Uptake of dissolved nitrogen by phytoplankton in spring in Huguangyan Maar Lake

Abstract

利用¹⁵N稳定同位素示踪技术,采用现场挂瓶培养的方法测定了湖光岩玛珥湖浮游植物群落对铵态氮、硝态氮和尿素态氮的吸收速率,研究了湖光岩玛珥湖浮游植物群落氮吸收及其吸收动力学特征.结果表明:湖光岩玛珥湖共检测到浮游植物7门54种(包括变种和变型),主要为蓝藻门、硅藻门和绿藻门种类,分别占浮游植物总量的44.68%、26.70%和19.21%,其中水华微囊藻(Microcystis flos-aquae)与铜绿微囊藻(Microcystis aeruginosa)为绝对优势种,优势度分别为0.39与0.28.湖光岩玛珥湖浮游植物群落对铵态氮的绝对吸收速率最高,分别是对硝态氮、尿素态氮绝对吸收速率的5.8和4.2倍,占3种溶解态氮总吸收量的73.3%.铵态氮、硝态氮和尿素态氮的相对优先指数分别为2.907、0.190和1.192,说明浮游植物群落优先吸收铵态氮,其次为尿素态氮,最后为硝态氮.铵态氮、硝态氮和尿素态氮的周转时间分别为3.72、57.03和9.07h.湖光岩玛珥湖浮游植物对溶解态氮的吸收可用Michaelis-Menten酶动力学方程描述,最大比吸收速率表现为铵态氮 >尿素态氮 >硝态氮,亲和力表现为硝态氮 >铵态氮 >尿素态氮.湖光岩玛珥湖浮游植物群落对铵态氮具有较高的吸收潜力,并且对硝态氮具有一定的亲和力,具备利用硝态氮的能力.;Using ¹⁵N stable isotope tracer technique by adopting the in-situ flask culture, the uptake rates of ammonium, nitrate and urea by phytoplankton community were measured in Huguangyan Maar Lake, in order to characterize the nitrogen absorption and the characteristics of absorption kinetics by phytoplankton community in spring in the lake.The results showed that there were 54 species (including varieties and forms belonging to 7 phyla) of phytoplankton in the lake, mainly from the Cyanophyta, Bacillariophyta and Chlorophyta, which accounted for 44.68%, 26.70% and 19.21%, respectively.Microcystis flos-aquae and M.aeruginosa were the absolute dominant species, and the dominance indexes were 0.39 and 0.28, respectively.Uptake rate of ammonium of phytoplankton community was the highest, about 5.8 times of nitrate, 4.2 times of urea, and accounted for 73.3% of the total nitrogen uptake of the three kinds of dissolved nitrogen.The relative preference indices for ammonium, nitrate and urea were 2.907, 0.190 and 1.192, respectively.Phytoplankton communities prefer uptaking ammonium, followed by urea, and finally nitrate.The turnover time for ammonium, nitrate and urea were 3.72, 57.03 and 9.07h, respectively.Nitrogen uptake kinetics of phytoplankton community agree with Michaelis-Menten equation.The maximum uptake rate was ammonium >urea >nitrate, and affinity (1/Ks) was nitrate >ammonium >urea.Phytoplankton community of the Huguangyan Maar Lake has a high absorption potential of ammonium, and a certain affinity to nitrate, therefore, the lake has the ability to use nitrate.