长孢藻(Dolichospermum)丝体长度与丰度的变化关系及其水华指示作用

The Relationship between Abundance and Filament Length of Dolichospermum and Its Indicativefunction of Bloom

长孢藻属(Dolichospermum)是南亚热带水体中常见水华蓝藻之一,常以丝状群体形式存在,其丝体长度变化具有高度可塑性。为探讨长孢藻丝体长度变化与哪些环境因子有关、丝体长度与丰度之间的关系以及丝体长度能否指示长孢藻水华发生的趋势及状况,选择了一座以长孢藻为主要优势种的南亚热带水库为研究对象,于2010年1月至2013年12月对该水库进行逐月采样,研究了长孢藻丰度、丝体长度和环境因子的季节变化,分析了影响长孢藻丝体长度的关键因子及其与丰度的关系。结果表明:在调查期间,长孢藻丝体长度介于15~2 400μm之间,丝体长度和丰度具有极显著的正相关关系,两者的回归方程为log L=1.32+0.26log N(R_(adj)~2=0.30,P=0.000)。营养盐(TN、TP、NO_3^--N)和光照条件(SD、Zeu/Zm)是影响长孢藻丰度和丝体长度变化的主要环境因子,其中营养盐对丰度影响更大,两者呈极显著正相关关系;光照条件则对丝体长度影响更显著,两者呈极显著负相关关系。长孢藻丝体长度的变化可以作为自身水华预测的指示参数,其种群整体丝体变长是对营养盐升高、光限制增强的响应,长丝体预示着长孢藻丰度升高,漂浮能力增强,水华暴发风险增加。

Dolichospermum, one of the most common cyanobacterial species in South China, usually occurs as filaments, the length of which highly varies. In order to fully understand the influence of environmental factors on the filament length ofDolichospermum, and to examine whether the filament length could indicate the timing and extent of bloom development, field investigations were performed monthly from January, 2010 to December, 2013 in Dashahe Reservoir which was dominated byDolichospermumin bloom season. TheDolichospermum filament length, abundance and environment variables were monitored. Statistical analysis showed that the filament length ofDolichospermumranged from 15 to 2400μm, and was significantly correlated with abundance (logL=1.32+0.26logN,Radj2=0.30,P=0.000). Nutrients (TN, TP, NO3--N) and light availability (SD, Zeu/Zm) were the key factors influencing the filaments length and abundance. Nutrients, compared with light availability, showed relatively higher explanation power for abundance which was significantly and positively correlated with nutrients. Light availability showed relatively higher explanation power for filament length, which was significantly and negatively correlated with light availability. The filament length could be regarded as the indicative parameter of theDolichospermumbloom. The filament elongating ofDolichospermum, resulting from the nutrients increasing and light limitation, may indicate the relative abundance, buoyancy and bloom risk ofDolichospermum.