南黄海浮游植物的固碳强度与污染物胁迫下海水碳源/汇格局的变化

IOCAS-IR > 海洋环流与波动重点实验室

	南黄海浮游植物的固碳强度与污染物胁迫下海水碳源/汇格局的变化
其他题名	The carbon fixed production of phytoplankton in the southern Yellow Sea and change of marine CO2 source/sink pattern under pollutant stress
	郑国侠
学位类型	博士
	2007-06-02
学位授予单位	中国科学院海洋研究所
学位授予地点	海洋研究所
关键词	浮游植物固碳强度生物地球化学机制模拟实验污染物胁迫碳源/汇格局南黄海
摘要	本论文在解析了南黄海生态环境的基础上，首次研究揭示了浮游植物固碳强度的年际变化及生态反馈机制，获得了东中国近海浮游植物固碳强度及对海域源/汇格局的影响程度；同时，用室内模拟实验探讨了重金属和有机污染物胁迫下海水无机碳体系和源汇格局的变化过程，获得了一些新的认识。主要结论如下： 1. 南黄海浮游植物固碳强度具有明显的时空变化特征，与海域光照、流系和水团变化、海水磷的浓度等因素密切相关，并在一定程度上决定海区碳源/汇的性质。2005年秋季浮游植物日固碳量达9.5万吨，1983-2005年间，南黄海浮游植物固碳强度有降低的趋势，与海水关键营养盐－磷的限制有关。东中国近海浮游植物年总固碳量约为2.2亿吨，约占全球近海浮游植物的年固碳量的2.0%。在综合分析秋季南黄海水文、化学、生物背景的基础上，系统阐明了海域浮游植物固碳体系的生物地球化学机制。结果表明，2005年秋季南黄海浮游植物固碳强度，即初级生产力变化在 97−701 mgC m-2 d-1之间，平均为307 mg C m-2 d-1；与其关系比较密切的环境因子为海水透明度、盐度、pH、氨氮 (NH4-N)、磷酸盐 (PO4-P) 以及Chl a。在这些因素中，PO4-P对初级生产力的影响最大，显然11月份南黄海的磷是浮游植物生长的限制因子，次之的影响因素是Chl a和NH4-N。对南黄海源汇格局的研究发现，如果除去涌升流较为活跃的站位（A9、B7、B8、B9、C8、C9、 D9和A1），2005年秋季表层海水pCO2与浮游植物固碳强度明显负相关（r=-0.8，n=23, p<0.001）。在南黄海东部浮游植物固碳强度较高，pCO2值较低；而在西部海区浮游植物固碳强度较低的区域，其pCO2值较高。碳源/汇转折点浮游植物固碳强度为230 mgC m-2 d-1，即小于此值，海区为大气二氧化碳的源，反之为汇，并且CO2汇区浮游植物固碳强度平均值约是CO2源区的2倍多；浮游植物固碳作用，在某一时间和空间尺度内，基本决定了海区的源汇格局。估算结果显示，东中国近海浮游植物固碳量约为222×106t a-1，约为东中国近海通过海－气界面总表观碳汇强度每年1369万吨的16.2倍，仅就浮游植物的年固碳量而言，东中国近海约占全球近海浮游植物的年固碳量的2.0%。研究揭示了近年来南黄海浮游植物固碳强度具有区域与年际变化明显这一显著特点。一般，近岸区（由黄海沿岸水和表层水控制）内，光照是浮游植物固碳的主要限制因子；从2001年后的大多数年份中，中央区（黄海冷水团控制）的浮游植物固碳强度均与磷酸盐浓度显著正相关，但与氮浓度的相关性不大，说明南黄海生态系统普遍存在着磷限制而非氮限制；混合区终年受黄、东海混合水控制，受到光照条件和营养盐浓度同时影响。根据本次观测所获数据，结合以前研究者的调查资料，我们发现从1983年到2005年，南黄海浮游植物优势种由Bacillariophyta变为Pyrrophyta，浮游植物细胞丰度和Chl a明显下降，浮游植物固碳强度几乎下降了二分之一（由569.50 mgC m-2 d-1下降至306.83 mgC m-2 d-1），说明南黄海在世界边缘海固碳过程中的作用在降低。经过相关水质参数及生态环境变化的分析，以上现象是对关键营养盐磷的限制以及光限制响应的缘故。此外，研究还发现，由于南黄海初级生产者产量下降所引起的一些生态反馈信息，如浮游动物固碳量的下降和鱼类产量的锐减。 2. 室内模拟实验显示，重金属（铅、铜、镉和锌）及有机污染物（乙醇、丙酮、尿素和多灭磷）对水体生物固碳体系有重要影响，较低浓度时可提高水体的固碳能力，相应水体中的DIC、HCO3-和 Pco2 与对照组相比都明显下降 (P<0.01)；当污染物达到一定浓度后，水体生物的固碳能力明显下降，其有机碳可降解转化为无机碳。当污染物小于转折浓度水体为大气二氧化碳的汇，反之为源。水体固碳体系对于不同种类、不同浓度的污染物质所表现的受胁迫情况不同，低浓度各污染物（包括重金属和有机污染物）添加组中（对于重金属为0.1和1µmol•L-1，醇和酮分别为<0.5 mol L-1和<0.75 mol L-1），藻干重及固碳量均要大于初始值，说明适量的外源污染可能会促进藻类生长，提高水体的固碳能力，相应水体中的DIC、HCO3- 和PCO2与对照组相比都明显下降 (P<0.01)。当污染物达到一定浓度后，由于其毒害作用，使得水体内生物的固碳能力下降，甚至分解并转化为无机碳，从会引起DIC、HCO3- 和PCO2含量的升高，其含量上升幅度会因固碳体系对不同种类污染物耐受程度的差异而不同。对于尿素和多灭磷，二者浓度分别达到80和20mgL-1时，水体中二氧化碳各参数仍呈现下降趋势，说明在该浓度范围内，大型藻类（如石莼）仍可利用添加物中的氮和磷，将其做为氮源或磷源，促进水体总固碳量的增加。污染物胁迫对水体碳源汇能力及格局可起到一定的调控作用，与污染物的浓度密切相关，污染物存在着一转折浓度，分别为5µmol L-1（铜）、20µmol L-1（镉） 0.75mol L-1（酮），当污染物添加小于转折浓度并排除其他影响因素时，水体表现为大气CO2的汇，并且适量的增加污染物浓度会使海洋碳汇能力有所增强；而当污染物超出转折浓度时，水体成为CO2的源，其CO2的释放量是随着污染物浓度的增加而增大。对与研究中其他种类的污染物，在实验室设计范围内，水体始终表现为大气CO2的汇。
其他摘要	In the dissertation, temporal-spatial variability for the carbon fixed production of phytoplankton (CFP) and the response of ecosystem were discussed in detail for the first time. The annual value of CFP in the entire marginal seas of eastern China and its contribution to the absorption of atmospheric CO2 were also gained. Furthermore, simulated experiments coupled with ocean biota dynamics were performed in laboratory. In these experiments, effects of pollutants on marine carbon fixation system and CO2 fluxes were investigated. A series of results and viewpoint are presented as followed: 1. The CFP of the SYS in recent years were characterized of distinguished spatial and temporal change which was significantly correlated with phosphate concentration, light availability and chemical hydrographic condition. It had significant influence on the carbon sink/source pattern in the SYS. The value of CFP was estimated to be 9.5104t d-1 in 2005 and found to show a negative trend since 1983 which should mainly attribute to the deficiency of phosphorus in the SYS through our analysis. The annual value of CFP in the entire marginal seas of eastern China was estimated to be 222×106t, which accounted for 2% of the annual value of CFP in global marginal sea areas. Carbon fixation system of phytoplankton was examined for its biogeochemical mechanism based on the compositive investigations of hydrography, chemistry and biology in the SYS. The value CFP in autumn of 2005 of the SYS ranged from 97 to 701 mg C m-2 d-1 with an average of 307 mg C m-2 d-1. Study showed that the correlated factors to CFP were transparency, salinity, pH, ammonia, phosphate and Chl a. Among these factors, the most correlated was phosphate which was controlling factors to phytoplankton growth in autumn of the SYS, and the second was Chl a and ammonia. Investigation showed that if excluding data gained from the stations occupied by upwelling （A9、B7、B8、B9、C8、C9、 D9和A1）, a good negative correlation （r=-0.8，n=23, p<0.001）between CFP and pCO2 of the surface water would be found. In the eastern region of the SYS where the CFP value was relatively high, pCO2 was low; however, in the western region of the SYS where the CFP value was relatively low, pCO2 was high. The average value of CFP corresponding to the transition from CO2 source area to CO2 sink area was 230 mgC m-2 d-1, namely while CFP lower than this transition, the corresponding sea area was presented as a source to atmospheric CO2. By contrast the sea area became a CO2 sink area. It illustrated that carbon fixation of phytoplankton had significant influence on the carbon sink/source pattern in the SYS. Furthermore, according to the present study results together with previous investigations, the annual value of CFP in the entire marginal seas of eastern China was estimated to be 222×106t, which accounted for 2% of the annual value of CFP in global marginal sea areas. Besides, it was as 16.2 times as the annual value of apparent carbon sink strength (1396×104t) in the entire marginal seas of eastern China. The study of spatio-temporal mechanism of CFP showed that from 1999-2005 the CFP in the costal waters has been positively related to transparency. Since 2001 the CFP in the central region of the SYS has been positively related to phosphate concentration with a reasonably good correlation but had lack of correlation with TN concentration, which indicated that SYS ecosystem has probably been experiencing limitation of P rather than N. The factors correlated to CFP in the YS and ECS mixed Water were relatively complicated than in other water types. It was controlled by light availability and nutrients supplement simultaneously in such water type. Moreover, we found that there were pronounced responses of ecosystem to the changes of the water quality parameters in the SYS during observation years, including strengthening nutrient limitation, declining Chl a and phytoplankton abundance, succession of dominant phytoplankton species from diatoms to non-diatoms and zooplankton biomass, especially the negative trends of CFP (decrease from 536.52 mgC m-2 d-1 to 353.02 mgC m-2 d-1). It means that the role of the SYS playing in the process of photosynthesis carbon fixation has declined. Furthermore, zooplankton abundance and fish production were also declined during the observation years. 2. Simulated experiments coupled with ocean biota dynamics were performed in laboratory and the changes of marine biological carbon fixation system and CO2 sink/source pattern under the stress of heavy metal (copper, cadmium, zinc and lead) and organic pollutants (ethanol, acetone, organic nitrogen and organic phosphorus) were investigated. The results indicated that changes of carbon fixation system and CO2 sink/source pattern were correlated with the concentrations and kinds of pollutant. In the groups of low concentration of pollutant (0.1and1µmol L-1 for heavy metal , <0.5 mol L-1and <0.75 mol L-1 for ethanol and acetone, respectively), the dry weight of alga and carbon fixation strength of marine biological carbon fixation system were increased and DIC、HCO3-and Pco2 significantly decreased comparing to the control experiment data (P<0.01), correspondingly. However, when the pollutant infusions were higher than the “critical concentration”, the carbon fixation strength were decreased and organic carbon might change into inorganic carbon. As a result, the concentration of DIC、HCO3-and Pco2 were ascended and the ascending range was correlated with the kind and dose of pollutant. As for organic nitrogen (ON) and organic phosphorus (OP), when they were 80 and 20mgL-1, decreasing trend of inorganic carbon in sea water was still found. It showed that nitrogen and phosphorus in the pollutant could be used by alga as nutrient source and promoted carbon fixation. Moreover, the results indicated that CO2 source/sink pattern might be controlled by pollutant and were correlated with the concentrations and kinds of pollutant. The critical concentration was 5µmol L-1for copper, 20µmol L-1for cadmium and 0.75mol L-1for acetone, respectively. When the pollutant infusions were lower than that critical concentration, the corresponding sea water was presented as a sink to atmospheric CO2 and when the pollutant infusions were higher than that critical concentration, the sea water became a CO2 source area. For the other pollutant, in the range of our experiment dose, the sea water was always present as an atmospheric CO2 sink.
页数	127
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/927
专题	海洋环流与波动重点实验室
推荐引用方式 GB/T 7714	郑国侠. 南黄海浮游植物的固碳强度与污染物胁迫下海水碳源/汇格局的变化[D]. 海洋研究所. 中国科学院海洋研究所,2007.

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