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.

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.

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.

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.

Carnivals between Cangshan Mountain and Erhai Lake

THE Bai people are China’s 15th largest ethnic minority.They live mainly in Yunnan Province,specifically in Dali Bai Autonomous Prefecture,and some in Guizhou and Hunan provinces.Dali is where the Bai people’s ethnic roots are.From the 23rd to 25th day of the fourth lunar month every year,Bai people in Dali pray for

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.

Eddy covariance measurements of water vapor and CO_2 fluxes above the Erhai Lake

Measurement of turbulence fluxes were performed over the Erhai Lake using eddy covariance(EC) method.Basic physical parameters in the lake-air interaction processes,such as surface albedo of the lake,aerodynamic roughness length,bulk transfer coefficients,etc.,were investigated using the EC data in 2012.The characteristics of turbulence fluxes over the lake including momentum flux,sensible heat flux,latent heat flux,and CO2 flux,and their controlling factors were analyzed.The total annual evaporation of the lake was also estimated based on the artificial neural network(ANN) gap-filling technique.Results showed that the total annual evaporation in 2012 was 1165 ± 15 mm,which was larger than the annual precipitation(818 mm).Local circulation between the lake and the surrounding land was found to be significant throughout the year due to the land-lake breeze or the mountain-valley breeze in this area.The prevailing winds of southeasterly and northwesterly were observed throughout the year.The sensible heat flux over this plateau lake usually had a few tens of W m-2,and generally became negative in the afternoon,indicating that heat was transferred from the lake to the atmosphere.The sensible heat flux was governed by the lake-air temperature difference and had its maximum in the early morning.The diurnal variation of the latent heat flux was controlled by vapor pressure deficit with a peak in the afternoon.The latent heat flux was dominant in the partition of available energy in daytime over this lake.The lake acted as a weak CO2 source to the atmosphere except for the midday of summer.Seasonal variations of surface albedo over the lake were related to the solar elevation angle and opacity of the water.Furthermore,compared with the observation data,the surface albedo estimated by CLM4-LISSS model was underestimated in winter and overestimated in summer.

A comprehensive evaluation method for plateau freshwater lakes:a case in the Erhai Lake

The study first systematically assessed the ecosystem health status of the plateau freshwater lake of Erhai Lake in Yunnan Province of China,using the revised Freshwater Health Indicator methodology,which comprised three components,i.e.,“Ecosystem Vitality,”“Ecosystem Services,”and“Governance and Stakeholders.”To better reflect the real health status of the basin,the cask short board effect was considered during aggregation of the indicators.In addition,analysis of the coupling coordination relationship among the three components was conducted to study the mutual influences among them as well as the comprehensive development level of the studied area.Basically,the ecosystem of the Erhai Lake basin remained healthy during the studied period according to the research due to specific measures and actions taken to manage the environmental problems caused by a former local economic development and urbanization process.However,there were still aspects to improve for more sustainable ecosystem management and utilization in the basin.The“short boards”of the Erhai Lake basin show room for improvement in local freshwater ecosystem management and underline governance problems that need to be addressed.Suggestions are provided for the local stakeholders consequently for the more sustainable development of the studied basin.

Environmental evolution and southwest monsoon changes in mid-Holocene recorded by lake sediments in Erhai Lake

IN recent years, much progress has been made in the research of the temporal and spatial changes of East Asian monsoon. To research the environmental evolution and monsoon variations in Holocene in the region of Southwest China, a 310-cm continuous lake sediments core in Erhai Lake, Yunnan Province was sampled with Livingston sampler on July 6, 1996. The lake sediments were separated at 2-cm intervals and the core samples were analyzed with chronology, stable isotope ratios of organic carbon and diatoms determination. Three 14C ages are （4 473±40）a B.P. （98—102 cm）, （5 825±85） a B. P. （144—148 cm） and （7 754±45） a B.P. （198—202 cm）. By 137Cs dating, the sedimentation rate is about 0.3 mm/a and this result is close to the 14C dating results. The average sedimentation rates

Geochemical records of carbon in recent sediments of Erhai Lake, China: Implication of effects of the Himalayas uplift on global environmental changes

THE formation and uplift of the Himalayas and the Tibetan Plateau may have been responsible for the past150 Ma global environmental changes, resulting in the development of a three-tiered landform in southernChina. The Yunnan-Guizhou Plateau, as the middle tier in eastern slope of the Himalayas, has beencomplex environmental unit with great altitude gradients and plateau landform characters. Both monsoonsfrom the Pacific and the Indian resulting in apparent environmental changes on variable time scales influence it. Environmental geochemical effect of low latitude-high altitude could be yielded, and well recorded in the geological bodies in this region. To build and verify a quantitative model of environmental evolution it is necessary to obtain high-resolution data of elemental cycles and mass equilibrium.

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.

Climatic variations recorded by the sediments from Erhai Lake,Yunnan Province,southwest China during the past 8000 a

Erhai Lake is a large lake with important climatic significance in Yunnan Province, southwest China. The multi-proxy sedimentary records from Erhai Lake indicate the 9 stages of climatic changes with the alternation of warm-dry and cool-wet during the past 8000 a. The variations of Asian monsoon systems were the main cause for the climatic changes in southwest China. The warm-dry period was coincident with the intensification of India monsoon and Northwest Pacific Sub-tropical High Pressure, and the cool-wet corresponding to weak of India monsoon and its main rain belt moving back to southwest China.

High resolution environmental records in recent sediments of Erhai Lake, Yunnan Province

IN the past half a century, the global paleoclimate has been successfully reconstructed by natural recordssuch as ice core, loess and deep-sea sediments. However, these works mostly focused on long-timescale climatic changes. Along with the appearance of modern environmental problems including globalwarming, people are increasingly concerned about short-term climatic variations (annual to century scale)within the historical period. Therefore, it is an urgent and significant task for scientists to obtain continuous and high resolution natural records so as to reconstruct recent climatic changes truly and predict theclimate in the near future. As a main lodging of surface substances, the plateau-lake sediment continuously records the information of regional climate and environment with annual to decade resolution. Undoubtedly it is one

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。