温度和氮、磷限制对南海一株利玛原甲藻生长和产毒的影响

Effects of temperature,nitrogen and phosphorous limitation on the physiological and toxigenic characteristics of harmful benthic dinoflagellate Prorocentrum lima isolated from South China Sea

为评估我国南海海域分布的一株产毒底栖型利玛原甲藻(Prorocentrum lima,HN45株)的潜在风险,在不同温度(20℃、25℃、30℃)和氮、磷限制(氮磷比:4.08、8.17、16.3、24.5、73.5、147)条件下对其进行室内培养,比较了温度和氮、磷限制对该株赤潮藻的细胞数、比生长率和色素等生理特征及其腹泻性贝类毒素(diarrhetic shellfish toxins,DSTs)生产特性的影响。多因素方差分析结果表明,温度和磷限制均显著影响利玛原甲藻的细胞数、多甲藻素和大田软海绵酸(okadaic acid,OA)细胞内总毒素含量。单细胞产毒量在温度为25℃、磷浓度为6μM时呈现最高值,即11.34 pg/cell。磷限制抑制了藻细胞的生长和繁殖,但显著提高了其产毒能力。研究结果显示,该株藻细胞产毒以游离态DSTs毒素为主,其相应酯化态毒素含量仅占单细胞产毒总量的3%~14%,含量远低于游离态毒素。研究还发现,利玛原甲藻所产叶绿素a(chlorophyll a,Chl a)含量随生长周期的变化与DSTs含量呈负相关,进一步证实了Chl a与DSTs存在竞争关系,这对于解析环境胁迫条件下利玛原甲藻生存策略提供了重要科学依据。

This study evaluated the potential risk for a harmful benthic dinoflagellate Prorocentrum lima(strain HN45),which was isolated from the South China Sea.In this experiment,P.lima was cultured in laboratory under different temperatures(20℃,25℃,30℃)and nitrogen phosphorous limitation conditions(nitrogento-phosphorus ratio,N/P:4.08,8.17,16.3,24.5,73.5,147).Then the physiological characteristics,including cell density,growth rate and pigments,as well as the production characteristics of diarrhetic shellfish toxins(DSTs)were investigated and analyzed.Based on the multi-factor analysis of variance,the results showed that the temperature and phosphorus-limited levels had significant effect on cell density,peridinins(the typical pigments of dinoflagellates)and intracellular toxin of P.lima.The DSTs production ability of single cells reached to the highest value(11.34 pg/cell)at the temperature of 25℃and phosphorus concentration of 6μM.Phosphorus deficiency reduced cells density and specific growth rate of P.lima,but significantly increased their ability to produce DSTs.Moreover,esterified toxins accounted for 3%to 14%of intracellular total toxins in P.lima,which was much lower than the free content toxins.In addition,chlorophyll a concentration of P.lima was negatively correlated with DSTs content.Which further confirmed the competition of the production of chlorophyll a and DSTs.Further research was needed to study the survival selective strategies of Prorocentrum lima under the ambient pressures.