【作者】 李俭平；

【导师】 赵卫红；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 海洋化学， 2011， 博士

【摘要】 2008年7月青岛近海大型绿藻爆发,主要肇事物种为浒苔。浒苔在青岛附近海域覆盖面积约为400平方公里。是目前世界上规模最大的绿潮,仅在青岛海域打捞出的生物量就超过100万吨。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。据专家推测,可能是由于富营养化和青岛近海适宜的条件,使海藻通过旺盛的营养生长和放散生殖细胞进行繁殖,因而生物量快速增长,爆发了大规模的绿潮。本文通过选取浒苔为实验对象,在实验室内进行可控实验,选取氮营养盐作为研究对象,考察氮营养盐对浒苔生长的影响以及浒苔对氮营养盐的吸收动力学机制。具体内容包括:1.选取几种无机氮、有机氮以及它们的混合物作为氮源,浒苔可以有效利用NO₃^-、NH₄⁺和有机N源酵母抽提物及中低浓度的NO₂^-和尿素;在NO₃^-、NH₄⁺、和NO₃^-: NH₄⁺=1:1几种无机N源中及urea-N为有机N源中,等量分批添加方式时浒苔的生长态势较好;在NO₃^-: urea-N=1:1和NH₄⁺: urea-N=1:1无机和有机混合N源中,一次性添加方式时浒苔的生长态势较好;在与其他N源共同存在时浒苔可以优先利用NH₄⁺。2.通过选取不同的理化指标,采用正交试验考察它们对浒苔氮营养盐吸收动力学及浒苔生理生态指标的影响,获得其对营养盐吸收的有关参数,并通过这些参数对浒苔的生态习性及生理特性作出判断和阐释。在相同条件下,浒苔有优先吸收NH₄⁺的趋势,而且浒苔对NH₄⁺的吸收速率大于对NO₃^-的吸收速率;浒苔藻体体内氮素同化首先受到吸收的制约,同时藻体体内NO₃^-含量也调节NO₃^-的吸收与同化;硝酸还原酶的活性不能用来指示浒苔对硝酸盐的吸收速率;谷氨酰胺合成酶活性来反映浒苔对NH₄⁺的吸收。3.选取海水中含量比较高的硝酸氮和氨氮,考察浒苔对NH₄⁺与NO₃^-的吸收及其相互作用,发现浒苔具有同时利用水体中较高浓度的NH₄⁺和NO₃^-的能力, NH₄⁺与NO₃^-对彼此的吸收具有抑制作用,但NO₃^-对NH₄⁺的吸收抑制作用较弱。4.针对日益严重而复杂的污染现状,单一的研究营养盐或重金属对海洋浮游植物生长的影响已远远不能解决实际问题,需要综合考虑多种因素的影响。选取Pb（II）、Cu（II）、Cd（II）、Zn（II）、Fe（III）等几种常见的微量重金属元素,考察它们对浒苔营养盐吸收动力学及浒苔生理生态指标的的影响。结果表明所选取的几种重金属对浒苔的硝酸还原酶活性、体内NO₃^-诱导浓度、体内累积NO₃^-浓度和谷氨酰胺合成酶活性等均有明显影响,从而影响了浒苔对NO₃^-和NH₄⁺的吸收。更多还原

【Abstract】 In late June 2008, the waters and shores of the Olympic sailing events’Qingdao venue on China’s north-eastern coast experienced a massive green-tide covering 400 km2. The green-tide lasted over two weeks and the resultant cleanup involved more than 10,000 people and removed over one million tonnes of algae from the beach and coast of Qingdao. The green-tide was comprised of Enteromorpha prolifera which has been previously reported as one of the dominant benthic algae in the littoral zone of China.The original source of this seaweed was suspected to be from the south of the Yellow Sea as revealed bysatellite images.The floating biomass drifted with water current northward and flourished in nearshore waters around Qingdao. The initial causes were attributed to coastal eutrophication and suitable conditions in Qingdao coasts by some scientists. The vegetative growth habit of the species and spore dispersal in the water helped to enlarge biomass in the water during the outbreak stage of green tide. Our investigation looked for the response to nitrogen nutrient, and the uptake kinetics mechanism of nitrogen and ecophysiological analysis of Enteromorpha prolifera. This will provide information about the link between E. prolifera blooms and nitrogen nutrient enrichment. The details were as follows:1. Several kinds of inorganic nitrogen, organic nitrogen, and their mixtures were selected as nitrogen sources. The growth of E. prolifera was affected by different N sources, N concentrations, and culture methods. Our results show that NH₄⁺ and NO₃^- were utilized effectively by E. prolifera, and that NO₂^- and urea at a range of several to dozens ofμmol L?1 were also effectively utilized. When supplied with another nitrogen source, NH₄⁺ was preferentially assimilated by E. prolifera. A single, high-concentration addition of the N source was favorable for rapid growth of E. prolifera, whereas intermittent addition of the N source was favorable for prolonged growth.2. By selecting different physical and chemical factors, the orthogonal design was used to investigate their impacts on absorption kinetics and ecophysiological indicators of E. prolifera, and access the relevant parameters of nutrient uptake kinetics for judging the ecological habits and physiological characteristics of E. Prolifera. Under the same conditions, NH₄⁺ was preferentially absorbed by E. Prolifera, and the absorption rate of NH₄⁺ was greater than that of NO₃^-. The nitrogen assimilation in vivo of E. prolifera was constrainted by its absorption firstly, while the accumulated NO₃^- concentration in vivo can adjust the absorption and assimilation of NO₃^-. Moreover, nitrate reductase activity （NRA） can not be used to indicate the absorption rate of NO₃^-, but glutamine synthetase activity （GS） can be used to reflect the absorption rate of NH₄⁺.3. NO₃^- and NH₄⁺ which are the most common N sources in seawater, and readily assimilated by E. Prolifera were selected as nitrogen sources to study the interaction between their absorption kinetics. The results show that E. Prolifera can take advantage of NO₃^-and NH₄⁺ with higher concentrations in seawater respectively, and NO₃^-and NH₄⁺ would inhibit the absorption of each other, but the inhibition action of NO₃^- on NH₄⁺ was weaker..4. For the increasingly serious and complex pollution status, the study about the impact of single nutrients or heavy metals on marine phytoplankton growth has been far from solving practical problems, it needs to consider many factors comprehensively. Pb（II）, Cu（II）, Cd（II）, Zn（II） and Fe（III） were selected to research their impacts on nitrogen uptake kinetics and ecophysiological indicators of E. Prolifera. The results show that these heavy metals selected can significantly affect NRA, the accumulated NO₃^- concentration in vivo, the induced NO₃^- concentration in vivo and GS of E. Prolifera, which thus affect the absorption rate of NH₄⁺ and NO₃^-.更多还原