共查询到20条相似文献，搜索用时 140 毫秒
1.
《中国科学:地球科学》2019,(12)
微生物是驱动海洋元素循环的主体,在调节全球气候变化中起着重要作用.近半个世纪海洋研究的一个谜团就是"为什么有着一个相当于大气CO2碳总量的惰性溶解有机碳(Recalcitrant Dissolved Organic Carbon, RDOC)库在海洋中长期存在?".生物泵(Biological Pump, BP)和微食物环(Microbial Loop, ML)研究加深了我们对生物在海洋碳循环中作用的理解,但直到微型生物碳泵(Microbial Carbon Pump, MCP)理论的提出,才真正阐释了海洋惰性溶解有机碳来源和存储的生物地球化学机制. MCP是由微型生物介导的溶解有机碳(非沉降)转化和迁移的海洋储碳新机制,提出了RDOC产生的3个重要途径:(1)微型生物特别是异氧细菌和古菌在有机质降解代谢过程中改造并分泌RDOC;(2)病毒颗粒裂解宿主导致细胞的死亡并释放RDOC;(3)原生动物等捕食者摄食微型生物并释放RDOC. MCP揭示了海洋RDOC的惰性机制,定义了两类RDOC组分(RDOCc和RDOCt),为调节气候和改善生态环境提供了可验证的理论.为纪念中国科学家在海洋碳循环领域的突出贡献,文章在回顾海洋微型生物与碳循环相关研究基础上,系统总结并讨论了MCP理论提出以来中国在此领域的国际引领地位和影响力,并展望了未来研究的方向. 相似文献
2.
《中国科学:地球科学》2017,(12)
埃迪卡拉纪(635~541Ma)记录了地质历史上最大的全球碳循环扰动事件(即"Shuram Excursion"事件,简称SE事件).在约25~50个百万年的时间里,全球海水无机碳同位素组成持续负偏,最大负偏至–12‰.这一碳同位素负偏被认为是当时古海洋中存在的超大型溶解有机碳库被完全氧化或空间差异性氧化的结果,同时也被认为是古海洋微型生物碳泵强烈储碳而形成超大型溶解有机碳库的关键证据.随着研究的深入,这一认识受到了挑战,新假说认为陆源沉积老碳的氧化或古海洋海底释放的富烃流体的氧化同样可以导致这一碳循环扰动事件.为解决这一争论,本文基于碳循环质量平衡原理对上述各种假说进行了数值模拟与评估,结果表明:(1)在给定的埃迪卡拉纪大气氧水平下(≤40%目前大气氧水平),全球规模的陆源有机碳氧化假说和溶解有机碳完全氧化假说受限于氧化剂,大气氧将分别在4Myr和6Myr内消耗殆尽,难以在长时间尺度上形成全球规模的–12‰碳同位素负偏信号;(2)全球范围内的富烃流体氧化假说由于对参加反应的流体烃类的需求量过大也面临挑战;(3)全球海洋溶解有机碳库的空间差异性氧化(部分氧化)假说所要求的DOC库部分氧化(50%)所需的氧化剂和DOC总量都具有可行性. 相似文献
3.
《中国科学:地球科学》2018,(12)
原绿球藻(Prochlorococcus)是地球上体积最小、丰度最高的光合自养生物.作为贫营养海区及大洋的优势微生物类群,原绿球藻是海洋初级生产力的重要组成部分和碳循环的重要贡献者.病毒对原绿球藻的生长、碳固定、进化、环境适应及生物地球化学意义等方面具有重要的影响.文章综述了原绿球藻病毒研究在研究方法、遗传多样性及其与宿主相互关系方面的研究成果,分析了原绿球藻病毒潜在的生物地球化学作用,并提出了研究展望,为海洋病毒及碳循环研究提供参考. 相似文献
4.
《地球物理学进展》1989,(3)
今天人类活动引起的全球碳循环的扰动,已经掀起人们对全球碳循环的历史及其与气候和其它地球化学旋回的关系的新的兴趣。碳同位素地层学作为近两亿年来碳循环历史的监测器,已被证明是最有效的。在本文的引言里,总结了全球碳循环的运行模型,并证明了碳循环及碳同位素地球化学之间的联系。提出了阿普弟阶至阿尔布阶(Aptian-Albian)期间全球碳循环扰动的情况。在深海沉积的碳同位素地层研究中,记录了持续达数百万年的碳循环扰动。它叠加在高频沉积旋回之上,后者与持续时间为二万年、四万年和十万年的气候及海洋循环有关。本文论述的资料表明,全球碳系统的变化与地球化学循环的全球加速变化有关,后者是由大气中CO_2的长期变化引起的,而海底沉积的速率和火山活动则控制着大气中CO_2的变化。 相似文献
5.
湖泊沉积物碳库作为湖泊生态系统的重要组成部分,对湖泊碳循环起重要作用,而蓝藻水华衰亡过程对湖泊碳库稳定性影响研究较少本研究采集太湖蓝藻、湖水、沉积物样品,建立蓝藻水沉积物室内模拟实验系统,分析蓝藻水华衰亡过程中沉积物碳库易氧化有机碳(EOC)、惰性有机碳(ROC)、微生物量碳(MBC)、轻组有机碳(LFOC)和重组有机碳(HFOC)的变化规律,探究蓝藻水华衰亡过程对湖泊碳库稳定性的影响结果表明,蓝藻水华衰亡前期(1～9天),ROC缓慢下降,EOC和LFOC快速下降,MBC有所增加;衰亡中期(10～45天),沉积物TOC和ROC含量升高;衰亡末期(46～63天),HFOC和ROC等稳定有机碳进入一个从缓慢分解逐渐趋于稳定的阶段周期性的蓝藻水华暴发、衰亡和湖泊稳定性有机碳的日渐累积,最终会对沉积物碳库有机碳组分及其稳定造成显著影响. 相似文献
6.
外源溶解性有机碳(DOC)是湖泊碳库的重要组成部分,关于外源DOC对浮游动物的贡献及途径需要深入研究.本研究在抚仙湖受控实验中添加13C标记的葡萄糖,通过分析样品中浮游植物与浮游动物的种类、数量、磷脂脂肪酸生物标志物及其稳定同位素特征,研究外源DOC对湖泊甲壳类浮游动物碳源的贡献比例及其变化.结果表明:细菌、甲壳类浮游动物(象鼻溞)的δ~(13)C值在加入葡萄糖后分别从-16.28‰和-23.88‰快速增加到5408.25‰和1974.7‰,而藻类磷脂脂肪酸(C18∶2ω6)δ~(13)C值从-27.07‰增加到342.44‰,增长的幅度表明添加的葡萄糖首先被细菌和浮游动物快速利用,而藻类只利用了一小部分.同时细菌、颗粒性有机物(POM)和浮游动物的δ~(13)C值在第1 d急剧增加,细菌的δ~(13)C值远大于浮游动物和POM的δ~(13)C值,之后细菌和POM的δ~(13)C值开始下降,但浮游动物的δ~(13)C值却仍在缓慢增加,进一步表明了DOC进入湖泊后首先被细菌吸收利用,而细菌吸收DOC后通过自身代谢作用形成细胞颗粒,浮游甲壳类动物通过摄食细胞颗粒来获得外源DOC. 相似文献
7.
滇东湖泊水生植物和浮游生物碳、氮稳定同位素与元素组成特征 总被引：3，自引：2，他引：1
稳定同位素示踪方法是研究生态系统组成与功能的重要手段,有助于认识湖泊食物网的基本组成与生物地球化学循环的主要过程.本研究选择了云南省东部地区营养水平不同的10个湖泊,开展了高等水生植物(沉水植物、漂浮植物)、浮游植物与浮游动物的空间调查,分析了不同生物在碳、氮稳定同位素信号与元素组成上的分布模式.在碳稳定同位素信号的分布上,漂浮植物在4种生物类型中最为偏负且变化幅度最小,为-28.99‰±0.86‰;浮游动物碳稳定同位素(-20.85‰±2.70‰)的分布特征与浮游植物(-21.88‰±2.97‰)显著相似;而沉水植物的碳稳定同位素显著偏正且变化范围较大,平均值为-12.04‰±4.57‰.结果表明,碳源及其传输途径的差异是导致湖泊生物体内碳同位素信号不同的主要驱动过程.在氮稳定同位素信号上,同为初级生产者的沉水植物(5.43‰±5.84‰)、漂浮植物(5.58‰±7.38‰)与浮游植物(7.26‰±3.83‰)较为相似,而浮游动物氮同位素信号(11.02‰±3.18‰)显著高于浮游植物且平均富集约3.46‰,反映了湖泊生物随着营养级的增加出现较为明显的同位素分馏效应.在空间分布上,湖泊生物碳同位素信号受到水温、水深等因素的明显影响,氮同位素信号则随湖泊营养水平的增加而逐渐偏正.与长江中下游等地区相比,云南湖泊生物的碳、氮元素含量总体偏高;同时,代表内源有机质组分的水生植物和浮游生物C/N质量比值都小于20.因此,本研究揭示的生物碳、氮同位素信号与元素组成特征可为评价高原湖泊食物网组成与生物地球化学循环提供重要的科学依据. 相似文献
8.
湖沼学是研究内陆水体的多学科整合科学——兼论我国湖沼学发展面临的挑战与机遇 总被引：1，自引：0，他引：1
湖沼学是研究内陆水体的多学科交叉综合性科学,自从Forel F.A.于1892年首次对湖沼学做出定义以来已有近130年历史.湖沼学的主要分支学科包括地质湖沼学(包括古湖沼学)、物理湖沼学、化学(生物地球化学)湖沼学和生物湖沼学.湖沼学的关键自然属性是通过跨学科的整合,从水生态系统水平综合分析相关过程与机理,并对生态系统变化进行预测.因此,湖泊学也是支撑水资源与生态系统保护、管理与修复的核心科学.然而,目前我国湖沼学发展面临分支学科发展不平衡、研究碎片化等问题,而人类活动加剧和气候变化对内陆水体生态系统的影响及管理对策是湖沼学研究面临的挑战与机遇.我国湖沼学研究亟需围绕人类活动、气候变化的影响,重点开展以下几个方面的工作:1)水动力与水文地貌特征变化及其环境生态效应; 2)营养盐和有机质生物地球化学循环及其环境生态效应; 3)食物网结构与功能; 4)外来入侵物种的影响与控制对策; 5)与水环境有关的传染病防治; 6)地表水生态评价; 7)生态系统演变机理与退化生态系统修复等. 相似文献
9.
稳定同位素技术应用于水域食物网的方法学研究进展 总被引：5，自引：0，他引：5
稳定同位素技术是揭示食物网中物质的循环路径和探究消费者、生产者间的营养关系的重要方法.但是,不同的样品处理方法可能引起同位素比值的变动,使得食物网模型的建立和各研究结果间的相互比较存在一定的困难.样品的预处理主要分为四个环节,即保存、分离、酸化和干燥.在水域生态系统中,水体中的颗粒,溶解性有机物质、细菌、浮游动物、藻类、水生植物、鱼类及底栖动物等采集后,通过分离纯化,得到目的样品,-20℃冷冻保存.对于含有无机碳酸盐的生物样品,例如沉积物、含有钙质结构的无脊椎生物、部分浮游生物等需要酸化处理以排除无机碳对6"c测定的影响,1mol/L.HCl滴加可以达到很好的去除效果.对于生物样品δ15N的测定则不需要酸化处理.最后,样品经冷冻干燥或40—70℃低温烘干以备稳定同位素的测定.另外,用福尔马林、乙醇等保存在博物馆里的样品,对于长时间尺度上食物网的重建具有重要的生态学意义.本文系统总结了不同研究中样品处理过程的差异,分析其干扰机制,为进一步的方法学研究奠定了基础. 相似文献
10.
深部碳循环及同位素示踪:回顾与展望 总被引：1，自引：0，他引：1
深部碳循环是全球碳循环中的重要组成部分,它指通过板块俯冲过程把大洋底部的碳酸盐岩带到地幔中,然后再通过火山作用以CO2气体形式释放到大气中.目前对于深部碳循环的研究仍处在一个起步阶段.其中一个很重要的科学问题是火山作用释放的CO2中与俯冲相关的碳和原始幔源碳的比例.传统碳同位素可以很好的区分有机碳和无机碳,但火山作用释放的CO2中,大约95%的与俯冲相关的碳和原始幔源碳均是无机碳,因此传统的碳同位素方法无法区分.近年来Ca和Mg同位素在示踪壳内物质循环方面的研究取得很大的进展,本文针对以上科学问题,总结了近年来对于深部碳存储总量、通量及存在形式,洋壳俯冲过程中碳的行为,含碳地幔的熔融,深入探讨了C,Ca和Mg同位素示踪深部碳循环的原理和途径,以及前人在C,Ca和Mg同位素示踪深部碳循环等方面的研究成果. 相似文献
11.
Banking carbon: a review of organic carbon storage and physical factors influencing retention in floodplains and riparian ecosystems 
下载免费PDF全文
下载免费PDF全文 Rivers are dynamic components of the terrestrial carbon cycle and provide important functions in ecosystem processes. Although rivers act as conveyers of carbon to the oceans, rivers also retain carbon within riparian ecosystems along floodplains, with potential for long‐term (> 102 years) storage. Research in ecosystem processing emphasizes the importance of organic carbon (OC) in river systems, and estimates of OC fluxes in terrestrial freshwater systems indicate that a significant portion of terrestrial carbon is stored within river networks. Studies have examined soil OC on floodplains, but research that examines the potential mechanistic controls on OC storage in riparian ecosystems and floodplains is more limited. We emphasize three primary OC reservoirs within fluvial systems: (1) standing riparian biomass; (2) dead biomass as large wood (LW) in the stream and on the floodplain; (3) OC on and beneath the floodplain surface, including litter, humus, and soil organic carbon (SOC). This review focuses on studies that have framed research questions and results in the context of OC retention, accumulation and storage within the three primary pools along riparian ecosystems. In this paper, we (i) discuss the various reservoirs for OC storage in riparian ecosystems, (ii) discuss physical conditions that facilitate carbon retention and storage in riparian ecosystems, (iii) provide a synthesis of published OC storage in riparian ecosystems, (iv) present a conceptual model of the conditions that favor OC storage in riparian ecosystems, (v) briefly discuss human impacts on OC storage in riparian ecosystems, and (vi) highlight current knowledge gaps. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
12.
13.
K. L. Hondula M. L. Pace J. J. Cole R. D. Batt 《Aquatic Sciences - Research Across Boundaries》2014,76(2):217-229
Large differences in δ 2H of primary producers between aquatic and terrestrial ecosystems are used to identify subsidies, discriminate organic matter sources, and reduce uncertainty in food web studies. Previous investigations of hydrogen isotope ratios suggest there may be predictable differences between the δ 2H of water and organic matter for different types of primary producers. We define the difference in the net isotopic discrimination between water and bulk organic matter (om) as: ΔH = (δ 2Hom ? δ 2Hwater) ÷ (1 + δ 2Hwater ÷ 1,000). We summarized ΔH values from published literature and we measured the δ 2H of water and primary producers in order to compare ΔH among aquatic and terrestrial primary producers. Measurements were made from three water body types (lake, river, coastal lagoon) and their associated watersheds. Although we predicted a large and equivalent net isotopic discrimination for aquatic primary producers, we found considerable variability among groups of aquatic producers. Macroalgae, benthic microalgae, and phytoplankton had more negative ΔH values (i.e. greater isotopic discrimination) than both aquatic macrophytes and terrestrial vegetation. The more positive δ 2Hom and hence lower ΔH of terrestrial vegetation was expected due to relative increases in the heavier isotope, deuterium, during transpiration. However, the more positive values of δ 2Hom and relatively low ΔH in aquatic macrophytes, even submerged species, was unexpected. Marine macroalgae had high variability in δ 2Hom as a group, but low variability within distinct species. Variability among types of primary producers in δ 2Hom and in ΔH should be assessed when hydrogen is used in isotopic studies of food webs. 相似文献
14.
15.
16.
17.
Cristian A. Vargas Rodrigo A. Martinez Valeska San Martin Mauricio Aguayo Nelson Silva Rodrigo Torres 《Continental Shelf Research》2011,31(3-4):187-201
Ecosystems can act as both sources and sinks of allochthonous nutrients and organic matter. In this sense, fjord ecosystems are a typical interface and buffer zone between freshwater systems, glaciated continents, and the coastal ocean. In order to evaluate the potential sources and composition of organic matter across fjord ecosystems, we characterized particulate organic matter along a lake–river–fjord corridor in the Chilean Patagonia using stable isotope (δ13C) and lipid (fatty acid composition) biomarker analyses. Furthermore, estimates of zooplankton carbon ingestion rates and measurements of δ13C and δ15N in zooplankton (copepods) were used to evaluate the implications of allochthonous subsidies for copepods inhabiting inner fjord areas. Our results showed that riverine freshwater flows contributed an important amount of dissolved silicon but, scarce nitrate and phosphate to the brackish surface layer of the fjord ecosystem. Isotopic signatures of particulate organic matter from lakes and rivers were distinct from their counterparts in oceanic influenced stations. Terrestrial allochthonous sources could support around 68–86% of the particulate organic carbon in the river plume and glacier melting areas, whereas fatty acid concentrations were maximal in the surface waters of the Pascua and Baker river plumes. Estimates of carbon ingestion rates and δ13C in copepods from the river plume areas indicated that terrestrial carbon could account for a significant percentage of the copepod body carbon (20–50%) during periods of food limitation. Particulate organic matter from the Pascua River showed a greater allochthonous contribution of terrigenous/vascular plant sources. Rivers may provide fjord ecosystems with allochthonous contributions from different sources because of the distinct vegetation coverage and land use along each river’s watershed. These observations have significant implications for the management of local riverine areas in the context of any human project that may modify terrestrial habitats as well as the productivity, food webs, and community structure of rivers, lakes, fjords, and the coastal ocean in the Chilean Patagonia. 相似文献
18.
《Limnologica》2014
Human development of watersheds can change aquatic ecosystems via multiple pathways. For instance, human rural development may add nutrients to ecosystems. We used naturally occurring stable isotopes in stream food webs to investigate how land use affects stream ecosystems across a gradient of land development in the San Lorenzo watershed, California. Road density was used as a proxy for land development. We found that streams in watersheds with higher road densities had elevated concentrations of phosphate and nitrate. Furthermore, algal δ15N values increased as a function of nitrate concentration, but saturated at approximately 6‰. This saturating pattern was consistent with a two-source mixing model with anthropogenic and watershed sources, fit using Bayesian model fitting. In sites that had >2.6 km roads km−2, anthropogenic sources of N were estimated to represent >90% of the N pool. This anthropogenic N signal was propagated to stream consumers: rainbow trout (Oncorhynchus mykiss), signal crayfish (Pacifasticus leniusculus), and benthic invertebrate δ15N were positively correlated with algal δ15N. Even relatively low density rural human land use may have substantial impacts on nutrient cycling of stream ecosystems. 相似文献
19.
沉水植物附植生物群落生态学研究进展 总被引：6，自引：4，他引：2
在高等水生植物表面经常附着生长着藻类、真菌和细菌等,这些有机群体组成附植生物群落,在大中型浅水湖泊中普遍存在.附植生物群落具有特定的物种组成和空间结构,并随季节推移和沉水植物生长表现出一定的动态变化特征.附植生物群落与宿主植物及周围水体环境联系密切,不仅能够表征水体营养盐、光照、温度等环境因子特征,与沉水植物、食草动物、浮游植物等水生生物类群也存在不同的相互作用.水生生态系统中,附植生物群落参与水体营养物质转化,在草-藻型湖泊生态系统的相互转化过程中起重要作用;其较高的初级生产力作为水生动物重要的食物来源,增加了食物网的多样性;同时,附植生物群落因其独特的生理生态特征正逐渐被应用于水质净化和水环境质量监测.本文在综述近年来附植生物群落研究进展的基础上,分析了附植生物群落的组成结构和动态变化特征,阐述了附植生物群落在水生生态系统中的功能,可为湖泊富营养化治理,尤其是沉水植被的生态修复和管理提供科学依据. 相似文献
20.
The use of seabirds as sentinels of the condition of aquatic ecosystems has been well-established. Large environmental perturbations to aquatic food webs (e.g., chemical contamination, overfishing, particulate pollution) have all been detected or monitored by tracking seabirds at colonies. However, seabirds may elicit more subtle, sublethal responses that can also be used to track ecosystem health, or the health of seabird populations. In this article, we advocate for field researchers to plan a priori to collect a broader suite of samples when handling seabirds, and to reach out for collaboration with specialists (e.g., parasitologists, wildlife veterinarians). Collectively, such efforts will greatly improve our ability to establish baseline physiological and chemical levels for seabirds, against which we can detect future changes in aquatic ecosystems. 相似文献