调控有毒甲藻多环旋沟藻孢囊形成和萌发的机理研究

Abstract: The toxic dinoflagellate Cochlodinium polykrikoides has been observed to rapidly expand its geographic distribution and form numerous catastrophic blooms in the past 30 years and therefore has been considered to be one of the few most important harmful algal bloom-forming species. During 1984-2014, many blooms with various scales or presence of C. polykrikoides were reported in coastal waters of Hong Kong, Guangdong, Zhejiang, Shandong and Jiangsu, China, and blooms of this species have become a potentially serious threat to aquiculture and fisheries, which have attracted great attention from the research community of HABs, local governments, and other stakeholders. Resting cyst formation and subsequent germination are currently widely accepted to play a key role in the recurrence and geographical expansion of harmful algal blooms (HABs). The recent confirmation of resting cyst production by C. polykrikoides, therefore, provides a viable explanation for the frequent recurrences and geographical expansion of C. polykrikoides blooms in many coastal areas. However, the regulating factors of resting cyst formation and germination in C. polykrikoides have not been carefully investigated yet. Hence, we propose here a systematic investigation into the regulating mechanisms of C. polykrikoides cyst formation and germination via laboratory experiments using multiple clonal cultures of the species obtained from different geographic locations. In these laboratory experiments, while the general life history of C. polykrikoides will be re-examined, particular attentions will be focused on factors that possibly regulate resting cyst formation or germination in C. polykrikoides, including temperature, depleted and unbalanced nutrients, irradiance, density effect, competitor, and predator. Accomplishment of the proposed research is anticipated to provide a more detailed and comprehensive reconstruction of the life history of C. polykrikoides, and further our understanding of the population dynamics, geographical expansion, and even measures of prevention and control for C. polykrikoides blooms.

有毒甲藻多环旋沟藻过去30多年来在全球迅速扩散，已成为世界上最重要的灾害性藻华种类之一。1984-2014年间在我国香港、广东、浙江、山东和江苏等地海域多环旋沟藻被报道或由其形成小规模藻华，已对沿海水产养殖业构成潜在威胁。因此，多环旋沟藻藻华已成为国内外藻华研究学界和沿海渔业部门共同关注的海洋生态问题。休眠孢囊已被证明在藻华的生消和地理扩散过程中起着非常重要的作用，因此，最近多环旋沟藻孢囊的发现为其藻华频发与全球扩散提供了一个合理的解释。然而，有关其孢囊形成和萌发的调控因素尚未被研究过。本项目将通过室内纯培养实验系统地研究多环旋沟藻的一般生活史特征，并重点关注温度、营养失衡、光照、密度效应、竞争者和捕食者等各种环境因子对多环旋沟藻孢囊形成或萌发的调控方式及其可能的机理。研究结果可望获得对多环旋沟藻生活史特征更为全面的认识，并为深入理解该藻藻华的生消过程、地理扩散和生态风险防控提供科学依据。

有毒甲藻多环马格里夫藻过去30多年来在全球迅速扩散，已成为世界上最重要的灾害性藻华种类之一。1984-2016年间在我国香港、广东、浙江、江苏、山东和天津等地海域多环马格里夫藻被报道或由其形成小规模藻华，已对沿海水产养殖业构成潜在威胁。因此，多环马格里夫藻藻华已成为国际国内藻华研究学界和沿海渔业部门共同关注的海洋生态问题。休眠孢囊已被证明在藻华的生消和地理扩散过程中起着非常重要的作用，因此，最近多环马格里夫藻孢囊的发现为其藻华频发与全球扩散提供了一个合理的解释。然而，有关其孢囊形成和萌发的调控因素尚未被研究过。为此，本项目首先从山东近海分离纯化获得多株多环马格里夫藻纯培养，研究了多环马格里夫藻营养细胞和孢囊的形态结构、多环马格里夫藻的有性生殖过程、孢囊的形成过程及萌发过程;开展了多种因子包括起始细胞密度、营养盐、颗粒添加物、捕食者的存在、微量元素等对孢囊形成的影响；开展了温度等多种环境因子对孢囊萌发的影响。在课题执行期间，在野外分离多环马格里夫藻的同时分离到了褐色马格里夫藻和Pseliodinium pirum（原名螺旋旋沟藻），并对这两种藻的形态和生活史进行了拓展性研究。通过研究得出以下主要结论：（1）多环马格里夫藻中国株孢囊呈圆形，孢囊表面无刺或凸起物；（2）多环马格里夫藻通过有性过程形成休眠孢囊，即：两个营养细胞进行交配，形成具双纵鞭毛的游动合子，游动合子失去鞭毛变成不动合子，不动合子成熟形成休眠孢囊；（3）休眠孢囊一般在2-4周内萌发，无明显强制休眠期；（4）营养盐、捕食者的存在、微量元素、颗粒添加物等均能影响多环马格里夫藻孢囊的形成，但是营养限制和捕食者的存在能明显促进孢囊的形成；（5）温度（20°Ϲ）能明显促进多环马格里夫藻孢囊的萌发；（6）在中国近海首次详细报道了褐色马格里夫藻和Pseliodinium pirum（原名螺旋旋沟藻）形态、分子特征和生活史等。研究结果获得了对多环马格里夫藻孢囊的生物学和孢囊形成的影响因素更为全面的认识，为进一步研究多环马格里夫藻藻华的种源、形成、年际复发等提供了更深入的认识，也为后续基于孢囊分布和丰度的藻华预测预警及防控研究提供科学依据。