南海北部浮游植物生长对营养盐的响应

Responses of phytoplankton growth on nutrient enrichments in the northern South China Sea

2004年夏季作者在南海北部海域研究了浮游植物生长的营养动力学,结合物理-化学过程对浮游植物生物量分布的影响与机制进行了研究,阐明了水平对流和中尺度涡对营养盐分布的影响及浮游植物生长和现存生物量对其的响应。受西南季风和东向沿岸流作用所形成的Ekman输送的影响,南海北部海岸带表层海水作离岸运动,使深层富含营养盐的冷水爬坡涌升到表层来补充,激发浮游植物生物量迅速增长。海区反气旋涡使海水辐聚下沉,造成水体具高温、低盐、高溶解氧浓度、低营养盐浓度和低浮游植物生物量。同时通过现场营养盐加富试验,发现该海域营养盐是浮游植物生长的主要限制因子,而且是多种营养元素共同限制了浮游植物的生长,添加单一的营养盐并不能促进浮游植物的生长。在生物量出现增长的试验组中,营养盐添加不仅促使浮游植物生物量的增长,而且也改变了浮游植物的粒级结构和群落结构。例如,在站S1008,培养前叶绿素a浓度为0.28 mg.m-3,加富培养60 h后浮游植物生物量在NP和NPSi的试验组中有显著的增加,叶绿素a浓度分别达1.07 mg.m-3和1.19 mg.m-3;培养前粒度分级叶绿素a主要以Pico级份占优势,而加富试验结束后,在NP和NPSi的试验组以Nano级份占优势,其它试验组仍以Pico级份占优势;同时,在培养后生物量出现增长的试验组,浮游植物群落的优势类群从甲藻向硅藻演替。

Abstract：The multidisciplinary oceanographic survey and in South China Sea during summer of 2004, aimed at better enrichments. Elucidated the effects of the coastal upwelling situ nutrient enrichment experiments were conducted in the northern understanding of the responses of phytoplankton growth on nutrient resulted from Ekman transportation formed by southwest monsoon and coastal current toward northeast and middle scale eddies on the distribution of nutrients, and effected ultimately on the phytoplankton growth and standing stock, and the responses of the latter to the former, the physical-chemical coupling processes. The water mass with the properties of high temperature, low salinity, high dissolved oxygen concentration, low nutrient concentration and low phytoplankton biomass was found in anticyclonic eddies, resulted from the downwelling induced by water convergence. Results of nutrient enrichment experiments showed that only multi-nutrients adding could stimulate the phytoplankton growth. At the station of S1008, for example, Chla obviously increased in NP and NPSi experimental groups from 0. 28 mg· m^-3 to 1.07 mg· m^-3 and 1.19 mg· m^-3 respectively after 60 hours incubation since nutrients adding. Furthermore, we also found that the nutrient enrichments resulted in the successions of not only size-structure but also species structure of phytoplank communities, i.e. the shifts from picophytoplankton to nanophytoplankton and netphytoplankton, and from dinoflagellates to diatoms .