不同营养条件下铜绿微囊藻(Microcystis aeruginosa)和小球藻(Chlorella vulgaris)的生长竞争行为

GROWTH COMPETITION BETWEEN MICROCYSTIS AERUGINOSA AND CHLORELLA VULGARIS UNDER NUTRITION CONTROL

蓝藻的暴发通常是藻类之间竞争的结果,了解环境中蓝藻与其它藻类的竞争特点和生存策略对揭示藻华暴发的机制及治理具有重要意义。本文以营养竞争为例,以铜绿微囊藻(Microcystis aeruginosa)和小球藻(Chlorella vulgaris)为受试对象,通过测定细胞密度、胞内C、N、P、S四种主要元素含量以及培养基中总氮(TN)、总磷(TP)的消耗,研究不同营养等级(超富营养、富营养、中营养、贫营养)以及单独N、P限制下两种藻在单独培养和共生培养条件下的生长特征和竞争行为。结果表明:(1)在超富营养、富营养、中营养、贫营养条件时,单独培养下的两种藻生物量与营养丰富程度呈正相关;(2)共培养条件下,在高营养水平时铜绿微囊藻在竞争中占优势,低营养水平时小球藻具有竞争优势;(3)胞内C、N、P、S的测定发现,随着营养水平的下降,两种藻胞内N、P的百分含量逐渐减少,而C、S并未呈现显著变化;(4)N限制时,铜绿微囊藻的半饱和常数Ks及最大比增长率μmax均大于小球藻;P限制条件下铜绿微囊藻的半饱和常数Ks小于小球藻,而最大比增长率μmax大于小球藻。综合分析,同一营养条件下,铜绿微囊藻竞争优势的先决因子是N,小球藻是P。因此,从营养竞争与生物适应力角度考虑,降低水体中富余的N或适当提高P的浓度可让小球藻获得竞争优势,对限制单一物种的形成具有平衡作用,可作为防治藻华的潜在方法。

Microcystis aeruginosa bloom is the consequence of competition among algae. To understand the impact of nutrient on the competition, we carried out experiments on interspecific competition between Microcystis aeruginosa and Chlorella vulgaris, two most common algae in a eutrophic water environment. Different nutrition status（over-eutrophication, eutrophication, below-eutrophication and oligotrophication） and limitation（N or P）, were designed in uni-culture and co-culture. Indexes analyzed were cell density, intracellular element content of C, N, P, S, and consumption of TN（total nitrogen） and TP（total phosphorus）. Results indicate that the maximum biomass for both M. aeruginosa and C. vulgaris decreased with the decrease of nutrition concentration in the uni-culture. However, in the co-culture, M. aeruginosa showed advantage in super-eutrophication condition, while C. vulgaris did so in the other. The intracellular element contents of N and P dropped with the decrease of nutrition level, but C and S. M. aeruginosa demanded more N but less P than C. vulgaris. In addition, both half-saturation constant（Ks） and maximum specific growth rate（μmax） of M. aeruginosa were greater than those of C. vulgaris in N-limitation, while in P-limitation, smaller Ks and greater μmax than those of C. vulgaris. Therefore, at a same nutrition level, N is a more important limiting factor for M. aeruginosa but P for C. vulgaris in growth competition. Controlling N in drainage could be effective to prevent algal bloom.