Excessive mitochondrial fission is associated with the pathology of several neurodegenerative diseases. Human SH-SY5Y cells were treated with different concentrations of DON (250-1000 ng/mL). Post 24 and 48 h DON treatment, the indexes were measured as follows: generation of reactive oxygen species (ROS), ATP levels, mitochondrial membrane potential, calcium levels, and cytotoxicity in SH-SY5Y cells. The results showed that cytotoxicity, intracellular calcium levels, and ROS in the DON-treated group increased, while the ATP levels and mitochondrial membrane potential decreased in a dose-dependent manner. With increasing DON concentrations, the expression levels of P-Drp-1, mitochondrial fission proteins Mff, and Fis-1 were elevated with reduced activities of MFN1, MFN2, and OPA1, further resulting in an increased expression of autophagic marker LC3 and beclin-1. The reciprocal relationship between mitochondrial damage and ROS generation is evident as ROS can instigate structural and functional deficiencies within the mitochondria. Consequently, the impaired mitochondria facilitate the release of ROS, thereby intensifying the cycle of damage and exacerbating the overall process. Using specific hydroxyl, superoxide inhibitors, and calcium chelators, our study confirmed that ROS and Ca2+-mediated signaling pathways played essential roles in DON-induced Drp1 phosphorylation. Therefore, ROS and mitochondrial fission inhibitors could provide critical research tools for drug development in mycotoxin-induced neurodegenerative diseases.

A simple method for the quantification of amidic bioavailable dissolved organic nitrogen in seawater

AbstractA targeted method for the quantification of bioavailable amide N found in marine DON (bDON) is presented. The method utilizes mild acid hydrolysis to convert amide N found in proteins and N‐acetyl amino polysaccharides to primary amine containing products that are measured using a highly sensitive (nanomolar range and precision) fluorometric technique with addition of O‐phthaldialdehyde. We find amidic bDON concentrations ranging from 0.08 to 1.82 μM N within waters from the upper 300 m in the southern California Current, Southern California Bight, and subtropical North Pacific representing 15–33% of bulk DON concentrations. Bioassay experiments from the North Pacific revealed consumption of ~20% of the in situ bDON within 5 days. The method represents a simple and rapid tool for the quantification of bioavailable DON concentrations in seawater with improved analytical precision over traditional estimates of bulk DON concentrations.

First Results on the Presence of Mycotoxins in the Liver of Pregnant Fallow Deer (Dama dama) Hinds and Fetuses.

Reproductive abnormalities have been observed in fallow deer populations in Hungary. We supposed mycotoxin contamination to be one of the possible causes because multi-mycotoxin contamination is known to be dangerous even at low toxin levels, especially for young animals. We investigated the spatial pattern of mycotoxin occurrences and the relationship between maternal and fetal mycotoxin levels. A total of 72 fallow deer embryos and their mothers were sampled in seven forested regions in Hungary in the 2020/2021 hunting season. We analyzed Aflatoxin (AF), Zearalenone (ZEA), Fumonizin B1 (FB1), DON, and T2-toxin concentrations in maternal and fetal livers by ELISA. AF was present in 70% and 82%, ZEA in 41% and 96%, DON in 90% and 98%, T2-toxin in 96% and 85%, and FB1 in 84% and 3% of hind and fetus livers, respectively. All mycotoxins passed into the fetus, but only Fumonizin B1 rarely passed. The individual variability of mycotoxin levels was extremely high, but the spatial differences were moderate. We could not prove a relation between the maternal and fetal mycotoxin concentrations, but we found an accumulation of ZEA and DON in the fetuses. These results reflect the possible threats of mycotoxins to the population dynamics and reproduction of wild fallow deer.

Spatial variability of nitrogen cycling in the sediments of the Danshuie River Estuary (Northern Taiwan)

Dissolved N species, TOC and total N (TN) in sediment cores (SC) collected from an eutrophic estuary were analyzed to understand the N geochemical variation in SC of the eutrophic estuary. Extremely higher concentrations of ammonium (6550 μM) and DON (2050 μM) were observed in pore water of the upper estuary and both concentrations generally accounted for 65–99 % and 1–34 % of the dissolved total N pool, respectively, in the three sediment pore waters. The DON and TN concentrations decreased with increasing depth in SC of the upper estuary, opposite the ammonium profile, suggesting that the mineralization of DON and TN provided the ammonium source to the SC. While, the TN mineralization was more profound than the DON mineralization in SC of the middle and lower estuary. The mineralization rate of DON and TN obviously differed from the different depth intervals of the three SC.

Characterization of Microplastic Leachate from Different Polymers and Its Effect on Seed Germination of Lettuce

Accumulation of microplastics in soil could interfere with the germination and growth of plants. However, the chemical risks raised by leachate of microplastics remain unknown. Here, we prepared microplastic leachate at different extraction temperatures (25 and 50℃) using microplastic fibers derived from polyamide (PA) and polyethylene (PE) and conducted the seed germination test of microplastic leachates to investigate the toxic effects of microplastic leachates on lettuce (Lactuca sativa L.). Furthermore, characteristics of the microplastic leachate, such as DOC and DON concentrations and parameters of UV-vis, were measured. The results revealed that the concentration of DOC and DON in the leachate of PA was significantly higher than that of PE. DOC and DON concentration in the leachate of PA increased with extraction temperature. Additionally, the aromaticity, hydrophobic component content, and molecular weight of leachates were significantly affected by the polymers of microplastic, whereas the extraction temperature had no effect. Compared to those in CK, the microplastic leachates reduced the indicators such as germination vigor, germination index, and vigor index of lettuce seeds; however, it had no impact on agronomic traits, such as plant height, root length, fresh weight, and dry weight. Meanwhile, some seeds had abnormal developments of radicles and cotyledons under the microplastic leachate treatments. This demonstrates that the substances leached from microplastics could interfere with the germination process of lettuce seeds. Therefore, the chemical risks exerted by the microplastics to the soil and plant system require further attention.

Controls on surface distributions of dissolved organic carbon and nitrogen in the southeast Pacific Ocean

Here we use data from three meridional survey cruises that took place in 1994, 2007/2008 and 2016/2017 in the southeast Pacific Ocean to investigate controls on surface distributions of dissolved organic carbon and nitrogen (DOC and DON, respectively). While DOC and DON production occur simultaneously in the euphotic layer of the gyre margins, budgets that account for horizontal transport, production and consumption are not balanced across the region. Our results show that while DOC concentrations increase inside the gyre, DON remains at similar levels in comparison to margins. There is little interannual variability in DOC and DON trends, except near the equator, explained by ENSO phases and seasonality. While the effect of evaporation (precipitation) did not significantly contribute to variable DOC and DON concentrations, differences in the naturally occurring 15N/14N isotope ratios from the most recent cruise suggest net consumption of allochthonous DON inside the gyre. In the northernmost and southernmost stations, where surface [NO3−] was detected, 15N-DON showed low signatures in the upper 300 m of 3.8 ± 1.5‰ and 2.5 ± 1.6‰, respectively. Inside the gyre where [NO3−] was undetectable, higher values averaging 5.0 ± 0.9‰ were observed. This suggests that a fraction of DON turns over more rapidly than the time scale of horizontal transport, with the isotopic change reflecting the gradient in 15N-DON of newly produced organic matter. Thus, allochthonous DON is likely a significant source of nitrogen to microbial communities inside this nitrogen-limited environment and should be taken into consideration when closing nutrient budgets to estimate productivity in the South Pacific Subtropical Gyre.

A Novel In Planta Enrichment Method Employing Fusarium graminearum-Infected Wheat Spikes to Select for Competitive Biocontrol Bacteria.

This work introduces an alternative workflow for the discovery of novel bacterial biocontrol agents in wheat against Fusarium head blight (FHB). Unlike the mass testing of isolate collections, we started from a diverse inoculum by extracting microbiomes from ears of field-grown plants at grain filling stage. Four distinct microbial communities were generated which were exposed to 3 14-day culture-independent experimental enrichments on detached wheat spikes infected with F. graminearum PH1. We found that one bacterial community reduced infection symptoms after 3 cycles, which was chosen to subsequently isolate bacteria through limiting dilution. All 94 isolates were tested in an in vitro and in planta assay, and a selection of 14 isolates was further tested on detached ears. The results seem to indicate that our enrichment approach resulted in bacteria with different modes-of-action in regard to FHB control. Erwinia persicina isolate C3 showed a significant reduction in disease severity (Fv/Fm), and Erwinia persicina C3 and Pseudomonas sp. B3 showed a significant reduction in fungal biomass (cGFP). However, the mycotoxin analysis of both these treatments showed no reduction in DON levels. Nevertheless, Pantoea ananatis H3 and H11 and Erwinia persicina H2 were able to reduce DON concentrations by more than 50%, although these effects were not statistically significant. Lastly, Erwinia persicina H2 also showed a significantly greater glucosylation of DON to the less phytotoxic DON-3G. The bacterial genera isolated through the enrichment cycles have been reported to dominate microbial communities that develop in open habitats, showing strong indications that the isolated bacteria can reduce the infection pressure of F. graminearum on the spike phyllosphere.

Impact of agronomic practices onFusarium mycotoxin accumulation in maize grain

In the Great Lakes region of North America,Gibberella ear rot (GER), caused byFusarium graminearum, affects grain quality due to the accumulation of mycotoxins. GER severity is strongly influenced by environmental conditions; however, agronomic practices can also influence disease severity and mycotoxin accumulation. In this study, three separate small-plot experiments were conducted at Ridgetown, ON, Canada during 2019 and 2020 under an inoculated-misted system to determineFusarium mycotoxin accumulation as affected by: (1) plant population density; (2) in-row-plant developmental variability; and (3) the effect of integrated Bt refuge genetics. In this study, DON concentrations were at least 49% higher in maize at 113,600 plants/ha compared to 79,000 plants/ha. Moreover, mycotoxin accumulation was higher in plants that were delayed developmentally in the crop row; total DON concentrations were at least 310% higher in late silked plants adjacent to early silked plants. Results of the plant population density and in-row-plant developmental variability suggest that the main driver for mycotoxin accumulation was stress induced by plant competition rather than environmental conditions; this highlights the importance of avoiding plant competitive stress as a strategy to reduce the risks of mycotoxin accumulation. In this study, there was no statistical difference in DON accumulation between the Bt component and the non-Bt component in each of the four hybrids tested; however, there was evidence that hybrids varied in susceptibility, including the Bt and non-Bt components that were paired commercially in a bag of seed maize. Reducing mycotoxins in maize requires integrated management, which includes agronomic considerations. These results indicate that mycotoxins are favoured with high plant populations and plant-to-plant variability in the row, especially in susceptible hybrids.

Erosion and covered zones altered by surface coverage effects on soil nitrogen and carbon loss from an agricultural slope under laboratory-simulated rainfall events

Soil erosion, one of the most serious environmental concerns, might remove topsoil and essential element from terrestrial land. However, few attentions have been given to investigating how soil erosion regimes affect soil carbon and nitrogen loss. Therefore, this study investigated the effects of surface coverage rates (83%, 67%, 50%, 33%, 17% and 0%) and two positions (up- and downslope) on erosion regimes and its associated soil nitrogen and carbon loss under a sequence of six rainfalls (R1-R6). These results showed that the sediment concentrations with 33% (R4) and 17% (R5) coverage downslope were significantly lower than those with coverage upslope, whereas there was no significant difference between the runoff rates of the two slopes. Thus, surface coverage at different positions induced two soil erosion regimes (deposition- and transport-dominated processes). Dynamics of the DON and DIN concentrations indicated different release processes of soil nitrogen into runoff. The DON contributed to a substantial amount of soil nitrogen loss, which accounted approximately 81% of the organic form. The SBOC is significantly correlated with sediment-enriched clay particles from the deposition-dominated processes and is higher than that from the transport-dominated processes. The DOC is significantly correlated with Rr for transport-dominated processes. These results illustrated the critical role of erosion regimes in soil organic carbon loss in dissolved or sediment-bound form. It is concluded that erosion/covered zones altered by surface coverage could produce transport- and deposition-dominated erosion regimes and consequently affect soil carbon and nitrogen loss. In addition, these results demonstrated that surface coverage pattern may efficiently control soil erosion and soil carbon and nitrogen loss.

冻融作用对金川泥炭沼泽土壤酶活性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 冻融作用对金川泥炭沼泽土壤酶活性的影响 DOI: 10.5846/stxb202107091856 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 中央高校基本科研业务费(2412019FZ001);吉林省自然科学基金项目(20210101397JC);国家自然科学基金项目(32071599) Effects of freezing and thawing on soil enzyme activities in Jinchuan peatlands Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为研究冻融作用对泥炭沼泽土壤酶活性的影响,选取金川草本泥炭沼泽为研究对象,采集表层(0-15 cm)和深层(15-30 cm)土壤样品,进行室内冻融模拟实验。实验设置(-5-5℃)和(-10-10℃)两个冻融幅度,分析经0、1、3、5、7、15次冻融循环处理后土壤3种水解酶活性(β-1,4-葡萄糖苷酶(BG)、β-1,4-N-乙酰葡糖胺糖苷酶(NAG)和酸性磷酸酶(AP))和2种氧化酶(过氧化物酶(PER)和多酚氧化酶(PPO))的变化特征,并结合土壤有机碳、氮组分,探讨泥炭沼泽土壤酶活性与土壤活性有机碳、氮组分间的相关关系。结果表明,冻融频次与冻融幅度均显著影响了土壤有机碳、氮组分及土壤酶活性。-10-10℃冻融作用下,土壤可溶性有机碳(DOC)与可溶性有机氮(DON)含量呈现先增加后降低的变化趋势。-5-5℃的冻融作用下土壤DOC与DON释放相对-10-10℃冻融作用更为缓慢,在冻融结束后呈现增加趋势。冻融循环增加了土壤微生物碳(MBC)含量,而降低了土壤微生物氮(MBN)含量。冻融幅度对土壤MBC和MBN的影响表现为-5-5℃ ＜ -10-10℃。随着土层的增加,土壤MBC、MBN和DOC含量的幅度变化表现为0-15 cm ＜ 15-30 cm,而土壤DON含量幅度变化表现为0-15 cm ＞ 15-30 cm。冻融循环降低了土壤水解酶活性和氧化酶活性。冻融幅度对土壤水解酶活性的影响表现为-5-5℃ > -10-10℃,对土壤氧化酶活性的影响表现为-5-5℃ < -10-10℃。随着土层深度的增加,土壤水解酶活性变化的幅度表现为0-15 cm ＜ 15-30 cm,土壤氧化酶活性变化的幅度表现为0-15 cm ＞ 15-30 cm。土壤酶活性与土壤MBC和MBN含量呈正相关,而与土壤DOC含量呈显著负相关(P ＜ 0.05)。研究结果表明冻融作用初期促使部分微生物死亡,其死亡残体释放的可利用养分,促进了适应冻融作用的微生物生长,但在培养后期随着土壤养分的消耗,土壤微生物量呈现下降趋势,进而最终降低了土壤酶活性。 Abstract:The aim of this study was to analyze the influence of freezing-thawing cycles on soil enzyme activity in peatland. A laboratory freezing-thawing simulation test was carried out using soil samples from surface layer (0-15 cm) and deep layer (15-30 cm) in Jinchuan herbaceous peatland. Two freezing-thawing cycles amplitudes, namely, (-5-5℃) and (-10-10℃), were tested. Soil samples were then processed during the 1st, 3rd, 5th, 7th and 15th freezing-thawing cycles. We analyzed the activities of three hydrolases (β-1, 4-glucosidase (BG), 4-N-acetylglucosaminosidase (NAG) and acid phosphatase (AP)), two oxidases (peroxidase (PER) and polyphenol oxidase (PPO)), dissolved organic carbon and nitrogen (DOC and DON), and microbial biomass carbon and nitrogen (MBC and MBN) which were compared to the values of the initial freezing-thawing cycle. We also analyzed the relationship between the soil organic carbon and nitrogen concentrations and soil enzyme activities in peatland. The results demonstrated that freezing-thawing cycles frequency and freezing-thawing amplitudes had significant effects on soil organic carbon and nitrogen fractions and soil enzyme activities. Soil DOC and DON concentrations increased first and then decreased under -10-10℃ freezing-thawing cycling. The release of soil DOC and DON concentrations under -5-5℃ freezing-thawing cycling was slower than those under -10-10℃ freezing-thawing cycling, which showed an increasing trend at the end of freezing and thawing. Soil MBC concentrations increased but MBN concentrations decreased after freezing-thawing cycles. The effects of freezing-thawing amplitude on MBC and MBN concentrations under the amplitude of -10-10℃ were greater than those of -5-5℃. The effects of freezing-thawing cycles on MBC, MBN, and DOC concentrations gradually increased with the increases in soil depth, but the opposite phenomenon was observed with respect to the effects of freezing-thawing cycles on DON concentration. Freezing-thawing cycles had a negative influence on the soil enzyme activities. The effects of freezing-thawing cycles on the hydrolase activities under the amplitude of -5-5℃ were greater than those of the amplitude of -10-10℃, whereas oxidase activities showed an opposite pattern. The effects of freezing-thawing cycles on hydrolase activities gradually increased with soil depth increasing, but the opposite phenomenon was observed with respect to the effects of freezing-thawing cycles on oxidase activities. Soil enzyme activities were positively correlated with MBC and MBN concentration, but negatively correlated with DOC concentration (P<0.05). The results indicated that, at the early stage of freezing-thawing cycling, the available nutrients released by the dead residues of some dead microorganisms promoted the growth of microorganisms to adapt to freezing-thawing. However, with the consumption of soil nutrients at the later stage of freezing-thawing cycling, soil microbial biomass showed a downward trend, which ultimately reduced soil enzyme activities. 参考文献 相似文献 引证文献

Is bog water chemistry affected by increasing N and S deposition from oil sands development in Northern Alberta, Canada?

Nitrogen and sulfur emissions from oil sands operations in northern Alberta, Canada have resulted in increasing deposition of N and S to the region’s ecosystems. To assess whether a changing N and S deposition regime affects bog porewater chemistry, we sampled bog porewater at sites at different distances from the oil sands industrial center from 2009 to 2012 (10-cm intervals to a depth of 1 m) and from 2009 to 2019 (top of the bog water table only). We hypothesized that: (1) as atmospheric N and S deposition increases with increasing proximity to the oil sands industrial center, surface porewater concentrations of NH4+, NO3−, DON, and SO42− would increase and (2) with increasing N and S deposition, elevated porewater concentrations of NH4+, NO3−, DON, and SO42− would be manifested increasingly deeper into the peat profile. We found weak evidence that oil sands N and S emissions affect bog porewater NH4+-N, NO3−-N, or DON concentrations. We found mixed evidence that increasing SO42− deposition results in increasing porewater SO42− concentrations. Current SO42− deposition, especially at bogs closest to the oil sands industrial center, likely exceeds the ability of the Sphagnum moss layer to retain S through net primary production, such that atmospherically deposited SO42− infiltrates downward into the peat column. Increasing porewater SO42− availability may stimulate dissimilatory sulfate reduction and/or inhibit CH4 production, potentially affecting carbon cycling and gaseous fluxes in these bogs.

PSIII-21 Efficacy of deoxynivalenol detoxification by sodium metabisulfite (SMBS) containing nanofibrous mats using an in vitro intestinal epithelial cell IPEC-J2

Abstract Deoxynivalenol (DON) occurs in many commonly used cereal grains. Pigs feed with DON concentrations as low as 0.6–2.0 mg/kg can result in reduced feed intake and growth rate, damage to intestinal epithelial cells, and increase susceptibility to enteric pathogens. Sodium metabisulfite (SMBS) can efficiently detoxify DON by converting it 8-DONS or 10-DONS in vitro. However, if SMBS is added directly to the feed, SMBS rapidly degrades under acidic aqueous conditions (e.g. pig stomach) and little SMBS is delivered to the intestinal absorption site where it can effectively detoxify DON. Thus, the objective of this study was to encapsulate SMBS into Eudragit L100-55 nanofibrous mats to deliver intact SMBS to the small intestine and evaluate the efficacy of DON detoxification in the simulated intestine fluid (SIF) using an in vitro intestinal epithelial cell (IPEC-J2) model. Nanofibrous mats were produced by coaxial electrospinning, with peak loading capacity and loading efficiency of SMBS reaching 32.00% and 80.01%. DON-induced cytotoxicity was not observed during in vitro analysis consisting of incubation of DON in the presence of SMBS-containing nanofibers (0.5% w/w) in simulated gastric fluid (SGF) for 2 h followed by incubation in a mixture of SGF and SIF (1:1) for 20 min. Meanwhile, compared to the DON treatment, incubation of DON in the presence of SMBS-containing nanofiber (0.5% w/w) in SGF for 2 h and SIF for 20 min decreased the gene expression of inflammatory cytokines in the IPEC-J2 cells and maintained the cell integrity. To conclude, SMBS released from Eudragit L100-55 nanofibrous mats in the SIF effectively decreased the adverse effects induced by DON in the IPEC-J2 cells. Nanofibrous mats can release a large amount of SMBS in a short time in SIF to achieve the effect of detoxifying DON.

Mycotoxins Exposure of French Grain Elevator Workers: Biomonitoring and Airborne Measurements.

It is now recognized that additional exposure to mycotoxins may occur through inhalation of contaminated dust at a workplace. The aim of this study was to characterize the multi-mycotoxin exposure of French grain elevator workers using biomonitoring and airborne measurements. Eighteen workers participated in the study. Personal airborne dust samples were analyzed for their mycotoxin concentrations. Workers provided multiple urine samples including pre-shift, post-shift and first morning urine samples or 24 h urine samples. Mycotoxin urinary biomarkers (aflatoxin B1, aflatoxin M1, ochratoxin A, ochratoxin α, deoxynivalenol, zearalenone, α-zearalenol, β-zearalenol, fumonisin B1, HT-2 toxin and T-2 toxin) were measured using a liquid chromatography–high-resolution mass spectrometry method. Grain elevator workers were highly exposed to organic airborne dust (median 4.92 mg.m−3). DON, ZEN and FB1 were frequent contaminants in 54, 76 and 72% of air samples, respectively. The mycotoxin biomarkers quantified were DON (98%), ZEN (99%), α-ZEL (52%), β-ZEL (33%), OTA (76%), T-2 (4%) and HT-2 (4%). DON elimination profiles showed highest concentrations in samples collected after the end of the work shift and the urinary DON concentrations were significantly higher in post-shift than in pre-shift-samples (9.9 and 22.1 µg/L, respectively). ZEN and its metabolites concentrations did not vary according to the sampling time. However, the levels of α-/β-ZEL were consistent with an additional occupational exposure. These data provide valuable information on grain worker exposure to mycotoxins. They also highlight the usefulness of multi-mycotoxin methods in assessing external and internal exposures, which shed light on the extent and pathways of exposure occurring in occupational settings.

The Pulse of the Amazon: Fluxes of Dissolved Organic Carbon, Nutrients, and Ions From the World's Largest River

AbstractThe Amazon River drains a diverse tropical landscape greater than 6 million km2, culminating in the world's largest export of freshwater and dissolved constituents to the ocean. Here, we present dissolved organic carbon (DOC), organic and inorganic nitrogen (DON, DIN), orthophosphate (PO43−), and major and trace ion concentrations and fluxes from the Amazon River using 26 samples collected over three annual hydrographs. Concentrations and fluxes were predominantly controlled by the annual wet season flood pulse. Average DOC, DON, DIN, and PO43− fluxes (±1 s.d.) were 25.5 (±1.0), 1.14 (±0.05), 0.82 (±0.03), and 0.063 (±0.003) Tg yr−1, respectively. Chromophoric dissolved organic matter absorption (at 350 nm) was strongly correlated with DOC concentrations, resulting in a flux of 74.8 × 106 m−2 yr−1. DOC and DON concentrations positively correlated with discharge while nitrate + nitrite concentrations negatively correlated, suggesting mobilization and dilution responses, respectively. Ammonium, PO43−, and silica concentrations displayed chemostatic responses to discharge. Major and trace ion concentrations displayed clockwise hysteresis (except for chloride, sodium, and rubidium) and exhibited either dilution or chemostatic responses. The sources of weathered cations also displayed seasonality, with the highest proportion of carbonate‐ and silicate‐derived cations occurring during peak and baseflow, respectively. Finally, our seasonally resolved weathering model resulted in an average CO2 consumption yield of (3.55 ± 0.11) × 105 mol CO2 km−2 yr−1. These results represent an updated and temporally refined quantification of dissolved fluxes that highlight the strong seasonality of export from the world's largest river and set a robust baseline against which to gauge future change.

Internal Nutrient Loading Controls Macroalgal and Cyanobacterial Succession in a Coastal Lagoon Restored by Managed Realignment of Agricultural Land

Managed realignment (MR) has been increasingly applied as an adaptation strategy to sea level rise in low-lying coastal areas, but the ecological consequences after flooding agricultural land with seawater are not well known. The restored Gyldensteen Coastal Lagoon represents one of the largest MR projects in Europe to date. The area served as agricultural land for about 150 years before being deliberately flooded with seawater in 2014. This study monitored for 5 years the succession of macroalgae and benthic cyanobacteria driven by changing internal nutrient (DIN = NH4+ + NO2– + NO3–, DON = dissolved organic nitrogen, and DIP = PO43–) loadings in the lagoon after flooding. A massive bloom of opportunistic green macroalgae (dominated by Cladophora spp.) occurred during the first year as response to a substantial loading of DIN and DIP from the newly flooded soils. The macroalgal cover was sparse the following years and the species richness increased with lower loading of particularly DIN. A cyanobacterial bloom controlled by declining DIN and steady DIP concentrations in the water dominated the lagoon and covered all solid surfaces 4 years after flooding. Highest macroalgal species richness with dominance of perennial Fucus vesiculosus and Agarophyton vermiculophylla was recorded 5 years after flooding following a temperature-induced stimulation of soil nitrogen transformation, leading to increased water column DON concentrations and DIN:DIP ratios. The lagoon remains therefore at an unstable tipping point where small and random changes in the DIN:DIP ratio control the balance between blooms of benthic cyanobacteria and high macroalgal species richness. Future MR projects involving agricultural land should prepare the soil to prevent algal blooms driven by sustained internal nutrient loading. Particularly P loading should be avoided to minimize the chances for recurrent blooms of benthic cyanobacteria.

Impact of Foliar Fungicides on Disease and Silage Quality of Brown Midrib Corn Hybrids in Wisconsin

Corn (Zea mays L.) is one of the most widely grown crops in the United States due to its importance as a feed, food, and fuel crop. Silage is a high-energy, fermented feed that uses the entire corn plant and is important for feeding dairy cows. Any disease that affects the plant’s physiology can reduce silage quality. The goal of this study was to evaluate fungicide treatments on silage corn hybrids to determine their effect on fungal diseases, including those caused by Fusarium graminearum, on silage quality. Foliar fungicide trials were conducted in Arlington, Wisconsin, in 2018 and 2019 and included two brown-midrib silage hybrids. In-field disease ratings were collected for foliar disease symptoms, ear rot severity, and lodging. Harvested silage was analyzed for yield, quality parameters, and mycotoxin (deoxynivalenol, DON) concentration. There were significant differences in all measured parameters between years and hybrids; however, only the foliar disease ratings were consistently reduced by the use of fungicide treatments. DON concentrations were significantly lower for two fungicide treatments in one hybrid in 2019. There were no significant differences among the treatments used on yield or any quality parameters in this study. More research needs to be done to find potential fungicides that can consistently reduce F. graminearum damage and DON concentration in silage corn.

Biogeochemical alteration and fluxes of dissolved organic matter and nutrients in coastal bays

We measured dissolved organic carbon (DOC), δ13C-DOC, fluorescent dissolved organic matter (FDOM), dissolved inorganic and organic nitrogen (DIN; DON), dissolved inorganic phosphate (DIP), and radium isotopes (223Ra, 224Ra, and 226Ra) in three different bays: Gwangyang Bay (GB), Suyoung Bay (SB), and Ulsan Bay (UB), Korea. The water residence times based on Ra isotopes were approximately 15 (±7) for GB and 1–3 days for SB and UB. UB and SB showed clear two (terrestrial and marine) endmember mixing trends for DOC, DIN, and DIP. In addition, significant “excess” DOC (10–50% of outer bay) was observed for SB under depleted nutrient conditions. GB, which had the longest water-residence time, showed depleted DIN and DIP, with large “excess” DOC (40–60% of the outer bay) and DON (10–40% of the outer bay) concentrations. The excess DOC observed in SB and GB was found to be marine in origin, although there was a slight influence of terrestrial DOC in the low-salinity waters of SB based on δ13C-DOC values. Terrestrial humic-like FDOM was conservatively mixed in the three bays. The net fluxes of these components, estimated using the water residence times, suggest that GB is a significant source of DOM (DOC, DON, and humic FDOM) but a sink of DIN and DIP. SB and UB are the sources of inorganic nutrients as well as DOM to the open ocean. Therefore, our study reveals that the residence time of coastal embayment play an important role in the biogeochemical production and alteration of nutrients and DOM.

Variability and controls of soil CO2 fluxes under different tillage and crop residue managements in a wheat-maize double-cropping system.

The spatial and temporal variability of soil CO2 emissions from agricultural soils is inherently high. While tillage and crop residue practices play vital roles in governing soil CO2 emission, their effects on the variability of soil CO2 fluxes across depths and seasons are still poorly understood. To address this, an experiment consisting of four treatments, namely conventional tillage with (CT+) and without crop residue application (CT-), as well as no tillage with (NT+) and without crop residue application (NT-), was conducted to investigate soil CO2 fluxes at top 40 cm soils with 10-cm depth intervals in a winter wheat-summer maize rotation system in the North China Plain. Our results showed soil CO2 fluxes increased with depth in both the wheat- and maize-growing seasons. However, the dominant factors in regulating soil CO2 fluxes changed with soil depth and seasons. In the wheat-growing season, increase in soil CO2 fluxes with depth was attributed to the increase of dissolved organic carbon-to-nitrogen ratio (DOC/DON) and a decline in soil DON concentration along the soil profile. These factors explained about 55-96% of the total variation in soil CO2 fluxes at different soil depths. In the maize-growing season, the dominant factors were soil DOC/DON ratio, soil DON concentrations, and soil moisture. These factors explained approximately 79-96% of the total variation in soil CO2 fluxes along the soil depth. Greater soil CO2 fluxes (except at 30-40 cm depth) were observed in NT- than CT- treatments. Furthermore, crop residue application enhanced soil CO2 fluxes across different depths, but the enhancement was more prominent in CT+ than NT+. Moreover, soil CO2 fluxes in the maize-growing season were greater than those in the wheat-growing season. Our results demonstrate that the effects of tillage regimes and crop residue management practices on soil CO2 emissions are not confined only to the plough layer but can extend to soils of over 30 cm depths. We also need to revisit the general conventional view that no tillage can significantly reduce soil CO2 emissions compared with conventional tillage for better climate change mitigation.

Spatiotemporal variations in soil CO2 fluxes under a winter wheat-summer maize cropping system in the North China Plain

Most studies on soil CO2 fluxes focus on the upper soil layers (i.e., 0–200 mm); however, there is a lack of investigation into soil layers below 200 mm, even though about half of soil organic carbon (SOC) is stored at these depths. In order to investigate the responses of CO2 fluxes in subsurface soils to crop residue incorporation in the topsoil, a field experiment comprising two treatments (i.e., conventional tillage with and without crop residue incorporation) was carried out under a winter wheat-summer maize cropping system from 2014 to 2016 in the Yucheng Agricultural Station, Shandong Province, China. The results showed that soil CO2 fluxes had large spatiotemporal variabilities and were significantly affected by crop residue applications (P < 0.05). Soil CO2 fluxes increased with soil depth. The CO2 fluxes from 100 to 400 mm soil depths were 1.1–5.1 times higher than those from 0 to 100 mm soil depths. Incorporation of crop residues into the soil significantly increased soil CO2 fluxes in all sampled layers (P < 0.05), and the magnitude increased with increasing soil depth. Soil moisture and the ratio of soil dissolved organic carbon to nitrogen (DOC/DON) were the dominant factors regulating soil CO2 fluxes in the wheat growing season, whereas soil DON concentrations dominated in the maize growing season. Our study indicated that deep soil C was more vulnerable to the incorporation of crop residues than the C present in surface soil. Incorporation of crop residues into surface soil might not increase SOC sequestration in the subsurface soil.

Characterizing property and treatability of dissolved effluent organic matter using size exclusion chromatography with an array of absorbance, fluorescence, organic nitrogen and organic carbon detectors.

In this study, size exclusion chromatography with an array of absorbance, fluorescence, organic nitrogen and organic carbon detectors was used for characterizing property and treatability of effluent organic matter (EfOM) from 12 wastewater treatment plants. According to their apparent molecular weight (AMW), EfOM fractions were assigned to biopolymers (>20 kDa), humic substances that comprise sub-fractions of humic-like acids (HA-I & HA-II, 2.3-7.0 kDa) and fulvic-like acids (FA, 1.5-2.3 kDa), building blocks (0.55-1.5 kDa) and low molecular weight neutral substances (<550 Da). The fractions of biopolymers and low molecular weight neutral substances didn't show humic-like fluorescence, while the fractions of HA-II, FA and building blocks usually had signatures of both humic-like and protein-like fluorescence. Humic substances generally contributed the largest proportion of dissolved organic carbon and nitrogen (DOC & DON) in effluents. Coagulation removed EfOM fractions following the order of biopolymers > HA subfraction > FA subfraction > building blocks, while little removal of protein-like fluorescence in HA-II and FA subfractions was detected. Anion exchange treatment could effectively reduce DOC and DON concentrations; the sequence of the treatment efficiency was humic substances > biopolymers > building blocks. Increasing O3 doses caused DOC and DON of EfOM to be gradually transformed from large AMW fractions into small AMW fractions, while chromophores and fluorophores in HA subfractions were relatively more refractory than those in the other fractions. Size exclusion chromatography with multiple detectors are suggested to be an informative technique for estimating treatability of EfOM by advanced wastewater treatment processes.