Analysis of Occurrence and Mixed Infection of Sugarcane Bacilliform Virus Disease in Hainan Sugarcane-growing Area

[Objectives]The paper was to explore the occurrence and mixed infection of sugarcane bacilliform virus disease in Hainan sugarcane-growing area.[Methods]A total of 348 sugarcane leaf samples were collected from 7 sugarcane-growing areas in Hainan Province.Molecular detection of sugarcane bacilliform virus(SCBV)was carried out by PCR using specific primers.[Results]SCBV was detected in 244 out of 348 sugarcane samples,with an average detection rate of 70.11%.The highest detection rate was 76.66%in the Danzhou sugarcane-growing area,while the lowest was 57.14%in the Baisha sugarcane-growing area.The SCBV-positive samples were subjected to testing for SCYLV,SCSMV,SrMV,and SCMV,respectively.The results indicated that 106 out of 244 positive samples exhibited a single infection with SCBV,while 138 samples exhibited mixed infections with SCBV and other sugarcane viruses.The proportion of mixed infections among the SCBV-positive samples was as high as 56.56%.Among the various types of mixed infections,two-virus and three-virus mixed infections were the most prevalent.[Conclusions]SCBV has emerged as a significant threat to the secure production of sugarcane in the Hainan sugarcane-growing region.It presents an explosive infection in the Hainan sugarcane-growing region and frequently combines with other sugarcane viruses to infect sugarcane.The findings of this study will provide a theoretical foundation for the prevention and control of sugarcane bacilliform virus disease.

甲型流感病毒宿主适应的分子基础及其相关宿主因子的研究进展

甲型流感病毒宿主广泛,传染性强,可引起人畜共患病,严重威胁人类健康和公共卫生安全。甲型流感病毒可以通过基因突变和基因重配等机制不断变异,如果新毒株打破宿主限制获得在人类传播的能力,有可能造成流感大流行。理解流感病毒突破种间屏障的遗传学基础和分子机制,是科学界亟待解决的问题,对有效监控和预防潜在流感大爆发的具有重要的提示作用。本文对目前研究流感病毒宿主适应的分子决定因素展开了综述,着重介绍了病毒本身的遗传变异以及和病毒相互作用的宿主因子的作用,以便为应对下次流感大流行做好理论储备,为抵抗流感寻找新策略。

Analysis of the mechanism of aldo-keto reductase dependent cis-platin resistance in HepG2 cells based on transcriptomic and NADH metabolic state

Background:Aldo-keto oxidoreductase(AKR)inhibitors could reverse the resistance of several cancer cells to cis-platin,but their role in resistance remains unclear.Methods:We verified the difference of AKR1Cs expression by Western blot,RNA sequencing and qRT-PCR.The differences of AKR1Cs expression were analyzed and inferred.Use Assay of NADH and NAD^(+)content to verify the inference.The Docking experience was used to verify the affinity between MPA,MCFLA,MLS and AKR1C3.Results:Our RNA-seq results showed de novo NAD biosynthesis-related genes and NAD(P)H-dependent oxidoreductases were significantly upregulated in cis-platin-resistant HepG2 hepatic cancer cells(HepG2-RC cells)compared with HepG2 cells.At least 63 NAD(P)H-dependent reductase/oxidases were upregulated in HepG2-RC cells at least twofold.Knockdown of AKR1Cs could increase cis-platin sensitivity in HepG2-RC cells about two-fold.Interestingly,the AKR1C inhibitor meclofenamic acid could increase the cis-platin sensitivity of HepG2-RC cells about eight-fold,indicating that the knockdown of AKR1Cs only partially reversed the resistance.Meanwhile,the amount of total NAD and the ratio of NADH/NAD^(+)were increased in HepG2-RC cells compared with HepG2 cells.The ratio of NADH/NAD^(+)in HepG2-RC cells was almost seven-fold higher than in HepG2 or HL-7702 cells.Increased NADH expression could be explained as a directly operating antioxidant to scavenge cis-platin-induced radicals.Conclusion:We report here that NADH,which is produced by NAD(P)Hdependent oxidoreductases,plays a key role in the AKR-associated cis-platin resistance of HepG2 hepatic cancer cells.

新辅助放化疗后直肠癌术后肺转移的多学科诊疗模式决策及结果评价

目的:了解多学科协作(multidisciplinary team,MDT)模式下直肠癌术后肺转移治疗决策现状和结局,为加强医疗质量管理、完善MDT模式提供依据。方法:回顾性收集2007年7月至2015年2月北京大学肿瘤医院680例接受术前新辅助治疗联合根治术的直肠癌患者临床资料,调查术后发生肺转移的患者在MDT模式下的治疗决策、执行情况和生存结局。结果:研究纳入85例术后肺转移患者,68例采用MDT模式治疗,其中28例建议行局部根治,40例建议行姑息治疗;决策总执行率为89.7%(61/68),未执行者均选择进一步保守治疗。局部根治的患者在直肠原发灶术后首次发生复发/转移后的3年复发/转移后生存率(survival after recurrence,SAR)高于姑息治疗患者(84.8%vs.37.6%,P<0.001)。结论:在MDT模式运行良好的情况下,直肠癌根治术后肺转移的治疗决策执行率较高,部分患者在该模式下有机会获得根治且预后良好;引入“患者参与”和“社会支持”将有助于构建全新MDT模式和提高医疗质量管理水平。

Ce/TiO2纳米抑菌剂的制备合成及其抑杀南丰蜜桔致病菌的保鲜应用

本项研究采用溶胶-凝胶法合成一种新型的南丰蜜桔纳米抑菌剂,并将其涂膜覆盖采摘后的南丰蜜桔果实表面,进行保鲜贮藏实验。研究表明,此类抑菌剂能高效抑杀南丰蜜桔果实致病菌,并充分保证其营养品质。

Anlotinib has good efficacy and low toxicity: a phase Ⅱ study of anlotinib in pre-treated HER-2 negative metastatic breast cancer

Objective:Anlotinib is a novel tyrosine kinase inhibitor blocking angiogenesis.This study was performed to assess the efficacy and safety of anlotinib in patients with metastatic breast cancer.Methods:Patients with HER2-negative breast cancer,who were pre-treated with anthracycline or taxanes in a neoadjuvant,adjuvant,or metastatic setting,and had treatment failure after at least one prior chemotherapy regimen in the metastatic setting were enrolled.Anlotinib was administered at 12 mg daily for 14 days in a 21-day cycle until disease progression or unacceptable toxicity occurred.Simultaneously,5–10 m L of venous blood was collected to perform circulating tumor DNA(ct DNA)testing every 2 treatment cycles.The primary endpoint was the objective response rate(ORR).Secondary endpoints included the disease control rate(DCR),progression-free survival(PFS),overall survival,safety,and biomarkers.Results:Twenty-six eligible patients were enrolled,with a median age of 56(30–75)years.The median follow-up time was 10.5 months.The ORR was 15.4%,the DCR was 80.8%,and the median PFS was 5.22 months(95%confidence interval 2.86–6.24).Fourteen(53.8%)patients survived for more than 10 months.The changes in the detectable ct DNA variant allele frequency were consistent with the tumor response.The most common treatment-related adverse events were hypertension(57.7%),thyroidstimulating hormone elevation(34.6%),and hand-foot syndrome(23.1%).Conclusion:Anlotinib showed objective efficacy with tolerable toxicity in heavily pre-treated,metastatic HER2-negative breast cancer.The dynamic changes in the ct DNA variant allele fraction may be predictive of the tumor response.

Population-based cancer incidence analysis in Beijing, 2008-2012

Objective： To analyze the incidence of cancer during 2008-2012 in Beijing, China, and compare the cancer spectrum with that during 1998-1999. Methods： Data from the Beijing Cancer Registry （BCR）, which covered 12 million residents and 16 administrative regions in Beijing, were checked and evaluated on basis of the criteria of data quality from the National Central Cancer Registry （NCCR） of China. Incidences were calculated stratified by cancer type, sex, areas （urban/rural）, and age. The Chinese census population in 1982 and the world Segi＇s population were used for calculating the age-standardized incidences. Results： A total of 177,101 new cancer cases were diagnosed in Beijing between 2008 and 2012. The crude incidence rate （CR） of all cancers was 282.64/100,000 （290.71/100,000 in males and 274.45/100,000 in females）. The age-standardized rates by Chinese standard population （ASR-China） and by world standard population （ASR-world） were 124.46/100,000 and 161.18/100,000, respectivel）a Female breast cancer was the most common cancer, followed by lung cancer, colorectal cancer, liver cancer, and stomach cancer, with the CR of 59.87/100,000, 59.21/100,000, 32.49/100,000, 19.81/100,000 and 17.96/100,000, respectively. In urban areas, female breast cancer （68.50/100,000） was still the most common cancer, followed by lung cancer （61.23/100,000）, colorectal cancer （37.23/100,000）, prostate cancer （20.49/100,000） and stomach cancer （20.07/100,000）. In rural areas, lung cancer （55.94/100,000） was the most common cancer, followed by female breast cancer （45.87/100,000）, colorectal cancer （24.77/100,000）, liver cancer （20.68/100,000） and stomach cancer （14.52/100,000）. Great changes of the cancer spectrum were found from the period of 1998-1999 to the period of2011-2012 in Beijing. Conclusions： The cancer burden in Beijing was heavier than the national average level. Cancer prevention and control strategies, especially for lung, colorectal, prostate and female thyroid cancers, should be enhanced.

Characteristics and trends in incidence of childhood cancer in Beijing,China,2000-2009

Objective： To investigate the characteristics and incidence trends of childhood cancer in Beijing, China, from 2000 to 2009. Methods： A total of 1,274 cases with childhood cancer in Beijing from 2000 to 2009 were included in the study. All rates were age-standardized using the direct method to the world standard population and expressed per million person-years. Incidence trends were characterized by calculating annual percent change （APC） usingJoinpoint Regression Program. Results： The crude incidence rate was 106.47 per million [age-standardized rate （ASR） 113.34] between 2000 and 2009 in Beijing with the most common diagnoses, leukemia （N=505, 39.64%, ASR 45.20）, followed by central nervous system （CNS） tumors （N=228, 17.90%, ASR 19.28） and lyrnphoma （N=91, 7.14%, ASR 6.97）. The incidence for all childhood cancers combined has increased during the study period, with an APC of 5.84% [95% confidence interval （95% CI）： 1.0-10.9] after adjusted by world population. The ASR of all combined cancers in boys showed a slight, but no significant increase, with an APC of 5.33 % （95 % CI： -0.6- 11.6）; for girls, the trends increased significantly, with an APC of 6.54% （95% CI： 1.5-11.8）. Conclusions： The incidence rate of childhood cancer in Beijing was higher than the average level of China and lower than that of western countries. The incidence trends of childhood cancer, especially leukemia among girls showed a significantly increase from 2000 to 2009. While among boys, no substantially change was seen during the observed time period. Some sex-specific trends by subcategories and trends of major cancers in different age groups by cancer site merit further investigation.

Interference Coordination for FD-MIMO Cellular Network with D2D Communications Underlaying

In this paper, we investigate the interference coordination for downlink full-dimension multiple-input multiple-output(FD-MIMO) systems with device-to-device(D2 D) communications underlaying. With three-dimensional(3 D) beamforming transmission applied for cellular users(CUEs), an approximation of the interference to signal ratio for CUEs is derived, and a coordination strategy is proposed to mitigate the interference from D2 D pairs to CUEs. Based on the lower bound of the interference to signal ratio for D2 D pairs, we propose coordination strategies for D2 D pairs to mitigate the interference caused by base station(BS) and the interference between D2 D pairs. The proposed strategies require only some statistical channel state information(CSI) of each user and the reduced-dimensional effective CSI of a few CUEs and D2 D pairs. Simulation results show that the proposed coordination strategy performs well in terms of achieving good tradeoff between the achievable rate of CUEs and D2 D pairs.

Transcriptome exploration to provide a resource for the study of Auricularia heimuer

Auricularia heimuer,an edible jelly fungus,is in considerable demand in Asia due to its high nutritive,economic and medicinal values.RNA-Seq was used to investigate and analyze the mycelium transcriptome of A.heimuer for gene discovery.A total of 26,857 unigenes with an N50 length of 1333 bp were assembled by de novo sequencing.In addition,unigenes were annotated by publicly available databases,including gene descriptions,gene ontology(GO),clusters of orthologous group(COG),Kyoto Encyclopedia of Genes and Genomes(KEGG)metabolic pathways,and protein family(Pfam)terms.A.heimuer was also studied for its wood degradation ability.Thirty-eight putative FOLymes(fungal oxidative lignin enzymes)and 251 CAZymes(carbohydrate-active enzymes)were located from A.heimuer transcriptome.Our study provides a comprehensive sequence resource for A.heimuer at the transcriptional level,which will lay a strong foundation for functional genomics studies and gene discovery of this promising fungus.

Activation of calcium-sensing receptors is associated with apoptosis in a model of simulated cardiomyocytes ischemia/reperfusion

Objective： Calcium-sensing receptors （CaSRs） are G-protein coupled receptors which maintain systemic calcium homeostasis and participate in hormone secretion, activation of ion channels, cell apoptosis, proliferation, and differentiation. Previous studies have shown that CaSRs induce apoptosis in isolated adult rat heart and in normal neonatal rat cardiomyocytes by G-protein-PLC-IP3 signaling transduction. However, little knowledge is presently available concerning the role of CaSRs in the apoptosis induced by ischemia and reperfusion in neonatal cardiomyocytes. Methods： Primary neonatal rat ventricular cardiomyocytes were incubated in ischemiamimetic solution for 2 h, and then re-incubated in normal culture medium for 24 h to establish a model of simu- lated ischemia/reperfusion （I/R）. Cardiomyocyte apoptosis was detected by terminal deoxynucleotidyl transferase- mediated dUTP nick end labeling （TUNEL）. The expression of CaSRs mRNA was detected by real-time reverse transcription polymerase chain reaction （RT-PCR）. In addition, the expressions of caspase-3 and Bcl-2 were analyzed by western blot. Results： The simulated I/R enhanced the expression of CaSRs and cardiomyocyte apoptosis. GdCl3, a specific activator of CaSRs, further increased the expression of CaSRs and cardiomyocyte apoptosis, along with up-regulation of caspase-3 and down-regulation of Bcl-2. Conclusion： CaSRs are associated with UR injury and apoptosis in neonatal rat ventricular cardiomyocytes via suppressing Bcl-2 and promoting caspase-3 expression.

Predictors of pathologic complete response in patients with residual flat mucosal lesions after neoadjuvant chemoradiotherapy for locally advanced rectal cancer

Objective:The accurate prediction of tumor response to neoadjuvant chemoradiotherapy(nCRT)remains challenging.Few studies have investigated pathologic complete response(ypCR)prediction in patients with residual flat mucosal lesions after treatment.This study aimed to identify variables for predicting ypCR in patients with residual flat mucosal lesions after nCRT for locally advanced rectal cancer(LARC).Methods:Data of patients with residual flat mucosal lesions after nCRT who underwent radical resection between 2009 and 2015 were retrospectively collected from the LARC database at Peking University Cancer Hospital.Univariate and multivariate analyses of the association between clinicopathological factors and ypCR were performed,and a nomogram was constructed by incorporating the significant predictors.Results:Of the 246 patients with residual flat mucosal lesions included in the final analysis,56(22.8%)had ypCR.Univariate and multivariate analyses showed that pretreatment cT stage(pre-cT)≤T2(P=0.016),magnetic resonance tumor regression grade(MR-TRG)1-3(P=0.001)and residual mucosal lesion depth=0 mm(P<0.001)were associated with a higher rate of ypCR.A nomogram was developed with a concordance index(C-index)of0.759 and the calibration curve showed that the nomogram model had good predictive consistency.The follow-up time ranged from 3.0 to 113.3 months,with a median follow-up time of 63.77 months.The multivariate Cox regression model showed that the four variables in the nomogram model were not risk factors for disease-free survival(DFS)or overall survival(OS).Conclusions:Completely flat mucosa,early cT stage and good MR-TRG were predictive factors for ypCR instead of DFS or OS in patients with LARC with residual flat mucosal lesions after nCRT.Endoscopic mucosal re-evaluation before surgery is important,as it may contribute to decision-making and facilitate nonoperative management or organ preservation.

Molecular identifi cation and population diff erentiation of Aurelia spp.ephyrae in sea cucumber aquaculture ponds of northern China

Aurelia spp.ephyrae have been reported to form blooms in sea cucumber aquaculture ponds in the Bohai and Yellow Seas.To identify the species,we carried out a genetic analysis of Aurelia spp.ephyrae and medusae based on mitochondrial 16 S rRNA gene.Samples offour Aurelia sp.ephyrae populations were collected in sea cucumber aquaculture ponds and samples offour Aurelia sp.medusae populations were collected in coastal waters.Using a BLASTn search,we found that both the ephyrae collected in the aquaculture ponds and medusae collected in coastal waters belong to Aurelia coerulea.Seventeen haplotypes were recovered from the 16 S rRNA gene.The overall haplotype diversity and nucleotide diversity of the 166 A.coerulea individuals were 0.686%and 0.329%,respectively,indicating high haplotype diversity and low nucleotide diversity.Moreover,the haplotype diversity of ephyrae populations were generally lower than that of medusae populations with close sampling points.The genetic differentiation between ephyrae populations collected in the sea cucumber aquaculture ponds and A.coerulea medusae collected in coastal waters was not significant,suggesting the ephyrae populations in the sea cucumber culture ponds were part of the same genetic group as the medusae populations in the coastal waters.Phylogeographic analysis of the 16 S rRNA region revealed that there was no significant correlation between the haplotypes and the geographic distribution of populations.Pairwise fixation index values showed significant genetic differentiation and limited gene flow between A.coerulea population of Weifang and other locations.

Application of DNA metabarcoding to characterize the diet of the moon jellyfish Aurelia coerulea polyps and ephyrae

Dietary studies of polyps and ephyrae are important to understand the formation and magnitude of jellyfish blooms and provide important insights into the marine food web.However,the diet of polyps and ephyrae in situ is largely unknown.Here,prey species of the polyps and ephyrae of the moon jellyfish Aurelia coerulea in situ were identified using high-throughput DNA sequencing techniques.The results show that A.coerulea polyps and ephyrae consume a variety of prey items.The polyps consume both planktonic and benthic prey,including hydromedusae,copepods,ciliates,polychaetes,stauromedusae,and phytoplankton.A.coerulea ephyrae mainly feed on copepods and hydromedusae.Gelatinous zooplankton,including Rathkea octopunctata and Sarsia tubulosa,were frequently found as part of the diet of A.coerulea polyps and ephyrae.The utilization of highthroughput sequencing technique is a useful tool for studying the diet of polyps and ephyrae in the field,complementing the traditional techniques towards a better understanding of the complex role of gelatinous animals in marine ecosystems.

Bacterial communities associated with hydromedusa Gonionemus vertens in diff erent regions in Chinese coastal waters

Bacteria communities in cnidarian jellyfi sh can be harmful to many important aquaculture species,as they can be key vectors of bacterial pathogens.However,our knowledge of bacterial communities associated with jellyfi sh in culture ponds and their potential roles in the regulation of aquaculture species remains unclear.In this study,sequencing based on the bacterial 16S rRNA gene was used to investigate the composition and variation of the bacterial communities associated with hydromedusa Gonionemus vertens in sea cucumber culture ponds and natural marine environment.The associated bacterial communities of G.vertens from the culture ponds in the Yellow Sea and Bohai Sea had signifi cantly diff erent compositions,when compared with those from ambient seawater environment.Furthermore,bacterial communities associated with G.vertens had similar diversity and composition in culture ponds and natural marine environment in the Yellow Sea.There were 31 unique bacterial biomarkers identifi ed in three locations.The major communities were highly abundant in Kiloniellales,Octadecabacter,Polynucleobacter,and Polaribacter,and are related to the environmental information processing.Pathogen candidates such as Vibrionales and Chlamydiales had notably low relative abundances(<1%).The venom of the jellyfi sh was considered responsible for damage to the aquaculture.This study provides important data to help assess the impact of cnidarians-associated bacterial communities on pond aquaculture and the infl uences on material cycling and energy fl ow in marine ecosystems.

On the Application of Context Teaching in Teaching Chinese as a Foreign Language

Chinese culture is broad,profound and rich in connotation.Often a word,word,sentence in different chapters will have different meanings,which is undoubtedly a major difficulty for students learning Chinese as a second language.With the continuous development of context theory,the important position of context teaching method in the teaching process has gradually emerged.Therefore,this paper will combine the actual situation of TCFL classroom,analyze and research the application strategy of context teaching in TCFL classroom.

高效光催化二氧化碳还原钻单原子催化剂的多尺度结构工程

人工光合作用将二氧化碳转化为增值化学品和燃料,在克服全球环境能源危机方面具有巨大潜力.然而,由于CO_(2)的热力学稳定性和动力学滞后性,开发高效的CO_(2)RR光催化剂是一个巨大的挑战.本文在微介孔氮掺杂碳(0.8-Co-ISAS/MMNC-900)上制备了一种具有高度分散Co单原子位的分级多孔钴单原子光催化剂,该催化剂显著促进了CO_(2)-to-CO的光还原.0.8-Co-ISAS/MMNC-900催化剂的CO生成速率高达7261μmol g^(-1)h^(-1),CO选择性高达90.1%,并且在四次循环测试中表现出良好的稳定性.实验数据和理论结果表明,分层多孔结构可以促进电荷分离引起的外部局部电场的形成,Co隔离的单原子位和微介孔构型协同作用,促进光激发电子积累、CO_(2)吸附活化和*COOH中间体的形成.本研究通过多尺度多孔结构工程,提出了一种合成CO_(2)还原光催化剂的新策略.

植物NIP水通道蛋白的结构、功能和调控研究进展

类NOD26膜内在蛋白(nodulin 26-like intrinsic proteins,NIPs)又名根瘤素26-like内在蛋白、类根瘤菌26膜内在蛋白、类Nodulin26内在蛋白,是水通道蛋白(aquaporin protein,AQP)家族的亚家族之一.NIP由AqpN基因进化而来,广泛存在于植物体中,其对底物选择具有特异性,根据选择性过滤器(aromatic/arginine,ar/R区)的不同分为3个亚族.NIPs参与水分、尿素、甘油、硼、砷、硅等物质的吸收和转运,在维持植物生长过程中的水分平衡和渗透压及抵御逆境胁迫等方面发挥重要作用.近年来,有关NIPs对植物生长发育和逆境调控功能的研究越来越多.本文系统阐述了植物NIP家族的起源与进化、结构与分类、生物学功能及调控机制,并对目前NIP研究中存在的问题和未来的研究方向进行了讨论,为深入探究NIP家族在不同植物中的作用模式和遗传改良应用提供参考资料.

泌尿生殖系统超声对胎儿先天性泌尿生殖系统异常的临床应用价值

目的探讨泌尿生殖系统超声在胎儿先天性泌尿生殖系统异常(CAKUT)中的临床应用价值,并分析其指导产前遗传学诊断的临床意义。方法回顾性收集2016年1月至2020年12月在南京医科大学附属淮安第一医院进行产前系统筛查发现的125例CAKUT胎儿病例。根据是否合并其他结构异常分为孤立性CAKUT组与非孤立性CAKUT组。对CAKUT胎儿进行定期随访,对遗传学结果及妊娠结局进行分析。采用χ2检验比较孤立性CAKUT组与非孤立性CAKUT组妊娠结局和遗传学结果的差异。结果胎儿泌尿生殖系统超声随访中发现17例肾盂扩张的病例分别于晚孕期及产后6个月内自愈;41例病例异常持续存在,但未出现临床症状,生长发育均良好;2例误诊;1例漏诊;4例病情加重于出生后1年内死亡,2例肾盂扩张(包括漏诊的1例)随访至出生6个月,具有手术指征,行手术治疗;48例行泌尿生殖系统超声检查再次确诊后家属选择终止妊娠,11例失访。68例样本行产前遗传学检查,染色体微阵列分析(CMA)发现11例(11/68,16.2%)遗传学结果异常,包括:4例染色体非整倍体异常,8例基因组拷贝数变异(其中1例同时存在染色体非整倍体异常和基因组拷贝数变异);其中非孤立性CAKUT组(25.0%,3/12)遗传学结果异常检出率高于孤立性CAKUT组(14.3%,8/56),但差异无统计学意义(χ2=0.837,P=0.360);另外10例CMA检查未见异常的胎儿样本行全外显子测序,检出1例表型为巨膀胱胎儿携带遗传自母亲的AQP2基因杂合变异,致病位点为c.559C>T(p.Arg187Cys),判定为致病性。结论泌尿生殖系统超声检查作为胎儿产前系统结构筛查超声的补充,有利于提高CAKUT诊断精准率,减少漏、误诊率,进一步指导产前诊断及胎儿远期预后评估。

Changes of DOM and its correlation with internal nutrient release during cyanobacterial growth and decline in Lake Chaohu, China

The seasonal changes in dissolved organic matter(DOM),and its correlation with the release of internal nutrients during the annual cycle of cyanobacteria in the eutrophic Lake Chaohu,China,were investigated from four sampling periods between November 2020 and July 2021.The DOM fluorescence components were identified as protein-like C1,microbial humic-like C2,and terrestrial humic-like C3.The highest total fluorescence intensity(FT)of DOM in sediments during the incubation stage is due to the decomposition and degradation of cyanobacteria remains.The lowest humification of DOM and the highest proportion of C1 in waters during the initial cyanobacterial growth indicate that fresh algae are the main source.The highest molecular weight of DOM and FT of the C2 in sediments during cyanobacterial outbreaks indicate the concurrent deposition of undegraded cyanobacterial remains and microbial degradation.The components of DOM are affected mainly by the dissolved total phosphorus in waters,while the temperature drives the annual cycle of cyanobacteria.The decreasing C1 in sediments and increasing nutrients in waters from the cyanobacterial incubation to outbreak indicate that mineralization of algal organic matter contributes importantly to the release of internal nutrients,with the strongest release of phosphorus observed during the early growth of cyanobacteria.The humic-like C2 and C3 components could also affect the dynamics of internal phosphorus through the formation of organic colloids and organic–inorganic ligands.The results show that the degradation of DOM leads to nutrients release and thus supports the continuous growth of cyanobacteria in eutrophic Lake Chaohu.