南海浮游植物对沙尘和灰霾添加的响应

通过2016年5月~6月在南海3个站位开展的船基围隔培养实验，研究了沙尘和灰霾添加对南海浮游植物生长和群落结构变化的影响.结果发现，沙尘和灰霾添加由于提供了N、P等营养盐，整体上促进了浮游植物的生长，且促进程度与添加量密切相关.通过定量计算营养盐指数和叶绿素a累积浓度，发现培养期间叶绿素a累积浓度与沙尘添加浓度呈显著正相关关系（R²=0.87，P<0.01）；低浓度灰霾添加的作用与沙尘添加类似（R²=0.91，P<0.01），但当灰霾浓度增大时，叶绿素a累积浓度的增加受到一定程度的抑制，这可能与灰霾中含有较高含量的毒性物质有关.各粒级浮游植物叶绿素a浓度的变化表明，沙尘和低浓度灰霾添加使浮游植物优势种群由超微型向小型和微型转变；在高浓度灰霾添加组，由于营养盐与毒性物质的综合作用，浮游植物粒级结构变化不明显.超微型浮游植物细胞丰度测定结果表明，沙尘对聚球藻、原绿球藻和超微型真核浮游植物均表现出促进作用，高浓度灰霾添加能够抑制聚球藻和超微型真核浮游植物的生长.

Responses of phytoplankton to dust and haze particle additions in the South China Sea

On-board incubation experiments were conducted at three sampling stations from May to June 2016 in the South China Sea (SCS) to explore the impact of dust and haze addition on phytoplankton biomass and community structure. By providing the nutrients such as N and P, the addition of dust and haze in general promoted the growth of phytoplankton, and the promotion magnitude is tightly related to the amount of dust and haze addition. By calculation of nutrient index and chlorophyll a cumulative concentration, it was found that the accumulated chlorophyll a during the incubation experiment showed statistically significant positive correlation with the amount of added dust (R²=0.87, P<0.01); In terms of the dust, similar promotion mechanism was found when the haze concentration was low (R²=0.91, P<0.01). However, when the haze concentration continued to increase, the accumulation of chlorophyll a was hindered to some extent, likely an effect of the high content of toxic substances in haze. Size-fraction chlorophyll a showed that the addition of dust and low concentration of haze facilitated that the transition of dominant phytoplankton species from pico-sized phytoplankton to micro-and nano-sized phytoplankton, while the synthetic effect of nutrients and toxic substance, resulting from the addition of high haze concentration, yielded no obvious effect on the size structure of phytoplankton. The pico-sized phytoplankton abundance tests showed that the dust addition promoted the development of all three species including Synechococcus, Prochlorococcus and picoeukaryotes, whereas the addition of high concentration haze addition may inhibit the growth of Synechococcus and picoeukaryotes.