南黄海首次暴发“巨囊”生态型球形棕囊藻藻华

FIRST REPORT OF PHAEOCYSTIS GLOBOSA BLOOM CAUSED BY“GIANT-COLONY”ECOTYPE IN THE SOUTH YELLOW SEA

球形棕囊藻(Phaeocystis globosa)常在热带至温带近海海域形成有害藻华,该种具有种内遗传多态性,且有囊体大小、特征色素组成等性状分化。在我国南海形成有害藻华的球形棕囊藻可形成“巨型囊体”,以19′-丁酰氧基岩藻黄素(But-fuco)为特征色素,是一种独特的“巨囊”生态型。2021年11月底至12月初,南黄海青岛沿岸暴发大规模球形棕囊藻藻华。藻华发生期间,对青岛沿岸3个站位的水文和化学要素进行了观测,分析了球形棕囊藻囊体的数量、直径和色素组成,并应用一种高分辨率种下分子标记——叶绿体rbcS-rpl27基因间隔区分析了其遗传特征。结果表明,藻华发生期间青岛沿岸表层海水温度较低(12~14℃),海域营养盐组成具有高溶解有机氮、低溶解无机氮的特征;球形棕囊藻囊体丰度超过20个/L,最大囊体直径为18mm,以But-fuco为特征色素,rbcS-rpl27序列分析表明其与南海“巨囊”生态型球形棕囊藻具有相同的遗传特征。南黄海首次暴发的球形棕囊藻藻华是由“巨囊”生态型形成,该藻华可能对海洋生态系统、水产养殖业发展和核电设施运行等构成威胁,亟待开展藻华成因与监测预警对策研究。

Phaeocystis globosa,an important causative species of harmful algal blooms worldwide,exhibits varying morphological and physiological features and high genetic diversity.The bloom-forming P.globosa in the South China Sea(SCS)is proposed to be a unique“giant-colony”ecotype,which features giant colonies and possesses 19′-butanoyloxyfucoxanthin(But-fuco)as its diagnostic pigment,and is genetically distinct from other strains of P.globosa.P.globosa blooms occur frequently in the SCS,as well as several times in the Bohai Sea and the North Yellow Sea,but never in the South Yellow Sea(SYS).A P.globosa bloom broke out in the coastal waters of Qingdao from late November to early December,2021.During the bloom,it was found that the surface temperature ranged 12~14℃,and exhibited high DON(dissolved organic nitrogen)content and low DIN(dissolved inorganic nitrogen)content in the Qingdao coastal waters.The colony abundance was more than 20 colonies/L with the maximum diameter of 18 mm.The sampled colonies from the Qingdao coastal waters contained a unique diagnostic pigment But-fuco,and belonged to the same genetic clade of“giant-colony”ecotype of P.globosa distributed in the SCS.This study firstly reported that the P.globosa bloom in the SYS caused by the“giant-colony”ecotype.The“giant-colony”P.globosa bloom may threaten local plankton ecosystem,aquaculture,and coastal nuclear power plant.Therefore,it is our key task to detect and monitor P.globosa blooms,and study the mechanism of its occurrence in the northern waters of China.