氮、磷营养盐对链状亚历山大藻（东海株）生长和产毒的影响研究

IOCAS-IR > 海洋环流与波动重点实验室

	氮、磷营养盐对链状亚历山大藻（东海株）生长和产毒的影响研究
其他题名	Effects of Nitrogen and Phosphorus on Growth and Toxin Production of Alexandrium catenella (ACDH)
	李天深
学位类型	博士
	2007-06-08
学位授予单位	中国科学院海洋研究所
学位授予地点	海洋研究所
关键词	链状亚历山大藻硝酸盐磷酸盐东海长江口有害赤潮产毒
摘要	近年来，东海长江口邻近海域春季常常发生大规模链状亚历山大藻（Alexandrium catenella）赤潮。通常认为，由长江携带入海的大量营养盐导致的富营养化是该海域大规模赤潮频繁发生的重要原因。为阐明该海域富营养化特征与链状亚历山大藻赤潮的发生及其危害效应之间的关系，本文根据东海氮、磷营养盐的浓度与结构特征，设计实验研究了营养盐对链状亚历山大藻（东海株ACDH）的生长和产毒的影响。实验结果表明，ACDH 藻株的比增长率在硝酸盐浓度大于 28.0 µM 时接近最高水平，长江口邻近海域海水中硝酸盐的浓度可以使 ACDH 藻株的比增长率接近最高值；藻株的比增长率在磷酸盐浓度大于 2.5 µM 时也接近最高水平，现场海水中磷酸盐的浓度可能对ACDH藻株的生长构成限制。ACDH藻株生长的最适氮磷比在9到11之间，表明链状亚历山大藻的生长需要较多的磷。ACDH 藻株对磷酸盐的最大吸收速率 (Vm) 和半饱和常数(Ks) 分别为 0.22 pmol/cell•h 和 0.75 µM，与中肋骨条藻等东海常见赤潮藻种相比并不利于其对低浓度磷酸盐的竞争吸收，但处于磷限制的链状亚历山大藻细胞有明显的碱性磷酸酶表达，这将有助于其吸收利用有机态的磷营养物质，获取所需的磷维持生长。链状亚历山大藻可以利用尿素、硝酸盐和铵盐这三种氮源进行生长，有相近的比增长率和最大细胞密度。综合本实验得到的结果与以往的文献资料可以认为，东海链状亚历山大藻的适应策略利于其在长江口邻近海域形成赤潮，但东海长江口邻近海域的富营养化并非链状亚历山大藻赤潮形成的唯一原因，链状亚历山大藻赤潮的形成还应与其生活史和垂直迁移等行为特征有关。而高浓度的营养盐对于亚历山大藻赤潮规模的增加可能具有直接作用。在常见的铵盐、硝酸盐和尿素这三种氮源中，铵盐和硝酸盐的加入会导致细胞毒素含量的迅速增加，但是，添加尿素却不能显著提高藻细胞的毒素含量。长期以尿素作为氮源甚至会使藻细胞的毒素含量低于氮限制条件下的细胞毒素含量。磷限制能显著提高其细胞毒素含量，对野外采集的浮游植物样品分析结果显示，其细胞毒素含量在 34.7-88.4 fmol/cell 之间，显著高于室内培养的营养盐充足条件下的链状亚历山大藻的细胞毒素含量，而与磷限制条件下培养的藻细胞毒素含量接近，说明东海海水中磷酸盐的限制有可能提高藻细胞的毒素含量，从而增加其潜在的危害效应。总之，通过我们的研究可以看出，东海的富营养化特征直接影响链状亚历山大藻赤潮的形成与潜在的危害效应。东海链状亚历山大藻的适应策略利于其在长江口邻近海域形成赤潮，同时，该海域高氮磷比和磷酸盐浓度限制会提高藻细胞的毒素含量，增加其危害效应。以上研究将有助于了解链状亚历山大藻赤潮的爆发机理，并对赤潮危害的预测和防范提供科学依据。
其他摘要	Blooms of Alexandrium catenella were frequently observed in sea areas adjacent to the estuary of the Changjiang River in spring during the harmful algal bloom (HAB) studies in the last several years. It was considered that the increasing intensity of these dinoflagellate blooms was related to the incremental nutrient influx from the Changjiang River over the last 40 years. Based on the nutrient status in situ in sea areas adjacent to the estuary of the Changjiang River, the effects of major nutrients on growth and toxin production of Alexandrium catenella (strain ACDH) was studied to understand the relationship between eutrophication and the population dynamics, as well as potential impacts, of A. catenella blooms. The results showed that strain ACDH reached the maximum specific growth rate when nitrate concentration was above 28μM. Nitrate concentration in situ could support strain ACDH to grow at a rate close to the maximum specific growth rate. Strain ACDH reached the highest specific growth rate when phosphate concentration was above 2.5μM, suggesting that the phosphate concentration in situ would be a limiting factor for the growth of strain ACDH. The optimal N:P ratio for the growth of A. catenella is about 9-11, which is much lower than the ratio of nitrate to phosphate in sea areas adjacent to the Changjiang River estuary. The maximum uptake rate (Vm) and half saturation concentration (Ks) of strain ACDH for phosphate uptake are 0.22 pmol/cell.h and 0.75 µM, respectively. ACDH is not competitive in utilization of low-concentration phosphate in seawater. ACDH could use nitrate, ammonium and urea as sole N source to grow, with similar specific growth rate and maximum cell density. The results, in association with the published references, indicate that the nutrient uptake and utilization characteristics, as well as the specific life history and behavior features of A. catenella, are the major reason accounting for the formation of A. catenella blooms. However, the high nutrient concentrations in seawater should be the major reason for the increasing intensity of A. catenella blooms. The addition of both nitrate and ammonium to N-starved cells of strain ACDH will lead to rapid and dramatic increases of cellular paralytic shellfish poisoning (PSP) toxin content, however, only a slight increase of cellular toxin content can be observed after the addition of urea. And the utilization of urea as a sole nitrogen source by strain ACDH will lead to decreased cellular toxin content, even lower than the cells cultured under nitrogen-limitation condition. The cellular toxin contents of A. catenella cells collected from the field are much higher than those growing on sufficient nutrients in the lab, but comparable to those cultured under phosphorus limitation condition. It is indicated that the high N:P ratio and phosphate limitation in the East China Seal might lead to high cellular toxin content. In summary, our results suggest that eutrophication characteristics in the Changjiang River estuary have direct effects on the bloom dynamics and potential impacts of A. catenella blooms. The adaptive strategies of A. catenella, such as the capability in utilizing organic phosphorus compounds, are critical for the bloom formation in this region. More importantly, the nutrient structure of high N:P ratio and phosphate limitation in this area might lead to elevated cellular toxin content, and potential impacts, of the A. catenella algal blooms.
页数	88
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/1085
专题	海洋环流与波动重点实验室
推荐引用方式 GB/T 7714	李天深. 氮、磷营养盐对链状亚历山大藻（东海株）生长和产毒的影响研究[D]. 海洋研究所. 中国科学院海洋研究所,2007.

条目包含的文件
文件名称/大小	文献类型	版本类型	开放类型	使用许可
10001_20042800681201（5058KB）			限制开放	--	浏览