不同形态磷源对球形棕囊藻生长及囊体形成的影响

球形棕囊藻(Phaeocystis globosa)是中国近海常见的有害藻华原因种,游离单细胞和球形囊体是其异型生活史的两种形态。本研究通过添加KH₂PO₄(PO₄^3-)、卵磷脂(LEC)、三磷酸腺苷二钠(ATP)、葡萄糖-6-磷酸钠盐(G-6-P)、和核糖核酸(RNA)5种不同磷源进行室内培养,以阐明不同磷源对球形棕囊藻生长及囊体形成的影响。结果表明,5种磷源培养条件下皆可形成囊体,以G-6-P为磷源的球形棕囊藻生长最优,囊体密度最大可达(5.7±0.5)×10⁵colonies·L^-1,在培养中后期诱导产生较高的碱性磷酸酶活性(181.1±41.6)nmol·h^-1·L^-1有利于其高生物量及囊体形态的维持。以PO₄^3-为磷源时,囊体密度最大可达(6.1±0.7)×10⁵colonies·L^-1,但对囊体形态的维持较G-6-P组差。以LEC或RNA为磷源时,囊体密度及叶绿素a含量较低,囊体单位表面积的细胞密度更高,结构更紧致。LEC组的囊体直径最大,可达(488.2±220.6)μm。以ATP为磷源时,囊体细胞分布稀疏,囊体衰退较快。4种有机磷源对球形棕囊藻囊体的构建存在不同程度的影响,在自然水体棕囊藻藻华形成及维持中,除无机磷源外部分形态的有机磷源可能会发挥重要作用。

Effects of different phosphorus sources on the growth and colony formation of Phaeocystis globosa

Phaeocystis globosa frequently causes extensive harmful algal blooms in coastal waters of China.It had a complex life cycle alternating between solitary cells and colonies.In order to reveal the effects of different phosphorus sources on the growth and colony formation of P.globose,the alga was cultivated in five different phosphorus sources including KH₂PO₄(PO₄^3-),lecithin(LEC),adenosine disodium triphosphate(ATP),glucose-6-phosphate(G-6-P)and RNA.The results showed that colonies form in each culture conditions.The growth of colony was optimal in G-6-P group with the maximum density of 5.7±0.5×10⁵ colonies·L^-1.A high alkaline phosphatase activity,181.1±41.6 nmol·h^-1·L^-1,that was elevated in G-6-P group facilitated the high biomass and colony maintenance.The maximum density reached 6.1±0.7×10⁵ colonies·L^-1 in PO₄^3-group,but the colony maintenance was poorer than that in G-6-P group.Colony density and chlorophyll a content were significantly lower in LEC or RNA groups than in other groups,but a relatively high cells per unit surface area was observed,indicating a compact colony architecture.The colony diameter reached the maximum,488.2±220.6μm,in LEC group.Colony cells distributed sparsely in ATP group,which may cause the rapid decay in colonies.The four different dissolved organic phosphorus impacted the colony formation in different ways.Dissolved organic phosphorus in sea waters may be one of the reasons that is responsible for the forming and maintaining algal blooms.