【作者】 金海燕；

【导师】 翁焕新；

【作者基本信息】 浙江大学 ， 环境科学， 2009， 博士

【摘要】 通过现场调查,利用光合色素组成信息探讨了东海31°N纬度断面上浮游植物群落组成结构。通过分析长江口及东海海域水体颗粒有机碳的组成特征及沉积物中有机碳、氮及其稳定同位素组成、生物硅、绿素、光合色素等标志物,讨论了调查海区沉积物中有机碳的来源、保存情况及影响因素;结合¹³⁷Cs定年揭示了20世纪40年代初至90年代末近60年来长江口赤潮多发区古生产力及其浮游生物群落结构的变化。2007年夏季光合色素表征的东海海域31°N纬度断面浮游植物群落结构组成表现为:近岸营养盐丰富海域（N/P＞16,表现为潜在的P限制海区）,浮游植物生物量较高,主要以硅藻为主,其次为隐藻。同时还有少量的绿藻、定鞭藻、甲藻、蓝细菌等,未检测出原绿球藻和金藻。外陆架海域,营养盐绝对浓度低且表现出明显的氮限制,浮游植物生物量低,上层海水中主要以蓝细菌为主,其次为金藻、定鞭藻、绿藻和原绿球藻,而硅藻很少。蓝细菌在水柱过程中多发生降解作用而很少沉降到海底,硅藻则在底层海水中存在由近岸向外陆架的侧向输运过程。东海颗粒有机碳（POC）分析结果表明由于受到悬浮泥沙量的影响,浓度变化范围大,且表现出近岸高、远岸低的特征。表层海水POC主要为海洋生物来源,底层颗粒有机碳中碎屑有机碳对POC有较大贡献,尤其在近岸海域。沉积物有机碳（TOC）、生物硅（BSi）、绿素（chlorin）等对海区古生产力的指示有显著差异。研究海域TOC含量为0.10%～0.72%,由于长江口近岸海域和杭州湾受陆源输入影响较大,因此有机碳含量总体表现为近岸高,远岸低的特征。BSi主要表现为硅藻的生产力,浓度变化为0.05%～0.30%,表现出近岸海域硅藻生产力高,而向外海降低的趋势。绿素表征总浮游植物生产力,浓度范围为0.03μg/g～7.71μg/g,高值分布在122.5°E～123.5°E范围内,与长江口外高生产力区相对应。有机碳同位素(δ¹³Corg)、氮同位素(δ¹⁵N)及有机质C/N比值分析表明研究海区使用δ¹³Corg信息来表征有机质来源更为合适,研究海区δ¹³Corg值为-24.45‰～-20.48‰,表明其有机质为陆源和海源的混合来源。δ¹⁵N则更多的显示出生物地球化学过程改造的信息,在东海外陆架海区由于受固氮作用的影响,δ¹⁵N偏轻,而近岸海域沉积物δ¹⁵N信息则是受到营养盐过剩、有机质选择性降解以及脱氮等过程的综合改造结果。调查海区C/N比值在5.27～11.29间变化,一定程度上可反映有机质来源,但受到沉积物中吸附的无机氮以及有机质选择性降解等因素的干扰。长江口外赤潮多发区沉积物柱状样G1柱沉积速率为1.55±0.03 cm/a,年代最早可追溯到20世纪40年代初期。δ¹³Corg为-19.50‰～-26.15‰,Corg/N为4.03～19.4,沉积有机质为混合来源。δ¹⁵N为2.23‰～6.39‰,生物地球化学过程对δ⁽150N改造影响了物源信号,在60～80年代时间段存在低值,与该时段环境中营养盐持续输入,氮盐过剩及固氮作用增强等相对应。古生产力替代指标TOC、BSi及绿素的研究表明50年代初海区生产力较低。在50年代至80年代期间,海源输入比重加大,且硅藻生产力大幅提高,与此阶段长江口营养盐浓度迅速增加相应。沉积物中浮游植物色素组成信息还表明在该时段绿藻、蓝藻等生产力也有增加。80年代后,BSi显示硅藻生产力降低。色素信息则表明青绿藻、隐藻或甲藻等藻类生物量增加。这与海区氮盐持续增加,但Si、P等则呈降低趋势,N/P、P/Si值迅速增大密切相关。营养盐结构的变化对海区浮游植物群落组成比率有显著影响。有机碳同位素数据表明此阶段陆源有机碳的贡献增强。更多还原

【Abstract】 Particulate organic carbon and photosynthesis pigments were investigated to know the characteristics of organic carbon and the structure of the phytoplankton communities in Changjiang Estuary and East China Sea.Then the paleoproductivity and the changing environment conditions in the past 60 years were discussed based on the studies of some proxies such as organic carbon and nitrogen with their stable isotopes,biological silicon,chlorin and photosynthesis pigments of surface sediments and a sediment core.The results indicate that the primary production is high in the inshore water with high nutrient levels（N/P＞16,displays as potential P limits sea area）,and the phytoplankton communities derived by HPLC photosynthetic pigments dominated by diatom,next as the cryptophytes,chlorophytes,prymnesiophytes,dinoflagellate and cyanobacteria,but no chrysophytes and prochlorophytes in summer along the latitude of 31°N in East China Sea.While in the outside continental shelf sea area,with low nutrient levels and obvious nitrogen limitation,the primary production was low,and the phytoplankton was dominated by cyanobacteria in the surface water,next as the crysophyes,prymnesiophytes,chlorophytes and prochlorophytes.The diatom was few in the surface water while in the bottom there was some,indicated outward lateral transport.Most of cyanobacteria degraded during deposition in the water column and only a few can deposited in the sedimens.The concentrate of particulate organic carbon was high near the shore affected by the contents of suspended particles while it decreased outwards in the East China Sea.POC in surface layer sea water mainly originates from the marine organisms,while the detritus organic carbon contributes greatly in the bottom layer,especially in inshore water.The contents of total organic carbon（TOC）,biological silicon（BSi） and chlorin were used as "proxies" for paleoproductivity.The contents of TOC ranged from 0.10 %to 0.72%in surface sediments with high values in the inner shore and low values off shore.The terrestrial inputs in the Changjiang Estuary and Hangzhou Bay affected the use of TOC as the proxy of paleoproductivity.BSi mainly performance for diatom’s productive forces,and the contents ranged from 0.05%to 0.30%.Diatom productive displayed high in the inshore which reduced to the open sea.Chlorin attribute to marine phytoplankton productive forces,the contents is 0.03μg/g～7.71μg/g,the high value distributes in the area of 122.5°E～123.5°E,corresponds with the high productive forces area in the Changjiang Estuary.Studies of Organic carbon isotope(δ¹³Corg),Nitrogen isotope(δ¹⁵N) and the Corg/N ratio indicate thatδ¹³Corg information was relatively appropriate for difference the originate of organic matters in study area.δ¹³Corg ranged from -24.45‰to -20.48‰,indicates the mixing source of organic matter from terrestrial origin and marine organisms.δ¹⁵N value demonstrates the information of biogeochemistry process transformation.δ¹⁵N was light as a result of nitrogen fixation influence in the outshelf of East China Sea,but the inshore water depositδ¹⁵N was the result of synthesis information of the nitrate surplus,selectivity degradation of organic matter and denitrification transformation process.Corg/N ratio was changed from 5.27 to 11.29 in study area,reflect the organic matter originates in certain degree,but affected by the absorbance of NH₄⁺ as well as organic matter selectivity degradation.Stable organic carbon isotope,biogenic silicate and pigments were studied from a sedimentary core for discussing the variation of paleoproductivity and the environmental implications in the past decades in Changjiang Estuary.The sedimentary rate was 1.55±0.03 cm/a and the core had recorded the information from the beginning of 1940s to 1997.The sedimentary organic carbon was mixing originate derived from the signature ofδ¹³Corg（-19.50‰～-26.15‰） and Corg/N values （4.03～19.4）.The changing value ofδ¹³Corg indicated that the riverine organic carbon increased after 1980s..δ¹⁵N was 2.23‰～6.39‰,demonstrates the information of biogeochemistry process transformation.Lowδ¹⁵N value in the middle of the core, corresponds with the time of 60s～80s was affected by the increasing nitrate inputs and increasing nitrogen fixation.The biogenic proxies present three stages of paleoproductivity changes:Before 1950s,Marine primary production was low,and it increased during 1950s-1980s with diatoms dominated,consistent with increasing of nutrients concentrations.Chlorophytes and cyanobacteria were increased either in this stage.Then the production decreased Later than 1980s.In this stage,the diatom production decreased while the production of other phytoplankton communities such as prasinophytes,crysophytes or dinoflagellate increased.It was affected by continually inputs of high nitrate,but Si,P and so on assume reduce the tendency,and it results high N/P,P/Si nutrients ratios in changjiang Estuary.更多还原