水温和营养盐增加对太湖冬、春季节藻类生长的影响

为探讨水温和营养盐增加对冬、春季节太湖藻类生长和群落演替的影响,研究了不同水温(不增温、12.0、14.0、16.0、18.0、20.0℃)和不同营养盐浓度(低、中、高营养盐浓度)下藻类的生长及优势种群变化. 结果表明:藻类∑ρ(Chla)〔蓝藻、绿藻及硅藻中ρ(Chla)总量,下同〕随着水温的升高呈增加趋势,在20.0℃下∑ρ(Chla)为0.19~12.94μg/L,显著高于其他水温试验组(0.01~6.83μg/L)；与较低水温(不增温、12.0、14.0℃)相比,较高水温(16.0、18.0、20.0℃)更能显著促进藻类对氮、磷营养盐的吸收利用. 添加营养盐后,硅藻、绿藻ρ(Chla)的日均值分别为0.52~4.07、0.17~0.52μg/L；湖水中∑ρ(Chla)呈增长趋势,并且浮游植物群落结构的优势种由绿藻转变为硅藻,硅藻ρ(Chla)所占比例从试验初始的50%升至75%~98%, 说明营养盐增加可加大硅藻的竞争优势；而绿藻的生长则可能同时受水温和营养盐共同作用的影响,因此太湖冬、春季节藻类的演替同时受到水温和营养盐的影响. 

Effects of Enhanced Water Temperature and Nutrient Concentration on Algal Growth in Winter and Spring Season in Lake Taihu, China

Bacillariophyta and Chlorophyta are main dominant phytoplanktons in winter and spring in Meiliang Bay, located in the north of Lake Taihu. Changes of algal growth and phytoplankton community were studied in an experiment within different water temperatures and nutrient conditions, which was conducted in Taihu Laboratory for Lake Ecosystem Research (TLLER) in January 2013.Non-enhancive temperature was set as control, and five water-temperature gradients (i.e., non-enhancive temperature, 12.0,4.0,6.0,8.0and 20.0℃) and three nutrient gradients (i.e., low, middle and high) were designed in the experiment. The results showed that total Chla concentration of lake water increased as the water temperature increased and was significantly higher under temperature of 20.0℃(0.19-12.94μg/L) than other water temperature treatments (0.01-6.83μg/L). Meanwhile, concentrations of nitrogen and phosphorus significantly declined under higher water temperature(16.0,8.0and 20.0℃)compared with lower water temperature (non-enhancive temperature, 12.0and 14.0℃). Furthermore, total Chla concentration increased when nutrient was added in the lake water. Chlorophyta was dominant phytoplankton species at the beginning of the experiment. However, Bacillariophyta rather than Chlorophyta became main algae especially under the middle and high nutrient conditions with the proportion of Chla concentration from 50% to 75%-98%. The study revealed that Bacillariophyta had an advantage in the competition with Chlorophyta in nutrient-added treatments with daily average value of Chla concentrations from 0.52-4.07μg/L and 0.17-0.52μg/L respectively. It suggests that enhanced water temperature limited the growth of Chlorophyta added nutrient treatments, and the Chla concentration of Chlorophyta was influenced by nutrient concentration as well. Therefore, the effect of water temperature on phytoplankton community are as important as that of nutrient concentration in winter and spring season in Lake Taihu and more researches should be further taken in the future.