大亚湾核电站运行以来, 其温排水造成了局部区域海水明显升温, 区域浮游植物群落结构也发生显著改变。为研究海水升温对浮游植物群落结构及光合活性的影响, 于2013年夏季采集大亚湾核电站温排水区域浮游植物, 进行室内升温胁迫和恢复培养, 每天观测其群落结构和不同粒级(小型、微型、微微型)浮游植物光合活性的变化。结果表明, 升温实验中, 3个处理组(35℃、33℃、29℃)在培养前期均是硅藻占优势, 在培养后期变为蓝藻(念珠藻Nostoc sp.或微囊藻Microcystis sp.)占优势; 高温处理组(35℃和33℃), 前2天浮游植物生物量均持续增加, 最大光量子产量基本恒定在正常状态, 而后均开始下降, 且35℃下降幅度较33℃高, 培养过程中小型和微型浮游植物的生物量与光合活性均大于微微型; 29℃对照组中, 不同粒级浮游植物生物量和光合活性与实验前相差不大。恢复实验结果显示, 虽然受到高温胁迫, 排水口小型和微型浮游植物在正常温度(29℃)和较低温度(25℃)下均可恢复到正常光合水平, 而微微型浮游植物的恢复活性相对较低。总体而言, 35℃和33℃均对浮游植物造成了高温胁迫, 35℃的胁迫效应更为严重; 小型和微型浮游植物的高温耐受能力及相应的受损恢复能力均高于微微型。由此推测, 在大亚湾核电站温排水区, 短期高温刺激造成的浮游植物光合损伤在其被带离高温区后可得到恢复, 甚至可促进浮游植物快速生长。

Since the start of operation of Daya Bay Nuclear Power Plant, a distinct temperature increase has happened in the surrounding waters, resulting in changes of phytoplankton community structure. To evaluate the warming effects on the phytoplankton community structure and photosynthetic efficiency, warming-up and recovery experiments were conducted on different granulometric classes (micro-, nano-, pico-) from the waters infall and outfall of the plant in the summer of 2013. The results are as follows. In the warming-up experiments, the dominant community changed from the diatom on the early stage to the cyanobacteria (Nostoc sp. and microcystis sp.) on the later stage in all of the three groups (35℃, 33℃ and 29℃). In the high-temperature incubation groups (35℃ and 33℃), the phytoplankton biomass increased continuously while the maximum quantum yield maintained almost at the normal state on the first two days. Then, both parameters began to decline, and the effects of 35℃ were stronger than those of 33℃. Photosynthetic efficiency of micro- and nano-phytoplankton was stronger than that of pico-phytoplankton in both groups of 35℃ and 33℃. However, the biomass and photosynthetic efficiency showed no significant differences among different granulometric classes in the control group (29℃). In the recovery experiments, photosynthetic efficiency of the micro- and nano-phytoplankton recovered quickly at normal (29℃) or lower (25℃) temperatures after experiencing the temperature stress from thermal discharge, while that of the pico-phytoplankton was relatively weak. In summary, the high temperature stress happened to phytoplankton at 35℃ and 33℃, and the threatening effects of 35℃ were more seriously. Both micro- and nano-phytoplankton showed greater capacity than pico-phytoplankton in terms of tolerance to high temperature and recovery. Our results suggested that the short-term stimulus of high temperature could promote rapid growth of phytoplankton from the outfall of the Daya Bay Nuclear Power Plant, and photosynthetic damage could be recovered after phytoplankton being carried away from the high temperature region.