湖泊富营养化研究中的主要科学问题——代“湖泊富营养化研究”专栏序言

湖泊富营养化是我国湖泊当前面临的最为突出的环境问题之一,入湖生源要素循环失衡,蓝藻水华暴发与成灾机理,湖泊水生态系统退化与修复机制,以及湖泊管理科学基础等均是我国湖泊富营养化防治研究中急待解决的科学问题与理论基础.     

太湖梅梁湾理化指标分层的空间分布特征

为了解大型浅水湖泊水体理化指标的空间分异特征,在太湖梅梁湾布设62个采样点,垂向分为3层,调查水体中Chla、TN、TDN(溶解性总氮)、TP、TDP(溶解性总磷)的质量浓度及SD(透明度)、DOS(溶解氧饱和度)等水体理化指标,统计分析了夏季太湖水体理化指标空间分布特征及影响因素. 结果表明:①梅梁湾水体理化指标垂向时空变幅不同,垂向相对变幅平均值ρ(TN)为68.0%,ρ(TDN)为40.1%,ρ(TP)为138.0%,ρ(TDP)为35.7%,ρ(Chla)为66.0%,DOS为79.0%,营养盐总量的垂向差异比溶解态大;②平面上,水华堆积区ρ(TN)、ρ(TDN)、ρ(TP)、ρ(TDP)、ρ(Chla)、DOS平均值分别为梅梁湾平均值的4.45、2.45、6.45、4.74、2.08、1.02倍,比垂向差异大;③风场驱动下蓝藻堆积对水体各理化指标空间分布的影响巨大;④ρ(Chla)垂向分层明显,ρ(Chla)的垂向变幅表层0.2m处显著高于下层,可达89.7μg/L. 浅水湖泊的水体理化指标时空变异大,受气象条件、水动力条件等因素的影响,故在监测点位布设及数据分析时,应考虑垂直分层采样、滨岸带采样并详细记录采样条件.      

蓝藻水华优势藻高效防控铜制剂的筛选

在对比络合铜、有机铜和无机铜3类5种典型铜制剂对蓝藻水华优势藻--铜绿微囊藻(Microcystis aeruginosa)和2种非靶标藻种--普通小球藻(Chlorella vulgaris)和斜生栅藻(Scenedesmus obliquus)的96 h生长抑制效果的基础上,进一步开展了3类铜制剂抑制铜绿微囊藻生长的15 d延长效应研究.试验结果表明,质量分数为25%的络氨铜水剂、30%琥胶肥酸铜可湿性粉剂和20%乙酸铜可湿性粉剂对蓝藻水华优势种有较好的生长抑制效果,其对初始密度为2×105～4×105mL-1铜绿微囊藻的96 h半抑制浓度(以下均以有效成分的质量计)分别为0.03、0.06和0.05 mg·L-1,且初始藻密度对抑藻效果并无明显影响.试验质量浓度为0.25 mg·L-1的25%络氨铜水剂、0.30 mg·L-1的30%琥胶肥酸铜可湿性粉剂或0.20 mg·L-1的20%乙酸铜可湿性粉剂均能抑制铜绿微囊藻增长,且在0～15 d内都不会出现藻细胞再次复苏和增长.此外,由于铜制剂对铜绿微囊藻的96 h半抑制浓度远低于其对普通小球藻和斜生栅藻的96 h半抑制浓度,因此可在有效控制靶标藻种的同时不对非靶标藻种的生长造成严重威胁.络氨铜、琥胶肥酸铜、乙酸铜有望被开发成为高效、绿色的蓝藻水华控制剂.     

三峡水库香溪河库湾春季水华暴发藻类种源研究

2008年2月18日-4月17日,在距离香溪河河口约19 km处设一野外观测站,对观测站附近一定点进行持续监测,并在观测站进行围隔试验,探索香溪河库湾春季水华暴发藻类的种源,揭示水华暴发过程.监测结果表明:香溪河库湾春季硅藻(Diatom)(主要是针杆藻Synedra、星杆藻Asterionella)冰华藻类种源是原地水体,底泥对硅藻水华暴发影响不明显;2008年观测站附近的甲藻(Protoperidinium sp .)种源不是底泥中的孢囊.2008年春季香溪河库湾水华暴发过程可以分为"复苏-增长-衰亡"三个阶段,其中溶解性硅酸盐(D-Si)和光照是水华藻类复苏阶段的主要影响因子,而增长阶段的主要影响因子则是溶解性硅酸盐(D-Si)和总磷(TP),衰亡阶段由于4月8日骤降暴雨,浊度和降雨量是该阶段的主要影响因子.     

太湖蓝藻水华预警监测与风速风向的关系研究

太湖蓝藻水华预警监测的启动问题基本解决,但监测响应日期和周期却一直难以确定。统计分析了太湖2007-2009年蓝藻预警监测、现场观测的历史资料,研究蓝藻水华在水体中的分布与风速风向之间的关联规律,从环境监测部门蓝藻预警监测工作的实际出发,划分出了蓝藻水华预警监测的响应级别,提出具体的监测要求,较好解决了预警监测的响应周期问题。为环太湖地区相关部门更好地开展蓝藻预警监测工作提供了科学依据。     

Spatial analysis for spring bloom and nutrient limitation in Xiangxi bay of three Gorges Reservoir

The spatial and temporal dynamics of physical variables, inorganic nutrients and phytoplankton chlorophyll a were investigated in Xiangxi Bay from 23 Feb. to 28 Apr. every six days, including one daily sampling site and one bidaily sampling site. The concentrations of nutrient variables showed ranges of 0.02–3.20 mg/L for dissolved silicate (Si); 0.06–2.40 mg/L for DIN (NH₄N + NO₂N + NO₃N); 0.03–0.56 mg/L for PO₄P and 0.22–193.37 μg/L for chlorophyll a, respectively. The concentration of chlorophyll a and inorganic nutrients were interpolated using GIS techniques. The results indicated that the spring bloom was occurred twice in space during the whole monitoring period (The first one: 26 Feb.–23 Mar.; the second one: 23 Mar.–28 Apr.). The concentration of DIN was always high in the mouth of Xiangxi Bay, and PO₄P was high in the upstream of Xiangxi Bay during the whole bloom period. Si seems no obvious difference in space in the beginning of the spring bloom, but showed high heterogeneity in space and time with the development of spring bloom. By comparing the interpolated maps of chlorophyll a and inorganic variables, obvious consumptions of Si and DIN were found when the bloom status was serious. However, no obvious depletion of PO₄P was found. Spatial regression analysis could explained most variation of Chl-a except at the begin of the first and second bloom. The result indicated that Si was the factor limiting Chl-a in space before achieved the max area of hypertrophic in the first and second bloom period. When Si was obviously exhausted, DIN became the factor limiting the Chl-a in space. Daily and bidaily monitoring of Site A and B, representing for high DIN: PO₄P ratio and low DIN:PO₄P ratio, indicated that the concentration of Si was decreased with times at both site A and B, and the dramatically drop of DIN was found in the end monitoring at site B. Multiple stepwise regression analysis indicated that Si was the most important factor affect the development of spring bloom both at site A and B in time series.     

中国海域赤潮发生趋势的年际变化

回顾了中国海域的赤潮发生频次等数据的年际变化,尤其是进入21世纪的赤潮发生趋势,以期为赤潮灾害分析和防治提供帮助。数据表明,赤潮问题已不容忽视。总体上,赤潮发生的频次和累计面积呈现增长趋势,尤其是21世纪前10年的赤潮发生频次和规模是20世纪后50年的2倍多。与20世纪不同,东海的赤潮问题最严重,远远超过了南海;而渤海的赤潮规模也明显增加,此2海区成为赤潮的重灾区。赤潮多发生在5、6月份,但有延长的态势,对赤潮监测和预防提出了新的要求。赤潮生物,特别是有毒藻类不断增加,对渔业和人类健康造成威胁。同时也看到,赤潮的发生并非持续上涨,赤潮是可以防治的。     

2017年夏季巢湖水华期间浮游植物与蓝藻毒素的时空变化特征

蓝藻水华暴发过程中水华物种的演替及其与蓝藻毒素的关系,对于湖泊的风险评估具有重大意义。于2017年水华暴发较为严重的夏季（6-8月）对巢湖水体的理化参数、浮游植物和蓝藻毒素进行了调查和分析。结果表明：夏季巢湖基本上处于富营养-超富营养的状态。24个样本共鉴定出浮游植物7门72属117种,以绿藻门、蓝藻门和硅藻门为主。浮游植物的群落组成和细胞密度存在明显的时空差异性,其中6月浮游植物平均细胞密度为1.35×10⁸ cells/L,优势种属主要为微囊藻（Microcystis spp.,优势度为0.397）、水华长孢藻（Dolichospermum flos-aquae,优势度为0.195）和水华束丝藻（Aphanizomenon flos-aquae,优势度为0.181）;7月浮游植物平均细胞密度为1.31×10⁸ cells/L,优势种属主要为微囊藻（优势度为0.741）和黏伪鱼腥藻（Pseudanabaena mucicola,优势度为0.072）;8月浮游植物平均细胞密度为1.01×10⁸ cells/L,优势种属主要为微囊藻（优势度为0.646）。11种蓝藻毒素在夏季巢湖水体中均有不同程度的检出,其中以微囊藻毒素MC-LR、MC-RR和MC-YR为主,最高检出浓度分别为0.115、0.107、0.018 μg/L。此外,分析了拟柱孢藻毒素浓度与水华束丝藻细胞密度的关系,显示两者之间存在非常显著的正相关性（P<0.01）,表明水华束丝藻可能是其最主要的产毒蓝藻。11种蓝藻毒素的浓度均未超过饮用水安全标准的规定,但其潜在的安全风险依然需要密切注意。     

三峡水库小江夏初水华暴发特征及原因分析

2013年5月对三峡水库小江回水区的水华发生过程进行了连续的动态监测与分析,以期了解水华过程中浮游植物群落结构的变化情况、小江夏初水华暴发特征及其主要的影响因素。期间共鉴定出浮游植物8门80属136种(含变种),以绿藻类为主(35属48种),蓝藻类(10属31种)和硅藻类(18属30种)次之,水华发生后期浮游植物及其蓝藻类的种类数少于初期和中期。浮游植物群落组成表现为蓝藻-绿藻型,且蓝藻门微囊藻占绝对优势,细胞丰度最高可达90%以上。浮游植物数量最高达10⁷cells/L以上,表层水体大于中层和底层水体。水华过程中,总氮处于重富营养水平,总磷处于轻-中富营养水平,不同水层的流速变化规律不同,其中中层与底层水体理化因子的变化特征基本一致,与表层水体有显著差异。冗余分析结果表明,浮游植物细胞总数与蓝藻数量及其微囊藻数量密切相关,与溶解氧、氮磷比等呈正相关,与总磷、流速等呈负相关,氮磷比及流速是水华发生的主要环境影响因素。     

Environmental factors influencing cyanobacteria community structure in Dongping Lake, China

The present study was conducted to provide a detailed understanding of the variation in cyanobacterial communities of Dongping Lake, which is the final water volume adjusting and storing lake in the east route of the South-to-North Water Diversion Project in China. The spatial and temporal distribution of cyanobacteria was assessed from May 2010 to October 2012 based on monthly samples collected from three stations. Over the 30-month survey, 15 genera and 25 species of cyanobacteria were identified, with cyanobacterial abundance at each monitoring station ranging from undetected to 3.04×107 cells/L, average of 4.27×106 cells/L. The dominant cyanobacterial species were Pseudanabaena limnetica and Aphanizomenon issatschenkoi and not the usual bloom-forming genera such as Microcystis and Anabaena. Cyanobacterial community structure and water quality variables exhibited substantial changes over the period of survey. Redundancy analysis, Pearson correlations, and regression analysis were applied to analyze the relationships among the variables. The results suggested that temperature and chemical oxygen demand were key drivers of the cyanobacterial community composition in Dongping Lake. In addition, the concentration of inorganic nitrogen in the lake had a profound efect on the cyanobacterial abundance as a non-limiting factor in warm periods.