夏季台湾暖流的水文、化学特性及其对东海赤潮高发区生源要素补充的初步研究

【作者】 王颢；

【导师】 石晓勇；

【作者基本信息】 中国海洋大学 ， 海洋化学， 2007， 硕士

【摘要】 近年来,有害赤潮(HAB)成为严重影响我国东海海洋环境和水产事业的灾害之一。对东海赤潮高发区长时间的调查已使人们对生源要素在该海域的分布状况及长江冲淡水对该海区的营养盐补给作用有了较为深入的了解,但对于来自外海的台湾暖流对该海域生源要素所存在的影响仍不清楚。为此本文通过于2006年夏季对东海区水文化学数据的调查,对台湾暖流的水文化学特性进行了初步分析,并利用海流资料对台湾暖流源地区的两种水团-台湾海峡水和黑潮次表层涌升水的向东海内陆架区的营养盐通量进行估算。对台湾暖流的营养盐结构进行了探讨,并估算了其在东海赤潮高发区典型断面上升流作用下的营养盐垂直通量。最后对台湾暖流自身的水文特性对东海赤潮高发区的影响进行了初步探讨。主要结论如下:(1)夏季东海海区可划分为11个水团,其中的台湾暖流水具有台湾海峡水和黑潮次表层涌升水两个来源,它们分别构成台湾暖流的表层水和深层水。台湾暖流表层水具有较低的磷酸盐、硅酸盐和硝酸盐,而其亚硝酸盐含量极高,台湾暖流深层水则完全相反。亚硝酸盐可对表层水和深层水进行很好的区分。台湾暖流具有双层结构,在形成初期为垂向双层结构。当其北进至浙江中部海区时则为水平双层结构。表层水受到挤压而向外陆架一侧运动、下沉并扩散进入东海陆架。深层水在与表层水剥离后能够继续北进,并在此过程中产生强烈的变性,势力也逐渐缩小,穿越长江口区后台湾暖流深层水的势力已较微弱。(2)在夏季,台湾海峡水由南海水和部分黑潮水混合而成,在台湾海峡内流速较快。在海峡北部,势力较强的海峡水甚至有进入黑潮区的迹象。黑潮水在表层不能入侵陆架,但在50米以下存在黑潮入侵的迹象,100米处则非常明显。通过对位于台湾海峡以北截面和台湾-钓鱼岛间的两个截面营养盐通量的计算发现:在夏季黑潮涌升水对东海陆架区的磷酸盐、硅酸盐和硝酸盐输入通量较台湾海峡水略高。而由于流速较慢,其通量密度反而不及台湾海峡水。但主要由黑潮次表层水组成的台湾暖流深层水可直接到达东海赤潮高发区,因此对赤潮高发区的贡献仍较台湾海峡水重要。(3)通过对台湾暖流的氮磷比进行分析,发现台湾暖流表层水和深层水均具有较低的氮磷比,从而能够对东海赤潮高发区的营养盐结构进行调节,缓解海区“过剩氮”所导致的磷限制。台湾暖流引发的上升流对东海赤潮高发区营养盐尤其是磷酸盐的补充具有重要作用。同时也从另一个角度反映出长江冲淡水和沿岸水的对东海赤潮高发区营养盐的补充的重要性,没有两者的补充,赤潮高发区将很可能出现氮限制。(4)此外,夏季台湾暖流在浙江沿海出现的上升冷水给赤潮生物提供了适宜的温度,有利于赤潮的暴发。密跃层的出现一方面可促使赤潮生物的聚集而引发赤潮,而另一方面其可使陆地径流输入的颗粒物难于下沉,降低真光层的厚度,限制赤潮生物的生长,因此具有两面性。更多还原

【Abstract】 In recent years, Harmful Alga Bloom (HAB) became one of the most serious problems that affected marine environment and fishery industries in East China Sea (ECS). Based on long term investigations, nutrient distributions in ECS and the nutrient import from YRDW to the High Frequency HAB Occurrence Areas of ECS was studied in detail. However, nutrient import from off shore areas (especially from Taiwan Warm Current) still remained unknown. In this text, based on the cruise carried out in summer 2006, the hydrological and chemical properties of TWC was studied, nutrient flux in the TWC original area and upwelling area were calculated, nutrient structure of TWC was analyzed and its hydrological affections to the High Frequency HAB Occurrence Areas of East China Sea was discussed. Conclusions were summarized as follows:(1)In summer, eleven water masses could be divided in the East China Sea. Taiwan Warm Current has two origins: Taiwan Warm Current Surface Water originates from Taiwan Strait Water which is low in phosphate, silicate and nitrate, but high in nitrite. While Taiwan Warm Current Deep Water originates from intruded Kuroshio Subsurface Water(KU), which is low in nitrite, but high in phosphate, silicate and nitrate. Nitrite is a good indicator for distinguishing TWCSW and TWCDW. Taiwan Warm Current has a two-layer structure. In its early period, the two-layer structure is vertical, but when it reaches the middle of Zhejiang coast, the structure becomes horizontal. In this area, suffered from extrusion, TWCSW moves in outer-shelf direction, sinks and diffuses into East China Sea Shelf Water. Meanwhile, TWCDW could still moves northward and goes across the Yangtze River mouth, with its boundary shrinks.(2)In summer, the Taiwan Strait Water originates from South China Sea Surface Water and part of the Kuroshio Water. Current speed is relatively high in Taiwan Strait In the north of Taiwan Strait, Taiwan Strait Water could intrud into Kuroshio region. Kuroshio Water could not intrude into the shelf in the surface, however it could reach the shelf below 50 meters and become a stronger intruder in 100 meter layer. Horizontal nutrient flux is calculated based on the current velocity and nutrient data of three sections: S10 in the north of Taiwan Strait and section a and b between Taiwan, Pengchiahsu island and Diaoyutai Island (Senkaku jima). Results show that in summer, nutrient flux of Kuroshio Subsurface Water is a little higher than Taiwan Strait Current. Due to lower velocity, the nutrient flux density of Kuroshio Subsurface Water is much lower than Taiwan Strait Current, but since KU could constitute TWCDW which could directly reach the High Frequency HAB Occurrence Areas of East China Sea, its contribution is still greater than Taiwan Strait Current.(3) N/P Ratio of both TWCSW and TWCDW are low. Thus the TWC does play an important role in phosphate complementarity. In the TWC led upwelling areas in Zhejiang coast, nutrient vertical flux that calculated from upwelling velocity and nutrient data also confirms in this viewpoint. At the same time, the importance of YRDW and CW are recognized again, without them the area will probably suffer from N limitation.(4) In summer, TWC provide favorable temperature for Harmful Alga. At the same time, the appearance of pycnocline could urge the phytoplankton conglomeration, which could further induce the HAB occurrence. However, the appearance of pycnocline could prevent particles that input from land runoffs from sedimentation. Thus reduces the thickness of euphotic zone, which further limit the growth of phytoplankton.更多还原