热带水库浮游植物形态性状的季节变化及影响因子分析——以高州水库为例

Seasonal dynamics of phytoplankton morphological characters and driving factors in tropical reservoirs: A case study from Gaozhou Reservoir

体积、比表面积和最大轴性长度是浮游植物主要的形态性状,反映浮游植物资源竞争和反牧食能力.群落中物种的性状分布会随着环境条件的季节改变而变化,热带水库环境条件的季节性变化小,可能导致群落形态性状变化不显著.本文以热带大型水库——高州水库为研究对象,分析浮游植物形态性状季节动态及关键影响因子.高州水库浮游植物以丝状和单细胞藻类为主,群落水平的平均细胞体积在108.52～753.25μm3之间,平均比表面积在0.93～2.08μm-1之间,平均最大轴性长度在5.21～17.44μm之间,均有明显的季节特征.浮游植物群落平均细胞体积、最大轴性长度与总氮浓度呈负相关,与水温呈正相关;平均比表面积与硝态氮浓度呈负相关.粘质长孢藻(Dolichospermum mucosa)和光角星鼓藻(Staurastrum muticum)是高州水库浮游植物优势种,其形态性状均具有明显的时空差异,表现出明显的形态可塑性.粘质长孢藻的平均细胞体积、最大轴性长度与总氮浓度呈正相关,与水温呈负相关;平均比表面积与总氮浓度呈负相关,与水温呈正相关.光角星鼓藻的平均细胞体积、最大轴性长度与正磷酸盐浓度呈正相关.总体上高州水库浮游植物在群落和种群水平形态性状均有明显的季节差异,夏季以大细胞为主,其他季节以小细胞种类为主,水温、氮和磷的可利用性是导致浮游植物形态性状季节差异的关键因子.

Volume, specific surface area and the longest axial linear dimension are main morphological characters of phytoplankton. These characters reflect the ability of phytoplankton in competing for resources and resisting grazing. The morphological characters of cells change with the seasonal environmental conditions. It was assumed that limited seasonal changes occurred on phytoplankton cells morphological characters in community, due to the small seasonal variation of environmental conditions in tropical reservoirs. To test this assumption, the seasonal dynamic of phytoplankton morphological characters and the affecting factors in large tropical reservoir (Gaozhou Reservoir)were analyzed. The phytoplankton community was dominated by filamentous species and unicellular algae in Gaozhou Reservoir. In community level, the average cell volume was 108.52-753.25 μm^3 , the average cell specific surface area was 0.93-2.08 μm^-1 , the average cell longest axial linear dimension was 5.21-17.44 μm, and the three morphological characters all showed seasonal dynamics. The average cell volume and the average cell longest axial linear dimension were correlated negatively with total nitrogen, and positively with temperature, the average cell specific surface area was correlated negatively with nitrate nitrogen. Dolichospermum mucosa and Staurastrum muticum were the dominant phytoplankton species in Gaozhou Reservoir, and they both showed morphological plasticity and seasonal dynamics in the morphological characters. The average cell volume and the average cell longest axial linear dimension of D. mucosa were correlated positively with total nitrogen, and negatively with temperature. The average cell specific surface area of D. mucosa was correlated negatively with total nitrogen, and positively with temperature. The average cell volume and the average cell longest axial linear dimension of S. muticum were correlated positively with soluble reactive phosphate. In conclusion, the morphological characters of phytoplankton in community and species were different with seasonal dynamics in Gaozhou Reservoir. The large cells dominated phytoplankton community in summer, but small cells in other season. Temperature, the availability of nitrogen and phosphorus were the primary factors to explain the morphological variation of phytoplankton.