Alkaline phosphatase (AP) is one of the enzymes that can hydrolyze dissolved organic phosphate (DOP) to set orthophosphate free which can be absorbed by phytoplankton directly,and the expression of this induced enzyme always happened in the case of phosphorus (P) stress,so AP activity (APA) can be used to indicate the P stress status of phytoplankton in the seas.In this study,the spatial distribution of inorganic and organic phosphorus,and the regulation of relationship between APA distribution and phosphorus were investigated in the Qinzhou Bay by 4 voyages (spring,summer,autumn,winter) between 2015-2016.During the investigation,the APA in spring,summer,autumn and winter were 20.42 ± 5.32 nmol/μg Chl a/h,138.17 ± 94.32 nmol/μg Chl a/h,142.60 ± 72.60 nmol/μg Chl a/h and 29.48 ± 18.52 nmol/μg Chl a/h,respectively.The correlation analysis results showed that there was significant negative correlation between APA and inorganic phosphorus (P ＜ 0.05),which indicates that APA can be used to show the P stress status of phytoplankton in the Qinzhou Bay.The Qinzhou Bay is potential phosphorus limited area because N/P is higher than 35 in most seasons except for spring,and phytoplankton under serious phosphorus stress in summer and autumn.AP is abundantly expressed in summer and autumn by phytoplankton,so it is possible that DOP plays a key role on the phytoplankton biomass and the occurrence and maintenance of algae bloom in the Qinzhou Bay.%碱性磷酸酶(Alkaline phosphatase,AP)是浮游植物在磷胁迫的情况下诱导表达的一种酶,其作用是能够将溶解有机磷(Dissolved organic phosphate,DOP)水解成浮游植物可以直接利用的正磷酸盐形式,因此碱性磷酸酶活性(Alkaline phosphatase activity,APA)可用来指示海区浮游植物的磷胁迫状态.本研究以2015-2016年钦州湾4个航次(春季、夏季、秋季、冬季)的调查资料为依据,研究了钦州湾海域表层无机及有机磷的空间分布特征、APA的分布及其与磷营养之间的调控关系.调查期间,钦州湾海域春季、夏、秋、冬的单位叶绿素APA的平均值分别为20.42±5.32 nmol/μg Chl a/h,138.17±94.32 nmol/μg Chl a/,142.60±72.60 nmol/μg Chl a/h和29.48±18.52 nmol/μg Chl a/h.经分析,APA与无机磷之间存在显著的负相关(P＜0.05),与N/P呈极显著负相关(P＜0.01),该海区APA可以反映钦州湾浮游植物的磷胁迫水平.海区氮磷比平均值在除春季外的三个季节均高于35,存在潜在的磷限制,浮游植物在夏季和秋季遭受较严重的磷胁迫.夏季和秋季浮游植物大量表达AP,由此推测DOP可能在钦州湾浮游植物生物量的维持甚至赤潮发生期间的磷补给上起着重要作用.
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