【作者】 张传松；

【导师】 王修林；

【作者基本信息】 中国海洋大学 ， 海洋化学， 2008， 博士

【摘要】 近年来，长江口及邻近海域已成为我国著名的赤潮高发区，该海域赤潮频发与其每年氮、磷等营养物质的排海通量不断增加密切相关。因此，确定我国长江口及邻近海域主要营养物质的来源、通量，了解其对赤潮发生规模的影响，确定营养盐在东海赤潮生消过程中的作用，是阐明当前该海域赤潮发生机制的重要科学问题。本文以长江冲淡水及陆源影响区为研究区域，以2002～2007年长江口及邻近海域多个航次现场调查资料为基础，系统计算了该海域各主要营养盐来源的排海通量；分析了该海域营养盐平面分布特征及季节变化特征，比较了赤潮高发区与非赤潮高发区营养盐水平的差异；分析了该海域赤潮生消过程的特征，并对营养盐输入通量和赤潮发生状况之间的关系进行了总结。得出的主要结论如下：1、长江口及邻近海主要营养盐来源及通量1)在长江口及邻近海域淡水和海水的混合过程中，SiO₃-Si具有很好的保守性，其浓度与盐度之间呈现出良好的直线关系，DIN和PO₄-P具有明显的补充作用，它们的浓度与盐度之间呈现出良好的曲线关系，该曲线符合MnMolecular方程式。2)长江营养盐排海通量变化主要受长江径流量影响，研究海域的营养盐通量存在明显的季节变化，输入高峰期在每年的5～8月，其中6月为高峰期；调查期间2002、2003和2005年长江营养盐输入通量较大，2006和2007年较小，2004年最小。3)长江是研究海区最大的营养盐来源，其DIN入海通量占排海总量的52％，PO₄-P占33％，SiO₃-Si占56％；东海外海交换对研究海域PO₄-P （27％）和SiO₃-Si（21％）入海通量有较大贡献；其它入海径流对DIN（17％）和SiO₃-Si（23％）入海通量有较大贡献；大气沉降对DIN（18％）入海通量也有较大贡献。此外，沉积物-海水界面的营养盐交换对研究海域的营养盐收支状况也起到重要作用。2、长江口及邻近海主要营养盐状况1)长江口及邻近海域DIN、PO₄-P、SiO₃-S的等值线在122．0～122．5°E之间存在较大的浓度梯度，且均表现为近岸向离岸方向逐渐降低的特点。冬春季节营养盐等值线与海岸线基本平行，营养盐高值区主要集中在长江口至浙江南部的狭长地带，夏秋季节营养盐等值线转变为以长江口和杭州湾为中心呈扇面状向外海扩展，营养盐高值区主要集中在舟山群岛以北的区域。2)影响长江口及邻近海域营养盐平面分布特征的主要因素是长江等陆源输入，营养盐高值区随长江营养盐排海通量的增加而外扩，随长江冲淡水的改向而转移，长江营养盐输入通量的多少及其扩散模式，直接影响该海区营养盐平面分布特征和富营养化程度的大小。3)长江口及邻近海域营养盐的浓度水平及季节变化模式取决于营养盐补充和浮游植物消耗之间的消长和平衡。夏季该海区浮游植物的爆发性生长与增殖导致了对营养盐的需求高于营养盐的补充，从而造成该海区各项营养盐平均浓度整体表现为秋季最高、夏季最低，秋冬季节普遍高于春夏季节的变化特征。4)研究海域赤潮高发区和非赤潮高发区S、PO₄-P、SiO₃-S和DIN存在显著性差异，赤潮发生区主要集中在营养盐浓度水平相对较高、变化范围较小的富营养化的区域。3、长江口及邻近海赤潮生消过程特征1)依据该海区赤潮发生的实际状况和叶绿素浓度变化将该海域硅藻或甲藻赤潮生消过程划分别划分成5个阶段：延滞期(叶绿素低于1．5μg·L^-1)、孕育期、指数生长期(叶绿素低于10μg·L^-1)、维持期(叶绿素高于10μg·L^-1)和消散期(叶绿素低于10μg·L^-1)。2)确定了该海区赤潮生消过程中各主要参量的变化特征：温盐：硅藻赤潮发生时低温低盐，甲藻赤潮发生时高温低盐；营养盐浓度：硅藻赤潮发生前各项营养盐浓度均较高，甲藻赤潮发生前各项营养盐浓度均较低，各项营养盐浓度随硅藻赤潮的发生、发展快速大幅度下降，随甲藻赤潮的发生、发展缓慢小幅度下降；营养盐补充：硅藻赤潮随高温高盐外海海水的入侵近岸而发生、发展并消散，甲藻赤潮随低盐度长江冲淡水的补充而发生、发展并消散；赤潮生消过程中各项营养盐浓度主要取决于该过程中各项营养盐的补充速度与浮游植物消耗速度。3)确定了2005年研究海区赤潮生消过程中各要素的时间变化特征：硅藻赤潮爆发前，研究海区温度盐度较低，营养盐浓度较高且处于富营养化状态，此后硅藻赤潮优先爆发，最后随PO₄-P和SiO₃-S浓度的快速降低，硅藻赤潮迅速消亡；甲藻赤潮爆发前，研究海区温度较高盐度降低，营养盐浓度整体较低，大规模甲藻赤潮爆发期间营养盐补充加大，长时间的维持期后，温度超过了甲藻适温范围，同时DIN含量降低到最低值，甲藻赤潮消亡。4)确定了长江营养盐输入通量年变化、季节变化与赤潮发生状况之间的关系：各项营养盐输入通量与赤潮规模之间具有良好的指数增长型曲线关系，营养盐通量的增加将导致研究海区赤潮爆发频率／面积呈指数增长。其中，DIN输入通量与赤潮规模相关性最好。5)确定了各航次长江营养盐输入通量与海区叶绿素平均浓度之间的关系：春夏季节研究海区叶绿素平均浓度的高低与长江营养盐输入通量的大小之间具有非常好的直线关系，营养盐输入通量的增加将导致该海区生物量的直线上升。更多还原

【Abstract】 The Changjiang River Estuary and its adjacent area has become the frequentHarmful Algal Blooms （HAB） occurrence area of our country in recent years.Thehigh frequency of HAB in this area is closely related to the increment of nitrogenousand phosphorous fluxes drainaged to this area by many resources year after year.Therefore one of the most important tasks about researching mechanism of HAB inthis area is to study the main nutrient resources and their fluxes,recognize theirinfluences on the HAB scale and realize the role of nutrient during the process ofHAB in East China Sea （ECS）.Based on the data of field investigations through cruises in the area influenced byChangjiang Diluted Water from 2002 to 2007,the nutrient fluxes to ECS from mainresources and their variation patterns were systematically calculated.Then thenutrient characteristic of spatial distribution and seasonal variation in this area wereanalyzed.The difference of nutrient level between frequent HAB occurrence area andrare HAB occurrence area was compared.The characteristic of the nutrient during theprocess of HAB is analyzed and the relationship between nutrient flux and HABoccurrence is summarized.The main results are as follows:1.The main nutrient resources and their fluxes in Changjiang River Estuary and itsadjacent area1) During the mixture process of freshwater and seawater in Changjiang RiverEstuary and its adjacent area,SiO₃-Si is of conservative characteristic according to thegood linear relationship between its concentration and salinity.While DIN and PO₄-Pis of complemental function.The relationship between concentration and salinity ofDIN and PO₄-P shows a well curve,which accords with the equation of MnMolecular.2) The Changjiang River nutrient flux varies with its runoff.There is an obviousseasonal variation of nutrient flux in studied area.The input fastigium period occursfrom May to August every year and June is the fastigium.During the wholeinvestigation period,the nutrient input fluxes of the year 2002,2003 and 2005 arerelatively high while those of 2006 and 2007 are relatively low.The nutrient inputflux reached the lowest level in year 2004.3) The main nutrient resource of the research area is the Changjiang River,whose DIN flux to ECS accounts for 52%,PO₄-P accounts for 33% and SiO₃-Siaccounts for 56% of the whole drainge.The nutrient flux exchange with the open seawater makes great contributions to the flux PO₄-P （27%） and SiO₃-Si （21%） of thisarea.Some other rivers runoff makes great contribution to the flux of DIN （17%） andSiO₃-Si（23%）.The atmosphere deposition accounts for the DIN （18%） flux.Besidesthe sediment-water nutrient flux works well with the nutrient budgets in the researcharea.2.The nutrient condition of Changjiang River Estuary and its adjacent area1) The contour of DIN、PO₄-P、SiO₃-S in this area has a relatively largeconcentration grads between 122.0～122.5°E.In winter and spring,the nutrientcontour parallels with the coastline and the high value nutrient area mainly locating inthe long and narrow zone from Changjiang Estuary to south coastal area of Zhejiang.While in summer and autumn,the contour turns to a fan-shape extending to the opensea and the high value nutrient area mainly locates north area of Zhoushanarchipelago.2) The primary factor affecting the horizontal distribution characteristic ofnutrient in Changjiang River Estuary and its adjacent area is such terrestrial input asChangjiang River.The high concentration value of nutrient extends as the increase ofthe Changjiang nutrient flux and the eutrophic area transfers as the ChangjiangDiluted Water turns around.Therefore attempering the amount and pervading mode ofChangjiang nutrient flux will affect the nutrient horizontal distribution characteristicand the eutrophic condition of the research area.3) The nutrient concentration level and its seasonal variation pattern in theChangjiang River Estuary and its adjacent area depends on balance between nutrientsupplement and consume of phytoplankton.In summer,the explosive growth andreproduction of phytoplankton in this area cause the huge demand of nutrientexceeding the supplement,which can explain the variation characteristic of averagenutrient concentration in this area reaches the highest in autumn,the lowest insummer,relative higher in autumn and winter and lower in spring and summer.4) There is an obvious difference of the value of S、PO₄-P、SiO₃-S and DINbetween frequent HAB occurrence area and rare HAB occurrence area.FrequentHAB occurrence area is mainly located on those areas who have nutrient relativelyhigh concentration and lower variation range.3.The characteristic of HAB in Changjiang River Estuary and its adjacent area1) According to the HAB records and Chlorophyll a concentration variationmode in the research area,the process of blooms of Diatom or Dinoflagellate can becompartmentalized to 5 stages:lag phase(Chlorophyll a＜1.5μg·L^-1),initiation stage,exponential phase(Chlorophyll a＜10ug·L^-1),stationary phase (Chlorophyll a =10μg·L^-1) and dissipation phase （Chlorophyll a＜10μg·L（-1））.2) The variation characteristic of several main parameters in the process of HAB is concluded.The bloom of diatom is initialized usually with low temperature and lowsalinity while the blooms of dinoflagellate usually with high temperature and lowsalinity.Before blooms of diatom,the nutrient concentration is relatively high whilelow before blooms of dinoflagellate.DIN、PO₄-P、SiO₃-S concentrations drop rapidlyduring the process of diatom bloom while slowly in dinoflagellate bloom..TheDiatom bloom would be initiation,exponential growth and dissipation with theinvasion of open seawater,while dinoflagellate bloom with the supplement ofChangjiang Diluted Water.During the whole process of HAB,the value of nutrientconcentration mainly depends on the phytoplankton’s consuming speed and thesupplementing speed of nutrient.3) The temporal variation characteristic of each element during the process ofHAB in this area in 2005 is concluded.Before diatom blooms breakout,thetemperature and salinity is relatively low,the nutrient concentration is relatively highand in eutrophic condition.Then the diatom blooms would be prior occurred.Finallydiatom bloom would be dissipated quickly following with the sharp concentrationdecrease of PO₄-P and SiO₃-S.Before dinoflagellate bloom breakout,the temperatureis high and salinity and nutrient concentration are relative low.When dinoflagellatebloom occurs in large scale,the nutrient supplement increases.After a long retentionstage,dinoflagellate blooms dissipates when the temperature is too high fordinoflagellate and the DIN content reaches the lowest.4) The relationship of HAB condition and Changjiang nutrient flux’s annualvariation and seasonal variation is concluded.There is a good exponential increasingcurve relationship between nutrient flux and HAB scale.The increment of nutrientflux will cause the exponential increase of frequency and area of HAB.The DIN inputflux has the best pertinency with HAB scale.5) The relationship of Changjiang nutrient flux in each cruise and averageconcentration of Chlorophyll a is concluded.In spring and summer,the averageconcentration of Chlorophyll a has a perfect lineal relationship with Changjiangnutrient flux.The increase of nutrient flux will cause the biomass linear increase inthis area。更多还原