北部湾棕囊藻藻华原因种分析

近年来, 棕囊藻已成为我国北部湾海域藻华发生的主要原因种, 严重影响北部湾海洋生态环境、水产增养殖业和防城港核电安全, 急切需要对棕囊藻藻华原因种作进一步分析确认。2017年2月和3月在钦州湾和涠洲岛藻华发生海域分离得到9株棕囊藻, 采用光学显微镜进行形态学初步鉴定, 并通过核糖体小亚基序列(SSU rDNA)进行系统进化分析。研究结果表明, 北部湾9株棕囊藻与球形棕囊藻形态特征基本符合, 系统发育树与不同海域来源的球形棕囊藻聚在同一大分支上, 与其他海域来源的球形棕囊藻遗传距离为0.0000~0.0071, 其中北部湾WZS3-1株与墨西哥湾株CCMP627、苏里南株CCMP628、厄瓜多尔株CCMP1528、南非株P162、中国海株RCC:K1398及汕头株Santou97的球形棕囊藻亲缘关系最近, 遗传距离为0.0000, 而北部湾WZS1、WZS2、WZS4、WZS5株与香港株SKLMP_T005和渤海株BOHAI1亲缘关系最近, 遗传距离为0.0000。球形棕囊藻的种内遗传距离(0.0000~0.0073)明显小于种间遗传距离(0.0084~0.0440), 因此可确定来自北部湾不同海域的9株棕囊藻均为球形棕囊藻。此外, 球形棕囊藻各藻株间的亲缘关系远近与其地理位置分布不能完全对应。本研究结果将为我国棕囊藻藻华藻种库构建、棕囊藻北部湾株生理生态研究和北部湾棕囊藻藻华发生机理研究等提供参考。

Causative species of Phaeocystis blooms in Beibu Gulf

In recent years, Phaeocystis has become the main causative species for algal blooms in the Beibu Gulf of China. It has deleterious effects on marine ecosystem and aquaculture, and causes nuclear power plant safety problems in Fangcheng. It is thus urgent to further analyze the causative species of Phaeocystis in the region. In February and March 2017, nine strains of Phaeocystis sp. identified by optical microscope were isolated during algal blooms in Qinzhou Bay and Weizhou Island; their SSU rDNA sequences were then analyzed using Maximum Likelihood (ML) phylogenetic tree. The results showed that all nine strains of Phaeocystis sp. were morphologically consistent with those of Phaeocystis globosa. Their genetic distance varied between 0.0000-0.0073; and in the phylogenetic tree, all clustered in the same branch with those P. globosa from other seawaters. Among them, WZS3-1 strain in the Beibu Gulf had the closest genetic relationship with P. globosa from Gulf of Mexico CCMP627, Surinam CCMP628, Ecuador CCMP1528, South Africa P162, China Sea RCC:K1398 and Santou97, exhibiting a genetic distance of 0.0000. Strains of WZS1, WZS2, WZS4, and WZS5 in the Beibu Gulf had a genetic distance of 0.0000 with Hong Kong SKLMP_T005 and Bohai BOHAI1. The intraspecific genetic distance of P. globosa (0.0000-0.0071) is significantly smaller than the interspecific genetic distance of P. globosa (0.0084-0.0440). As a result, these nine strains from Beibu Gulf all belong to P. globosa. The phylogenetic distance for strains of P. globosa do not reflect their geographical distance. The findings of this study are essential for Phaeocystis culture collection, their further ecophysiological study and understanding of occurrence mechanisms for Phaeocystis blooms in the Beibu Gulf.