珠江三角洲城市周边典型中小型水库富营养化与蓝藻种群动态

Eutrophication and Dynamics of Cyanobacterial Population in Small and Medium-sized Reservoirs Nearby Urban Districts in the Pearl River Delta

为了解珠江三角洲地区城市周边中小型水库的水质状况,于2009年8月（丰水期）和2010年3月（枯水期）调查了4座典型中小型水库——横岗水库、水濂山水库、契爷石水库和东风水库,分析了水库的富营养化与蓝藻种类组成、种群动态及微囊藻毒素水平.丰水期总磷浓度为0.05~0.083 mg L-1,枯水期为0.026~0.082 mg L-1,丰水期高于枯水期;丰水期总氮浓度为0.75~1.807 mg L-1,枯水期为0.965~2.646 mg L-1,枯水期高于丰水期.4座水库的营养状态指数（TSI）均大于40,处于中富营养或富营养化状态.4座水库中共检出蓝藻16种（属）,大部分蓝藻为丝状蓝藻和群体蓝藻;常见种主要为湖泊假鱼腥藻（Pseudanabaena limnetica）、泽丝藻（Limnothrix sp.）、微小色球藻（Chroococcus minutus）、针状蓝纤维藻（Dactylococcopsis acicularis）和平裂藻（Merismopedia sp.）;湖泊假鱼腥藻为绝对优势种.丰水期蓝藻丰度为37.06×106~557.78×106 cells L-1,生物量为1.34~15.76 mg L-1,在枯水期则分别为5.89×106~69.29×106 cells L-1和0.34~3.43 mg L-1.蓝藻种群在丰水期和枯水期有较大差异,枯水期以湖泊假鱼腥藻为代表的丝状蓝藻在数量上明显下降.丰水期蓝藻种群主要受光限制影响,而枯水期的主要限制因子是磷的缺乏.4座水库的主要优势蓝藻种类均为不产微囊藻毒素的种类,因此微囊藻毒素浓度都比较低,为0~0.174μg L-1,发生微囊毒素危害的风险较小.

With rapid urbanization,human activity exerts a strong impact on reservoirs near the cities.In order to understand eutrophication and dynamics of cyanobacterial population in such reservoirs,four typical small and medium-sized reservoirs in the Pearl River Delt were investigated in wet（August,2009） and dry（March,2010） seasons.TP in wet season（ranging from 0.05 to 0.083 mg L-1） was higher than that in dry season（ranging from 0.026 to 0.082 mg L-1）.TN in wet season（ranging from 0.75 to 1.807 mg L-1） was lower than that in dry season（ranging from 0.965 to 2.646 mg L-1）.The TSI values of all the reservoirs were more than 40,which showed that they were mesotrophic or eutrophic.In total,16 species of cyanobacteria were observed and dominated by filamentous and colconial species.Dactylococcopsis acicularis,Chroococcus minutus,Pseudanabaena limnetica,Limnothrix sp.and Merismopedias sp.were common species.A filamentous species,P.limnetica,was the predominant species.The abundance and the biomass of cyanobacteria ranged from 37.06 × 106 to 557.78 × 106 cells L-1 and from 1.34 to 15.7 6 mg L-1,respectively in wet season,and ranged from 5.886 × 106 to 69.29 × 106 cells L-1 and from 0.34 to 3.43 mg L-1,respectively in dry season.The population structure of cyanobacteria in the four reservoirs in dry season was markedly different from that in wet season with the abundance of the predominant species,P.limnetica,declining dramatically.The population dynamics of cyanobacteria was mainly explained by optical limitation in wet season and phosphorus limitation in dry season.Because the dominant cyanobacterial species didn＇t produce microcystin,the four reservoirs had low microcystin concentration of less than 0.174 μg L-1.Fig 5,Tab 2,Ref 32