【作者】 刘峰；

【导师】 逄少军；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 海洋生物学， 2010， 博士

【摘要】 2008年5 7月青岛近海出现了世界上规模最大的绿潮,绿潮的优势种是浒苔Ulva prolifera,仅在青岛海域打捞出的生物量就超过100万吨(湿重)。卫星数据分析表明这次绿潮是在江苏外海形成,并在风场和流场的作用下漂移到青岛。然而有两个值得关心的问题是:8月份以后绿潮逐渐消亡后,在青岛近海环境中是否仍然存在一个绿潮浒苔的繁殖体库(包括海藻微观断枝、孢子、配子、合子以及其发育不同阶段的显微个体);如果存在,其数量有多大,是否会成为来年青岛海域再次暴发绿潮的种子库。对此,从2008年12月到2009年4月,作者系统采集分析了青岛近海6个站位的水样。这些水样在实验室标准条件下培养后都获得了石莼属海藻,依据形态特征区分为9个形态组。ITS和rbcL序列的分子系统数据表明,在整个采集过程中所有站位的水样都没有发现2008年黄海绿潮的优势种浒苔。这一结果说明黄海绿潮浒苔不是青岛本地种,这种海藻很可能无法适应青岛海域的环境特点,因此没有在青岛沿海形成自然种群。这些结论排除了在青岛近海由于残留大量绿潮浒苔显微阶段繁殖体而暴发绿潮的可能性。这与2009年春夏季在6个站位对石莼属海藻种类的调查结果相吻合。卫星图像表明2008年青岛出现的绿潮是由江苏外海漂移到青岛海域,但是关于黄海绿潮浒苔的确切来源地,一直没有得出令人信服的结论。在2009年4 5月,作者对江苏沿海的6个站位进行了一系列调查,采集和分析了不同站位石莼属海藻样品和水样。对不同站位的海水水样进行培养定量,结果表明水样中广泛存在石莼属海藻微观繁殖体,但是数量差别很大,从7株L1到3140株L1不等。形态学、分子系统学和生殖生理学分析表明沿岸水产养殖池中存在与2008年黄海绿潮优势种浒苔完全一致的海藻样品。绿潮的发生和紫菜栽培周期的不同步,以及紫菜筏架的石莼属海藻样品与黄海绿潮优势种不一致,这两方面的结果排除了黄海绿潮优势种来源于紫菜栽培筏架的可能,同时也否认了黄海绿潮的暴发是由紫菜栽培规模扩大造成的这一结论。同时沿岸水产养殖业在操作过程中大量使用有机肥料,导致这些养殖池富含很高的营养盐。养殖海水排放到外海后,造成了外海富营养化,这为绿潮的暴发蓄积了物质条件。调查发现江苏沿海海水浑浊,穿透光辐射弱,这排除了在江苏外海存在浒苔藻床的可能性。在黄海,从2007年到2009年,已经连续三年暴发了大规模的绿潮。为了进一步调查绿潮构成种的来源,在2009年绿潮的初期、暴发期和后期,作者先后参与了5个航次的研究工作,采集了表面漂浮的海藻样品、沉底的海藻样品和不同站位的海水水样,并对漂浮的和从水样中培养得到的海藻样品进行了形态学和分子系统学分析。研究表明所有海面上漂浮的优势种海藻样品和从海水水样中培养得到的分枝发达的海藻样品聚到了一个U. linza-procera-prolifera (LPP)进化枝中,2008年和2009年黄海绿潮的构成种属于同一种海藻。从黄海水样中培养检测到了绿潮构成种,表明在黄海绿潮的暴发阶段,绿潮海藻除了快速的营养生长外,也通过放散孢子或配子等生殖细胞来不断扩增生物量和范围。同时也发现在黄海海水中广泛存在着石莼属海藻的微观繁殖体,并且在数量上从5月到8月有一个上升的趋势。研究表明海水中石莼属微观繁殖体数的定量方法是可靠的,可以准确评估石莼属海藻微观生物量的变化,及时预测海水中潜在绿潮海藻的生物量和绿潮暴发的规模。同时发现绿潮后期沉底浒苔遭受到严重的胁迫,沉到海底后很有可能死亡。为了研究石莼属海藻微观繁殖体在冬季的存在形式以及黄海绿潮浒苔的来源,在2009年冬季采集了江苏沿海北部(连云港)和南部(启东和如东)4个站位潮间带的底泥样品,并对泥样进行了石莼属海藻显微阶段繁殖体的定量研究,发现冬季江苏沿海潮间带的底泥中,有大量与泥颗粒结合的石莼属海藻微观繁殖体。在实验室模拟江苏潮间带底泥环境的实验中,发现显微阶段繁殖体对低温和黑暗有很强的耐受能力。形态学和分子系统学研究表明,4个站位的潮间带泥样中检测到3种石莼属海藻,但是没有发现黄海绿潮浒苔。发明的定量泥样中石莼属海藻微观繁殖体的标准方法,对在江苏沿海开展更大规模的绿潮溯源调查具有重要的参考价值。更多还原

【Abstract】 The region of Qingdao, China, experienced the world largest green tide from May to July 2008. More than one million tons of fresh biomass of the green alga identified as Ulva prolifera was harvested. The original source of this seaweed was suspected to be from the south of the Yellow Sea as revealed by satellite images. The floating biomass drifted with water current northward and flourished in nearshore waters around Qingdao. However, it is unclear whether the bloom forming alga would have left the microscopic propagules which could survive in the Qingdao local coastal environment and pose future danger of potential bloom. Systematic and seasonal sampling of waters in the intertidal zone at six collection sites along the Qingdao coast was conducted from December 2008 to April 2009. Forty eight water samples were analyzed. From these, nine different morphotypes of Ulva were grown in the laboratory under standard temperature and light regimes. Growth of Ulva was observed in all water samples. However, morphological and molecular phylogenetic analyses revealed that the bloom forming alga was absent in all the water derived cultures during the sampling period. These results provide evidence that the bloom forming alga was not native and it was unlikely able to survive the coastal waters of Qingdao, even though all the sampling locations were heavily covered by this alga in June 2008.Qingdao experienced the world largest drifting macroalgal bloom composed of the filamentous macroalga Ulva prolifera in 2008. No convincing biological evidence regarding the algal source is available so far. A series of field collections of both Ulva samples and water samples in various sites along Jiangsu coasts were conducted in April to May of 2009. Density of microscopic Ulva germlings in the waters sampled from different sites ranged from 7 to 3140 individuals L?1, indicating the wide spreading and long term existence of the algae in the investigated region. Morphological and ITS nrDNA and rbcL gene comparisons revealed that the algae collected from land based animal aquaculture ponds was identical to the dominant bloom forming alga in 2008. Mismatch of Porphyra farming period with the occurrence of the green tide bloom, as well as the negative identification results of the sampled green algae from the Porphyra rafts eliminated Porphyra rafts as the principal and original source of the bloom forming alga.In the Yellow Sea of China, large scale green tides have broken out for three consecutive years from 2007 to 2009. As part of the efforts to localize the algal source, five open sea cruises were conducted in the period of the bloom in 2009. Drifting algal samples and the water samples were collected. Results showed the ubiquitous existence of the Ulva microscopic propagules in the Yellow Sea. The number of the Ulva individuals decreased with the increase of the water depth. In August 2009, the average number of Ulva microscopic stage individuals in 1 L seawater was more than that in May 2009. This quantitative method can be expected to predict the potential biomass of the green tide Ulva species in seawater and thus the scale of the potential drifting biomass. The drifting Ulva and those derived from the water samples were analyzed by morphological and molecular systematic comparisons. For phylogenetic analyses, the ITS nrDNA and rbcL gene were used. Our molecular and morphological data indicated that the dominant free floating Ulva species in 2008 and 2009 belonged to the same strain of the U. linza-procera-prolifera (LPP) clade. Microscopic individuals of the dominant Ulva strain were detected in eight stations, revealing that spore dispersal in the water helped to enlarge biomass in the water during the outbreak stage of green tide in the Yellow Sea.In November 2009, the potential recruitment and development of Ulva species from propagule banks in the muddy or sandy sediment of Jiangsu coasts were investigated. The results indicated that numerous Ulva microscopic propagules existed in the intertidal muddy sediment and the Ulva propagules could tolerate the low temperature and dark in the intertidal for at least three months. Morphological and molecular comparisons revealed that the bloom forming alga was not found in the four investigated locations. However, the stardand method to evaluate the number of Ulva propagules was proved to be effective and with significant value in the study of tracking the origin of bloom.更多还原