三峡水库香溪河库湾蓝藻水华暴发特性及成因探析

2008年夏季,香溪河库湾自三峡水库建库以来第1次暴发蓝藻水华,水华波及整个库湾,持续时间达1个月之余.为了解这次水华暴发特性及发生原因,本文对蓝藻水华的发生发展过程进行了跟踪调查,6-7月水华发生期间每周采样1次.调查表明本次蓝藻水华的优势种为鱼腥藻(Anabaena sp.)、铜绿微囊藻(Microcystis aeruginosa)、惠氏微囊藻(Microcystis wesenbergii)等,细胞密度高达3.82×10⁸ cells/L,蓝藻相对密度达到90%以上.本文将2008年5-7月与2007年同期理化指标比较发现,2007年5月的N:P为18.6,而2008年5月的N:P较低,为6.2,据文献报道N:P < 8有利于微囊藻的复苏,因此2008年水华前期的低N:P利于微囊藻的复苏,为微囊藻在适宜条件下的大量增殖提供了种源基础.方差分析表明,2008年5-7月各采样点真光层深度显著高于2007年同期,使得底泥中的微囊藻获得一定强度的光照而复苏,这可能是2008年蓝藻水华在香溪河库湾暴发的原因之一.综上所述,在具备充足的营养盐基础、较强的水体稳定性以及较高水温的前提下,香溪河库湾水华发生前期较低的N:P以及较高强度的光照可能是微囊藻复苏的诱导因子,为蓝藻水华暴发提供了种源基础.     

分层异重流背景下降雨对三峡水库香溪河水华消退的影响

为探究在三峡水库特殊分层异重流背景下降雨对水华消退的影响,以香溪河为例,对库湾降雨前后水动力、生态环境因子开展连续三维立体跟踪监测。结果表明:降雨对水华的消退作用显著,降雨后香溪河库湾叶绿素a(Chl.a)浓度明显下降。热分层稳定指数(RWCS/H)变化不大,库湾近河口处分层较弱、中上游分层较强的特性并未随此次降雨发生较大变动。受降雨影响,藻类在表层水体聚集程度降低,藻类聚集度指数(MI)、微藻群体平均深度(MRD)下降。库湾流态随降雨发生而变得复杂,库湾水体浊度明显增加,异重流倒灌形式由近表层倒灌向中下层倒灌转变,雨后又逐渐转变为中层倒灌,长江干流水体倒灌进入库湾的影响范围、潜入深度增加。水体水平输移增强,分散下沉的藻类易随水体环流流出库湾,水华消退。雨后库湾入库流量增加,大部分上游来流依旧由上层流向河口,与中层倒灌异重流形成逆时针环流,藻类无法在表层水体稳定生长,库湾Chl.a浓度能在较长时间内保持较低水平,不会再次迅速暴发水华。     

三峡水库香溪河流域梯级水库浮游植物群落结构特征

于2005年10月、2006年1、4、7月对三峡水库香溪河流域3座水库(古洞口一级水库、古洞口二级水库和香溪河库湾)组成的梯级水库的浮游植物种类组成、优势种、群落结构、密度和生物多样性指数进行了周年调查研究.共鉴定出浮游植物7门58属121种(含变种),以绿藻和硅藻种类最多,绿藻有26属49种,占40.50%;硅藻14属41种,占33.88%;其次是甲藻,3属11种,占9.09%;蓝藻5属7种,占5.79%;隐藻3属7种,占5.79%;其它藻类仅占4.96%.浮游植物在古洞口一级水库共有25属31种,古洞口二级水库29属40种,香溪河库湾46属81种.优势度分析显示:古洞口一级水库藻类优势类群为硅藻门、绿藻门,古洞口二级水库为硅藻门、隐藻门和甲藻门,香溪河库湾为绿藻门、硅藻门、甲藻门和隐藻门.3座水库浮游植物年均密度分别为1.110×106、4.837×105和1.734×106 cells/L;其中,最高密度出现在香溪河库湾(4.87×106 cells/L),最低密度出现在古洞口二级水库(5.76×105 cells/L).运用主成分分析对梯级水库进行水质分析,表明沿着水库的梯度水质逐渐恶化.Shannon-Wiener多样性指数和Pielou均匀度指数在3座水库间无明显差异,而香溪河库湾Margalef丰富度指数显著大于古洞口一级、二级水库.前两个指数与浮游植物优势种的评价结果显示,香溪河流域梯级水库处于中污染状态.     

三峡水库香溪河库湾拟多甲藻(Peridiniopsis)的昼夜垂直迁移行为对碳磷分布的响应

于2015年2月26-27日在香溪河库湾高岚河段拟多甲藻(Peridiniopsis)水华发生地昼夜监测其在水体中的垂直迁移,分别在6个时间段(8:00、12:00、16:00、20:00、0:00、4:00)分层取样分析拟多甲藻在水中的叶绿素a浓度、细胞密度、碳酸酐酶(CA)与碱性磷酸酶(AP)活性;分析总磷(TP)、溶解性总磷(DTP)、溶解性反应磷(SRP)与溶解性有机磷(DOP)浓度在水中的垂直分布.结果显示,水华发生期拟多甲藻为绝对优势种,监测的6个时段中,拟多甲藻呈显著的昼夜垂直迁移规律,正午12:00,表层细胞密度最大,可达5.2×10~6cells/L,凌晨0:00表层细胞密度最低,仅为0.4×10~6cells/L;TP与DTP浓度无垂直分布规律,但SRP与DOP浓度呈现显著的垂直分布规律,SRP浓度随水深增加而减小,DOP浓度随水深增加而增加;CA活性日间高于夜间,日间CA活性呈垂直分布规律,随水深增加而减小,但夜间无垂直分布规律;AP活性在水中昼夜呈极其显著的垂直分布规律,随着水深增加逐渐增加.相关性分析结果表明,拟多甲藻细胞密度与水深、DOP浓度呈极显著负相关,水深与CA和AP活性分别呈极其显著负相关与正相关,拟多甲藻细胞密度与CA和AP浓度分别呈极其显著正相关与负相关.因此,拟多甲藻的垂直迁移行为可能是对日间迁移至表层获取光能和无机碳来源、夜间迁移至水下获取磷源的一种适应.     

三峡水库蓄水后对支流大宁河富营养化特征及水动力的影响

三峡水库蓄水后支流大宁河水华频发,为了揭示水库蓄水以来,大宁河富营养化变化趋势以及水华暴发期间水动力等环境因子的影响特征,自2005年长期跟踪监测大宁河的水质状况,并于2010年针对东坪坝库湾2次典型水华事件,初步探讨了水华暴发期间的主要影响因素.结果表明:2005年以来,大宁河水体处于中度营养状态,水质尚好,但低估了水华敏感期的富营养化状况.东坪坝3月水华暴发期间,叶绿素a浓度与流速呈显著负相关,与pH、DO也呈显著相关,表明在此次水华期间,流速对藻细胞的增殖或聚集产生直接或间接的影响,pH和DO是引起水华暴发的主要水质因子;5月水华暴发期间,叶绿素a浓度与流速呈显著负相关,与流量呈显著正相关,同时与pH、透明度(SD)呈显著相关,表明在这次水华期间,流速和流量都对藻细胞增殖或聚集产生直接或间接的影响,pH和SD成为水质敏感因子.3月和5月水华暴发时间分别处于水库高水位运行期和泄水期,这可能是导致水华影响因子不同的主要原因,但具体机理还有待于进一步研究.本文结果表明在三峡水库调度运行的不同阶段支流库湾水华暴发的机制不同,需要针对不同时段支流库湾水环境特征分别加以调查研究.     

三峡水库香溪河库湾浮游植物功能群对水位变化的响应

三峡水库每年经历“水位下降(4—5月)-低水位(6—8月)-蓄水(9—10月)-高水位(11月—次年3月)”的季节波动,年水位落差达30 m。为探究香溪河库湾浮游植物功能群对三峡水库水位变化的响应,于2017年对浮游植物群落和主要环境因子开展逐月调查。共检出浮游植物7门65属79种,隶属于21个功能群,其中优势功能群10个,分别为C、D、F、G、J、Lo、M、P、X2、Y。适应营养丰富环境的C、P功能群在全年维持优势,指示香溪河库湾为中-富营养水体。消落期偏好水体扰动较弱、中-富营养水体的功能群(F、G、X2、Y)成为优势类群;汛期偏好稳定富营养、耐受高光强且对冲刷敏感的功能群(G J、M)成为优势类群;蓄水期和高水位运行期偏好混合的中-富营养水体,耐受低光强且对水体分层敏感的功能群(C、P、D)是优势类群;浮游植物功能类群组成结构随水位变化明显改变。综合营养状态指数表明香溪河库湾在消落期和高水位运行期处于中营养状态,另外两个时期处于富营养状态(39.84≤TSI_M≤60.9);Q指数表明香溪河库湾整体水质为“好”(3.02≤Q指数≤4.17);且两者均随着水位下...     

三峡水库典型支流库湾沉积物CH4产生和氧化规律

以三峡水库香溪河库湾为研究对象,采用原位加密采样(2021年5月)和室内培养方法,结合沉积物特性与水环境因子分析,探讨了香溪河库湾沉积物甲烷(CH₄)释放潜力、沉积物-水界面CH₄产生和氧化通量空间分布规律及其影响因素。结果表明:三峡水库泄水期间,香溪河库湾沉积物CH₄释放潜力的变化范围是6.35-2029.37 mg/(kg·d),沉积物-水界面CH₄产生通量和氧化通量的变化范围分别为0.04～0.73、0.03～0.62 mmol/(m²·d);空间上,沉积物CH₄释放潜力、沉积物-水界面CH₄产生及氧化通量在香溪河库湾和各典型横切面(XX02、XX05和XX06)间表现出空间差异性,主要受水深、TOC和温度的影响。垂向上,CH₄产生速率随沉积物深度的增加而减小,表层20 cm沉积物CH₄释放潜力占整柱沉积物的70%,可以用于估算库湾沉积物CH₄释放潜力。此外,沉积...     

太湖梅梁湾春季浮游植物初级生产力

用黑白瓶测氧法对梅梁湾春季浮游植物初级生产力的变化特征进行研究,探讨了初级生产力的日变化、垂直变化、区域分布、浮游植物现存量与初级生产力的关系以及不同曝光时间对P-I曲线的影响.结果表明,梅梁湾浮游植物初级生产力存在明显的日变化,最大值出现在10:00-14:00;初级生产力在梅梁湾分布呈现为从湾内向湾口逐渐递减的趋势;除表层水受光抑制影响使其生产力相对较低外,初级生产力随水深的增加而降低;初级生产力与叶绿素a存在显著的正相关,用水柱层平均叶绿素a浓度来估算初级生产力比用表层叶绿素a浓度来估算要更为精确;短的曝光时间往往带来高的初级生产力和同化系数.     

城市湖泊春季绿藻水华特征及其影响因素——以宁波月湖为例

城市湖泊富营养化问题日趋严峻,以往对水华的研究多集中于大型自然淡水湖库,而对小型城市浅水湖泊的水华动态相对较少.以宁波月湖为研究对象,探讨水华暴发期间浮游植物变化特征及与影响因子之间的关系,以期判别影响城市湖泊水华的主控因子.月湖水华期间营养盐水平处于中富营养至极端富营养之间,此次共检出浮游植物8门61属,藻种组成以绿藻门（51.79%）和硅藻门（21.43%）为主,各点位浮游植物生长主要受水温、光照驱动,经历了隐藻门→硅藻门→绿藻门→蓝藻门的演替.水华种为雷氏衣藻（Chlamydomonas reinhardtii）,总藻密度最高达到1.55×10⁸ cells/L,水华暴发后各点位衣藻属比例升高（最高达到81.10%）,群落结构呈现单一化特征.通过Pearson相关性分析和RDA分析发现衣藻属生长与水温、pH、总磷浓度均呈显著正相关,春季气温回升、天气持续晴好,城市浅水湖泊高营养盐负荷、水体流动性差等特点为带鞭毛的衣藻属提供了适宜的生存条件,在环境条件均适宜的情况下拥有最大生长潜力的衣藻属在营养盐、光照等竞争中生长速率明显优于其他藻种,从而发生绿藻水华.     

三峡水库支流小江富营养化模型构建及在水量调度控藻中的应用

三峡水库蓄水以来,支流小江呈富营养化加重的趋势,且多次暴发春季水华.水库蓄水以后支流流速变缓,水体滞留时间增加,是引发支流水华的主要因素之一.基于MIKE软件,建立小江调节坝下游至河口的二维水动力-富营养化模型,考虑碳、氮、磷3种元素在浮游植物有机体、死亡腐屑和无机盐中的循环转化,模拟小江河段的春季水华过程.分析小江生态调节坝的水量调节抑藻作用,即人为制造"洪水脉冲",增加短时间内的水流流速,对下游流场进行扰动以控制水华.计算结果表明,增大泄水量对调节坝下游的小江河段的春季藻华总体上具有一定的抑制作用.小江上游河段调度作用效果明显,下游高阳至入汇口河段调节作用较小,上游调节坝水力调度可以作为三峡水库支流水华应急治理措施之一.营养盐控制应该是控制支流水华的根本措施.     

三峡水库香溪河库湾拟多甲藻(Peridiniopsis)水华对环境中磷的响应机制

于2015年春季拟多甲藻水华暴发期在香溪河支流高岚河、南阳河与干流设置9个采样点,探讨浮游植物种群与水体总磷浓度等环境因子的相关性;同时,分离纯化拟多甲藻后,设置5个不同磷浓度(0、0.005、0.020、0.100、0.600 mg/L)对其进行实验室培养,分别测定其比生长速率;在对数生长期,检测不同磷浓度培养下的藻细胞的快速光曲线及其参数;检测不同磷浓度培养下的藻细胞对外源无机碳的吸收效率及其参数.结果表明,水体中总磷浓度越高的河段,拟多甲藻细胞密度越高;培养基中磷浓度越高,拟多甲藻的比生长速率越大,光合效率越高,其对外源无机碳的吸收能力越强.这些结果表明高磷的水环境可能是促使拟多甲藻形成水华的关键因素之一.     

Patterns of asynchrony for phytoplankton fluctuations from reservoir mainstream to a tributary bay in a giant dendritic reservoir (Three Gorges Reservoir, China)

Seasonal fluctuations of phytoplankton have often been regarded as one of the important cyclic events in aquatic ecosystems, and have even been emphasized as an important sign of regional climatic variability in limnology. However, few attempts have been made to examine synchrony for phytoplankton fluctuations among different habitats in a single reservoir system. The present study employed Spearman rank correlation analysis and the Mantel test to assess levels of synchrony for phytoplankton abundance and taxonomic composition from reservoir mainstream to a tributary bay (Xiangxi Bay) in a giant dendritic reservoir, China (Three Gorges Reservoir, TGR). At the selected scale, asynchronous patterns of phytoplankton were found when looking at total abundance and taxonomic composition, suggesting that regional drivers were not strong enough to synchronize phytoplankton fluctuations, and local regulators were predominant. As a riverine system, the mainstream of TGR had high levels of algal synchrony, while asynchronous patterns of phytoplankton were detected within Xiangxi Bay, which is characterized as a lacustrine system. The present study further confirmed that external hydrological disturbances strongly homogenize habitat conditions and synchronize phytoplankton fluctuations within the mainstream, while spatial divergence of phytoplankton succession depend on local habitat conditions within Xiangxi Bay. Moreover, low synchrony of phytoplankton between the mainstream and Xiangxi Bay is probably caused by spatial divergence of phytoplankton succession within Xiangxi Bay and the lack of succession in the rapidly flushed mainstream. Independently of these mechanisms possibly explaining phytoplankton fluctuations, the present study has also an applied perspective to the improvement of a long-term observation program in which phytoplankton trends at the mainstream scale could be compiled from the data set in a single site, while a set of sampling sites should be required at the Xiangxi Bay scale.     

Variation of phytoplankton biomass and primary production in Daya Bay during spring and summer

Environmental factors, phytoplankton biomass (Chl a) and primary production of two water areas in Daya Bay (Dapeng'ao Bay and Aotou Bay) were investigated during the transition period from spring to summer. Chl a ranged from 3.20 to 13.62 and 13.43 to 26.49 mg m(-3) in Dapeng'ao Bay and Aotou Bay respectively, if data obtained during red tides are excluded. Primary production varied between 239.7 and 1001.4 mg Cm(-2) d(-1) in Dapeng'ao Bay. The regional distribution of Chl a and primary production were mostly consistent from spring to summer in both bays. Seasonal transition characters have been found in Daya Bay from spring to summer, including high values of DO, nitrate and silicate. Size structures of phytoplankton and its primary production do not change very much from spring to summer, with micro-phytoplankton dominating and contributing about 50% of the whole. In Daya Bay, phytoplankton is limited by nitrogen in spring, and by phosphate in summer. Artificial impacts are evident from high temperature effluent from nuclear power stations, aquaculture and sewage. During the investigation, a red tide occurred in Aotou Bay, with a maximum Chl a of 103.23 mgm(-3) at surface and primary production of 2721.9 mg Cm(-2) d(-1) in the red tide center. Raised water temperature and nutrient supply from land-sources help to stimulate annual red tides.     

三峡水库香溪河库湾水-气界面热交换过程及水体稳定性

水库或湖泊的热分层结构是其动力与环境过程的重要研究方面,虽然很多学者针对水体分层结构和演变机理开展了大量研究,但水体通过水-气界面与大气进行热交换的过程,各气象因子的贡献机理等研究成果还很缺乏。本文基于三峡水库香溪河库湾2019年3月-2020年2月期间的水温、水位及气象等监测数据,针对水-气界面热交换过程如何影响水温垂向结构及表层水体湍流混合作用开展研究。结果表明,(1)香溪河水体年内呈高温期分层、低温期混合的基本特征,高温期混合层深度小于8 m,低温期混合层深度超过30 m。(2)太阳短波辐射是香溪河水体的主要热源,潜热通量和长波辐射是香溪河水体的主要冷源,感热通量贡献极小。(3)香溪河平均风速较弱,约为1.6 m/s,主要通过增强潜热和感热通量的方式影响水体垂向稳定性结构特征,其机械扰动作用较弱。(4)表层水体湍能通量在高温期较低(10^-7m³/s³量级),此时水体处于分层状态,风应力大概率主导表层水体湍流发育;低温期表层水体湍能通量较高(10^-6 m³/s^3<...     

Asynchrony of spring phytoplankton response to temperature driver within a spatial heterogeneity bay of Three-Gorges Reservoir, China

The increased air temperature is expected to have important driver on spring phytoplankton dynamics. To test whether spatial heterogeneity modifies the synchronous responses of phytoplankton to regional temperature driver, we evaluate temporal coherences for physical factors (temperature, water stability and non-algal light extinction), nutrients (nitrogen, phosphorus and silicon), and biomass and density of phytoplankton by Pearson correlation analysis and synchrony for phytoplankton community dynamics by Mantel test and nonmetric multi-dimensional scaling (NMS), during spring bloom (February 23–April 28, 2005) within Xiangxi Bay, a high spatial gradient bay of Three-Gorges Reservoir (China). The high level of temporal coherences for surface water temperature (r = 0.946, p < 0.01) and relative water column stability (r = 0.750, p < 0.01) were found between pair sites (A and B), in which the increase trends occurred with increase in regional air temperature during the study period. However, the low synchrony for phytoplankton dynamics were indeed observed between Site A and B, especially for the density of common dominant taxa (Cyclotella spp.: r = 0.155, p = 0.388) and community structure (Mantel test: r = 0.351). Moreover, the local habitat characteristics such as nutrient (nitrogen and phosphorus) and non-algal light extinction showed low levels of temporal coherence. It indicated that local community of phytoplankton varies rather independently within the single lentic bay with high spatial heterogeneity and that dispersal of algal organisms among locations cannot overwhelm out these local dynamics. Contrary to many studies, the present results argued that, in a small geographic area (i.e., a single reservoir bay of approximately 24 km length), spatial gradients also may influence spring phytoplankton response to regional temperature driver.     

太湖长孢藻属(Dolichospermum)生物量长期动态变化及驱动因子

针对近年来太湖水体中长孢藻（Dolichospermum,曾用名鱼腥藻Anabaena）比例增加的趋势,本文研究了2005—2019年太湖春季不同湖区长孢藻生物量的长期变化趋势和空间差异,探究了冬、春季气象条件（气温、日照时长、风速、降雨量）和营养盐（总氮、总磷）水平对其的影响.结果表明,2005—2019年太湖监测数据显示春季长孢藻生物量有比较明显的升高现象,主要发生在竺山湖富营养程度较高的区域,其次是湖心区、梅梁湾和南部湖区.偏最小二乘路径建模（PLS-PM）结果表明,不同湖区长孢藻生物量变化的主要驱动因素存在差异.在湖心区,春季长孢藻的生物量主要受冬季气候条件（气温、风速、日照时长）的影响,其次受春季营养盐和春季气候条件的影响.在梅梁湾、竺山湖和南部湖区,春季长孢藻的生物量主要受春季气候条件的影响.在梅梁湾和竺山湖,春季风速、日照时长是春季长孢藻生物量的显著影响因子;在南部湖区,春季长孢藻生物量的主要驱动因素是春季的日照时长和春季气温.本研究从长时间序列角度,对太湖固氮蓝藻的时空分布特征和影响因素开展了研究,为太湖不同湖区开展针对性的藻类水华防控和富营养化治理提供理论基础.     

Seasonal and annual loads of hydrophobic organic contaminants from the Susquehanna River basin to the Chesapeake Bay

Water from the Susquehanna River was collected and analyzed for polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyl (PCB) congeners to estimate seasonal and annual riverine loads to the Chesapeake Bay. Temporal variations in the chemical loads resulted from the large changes in the water flow rates and in the particle-associated contaminant concentrations. Concentrations of PCBs and PAHs in river particles (ng/g) were twice as great as those in the northern Chesapeake Bay, indicating that the Susquehanna River is an important source of these contaminants to the bay. The river carries a majority of its hydrophobic organic contaminants (HOCs) in the particulate phase. During periods of high flow, large amounts of suspended particles in the river result in elevated HOC levels and increased loadings of these contaminants to the bay. From 1997 to 1998, 60% of the total annual HOC loading occurred in the early spring coincident with high river flows. The total PCB and PAH annual loadings from the Susquehanna River to the Chesapeake Bay were 76 and 3160 kg/year, respectively and 75% of the loaded organic contaminants were in the particulate phase. Principal component analysis of PAH and PCB congener patterns in the particles reveals that the river suspended particles were dominated by autochthonous production in the summer and by resuspended sediment and watershed erosion during the winter and early spring.     

Effects of hypoxia on benthic organisms in Tokyo Bay, Japan: a review

Bottom hypoxia (dissolved oxygen concentration ≤2 ml l(-1)) from anthropogenic eutrophication is a growing global concern. Here, we summarized characteristics of hypoxia and its effects on benthic organisms in Tokyo Bay. Despite recent decreases in nutrient inputs, hypoxia has been increasing in duration and spatial extent, suggesting that the substantial loss of tidal flats from reclamation is contributing to a decrease in the ability of Tokyo Bay to recycle nutrients. Hypoxia develops in the central to northern part of the bay and persists from spring to autumn, causing defaunation of benthic organisms. After the abatement of hypoxia in autumn, the defaunated area is recolonized, either through migration or larval settlement. Some megabenthic species with a spawning peak in spring and summer experience failure of larval settlement, which is probably due to hypoxia. The adverse effects of hypoxia are an impediment to recovery of benthic organisms in Tokyo Bay.