不同氮源对球形棕囊藻生长和囊体形成的影响

Effects of Different Nitrogen on the Growth and the Formation of Colony in Phaeocystis globosa

棕囊藻引发的有害藻华已经成为一种全球性的自然灾害,给海洋环境以及渔业经济带来了严重的损失。棕囊藻存在两种生活史形态:游离的单细胞形态和囊体形态,但是不同形态之间的转换和囊体形成机制尚不清楚。营养盐是浮游植物生长和藻华发生的物质基础,棕囊藻藻华以往多发生在硝酸盐限制海区。但是近年来,尿素等有机氮在河口区域浓度不断提高,有机氮源的增加可能对棕囊藻生长和生活史转换产生显著的影响。通过添加硝酸盐、铵盐、尿素三种氮源,研究不同氮源对球形棕囊藻生长和囊体形成的影响。研究表明:球形棕囊藻可以在硝氮、尿素中迅速生长,形成囊体,但是氨氮对其却有明显的抑制作用;球形棕囊藻单细胞在硝氮中丰度比较高,最大可达到(444.21±64.97)×10~3个·mL^(-1);在尿素中更容易形成囊体,最多能达到(12.61±6.5)个·mL^(-1)。球形棕囊藻可以利用硝酸盐和有机氮源使其具有更强的竞争力,尿素在海洋水体中浓度的提高,可能是近年来球形棕囊藻藻华在我国近海水域频发的原因之一。

The harmful algal bloom caused by Phaeocystis has become a global natural disaster,which bring serious losses of the marine environment and marine fisheries.Phaeocystis has a complex polymorphic life cycle,exhibiting alternation between free-living cells and colony.However,the mechanism regulating alternation remains unknown.Nutrients playa a key role in regulating phytoplankton growth and algal blooms.Phaeocystis bloom often occurred in the marine systems where nitrate was limited.In recent years,increased urea concentration has been observed frequently in the estuary area due to the use of chemical fertilizers.Different forms of nitrogen may have significant impacts on the life cycle of P.globosa.Growth and colony formation of P.globosaas a function of nitrate,urea and ammonium were examined.The results show that free-living cells abundances of P.globosa were significantly promoted by urea and nitrate that maximum abundances were（444.21±64.97）×10^3 cells·mL-1,but inhibited by ammonia.Colony formation was supported by urea and the maximum colony abundance with urea were（12.61±6.5）colonies·mL-1.P.globosa could utilize inorganic and organic nitrogen,thus providing P.globosa with competitive advantage.The increased urea concentration may be responsible for the occurrence of the P.globosa bloom in China coastal area in recent years.