球形棕囊藻囊体对典型生源要素的扩散通量及影响因素定量研究

The blooms of Phaeocystis globosa frequently occurred along the coastal areas of China in recent years. The most important characteristics of these blooms were that they form giant colonies while blooming, which caused tremendous threaten to the coastal nuclear power plant since the water intakes of cooling system were frequently blocked by these colonies. The hemolytic toxin produced by colonies near the fishing cages directly caused death of fish, thus being seriously harmful also to marine aquacultures. It is scientifically meaningful focusing researches on mechanisms and control of Phaeocystis globosa blooms..Once the colonies were formed, the diffusion flux of typical biogenic elements into or out of the colony envelop apparently determined the growth of the colonies and maintenance of the blooms. Focusing on the very specific life history (colonies) of Phaeocystis globosa, this research aimed at quantification of the diffusion flux of typical biogenic element (e.g. nitrate) of colonies, and aimed at discriminating the key factors impacting these fluxes. These were very important for answering the scientific questions on the nutrient sources, flux and their limiting/promoting effects to the colonies in the process of a Phaeocystis globosa bloom. These above work, as well as a model simulating the growth of colonies, will help us gaining the knowledge about the final size of the colonies, the health and mentenience of the colonies and lasting of a bloom, which provided important scientific basis in the control of these Phaeocystis globosa blooms.

球形棕囊藻赤潮是近年来在我国近海频繁发生的赤潮种类，其赤潮爆发特点是形成巨大的囊体。球形棕囊赤潮的这种特性已造成滨海核电冷源取水堵塞；网箱区域聚集的囊体产生溶血毒素，直接引起鱼类等死亡，对沿海养殖业也危害巨大。对棕囊藻赤潮爆发的成因和防控方面的研究具有重要的科学意义。.囊体形成后，对典型生源要素的吸收扩散，决定了囊体的生长、赤潮的维持等过程。本研究借助稳定同位素示踪技术定量化研究球形棕囊藻囊体形成后的这种极特殊生活史形态对典型生源要素的吸收扩散速率和通量，并甄别影响其扩散通量的关键环境因子，回答球形棕囊藻囊体形成和赤潮爆发后囊体内的营养物质来源、通量及其对囊内细胞生长限制或促进作用等关键科学问题，进而通过棕囊藻囊体生长动态模型预测囊体的最终尺寸、维持能力和赤潮持续时间等问题，为防控球形棕囊藻赤潮提供科学依据。

球形棕囊藻赤潮是近年来在我国近海频繁发生的有害赤潮种类，其赤潮爆发特点是形成巨大的囊体。球形棕囊赤潮的这种特性已造成滨海核电冷源取水堵塞，科学防控棕囊藻赤潮，具有重要科学意义。而科学认知和机理研究为其防控提供科学依据和保障。为此本研究的主要内容聚焦在掌握球形棕囊藻赤潮高发海域的硝酸盐、定量化分析囊体对典型生源要素的同化吸收速率、硝化速率等关键过程速率。.项目执行期间，项目组人员多次奔赴广西北部湾防城港核电厂冷源取水海域棕囊藻赤潮高发区，开展该海域环境要素调查、球形棕囊藻室内和现场过程速率实验，获得了一系列关键科学数据和重要结果。.发现硝酸盐浓度与棕囊藻赤潮暴发密切相关：球形棕囊藻赤潮暴发海域N营养盐（尤其是硝酸盐）充足是其赤潮暴发的必要条件和关键环境因子，囊体暴发期间营养盐（尤其是硝酸盐）大量消耗。而随着生物因素对硝酸盐的消耗，每年3月、4月后棕囊藻赤潮无法维持，逐渐消耗。.对于两种主要营养盐（硝酸盐和铵盐）来说，硝酸盐或铵盐加富，均会影响球型棕囊藻囊体细胞对另一种营养盐的吸收，但各组中棕囊藻对硝酸盐的平均吸收利用速率（6.28-7.38×10exp(−9) μmol per h per cell）始终高于铵盐（1.45-2.07×10exp(−9) μmol per h per cell）。结果表明球型棕囊藻囊体细胞对硝酸盐有着特殊的“偏好”。现场培养实验发现赤潮高发期，水体中硝化过程（速率最高达1.44 μmol·per L per day）能为赤潮暴发提供一定的硝酸盐。.初步拟合了实际获得的硝酸盐同化吸收速率下囊体可能的生长状况。结果发现在目前硝酸盐吸收速率下，对以往基于碳的囊体的生长速率并不构成对碳源吸收速率上的限制，反而在现场的硝酸盐同化吸收速率背景下，囊体生长过程可能提高囊体内细胞数量的增长斜率，即理论上囊体在较小时（比如3-5厘米）就能达到仅考虑碳模型时囊体很大（比如8-9厘米）才能达到的囊体内细胞密度。侧面验证了硝酸盐对囊体的快速生长具有重要促进作用。.相关环境要素调查和关键过程速率实验结果为揭示球形棕囊藻暴发原因并开展行之有效的防控提供科学依据。