Comparison of fish communities using environmental DNA metabarcoding and capture methods in a plateau Erhai Lake,China

Environmental DNA(eDNA)has been used as an important tool for fish diversity analysis,which can greatly solve the problems in traditional survey methodology.However,little work has been done on the actual monitoring accuracy of eDNA.In this study,we analyzed the current status of fish resources in Erhai Lake in Yunnan,SW China,by dividing the lake into three sectors according to habitat differences,and compared the results of eDNA and traditional capture methods to investigate the shortcomings of the current analysis of eDNA results.A total of 27 fish species were detected by eDNA and traditional capture methods,including 20 and 19 fish species,respectively,and additional differences in fish composition between the two methods.The alpha diversity showed higher fish abundance and lower fish diversity by eDNA method compared to the traditional capture method,demonstrating that eDNA was not superior for use in fish diversity analysis.Fish community similarity analysis showed that community differences were generally significant for eDNA(P<0.05).RDA analysis indicated that environmental factors did not significantly affect fish communities monitored by the eDNA method.However,water temperature,aquatic plants,and water depth had significant(P<0.05)effects on fish communities in the traditional capture method,suggesting that eDNA results are insensitive to the effects of environmental factors.Our results illustrate the effectiveness of eDNA in fish identification and the issues in quantification compared to traditional capture methods.Therefore,combining eDNA with traditional methods is a more effective method for analyzing eDNA metabarcoding,following which the protocols of both quantitative methods can be designed to explore the regularity of eDNA quantification.

Characteristics of Nitrogen and Phosphorus Losses in Different Crop Rotation Systems in the North of Erhai Lake Basin

[Objective] Nitrogen and phosphorus losses of surface runoff in various crop rotation systems in the north of Erhai Lake basin were studied with the objective to provide references for risk evaluation of environmental pollution and formulating countermeasures to control the nonpoint source pollution from agriculture.[Method] Water samples collected in four typical crop rotation systems distributed in seven towns（townships） in the north of Erhai Lake basin were investigated,as well as the fertilizer input,to explore the dynamic change of nitrogen and phosphorus content in surface water of farmland and ditch water,and the correlation between fertilizer input and the concentrations of nitrogen and phosphorus in the surface water of farmland and in the ditch water.[Result] The results showed that nitrogen loss in surface water of farmland in different crop rotation systems differed greatly,and the risk of nitrogen loss was 38% lower in broad bean-rice crop rotation than that in garlic-rice crop rotation.The water soluble nitrogen was the primary form of nitrogen loss.The content of water soluble nitrogen was significantly higher in garlic-rice crop rotation than that in the other rotation systems,and the concentrations of nitrogen in the surface water of farmland in different crop rotation systems followed the sequence below：garlic-rice crop rotationryegrass-rice crop rotationbroad bean-rice crop rotationrape-rice crop rotation.The loss of phosphorus in the surface water of farmland was relatively low and phosphorus combined with silt was the primary form for phosphorus loss.There was no significant difference of the loss of various forms of phosphorus in different crop rotation systems.The contents of total nitrogen and total phosphorus in the surface water of farmland were higher than that in ditch water,with increasing rates of total nitrogen and total phosphorus in ditch water of 72% and 82%,respectively.Topdressing was the critical reason for the high concentrations of nitrogen and phosphorus in the surface water,which also caused the increasing load to the ditch water.[Conclusion] Both the nitrogen and phosphorus loss were the highest in garlic-rice crop rotation.Reasonable crop rotation systems should be established based on both the environmental and economic benefits.This study provided references for controlling the nonpoint source pollution of farmland and improving the water quality of Erhai Lake.

Study on the Biological Diversity of Nematode-trapping Fungi in Erhai Lake

[Objective]The research aimed to investigate the biological diversity of nematode-trapping fungi in the sediment of Erhai Lake.[Method]616 pieces of sediments were collected from Erhai Lake.The traditional classification and identification methods were used to isolate,purify and identify.[Result]3 genera and 22 species of nematode-trapping fungi were isolated.Arthrobotrys oligospora,A.musiformis and Dactylella leptospora were the dominant species,and their detection rates were 28.05%,16.04% and 8.92% respectively.By analyzing the diversity of nematode-trapping fungi in four seasons,it was found that the biological diversity was richer in summer,spring and autumn,and the diversity indexes were 2.59,2.47 and 2.34 respectively.The diversity index in winter was 1.48 and was lower.Species forming the adhesive nets were predominant;positive rate was 41.00%.[Conclusion]The rich nematode-trapping fungi resource existed in Erhai Lake,and its biological diversity had the seasonal variation characteristic.The nematode-trapping fungi which formed the viscous net were the dominant species in Erhai Lake.

Sedimentary record of polycyclic aromatic hydrocarbons in Lake Erhai,Southwest China

The temporal distribution of polycyclic aromatic hydrocarbons （PAHs） was investigated in a sediment core from Lake Erhai in Southwest China using gas-chromatography/mass spectrometry （GC/MS） method. The total organic carbon （TOC） normalized total PAHs concentrations （sum of US Environmental Protection Agency proposed 16 priority PAHs） ranged from 31.9 to 269 ixg/g dry weight （dw）, and were characterized by a slowly increasing stage in the deeper sediments and a sharp increasing stage in the upper sediments. The PAHs in the sediments were dominated by low molecular weight （LMW） PAHs, suggesting that the primary source of PAHs was low- and moderate temperature combustion processes. However, both the significant increase in high molecular weight （HMW） PAHs in the upper sediments and the vertical profile of diagnostic ratios pointed out a change in the sources of PAHs from low-temperature combustion to high-temperature combustion. The ecotoxicological assessment based on consensus-based sediment quality guidelines implied that potential adverse biological impacts were possible for benzo（ghi）perylenelene and most LMW PAHs. In addition, the total BaP equivalent quotient of seven carcinogenic polycyclic aromatic hydrocarbons （BaA, CHr, BbF, BkF, BaP, DBA and INP） was 106.1 rig/g, according to the toxic equivalency factors. Although there was no great biological impact associated with the HMW PAils, great attention should be paid to these PAH components based on their rapid increase in the upper sediments.

Seasonal dynamics of crustacean zooplankton community structure in Erhai Lake, a plateau lake, with reference to phytoplankton and environmental factors

The seasonal dynamics of a crustacean zooplankton community in Erhai Lake was investigated from May 2010 to April 2011. In total, 11 species were recorded, including six(6 genera) cladoceran and five(5 genera) copepod species. The crustacean zooplankton densities ranged from 24.3 to 155.4 ind./L. In winter and spring, the large-bodied cladoceran Daphnia galeata dominated the crustacean plankton community. In summer and autumn, when the colonial or filamentous algae dominated the phytoplankton communities, the small-bodied species(e.g. B osmina fatalis, Ceriodaphnia quadrangular, and Mesocyclops leuckarti) replaced the large-bodied ones. One-way ANOVA and redundancy analysis revealed that community structure was dependent upon total nitrogen, total phosphorus, water temperature, transparency, and the biomass of small algae. The variation in both phytoplankton structure and environmental variables were important factors in the seasonal succession of crustacean zooplankton structure in Erhai Lake.

Study on Environmental Risk and Economic Benefits of Rotation Systems in Farmland of Erhai Lake Basin

This study was designed to find out an optimised planting system of reducing non-point （source） pollution by analyzing the reasons and the factors of influence non-point pollution in farmland of Erhai Lake basin. The results showed that incomes, residual nitrogen in soil, and the loss of nitrogen in surface water in rice-garlic system were higher than those in rice-fava bean system. There were positive correlations between the nitrogen loss of farmland, nitrogen inputs, residual nitrogen in soil, and incomes of farmland. Economic benefits and environment benefits are both appropriate, if the area of rice-garlic system would be reduced to 53% and the area of rice-fava bean system increased to 36% of total cropping area in the investigated watershed. Adjustment of planting structure and introduction of reasonable rotation systems is considered an effective measure of controlling agricultural non-point pollution in watersheds of Erhai Lake.

Status and historical changes in the fish community in Erhai Lake

Erhai Lake is the second largest freshwater lake on the Yunnan Plateau, Southwest China. In recent decades, a number of exotic fish species have been introduced into the lake and the fish community has changed considerably. We evaluated the status of the fish community based on surveys with multimesh gillnet, trap net, and benthic fyke-net between May 2009 and April 2012. In addition, we evaluated the change in the community using historical data （1952-2010） describing the fish community and fishery harvest. The current fish community is dominated by small-sized fishes, including Pseudorasbora parva, Rhinogobius giurinus, Micropercops swinhonis, Hemiculter leucisculus, and Rhinogobius cliffordpopei. These accounted for 87.7% of the 22 546 total specimens collected. Omnivorous and carnivorous species dominated the community. A canonical correspondence analysis （CCA） plot revealed that the distribution of fishes in the lake is influenced by aquatic plants, water temperature, pH, and season. The abundance of indigenous species has declined sharply, and a majority of endemic species have been extirpated from the lake （a decrease from seven to two species）. In contrast, the number of exotic species has increased since the 1960s to a total of 22 at present. The fishery harvest decreased initially following the 1960s, but has since increased due to the introduction of non-native fish and stocking of native fish. The fishery harvest was significantly correlated with total nitrogen, not total phosphorus, during the past 20 years. Based on our results, we discuss recommendations for the restoration and conservation of the fish resources in Erhai Lake.

Sediment Particle Size Distribution and Its Environmental Significance in Lake Erhai, Yunnan Province

A closed or semi\|closed plateau lake, whose sediment records can provide us with plenty of fine and high resolution information, is a sensitive indicator of climatic and environmental changes. During the reconstruction of various short\|time\|scale climatic and environmental changes, the geochemical records in plateau\|lake sediments are superior to other natural files. Based on fine dissection of the vertical profile of sediment particle sizes, this paper reveals the quasi\|periodical changes of sediment particle sizes, which indicates the quasi\|periodical fluctuations of the regional climate. A synthetic analysis of multiple indexes shows that sediment particle size is a more sensitive and more effective index of climatic and environmental changes than other geochemical indexes. High content of >20 μm sediment particles and low content of 2-10 μm sediment particles indicate a warm\|dry climate and conversely a cold\|humid climate, and their ratio can be used as an effective index of climatic changes. The basic climate succession in the region of Lake Erhai is characterized as being alternatively warm\|dry and cold\|humid and it has been developing into a warm\|dry climate as a whole. There exist at least 2 time\|scale quasi\|periodical fluctuations of the regional climate in Lake Erhai. At present, the region of Lake Erhai is at the end of the warm\|dry period and at the beginning of a cold\|humid period, so the temperature will go down and the water level will rise.

Factors controlling the latent and sensible heat FLuxes over Erhai Lake under different atmospheric surface layer stability conditions

The stratification of the atmospheric surface layer(ASL)plays an important role in regulating the water vapor and heat exchange across the lake–air interface.Based on one year of data measured by the eddy covariance technique over Erhai Lake in 2015,the ASL stability(ζ)was divided into six ranges,including unstable(-1ζ<-0:1),weakly unstable(-0:1ζ<-0:01),near-neutral1(-0:01ζ<0),near-neutral2(0ζ<0:01),weakly stable(0:01ζ<0:1),and stable(0:1ζ<1).The characteristics of ASL stability conditions and factors controlling the latent(LE)and sensible heat(H)fluxes under different stability conditions were analyzed in this study.The stability conditions of Erhai Lake have noticeably seasonal and diurnal variation,with the nearneutral and(weakly)stable stratification usually occurring before July,with frequencies of 51.7%and 23.3%,respectively,but most of the(weakly)unstable stratification was observed after July,with a frequency of 59.8%.Large evaporation occurred even in stable atmospheric conditions,due to the coupled effects of the relatively larger lake–air vapor pressure difference and wind speed.The relative controls of LE and H by different atmospheric variables are largely dependent on the stability conditions.In stable and unstable ranges,LE is closely correlated with the vapor pressure difference,whereas in weakly unstable to weakly stable ranges,it is primarily controlled by wind speed.H is related to wind speed and the lake–air temperature difference under stable conditions,but shows no obvious relationship under unstable conditions.

RECENT SEDIMENTATION AND SUSPENDED MATTER IN ERHAI LAKE,YUNNAN PROVINCE,CHINA

Ths study on the physico-geograpical environment of Erhai Lake focused on the suspended matter and recent deposition rates, 14 C, 210 Pb and 137 Cs methods were used to determine the ageand sedimentation rate, which was found to be 0.5 t0 2.0 mm/a, average of 0.9 mm/a. The authors calculated the budget of some elements by studying the deposition, and fuUnd that about 30% of nitrogen,and most of the phosphorous, were transported into the lake by the ediments.

Ectoparasite communities on Tupaia belangeri (Scandentia:Tupaiidae) in surrounding areas of Erhai Lake in Yunnan,China

Objective:To investigate the ectoparasite communities on Tupaia belangeri (T. belangeri) in the surrounding areas of Erhai Lake and their potential importance in medical and veterinary science. Methods: Different locations in surrounding areas of Erhai Lake in Yunnan were selected as the investigation spots. T. belangeri were randomly captured with baited mouse cages and then brought to the laboratory for identification according to their body shape, size and color, and measurements such as the lengths of their body, ear and hind feet. Ectoparasites on them were collected and identified to determine the species under microscope after specimens were mounted on slides, with the clearing and drying process completed. The constituent ratio (C), prevalence (P) and average ectoparasite abundance (A) were used to test the prevalence and density of ectoparasites; Non-parametric Mann-Whitney U-tests were used to test the differences in the abundance and richness of ectoparasites between female and male hosts; Spearman correlation analysis was used to analyze the relationship between ectoparasites and the body parameters of hosts. Results: There was very high species diversity of ectoparasites found on T. belangeri and some species of ectoparasites were reported associated with human diseases. A high proportion (88%) of 107 T. belangeri was found to be infested with ectoparasites. A total of 75 species of ectoparasites on them were collected, including 58 species of chigger mite, 12 species of gamasid mite, 4 species of flea and 1 species of sucking louse. Within this ectoparasite complex, 13 species were previously reported to be vectors of human disease agents. Non-parametric Mann-Whitney U-tests showed significant differences between male and female T. belangeri in terms of the abundance and richness of total ectoparasites. However, the species richness and abundance of chigger mites, sucking lice, fleas or gamasid mites presented no significant differences between male and female hosts. Spearman correlation analysis showed that none of correlations were observed between host body parameters with abundance and richness of total ectoparasites, chigger mites, suckinglice, fleas or gamatid mites. Conclusion: The results suggest that there is very high species diversity of ectoparasites on T. belangeri, consisting mainly of communities of sucking lice, fleas, chiggers and gamasid mites.

Temporal changes in wetland plant communities with decades of cumulative water pollution in two plateau lakes in China's Yunnan Province

Abstract： Wetland plant communities in the plateau lakes of Yunnan Province, China, have decreased significantly over the past decades. To better understand this degradation, we analyzed the processes and characteristics of changes in wetland plant communities in two of the largest lakes in Yunnan Province, Dianchi and Erhai lakes. We collected records of native and alien plant communities in the two lakes from literature published from the 195os to current period. We calculated plant community types and their area in some historical periods when related data were reported, and analyzed the relationship between chances in nlant communities and water nollution. InDianehi Lake, 12 community types of native plant communities, covering over 80% of the surface in the 195os and 196os, were reduced to four types covering 2.4% by the late 2ooos. Alien plant communities started to appear in the lake in the late 197os, and have since come to cover 4.9% of the lake surface, thereby becoming dominant. In Erhai Lake, 16 community types of native plant communities, covering 47.1% of the lake surface in the late 197os, declined to lo community types, covering 9.3% of the surface, by the late 2ooos. Alien plant communities appeared in the middle 198os, and at present cover 0.7% of the surface area. It was indicated that changes in plant communities were significant related to water eutrophication. The area occupied by native and alien plant communities was, respectively, negatively andpositively related to the content of nutrients in water. This showed lacustrine pollution played an important role in native plant loss and alien plant invasion in the two plateau lakes.

控制性供水湖泊旱限水位确定方法——以洱海为例

旱限水位作为干旱预警以及工程抗预案的重要指标和依据,对科学指导湖泊开展抗旱调度具有重要的作用。本文针对控制性供水湖泊的特征,在充分考虑湖泊自身生态健康稳定的同时,结合湖泊兴利调节逆序递推计算,提出了一种控制性供水湖泊旱限水位计算方法,以洱海为例,验证了该方法的合理性。结果表明:通过设定旱限水位,在考虑湖泊最小生态需求的基础上,通过在干旱前期预留水量,可有效缓解干旱年份的湖泊周边地区的严重缺水情况;在设置旱限水位后,连旱最不利年份下洱海环湖供水缺水量减少1023万m^(3),引洱入宾农业灌溉用水减少1016万m^(3),环湖城市供水、引洱入宾灌溉严重缺水月数分别减少11、10个,低于最低生态水位月数减少15个。本研究为水旱灾害防御部门制定湖泊旱限水位、指导湖泊开展抗旱调度提供了一套通用算法,能够为干旱防御决策提供科学依据和技术支撑。

南诏国的两个地震神话

南诏国(738—902)有两个地震神话传世:一为观音大士镇伏巨鳌,令其长眠不醒,但允其七十至九十春可醒片时。巨鳌醒时眨眼,仍会地动山摇,以致每七十余年地震一次,每四百年大震一次。因此,在望海台树立地震碑,告诫后人要警惕震害。二为洱海河神段赤诚预报地震:今夜亥时,地将大动,十室九倒。为保民平安,遂与两位山神、河东渔夫分工合作:两山神分别变化为鸡与犬,狂鸣、惊跳,以警醒万民;河东渔夫向洱海东部村民报告,洱海河神变化为老叟向西部村民报告。十有九成的村民离开房舍,避于平坦之地,人畜皆安;不相信预报的百余人,皆遭震害。

高原湖泊典型小流域农田氨挥发与近源沉降特征研究

氨(NH_(3))挥发是农田氮素损失的主要途径,进入大气的NH_(3)会通过干、湿沉降返回地表,成为湖泊外源营养盐输入的重要贡献源。针对近湖的农业生产区,系统定量农田NH_(3)挥发与大气氮沉降对优化农田氮素管理、防治水体面源污染等至关重要。以洱海流域典型近湖的古生片区农田为例,结合农户生产调研数据和大气氮沉降的连续监测数据,估算了2022年主要作物生长季(5-10月)农田NH_(3)挥发和大气NH_(3)及其他主要活性氮(如空气中硝酸、二氧化氮、颗粒态铵态氮和硝态氮;降水中铵态氮和硝态氮)的干、湿沉降通量,阐明农田NH_(3)挥发与NH_(3)干沉降之间的关系,明确大气NH_(3)干沉降在大气氮素总沉降中的贡献及近源的洱海湖区大气氮沉降量。结果表明,2022年主要作物生长季古生片区农田NH_(3)挥发总量为11.3 t,其中玉米生产的贡献最大,为4.7 t(约占挥发总量的41.7%),其次为烤烟和水稻(占比分别为34.0%和24.3%)。同一时期内,近湖监测点的大气无机氮沉降总量(干沉降与湿沉降之和)的月通量范围为0.66-1.57 kg·hm^(-2)(以N计,下同),总计为6.51 kg·hm^(-2)。不同月份大气NH_(3)干沉降量占相应月份大气无机氮沉降总量的42%-70%,说明气态NH_(3)是片区大气氮沉降的主要活性氮组分。此外,主要作物生长季NH_(3)干沉降总量占到农田NH_(3)排放的10.7%。据估算,在研究时期内,大气沉降监测点周边洱海水面的大气无机氮沉降量为35.9 t。这一结果表明大气氮沉降是洱海水体氮素的重要输入源。综上,减少农业NH_(3)排放将是降低大气氮沉降及洱海氮素入湖负荷的重要途径。

2017-2022年洱海水体营养状态的时空变化趋势及其成因分析

洱海是云贵高原重要湖泊,近年来经历了多次污染和治理。2017年以来,洱海全流域开展高水平保护治理,外源污染和水质发生了时空变化。为分析洱海水质的影响因素,于2017-2022年在洱海8个主要湖湾以及北部、中部、南部3个湖心水域进行连续6年的逐月水质监测,重点分析了总氮、总磷和叶绿素a浓度以及透明度4项水质指标,并用综合营养状态指数(TLI)法评价水体的富营养化程度。结果表明,1)洱海水体富营养化程度呈北高南低趋势,与外源污染物主要经由北三江入湖有关。2)2017-2022年,南部水域富营养化程度逐年降低,中部水域氮、磷浓度呈降低趋势,北部水域氮、磷浓度略有升高,表明中部和南部治理成效优于北部。3)洱海富营养化程度在汛期高于非汛期,北部水域富营养化程度的季节变异高于中部和南部水域。4)洱海北片区及汛期污染控制尤其是水体磷控制是洱海治理需要关注的重点问题。

典型挺水植物应用于湿地生态修复工程污染净化效应差异性研究

以洱海流域北部上游东湖片区库塘湿地中水生植物为研究对象,选取5种主要水生植物,寻求净化湿地水质的最佳植物组合。结果表明:东湖片区库塘湿地水体总磷、总氮、氨氮、化学需氧量分别为0.09~0.23、0.80~3.28、0.18~0.89、12.00~37.00 mg/L,总体符合《地表水环境质量标准》(GB 3838—2002)中Ⅳ类要求;综合比较发现,植物组合群落生物量和碳氮磷累积效应优于单一植物;植物组合对水体碳氮磷具有一定的吸收净化作用。

基于水声学和渔获物调查的洱海鱼类资源时空分布特征

为掌握洱海鱼类资源时空动态,研究于2022—2023年采用水声学和渔获物调查方法评估洱海鱼类群落结构及其时空分布,对鱼类群落结构、鱼类时空分布特征与环境因子之间的关系进行了研究和分析。研究共采集鉴定鱼类22种,隶属于4目8科17属,优势种为子陵吻虾虎鱼(Rhinogobius giurinus)。水声学调查结果显示:4个季节鱼类TS值主要集中在–70—–58 dB(全长1.2—5.0 cm),在夏、秋、冬和春季占比分别为88.40%、83.03%、84.53%和82.92%;鱼类在夏、秋、冬和春季4个季度的平均目标强度分别为(–59.08±0.08)、(–54.99±0.15)、(–55.90±0.16)和(–58.07±0.18)dB,鱼类密度分别为夏季(23851.61±889.30)ind./ha、秋季(14185.69±1106.54)ind./ha、冬季(2423.19±179.54)ind./ha和春季(3382.16±440.71)ind./ha。从各季节水平空间特征来看,夏季和春季主要集中在北部区域。在垂直方向上,夏、秋和春季均以2.5—6.5 m水层鱼类的占比较高,占比分别为32.99%、30.65%和62.78%;冬季以14.5—18.5 m水层鱼类占比较高,占比为34.05%;在冬季和春季鱼类在垂直方向上表现出明显的迁徙现象。冗余分析(RDA)结果显示,水温(WT)、氨氮(NH3-N)、透明度(SD)和高锰酸盐指数(CODMn)等水体理化因子对洱海小型鱼类的分布具有明显影响。研究证明了水声学调查与渔获物调查相结合评估鱼类资源时空分布的可行性,研究结果为洱海鱼类资源保护和恢复提供科学依据。

洱海螺蛳(Margarya)历史演替及保护现状研究

螺蛳是中国特有种,曾经是云南高原湖泊的优势种群,由于人类活动、湖泊污染和过度捕捞等原因,目前仅在滇池、洱海、海西海、泸沽湖等湖泊分布。目前有三个属:螺蛳属(Margarya)、玺螺蛳属(Tchangmargarya)和环螺蛳属(Anularya)。文章详细介绍了螺蛳的分类、生活习性、食性、繁殖方式等基本生物特性,深入探讨了螺蛳在洱海的历史演替、增殖放流情况、保护现状及濒危原因,并据此提出了针对性的保育措施,包括建立高原湖泊软体动物人工繁育基地,进行珍稀濒危物种拯救行动计划,以及恢复野外种群,旨在为洱海本土螺蛳恢复提供科学依据,促进螺蛳及其他本土特有珍稀软体动物的保护和恢复。