Lake regime shift from submerged macrophyte to phytoplankton affected phosphorus speciation in sediment and eutrophic state in Caohai Lake,Guizhou,China

To understand the effect of regime shift in Caohai Lake in Yunnan-Guizhou Plateau,SW China from submerged macrophyte dominance to phytoplankton dominance on the specification and distribution of phosphorus and on ecological and environmental states,changes in phosphorus specification in the sediments and water were studied.The form,composition,and distribution of phosphorus in sediment were sampled in July 2020(before regime shift)and July 2021(after regime shift)were analyzed.Results reveal that phosphorus content in sediment was lower than that those of Erhai Lake and Dianchi Lake,Yunnan,SW China,on the same plateau,and was lower than those of Taihu Lake,Chaohu Lake,and Poyang Lake in the middle-lower Changjiang(Yangtze)River Plain.Organic phosphorus(Or-P)was the main form(up to 60%),followed by inactive phosphorus(Ina-P),and the active phosphorus(Act-P),the least,which is opposite to those of Taihu Lake and Poyang Lake in the middle-lower Changjiang River Plain in the eastern China.Or-P content was high,indicating a high potential risk of phosphorous release.After the regime shift,the total phosphorus in sediment decreased from 0.87±0.13 to 0.70±0.13 g/kg.The proportion of Or-P and Act-P decreased from 68.23% to 65.32% and from 5.35% to 4.69%,respectively.In contrast,the proportion of Ina-P increased from 26.42% to 29.99%.The Moran’s I index revealed that the heterogeneity of the spatial distributions of the total phosphorus(S-TP)and Act-P in the sediments before regime shift was significant(P<0.1).However,the heterogeneity of the spatial distributions of S-TP and the various forms of phosphorus after regime shift was not significant(P>0.05).The regime shift aggravated the eutrophication of the lake,the trophic level index(TLI)increased from 48.42 to 54.49(P<0.01),and the previously mesotrophic lake became a mildly eutrophic lake.The results of this study revealed the impact of regime shift in the lake from submerged macrophyte dominance to phytoplankton dominance on the composition and spatial distribution of phosphorus in sediments and provided a basis for the restoration of eutrophicated and aquatic ecosystem degraded lakes.

Study on Water Conservation Capacity of Litter from Different Types of Forest in Caohai Basin

[Objective]The research aimed to understand water conservation capacity of litter from different forest types in Caohai basin. [Method] Current storage amount,water holding capacity and precipitation interception ability of litter from 4 types of forest were investigated and studied. [Result]The order of exist litter amount was grass slope ＆gt;shrub forest ＆gt;mixed broad leaf-conifer forest ＆gt;coniferous forest. The order of natural water holding capacity was mixed broad leafconifer forest ＆gt; coniferous forest ＆gt; grass slope ＆gt; shrub forest. The relevance between water holding capacity of litter and soaking time was in line with this formula： y = kln（ x） ＋ b. During 0-120 min of litter soaking,water holding capacity increased rapidly. After 120 min,the increasing trend remained flat until closing to the maximum water holding capacity. The relevance between water absorption rate of litter and soaking time was in line with this formula： y = a ＋ bx-1. In the beginning of soaking,water absorption rates of litter from different woodlands showed great difference. As soaking time went by,water absorption rates of litter from different woodlands all declined sharply. During 0-120 min,declining velocity of water absorption rate was quicker. After 120 min,the declining trend tended to be slow. The maximum water holding capacity of litter presented the order of shrub forest ＆gt; mixed broad leafconifer forest ＆gt; grass slope ＆gt; coniferous forest. The maximum precipitation interception amount of litter presented the order of shrub forest ＆gt; grass slope ＆gt; mixed broad leafconifer forest ＆gt; coniferous forest. Effective impounding capacity of litter presented the order of shrub forest ＆gt; mixed broad leafconifer forest ＆gt; grass slope ＆gt; coniferous forest. [Conclusion]The research could provide support for the construction of water conservation forest in Caohai basin.

Foraging habitat selection of overwintering Black-necked Cranes in the farming area surrounding the Caohai Wetland, Guizhou Province, China

Background: Understanding how overwintering birds choose foraging habitats is very important for conservation management. The overwintering Black-necked Crane(Grus nigricollis) feeds on crop remains in farmlands;thus, reasonable conservation management of this type of farmland that surrounds wetlands is critical for the overwintering populations of the Black-necked Crane;however, it is not clear how the Black-necked Crane chooses the foraging land in the farmland.Methods: A thorough field positioning survey of all foraging sites in farmland areas around the Caohai Wetland and a-sampling analysis of habitat selection by the Black-necked Crane were conducted during the winters from 20162017 and 2017-2018.Results: Multiple factors contributed to the selection of foraging habitat in farmlands, i.e., food factors(crop remains and tillage methods) > human disturbance factors(distance to road and settlement) > topography factors(slope aspect), listed according to the strength of influence. Additionally, Black-necked Cranes tend to choose farmland sites where there was no machine tillage, the crop remains were > 500 g/m^2, the distance to residences ranged from 100 to 500 m, the distance to roads ranged from 50 to 100 m, and the slopes exhibited western or eastern aspects. As the winters progressed, the volume of the edible crop remains declined, and the influences of the other main factors also changed, i.e., the factors of human disturbance(distance to road and settlement) became less important, while the effect of the food factor(crop remains) was strengthened. Thus, the foraging sites near the road became more important.Conclusion: The farming area surrounding the Caohai Wetland is very important for the overwintering Black-necked Crane. Food factors and human disturbance factors are the main factors that influence the choice of feeding ground.

Primary Establishment of EWE Model in Caohai Nature Reserve

According to environmental data,Ecopath with Ecosim (EWE) model can quantitatively describe the energy flow in the production and consumption of function components of system by using trophodynamics,and accurately assess the biomass and stable state of aquatic ecosystem.In the paper,the basic principle and parameters of EWE model were introduced firstly,and the relationship between Q/B (the important parameter of EWE model) and basic life indices of fish was discussed,then the current study and typical results of EWE model were analysed,finally the related parameters of EWE model in Caohai Nature Reserve were analysed.

Enrichment characteristics and risk assessment of Hg in bird feathers from Caohai wetland in Guizhou Province,China

Based on the analysis of the enrichment char- acteristics of Hg and MeHg in bird feathers from Caohai National Nature Reserve in Guizhou, the risks of Hg pol- lution to the birds from Caohai wetland have been evalu- ated. The total Hg content of bird feathers ranges from 40 to 5058 ng/g.vyjth an average of 924 ng/g. The content of MeHg is significantly correlated with total Hg （r = 0.68,p 〈 0.01）, and the content are among 0.75 and 113 ng/g. The total Hg content in the birds feathers is significantly dependent on their feeding habits, which is mainly in accordance with the following rule： carnivorous birds 〉 omnivorous birds that are mainly carnivo- rous 〉 omnivorous birds that are mainly herbivorous. There are also differences in the Hg enrichment ability in the different parts of bird feathers, and the total Hg and MeHg content in the wing feathers are significantly higher than that in the other parts of feathers. The bioaccumula- tion coefficients of aqueous Hg and MeHg by bird feathers are 0.9 × 10︿4-112.13× 10︿4 （mean value is 20.47 ×10︿4）and 0.47 × 10︿4-70.4 × 10︿4 （mean value is 9.52 × 10︿4）, respectively. Although the whole Hg level in Caohai bird feathers is not too high, the Hg content in some carnivorous birds exceeds over or approaches the abnormal threshold when birds are breeding （5μg/g）, which indicates that the birds in Caohai wetland are faced with some risks of ecological Hg pollution.

Atmospheric deposition fluxes and health risk assessment of potentially toxic elements in Caohai Lake(Guizhou Province,China)

In this study,the sources of potentially toxic elements(PTEs)from atmospheric deposition in the waters of Guizhou’s Caohai Lake were investigated in addition to the potential risks to human health.Moss bags were used to enrich PTEs from atmospheric deposition,and eight monitoring sites that best represented geographic variation were established around Caohai Lake.Moss bags were collected and examined at every 3 months to identify spatiotemporal patterns of dry and wet atmospheric deposition of PTEs.Zn was the most abundant metal identified from deposition in Caohai(72.07%–95.94%),followed by Pb and Cd,while Hg was the least abundant(0.008%–0.354%).The contributions of wet deposition of PTEs were greater than those of dry deposition,and deposition during the heating season from December to April was greater than that between April to July.Hg was mainly derived from atmospheric dry deposition(65.38%–84.44%).Spatial distribution analysis indicated that atmospheric deposition was associated with the intensity of human activities and heating emissions.Exposure via hand-to-mouth contact accounted for over 99%of the total exposure risk although overall exposure was lower than threshold acceptable levels for carcinogenic and non-carcinogenic metals,indicating an overall lack of risk towards human health.Nevertheless,the health risk from atmospheric deposition of PTEs in Caohai Lake may be reduced by focusing on Zn,Pb,and Cd deposition in rainfall and minimizing the hazards associated with hand-to-mouth exposure to PTEs.

Dynamic Assessment on Ecological Frangibility of the Caohai Wetland in Guizhou Province

By analyzing current situation of the Caihai Wetland, combining with "3S" technology, theory of ecosystem health, landscape ecology theory, applying the model of Pressure–State–Response, this paper assessed dynamic changes of ecological frangibility of the Caohai Wetland in Guizhou in 1992, 2000 and 2013. The results showed that the wetland ecosystem had sound principal functions, but also witnessed different degrees of degradation. The ratio of basic complete ecosystem landscape area in the Caohai Wetland reduced from 70.56% in 1992 to 66.26% in 2013, and the ratio of destructed landscape area increased from 12.11% in 1992 to 13.38% in 2013.

Research on the carbon isotopic composition of organic matter from Lake Chenghai and Caohai Lake sediments

The carbon isotopic composition of organic matter from lake sediments has been extensively used to infer variations in productivity. In this paper, based on the study of the contents and δ13C values of organic matter in different types of lakes, it has been found that δ13C values of organic matter have different responses to lake productivity in different lakes. As to the lakes dominated by aqutic macrophytes such as Lake Caohai, organic matter becomes enriched in 13C with increasing productivity. As to the lakes dominated by aquatic algae such as Lake Chenghai, δ13C values of organic matter decrease with increasing productivity, and the degradation of aquatic algae is the main factor leading to the decrease of δ13C values of organic matter with increasing productivity. Therefore, we should be cautious to use the carbon isotopic composition of organic matter to deduce lake productivity.

Spatiotemporal Evolution of Ecological Quality in Alpine Freshwater Lake Nature Reserves in the Past 20 Years

The Caohai Nature Reserve is one of the three major plateau freshwater lakes in China.Since the 1950s,human activities such as land reclamation and population relocation have greatly damaged Caohai.A rapid evaluation of the spatiotemporal evolution trend of the ecological quality of the Caohai Nature Reserve is significant for the maintenance and construction of the ecosystem in this area.The research is based on the Google Earth Engine(GEE)remote sensing cloud computing platform.Landsat TM/OLI images from May to October in five time periods:2000-2002,2004-2006,2009-2011,2014-2016,and 2019-2021 were obtained to reconstruct the optimal cloud image set by averaging the images in each time period.By constructing four ecological indicators:Greenness(NDVI),Wetness(Wet),Hotness(LST),and Dryness(NDBSI),and using Principal Component Analysis(PCA)method to obtain the Remote Sensing Ecological Index(RSEI)for the corresponding years,the spatiotemporal variation of ecological quality in the Caohai Nature Reserve over 20 years was analyzed.The results indicate:①the mean value of RSEI increased from 0.460 in 2000-2002 to 0.772 in 2019-2021,a 67.83%increase,indicating a significant improvement in the ecological quality of the reserve over the 20 years;②from the perspective of functional zoning of the Caohai Nature Reserve,the ecological quality of the core area showed a degrading trend,while the ecological quality of the buffer zone and experimental zone significantly improved;③with the implementation of ecological restoration projects,the ecological quality of the reserve gradually recovered and improved from 2014 to 2021.The trend of RSEI value changes is well correlated with human interventions,indicating that the PCA-based RSEI model can be effectively used for ecological quality assessment in lake areas.

贵州草海颗粒物和沉积物有机碳氮同位素特征及来源研究

探究湖泊有机质来源,为从源头上控制草海营养盐负荷提供参考。在草海湖泊及入湖河流上设置13个采样点,于2023年3月采集并测定湖泊和河流中颗粒物和沉积物的有机碳同位素(δ^(13)C)、有机氮同位素(δ^(15)N)、C/N及总有机碳(POC、TOC)和总氮(PON、TON),结合MixSIAR同位素模型分析颗粒物和沉积物的有机碳氮来源及贡献率。结果表明:颗粒物δ^(13)C为-27.56‰~-23.64‰,δ^(15)N为3.12‰~10.93‰,颗粒物有机碳主要来源于大气沉降(21.1%)和水生植物(20.7%),氮来源主要为土壤有机质(25.6%)和水生植物(25.3%);沉积物δ^(13)C为-28.18‰~-20.53‰,δ^(15)N为1.70‰~6.58‰,沉积物有机碳主要来源于大气沉降(34.4%)和水生植物(33%),氮主要来源于化肥(24%)。颗粒物和沉积物之间有机氮来源的差异反映出土壤有机质和水生植物来源的有机氮易降解,而化肥来源的氮则易沉积。

贵州草海生态监管平台研究与实现

立足贵州草海湿地生态系统的特点和治理管理需求,通过创建地理信息大数据条件下的环境监管技术框架,建立统一的环境监管数据库,构建基于全样本分析的生态异常自动变化监测技术体系、基于深度学习的自动或半自动要素提取技术体系以及大数据统计分析技术体系,研发“一张云图”共享平台及人类区域活动监测平台,为贵州草海的全数字化监管提供了坚强的科技支撑,助力草海实现“水清、山绿、景美、人和、鸟欢”目标。

Paleotemperature variations at Lake Caohai, southwestern China, during the past 500 years:Evidence from combined δ^(18)O analysis of cellulose and carbonates

The oxygen isotopic values of aquatic plant cellulose and carbonates in Lake Caohai sediments were measured using a continuous flow isotopic ratio mass spectrometer(CF-IRMS).Because of predictable oxygen isotopic fractionation between cellulose and its source water,the oxygen isotopic composition of paleo-lake water has been established quantitatively.Combined oxygen isotopic values of cellulose and carbonates were used in the‘Craig’equation to determine paleotemperatures and their variation in the lake during the past 500 years.Results show that the paleotemperature trend correlates well with meteorological records from Weining.There are four notable cold intervals at Lake Caohai over the past 500 years,namely 1540–1570AD,1670–1715AD,1780–1870AD and 1900–1930AD,and the former three cold intervals have been observed in the conventional Little Ice Age(LIA).These cold periods at Lake Caohai correspond well with those recorded from tree ring,peat,and ice core data from adjacent regions,particularly temperature those inferred fromδ18O of peat cellulose from Hongyuan Southwestern China.The trend in paleotemperature variations at Lake Caohai are also consistent with both the change of Indian summer monsoon,derived fromδ18O values of a stalagmite in Dongge,and a recorded shift in solar activity.The findings of this study illustrate that coupled analysis ofδ18O values of cellulose and carbonates from lake sediments may be used as a paleotemperature proxy.These results also provide further evidence of the existence of LIA in southwestern China.

草海及周边水库鱼类的种类组成及群落多样性

2017年6月至2018年12月,项目组分2次对草海及周边水库的鱼类资源进行了调查,共采集到鱼类标本5000余份。草海及周边水库现有鱼类12种,隶属于3目6科12属。渔获物种类主要为鲤鱼、鲫鱼、黄黝鱼、彩石鲋、麦穗鱼、泥鳅、黄鳝、普栉鰕虎鱼、棒花鱼、片唇鮈、鱼餐条、草海云南鳅。通过对草海及周边水库渔获物组成的分析测量发现,优势种群为麦穗鱼。鱼类多样性分析表明,东中部凹地冒水水库、乐溪水库、草海、杨湾桥水库和干海子水库多样性指数较高,西南部冲子河水库次之,西北高海拔地区的雪山水库和邓家营水库最低。本地特有种一个,为草海云南鳅,且只有杨湾桥水库有,其他水库包括草海均未采到标本。

贵州草海浮游植物群落结构特征及其与环境因子的关系

近年来贵州草海生态系统发生明显变化,水体水质和生态系统功能呈现降低趋势。浮游植物对生态环境变化具有重要指示作用,探究草海浮游植物群落结构特征及其与环境因子的关系,对掌握草海生态状况及制定生态恢复策略具有重要意义。本研究于2021年不同季节对贵州草海浮游植物的种类、细胞密度和生物量及水质状况进行采样调查。结果显示,共鉴定出浮游植物7门78种,浮游植物丰度为(3.89±2.08)×10^(7)~(2.38±8.01)×10^(8)cells·L^(-1),浮游植物生物量为(12.46±5.49)~(29.78±8.00)mg·L^(-1),均呈现夏季>秋季>春季>冬季的变化特征。不同季节浮游植物优势种组成不同,微囊藻(Microcystis sp.)、伪鱼腥藻(Pseudoanabaena sp.)、栅藻(Scenedesmus Meyen sp.)及小环藻(Cyclotella sp.)为全年优势种。浮游植物Shannon-Wiener多样性指数(H')全域均值为1.71~2.63,全年均值为2.20;Pielou均匀度指数(J)全域均值为0.52~0.78,全年均值为0.67;Margalef物种丰富度指数(D_(m))全域均值为1.30~1.62,全年均值为1.46;综合评价表明草海水体处于富营养化状态。运用Pearson相关性分析法筛选主要环境因子为溶解氧(DO)、高锰酸盐指数(COD_(Mn))、总氮(TN)和总磷(TP)。主要环境因子与浮游植物密度的冗余分析(RDA)及与浮游植物多样性指数的Pearson分析结果表明,TP和DO影响草海浮游植物群落结构的关键因素。与2004年以来的草海生态调查结果相比,2021年草海浮游植物群落结构发生了显著变化且丰度明显上升,处于“草型-藻型”转换的关键时期,须及时采取措施促进沉水植物恢复及防止水华发生。

贵州草海湿地夏季浮游植物群落结构及其与水环境因子的关系

为了解贵州草海湿地浮游植物群落结构及其与水环境因子的关系,于2022年夏季对贵州草海湿地浮游植物进行调查。结果表明,2022年夏季草海湿地的浮游植物有8门51科104属,其中绿藻门(Chlorophyta)种类最丰富,其次是硅藻门(Bacillariophyta)和蓝藻门(Cyanophyta)。浮游植物丰度平均值为18.82×10^(6) cell·L^(-1),各采样点之间差异较大;从浮游植物优势属和丰度看,均是蓝藻和绿藻占绝对优势。冗余分析(Redundancy Analysis,RDA)结果表明,草海湿地浮游植物群落结构主要受总氮(TN)、铵态氮(NH_(4)^(+) N)、硝态氮(NO_(3)- N)、总磷(TP)、有机碳(TOC)、悬浮物(TSS)等影响。浮游植物多样性指数和丰度评价结果表明,2022年夏季草海湿地处于富营养状态,为中度污染水平,水体有发生微囊藻水华的风险。

基于荧光定量PCR技术分析草海沉积物中氨氧化古菌和细菌的空间分布特征

【目的】探明贵州草海表层沉积物中氮循环微生物的丰度、群落结构及其分布规律,为研究湖泊沉积物氮循环机理和开展湖泊生态修复提供理论参考。【方法】通过实时荧光定量PCR技术测定不同季节草海表层沉积物中氨氧化古菌(AOA)与氨氧化细菌(AOB)的丰度,同时测定沉积物、间隙水及上覆水体理化因子,分析各环境因子对AOA amoA和AOB amoA的分布影响。【结果】AOA amoA和AOB amoA基因丰度分别为7.81×103~4.11×106 copies/g和3.50×10^(2)~8.11×10^(4) copies/g,amoA拷贝数在各采样区域差异显著,具有空间分布特征,湖岸带AOA amoA与AOB amoA基因丰度较低。草海沉积物中AOA/AOB为2.3~181.4。草海沉积物整体有机质含量为65.57~436.30 g/kg,总磷为3.870~5.640 g/kg,全氮为0.585~1.252 g/kg;间隙水氨氮和硝酸盐氮浓度分别为0.283~2.082 mg/L和0.007~0.060 mg/L。【结论】AOA在草海氨氧化过程发挥主要作用。AOA amoA基因丰度受有机质和总氮影响,AOB amoA基因丰度受溶解氧和总磷影响。

2013—2022年贵州草海水质变化与影响因素分析

在水环境精细化管理背景下,湖泊水环境演变特征分析在水治理过程中具有重要意义。基于2013—2022年草海逐月监测数据,利用Spearman秩相关系数法、综合营养状态评价法和主成分分析法分析草海水环境演变特征及其影响因素。结果显示:COD_(Mn)、TN和Chl a浓度为显著上升趋势,NH_(4)^(+)-N浓度为极显著上升趋势,TP浓度和SD为下降趋势;综合营养指数不断提高,富营养化状态呈加重趋势;影响草海水环境质量的主控因子为TN、NH_(4)^(+)-N和COD_(Mn);内源污染严重、气温上升、降雨量减少、水生态系统失衡等逐步成为影响草海水环境的主要因素。为改善草海水质,建议在强化控源截污的基础上,从水文节律调控、鱼类生态调控、水生植被恢复、生态清淤等方面进行综合治理。

贵州草海沉积物中磷的形态分布及释放通量研究

磷是湖泊水体富营养化关键性限制因子之一,为了解草型湖泊沉积物中磷形态的赋存特征及其释放风险,以典型草型湖泊——贵州草海为研究对象,运用化学连续提取法和孔隙水扩散模型分析了草海沉积物中磷的形态及释放通量。结果表明:草海沉积物TP含量为563.75~982.40 mg/kg,平均含量为(722.97±71.38)mg/kg,为3级污染,沉积物TP具有明显的空间差异,人类活动强度大的区域TP含量较高;磷形态含量依次为NaOH-NRP>Res-P>NaOH-SRP>BD-P>HCl-P>NH 4Cl-P,其中活性磷(NaOH-NRP、BD-P和NH 4Cl-P)是草海磷的主要存在形态,占沉积物TP的58.05%;释放通量为0.03~0.08 mg/(m^(2)·d),表明草海的磷自沉积物向上覆水扩散,表现为“源”。研究发现草海有机磷的占比较高,潜在释放风险大;草海沉积物磷含量和释放通量均较藻型湖泊的低。研究成果对草型湖泊的保护管理具有重要意义。

贵州草海光合有效辐射衰减特征及影响因素研究

水下光环境对湖泊生态系统具有重要影响,是限制沉水植物生长、发育的重要因素,研究光合有效辐射衰减特征对湖泊沉水植物恢复具有重要指导意义。于2022年3~8月对草海水下光合有效辐射(PAR)时空分布进行调查,研究了光合有效辐射衰减系数(K d(PAR))与总悬浮物(TSS)、无机悬浮物(ISS)、有机悬浮物(OSS)、叶绿素a(Chl.a)和有色可溶性有机物(CDOM)等光衰减物质的关系,以及真光层深层(Z_(eu))的时空分布特征。结果表明:草海春夏季K_(d)(PAR)平均值为(2.90±1.12)m^(-1),Z_(eu)平均值为(1.84±0.69)m;光衰减因子TSS、ISS、OSS、Chl.a浓度和CDOM(380)吸收系数分别为(20.11±4.76)mg/L、(8.68±4.91)mg/L、(11.66±12.43)mg/L、(21.88±8.49)mg/m^(3)和(3.11±0.68)m^(-1);草海K_(d)(PAR)北部水域高于南部;草海水体K_(d)(PAR)与TSS(P<0.01)、ISS(P<0.01)和浊度(P<0.001)相关性显著,与Chl.a相关性不显著;春季影响草海K_(d)(PAR)的主导因子是ISS,夏季影响草海K_(d)(PAR)的因子是由ISS和CDOM共同主导,以春夏季整体来看,影响草海K_(d)(PAR)的因子是由ISS和Chl.a共同主导,这主要是由于草海水生植被衰退后风浪等导致沉积物再悬浮的缘故,且CDOM和Chl.a浓度的增加也是影响K_(d)(PAR)的关键因子;草海Z_(eu)平均值大于水深平均值,说明草海水体总体光环境有利于沉水植物生长发育,但是草海水体悬浮物质含量较高,其遮蔽可能导致沉水植物生长发育受阻,这也许是草海降低水位后沉水植物恢复不理想的一个重要原因。