四川丘陵区水库浮游植物群落结构与蓝藻水华风险——基于优势种生态位与种间联结研究

为了解四川丘陵区中小型水库浮游植物群落结构周年变化，掌握其演替规律并预测其发展方向，于2016年-2017年分季节对该地区10个典型水库进行了周年研究。结果显示：共检出浮游植物9门104属188种，其中优势种4门16属16种，以湖泊假鱼腥藻（Pseudanabaena linmnetica）优势度指数为最高；蓝藻密度在各季节、各水库中均占据优势，尤其是夏季。优势种生态位宽度和生态位重叠度在存在明显的季节差异性，并受到水温、营养条件等环境因子的显著影响；优势种可分为3个类别，竞争力相对较强的7个种中有5种蓝藻；全年发展性最强的种类也多为蓝藻，特别是湖泊假鱼腥藻等具有产毒潜力的种类，其优势度存在进一步扩大的风险。种间联结性检验结果显示，群落种间大致表现出净的正联结，优势种种对间正负关联比大于1，该类水库群落结构较为稳定且存在正向演替的趋势，可能会导致夏季间断性产毒蓝藻水华的风险。研究结果可为四川丘陵区中小型水库浮游植物群落演替研究以及蓝藻水华预警提供基础资料。

Phytoplankton community structure and cyanobacteria bloom risk of reservoirs in hilly regions of Sichuan Province based on dominant species niche and interspecific association

Sichuan is known as a province with thousands of rivers and numerous reservoirs which play an important role in production and life. There is a general problem of pollution in small and medium-sized reservoirs in this area, which may affect the structure, function and utilization of aquatic ecosystem. Aiming to explore the annual changes and succession rules of phytoplankton community structure in small and medium-sized reservoirs in hilly regions of Sichuan Province and to predict its development direction, this study conducts an annual survey on 10 typical reservoirs in specific regions in different seasons from 2016 to 2017. The survey identifies a total of 188 species of phytoplankton in 104 genera of 9 phyla, including 16 species (9 species are cyanobacteria) of 16 genera of 4 phyla which are identified as dominant species. In particular, the dominance index of Pseudoanabaena linmnetica is the highest, and the density of cyanobacteria is dominant in all seasons and reservoirs, especially in summer. Furthermore, the improved Levins formula and Petraitis index are applied to determine the niche metrics of the phytoplankton dominant species. The results show that the niche breadth and niche overlap of each dominant species vary seasonally and are significantly affected by water temperature and nutrient. Based on their niche breadth in different seasons, the dominant species are classified into three categories, two of which are relatively competitive. These two categories include 7 species, of which there are 5 species of cyanobacteria, including P. linmnetica. The dominant species in four seasons are mostly in a state of developing, and the most promising species throughout the year are mainly cyanobacteria. In particular, species with the potential to produce toxins such as P. linmnetica have the risk of further expansion of their dominance. The results of interspecific association show a positive correlation among the community species throughout the year, indicating that the community structure in these reservoirs is relatively stable and there is a positive succession trend. In such a trend, intermittent toxic cyanobacteria bloom which affects the quality and function of water may occur in these reservoirs in summer, especially in reservoirs with simple dominant species composition.This paper provides research background for the study of phytoplankton community succession and the early warning of cyanobacteria blooms in small and medium-sized reservoirs in hilly regions of Sichuan Province. To prevent possible filamentous cyanobacteria bloom outbreak, water quality of the reservoirs should be effectively managed and immediately repaired under the dual promotion of high nutritional level and global warming.