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张亚锋,王旭涛,殷克东.南海台风引发藻华的生物机制探究.生态学报,2018,(16).http://dx.doi.org/10.5846/stxb201708141461  
南海台风引发藻华的生物机制探究
Biological mechanisms of typhoon-induced blooms in the South China Sea
投稿时间:2017-08-14  修订日期:2018-04-13
DOI: 10.5846/stxb201708141461
关键词浮游植物  小型浮游动物;藻华;光照;营养盐;南海
Key WordsPhytoplankton  micro-zooplankton  blooms  light  nutrient  South China Sea
基金项目国家自然科学基金重大研究计划(91328203);国家自然科学基金———广东联合基金(U1701247)
作者单位E-mail
张亚锋 中山大学 zhangyf66@mail.sysu.edu.cn 
王旭涛 水利部珠江水利委员会  
殷克东 中山大学 yinkd@mail.sysu.edu.cn 
摘要点击次数 63
全文下载次数 1
摘要:
海洋浮游植物的生长和小型浮游动物的摄食,与温度、光照和营养盐等因素密切相关。中国南海海盆是层化结构稳定的寡营养海,然而每年台风过后都有大量藻华的报道。为了探究台风引发藻华的生物形成机制,本研究通过南海海域表层和次表层叶绿素最大层(DCM)中的小型浮游动物的摄食活动以及浮游植物对光照和营养响应的现场实验,探究小型浮游动物摄食、光照和营养对海洋浮游植物生长和群落结构的调控作用。实验表明:1)表层水体中的小型浮游动物摄食速率明显大于DCM层;小型浮游动物摄食在表层水体中以大粒级的浮游植物(>5 μm)为主,在DCM层中没有明显粒级选择;自然光中的紫外线能增加小型浮游动物的摄食;营养盐添加会轻微降低小型浮游动物的摄食活动。2)营养盐和光照的增强能明显促进DCM层浮游植物的生长,并增加大粒级浮游植物的占比;而光照和营养盐变化对表层浮游植物的生长和粒级结构的改变相对不明显。因此,相对表层,深层浮游植物面临较小的摄食压力,拥有更大的光照和营养盐需求潜能;当台风引发的水体垂向混合后,获得营养盐补充的表层浮游植物并不能迅速生长,而获得光照的深层浮游植物能迅速生长,成为藻华爆发的优势种。
Abstract:
Phytoplankton growth and micro-zooplankton grazing are regulated by temperature, nutrients, and light in the ocean. Because of the different vertical distributions of light and nutrients, there is often a deep chlorophyll maximum (DCM) layer in the water column, which is widespread and almost a permanent ecological structure in the tropical oligotrophic ocean because of the stable stratification of the water column. Most parts of the South China Sea (SCS) are oligotrophic with strong underwater irradiance and low surface layer nutrients due to the stratification. The nutrient level is too low to support a phytoplankton bloom in the surface water, however, there are numerous reports of bloom events in the SCS after typhoons every year. It is commonly accepted that vertical mixing can weaken the nutricline and bring deep nutrient-rich waters to the euphotic zone, fueling phytoplankton blooms in the euphotic zone. However, few studies have compared the responses of phytoplankton and micro-zooplankton to the fluctuations of light intensity and pulses of nutrients simultaneously. In this study, an incubation experiment was conducted in the basin of the SCS during a cruise to compare the responses of surface and DCM phytoplankton to elevated irradiance and nutrients. Additionally, dilution experiments in different nutrient and irradiance conditions with surface and DCM water samples were conducted to explore micro-zooplankton grazing activity and their roles in the surface and DCM layers. We hypothesized that the DCM phytoplankton could be the seed population when the deep water is mixed upward with the surface layer in the case of a typhoon due to the changes in irradiance and micro-zooplankton grazing activity. The experimental results showed 1) micro-zooplankton grazing rates in the surface water were significantly higher than those in the DCM, and micro-zooplankton in the surface layer preferred the large size phytoplankton (>5 μm), whereas there was no such size selection in the DCM layer; UVR could promote the grazing rate of micro-zooplankton, whereas nutrient additions slightly decreased it; 2) the DCM phytoplankton assemblage responded more rapidly to the nutrient and light supplements and reached higher maximum biomass than surface phytoplankton, and the finial dominating size was larger in the DCM layer than that in the surface water. Therefore, the DCM phytoplankton assemblage is under less micro-zooplankton grazing intensity, and is more sensitive to light and nutrients. These results prove the hypothesis that DCM phytoplankton are seed populations when the deep water is mixed upward with the surface layer in a typhoon.
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