鄱阳湖阻隔湖泊浮游植物群落结构演化特征：以军山湖为例

人类改造自然的行为——建闸筑堤对湖泊生态系统有着重要影响,由于缺乏生态监测对比数据,对阻隔湖泊的浮游植物群落结构变化及其响应特征缺乏足够认识.为探明阻隔湖泊浮游植物群落结构演变趋势,选取了鄱阳湖典型阻隔湖泊——军山湖,于2007~2008年和2012~2013年对其浮游植物进行丰枯水期调查,重点分析群落结构特征.结果表明,2012~2013年共检出浮游植物6门53属,主要由绿藻(种属数占47.2%)、硅藻(22.2%)、蓝藻(14.8%)、裸藻(9.3%)等组成.丰水期优势种属为飞燕角甲藻(Ceratium hirundinella)(生物量百分比20.5%)、鱼腥藻(Anabeana spp.)(18.5%)和微囊藻(Microcystis spp.)(12.9%);枯水期优势种属为卵形隐藻(Cryptomonas ovata)(生物量百分比38.4%)、颗粒直链硅藻(Aulacoseira granulata)(15.2%)和微囊藻(10.5%).浮游植物细胞数量主要由蓝藻(85.4%~87.0%)构成;丰水期生物量主要由蓝藻(45.0%)、甲藻(21.1%)、硅藻(15.6%)和绿藻(11.5%)组成;枯水期生物量则由隐藻(38.2%)、硅藻(31.3%)和蓝藻(21.1%)组成.与2007~2008年军山湖浮游植物群落结构相比,主要变化趋势有:①丰水期,浮游植物优势种从2007~2008年的甲藻-硅藻,甲藻绝对优势型转变为2012~2013年的蓝藻-甲藻,蓝藻绝对优势型;枯水期,从2007~2008年的甲藻-硅藻,甲藻绝对优势型转变为2012~2013年的隐藻-硅藻-蓝藻,隐藻绝对优势型.②浮游植物细胞数量由2007~2008年的2.66×106cell·L-1上升至2012~2013年的6.77×107cell·L-1,生物量由2007~2008年的0.72 mg·L-1增加至2012~2013年的12.30 mg·L-1.总之,军山湖浮游植物群落结构中贫营养型的甲藻比例减少,金藻消失,富营养型的蓝藻和隐藻增加.因此,通过建闸筑堤对湖泊进行人为阻隔后,湖区水体交换时间的延长,水流流速的变缓等水文条件的改变均促进了浮游植物富营养指示种在军山湖湖区内的生长聚集.

Phytoplankton Community Structure and Its Succession in Isolated Lakes of Poyang-Junshan Lake

As one of the human activities that transform nature, construction of dams and dykes may impose significant effects on lake ecosystems. Due to lacking of comparative data for ecological monitoring, how the changes of phytoplankton community structure respond to altered hydrological connectivity between lakes and other water bodies is still unknown. This work chose Junshan Lake, the typical isolated lake from Poyang Lake floodplain, to investigate the succession in phytoplankton communities responding to altered connectivity. Phytoplankton samples were collected during the wet and dry seasons in Junshan Lake, to analyze the phytoplankton community structure. The results showed that, fifty three genera from six phyta were identified in Junshan Lake, with Chlorophyta (47.2%), Bacillariophyta (22.2%), Cyanophyta (14.8%) and Euglenophyta (9.3%) being the main phyta. The dominant species were Ceratium hirundinella (20.5%), Anabeana spp. (18.5%) and Microcystis spp. (12.9%) during the wet seasons. Cryptomonas ovate (38.4%), Aulacoseira granulata (15.2%) and Microcystis spp. (10.5%) dominated during the whole dry seasons. The total phytoplankton abundance was mainly composed of Cyanophyta (85.4%-87.0%). The total phytoplankton biomass was dominantly made up of Cyanophyta (45.0%), Dinophyta (21.1%), Bacillariophyta (15.6%) and Chlorophyta (11.5%) during the wet seasons. Cryptophyta (38.2%), Bacillariophyta (31.3%) and Cyanophyta (21.1%) were the main contributors of the total phytoplankton biomass during the dry seasons. The phytoplankton community structure changed from Dinophyta- Bacillariophyta type during the wet seasons of 2007-2008 to Cyanophyta-Dinophyta type during the wet seasons of 2012-2013, and changed from Dinophyta- Bacillariophyta type during the dry seasons of 2007-2008 to Cryptophyta- Bacillariophyta-Cyanophyta type during the dry seasons of 2012-2013. The abundance and biomass increased from 2.66×10⁶ cell·L^-1 during 2007-2008 to 6.77×10⁷ cell·L^-1 during 2012-2013, and from 0.72 mg·L^-1 during 2007-2008 to 12.30 mg·L^-1 during 2012-2013, respectively. The succession pattern of phytoplankton community in the Junshan Lake showed a decrease in the proportion of oligotrophic species as Chrysophyta and Dinophyta, and an increase in eutrophic species as Cyanophyta and Cryptophyta. Thus, being isolated from Poyang Lake might alter hydrologic factors so that the water exchange time became longer and the water flow became slower which could promote the growth and aggregation of phytoplankton eutrophication indicator species in Junshan Lake.