海洋酸化对固氮蓝藻束毛藻的影响及其作用机制

<正>海洋浮游植物贡献了地球上约一半的初级生产力,驱动着海洋生物泵将碳从海洋上层向深层输出.氮是浮游植物生长所必需的元素,而海洋固氮蓝藻束毛藻是海洋生态系统中"新氮"的重要来源之一,可贡献高达50%的全球海洋总固氮量[1],对海洋初级生产力以及碳、氮生物地球化学循环起着至关重要的影响.工     

南黄海及长江口邻近海域夏季溶解有机碳的分布特征及其影响因素

【目的】海水中溶解有机碳(DOC)的研究对于碳的生物地球化学循环具有重要意义。通过对南黄海及长江口邻近海域夏季溶解有机碳的分布特征及其影响因素的研究,为进一步丰富我国陆架边缘海碳循环的研究提供数据支持和参考依据。【方法】利用高温燃烧氧化法对2013年夏季南黄海及长江口邻近海域水体中的DOC进行测定,初步分析夏季南黄海DOC的分布特征,并结合水文、化学、生物同步观测参数,探讨影响DOC分布的主要因素。【结果】2013年夏季南黄海及长江口邻近海域DOC的含量为0.24~2.37mg/L,平均值为(1.34±0.42)mg/L。整体而言,调查海区平面分布呈现北部浓度高,向南部逐渐降低,近岸浓度高远岸浓度低的分布趋势。DOC的垂直分布呈现表层高,逐渐向底层减小,在底层又有所增加的趋势。【结论】研究海区DOC的分布受水团物理混合控制作用十分明显,近岸DOC高值区的分布主要受鲁北沿岸流和陆源输入影响,南部的低值区主要受黑潮表层水及台湾暖流的稀释作用影响,而生物作用对DOC的分布影响较弱。     

地球系统科学模拟有关重大问题

从20世纪70年代开始,科学家们已经开始把大气、海洋、冰雪和陆面四个圈层作为一个整体来考虑,既研究各圈层内部的物理过程也研究其间的相互作用,这实际上是一个物理气候系统.进入21世纪,人们的视野从物理气候系统扩展到了地球系统,进一步考虑生态系统、空间天气和固体地球系统,通过研究圈层内部的物理、化学和生物地球化学过程以及圈层之间的能量、动量和物质交换来了解地球能量过程、生态过程和新陈代谢过程的运行规律.人们越来越重视诸如碳、氮循环等生物地球化学耦合过程在气候系统中的作用及人类活动对这些循环过程的影响.地球系统模式基于地球各圈层中的物理、化学和生物过程建立起来的数学方程组,然后用数值计算方法求解,编制成一种大型综合性计算程序.地球系统模式是迄今为止最复杂和最具综合性的科学数值模拟工具,是地球系统科学理论和知识的集大成.地球系统模式的先进性,体现了一个国家在地球系统科学研究的核心竞争力,是衡量一个国家地球科学研究综合水平的重要指标.建成国际领先的地球系统模式对大幅度提升我国在地球系统科学领域的水平具有不可替代的作用.本文概述了地球系统数值模拟研究的科学意义、国家需求、国际发展趋势、我国已经取得的成就和未来的发展目标和任务.     

红树林种植-养殖耦合系统中尼罗罗非鱼的食源分析

 利用碳、氮稳定同位素技术和胃含物分析法,研究了滩涂红树林海水种植-养殖耦合系统中大规格尼罗罗非鱼的食物来源。镜检结果表明,红树种植塘和无红树的对照塘中尼罗罗非鱼的食物组成基本相同,主要以无机碎屑、底栖微藻、植物凋落物、浮游生物、腹足类、双壳类和泥土组成,摄食习性和它们的栖息环境有密切关系。稳定同位素分析表明,红树塘中罗非鱼的主要饵料为有机碎屑,浮游植物和植物凋落物,这3种食物来源的贡献比例依次5%~55%、10%~40%和15%~26%,而对照塘中这3者的比例依次为8%~64%、25%~55%和1%~12%。可见,无论在红树塘还是对照塘中,有机碎屑对尼罗罗非鱼食物组成的贡献比例都超过50%,表明尼罗罗非鱼是典型的碎屑食性鱼类。此外,栖息地生境的红树植物、盐沼植物和浮游植物,也是尼罗罗非鱼消化食物的重要组成部分。     

海洋超微型蓝细菌聚球藻的生态学研究进展

海洋超微型蓝细菌是地球上数量最多的光合自养原核类群,主要由聚球藻(Synechococcus)和原绿球藻(Prochlorococcus)两个属组成,贡献了约25%的海洋净初级生产力.聚球藻是一个古老且多样性非常高的类群,从赤道到极地都有分布.聚球藻与异养细菌及蓝细菌病毒的相互作用维系了微食物环的结构和复杂性,对于海洋生源要素生物地球化学循环过程至关重要.在全球变化的大背景下,基于模式预测,聚球藻将会在生态系统中发挥更重要的作用.本文从海洋聚球藻对初级生产力的贡献、遗传多样性,及其与异养细菌、蓝细菌病毒的互作机制4个方面综述该领域研究的新进展.     

厦门港西海域冬季微型浮游动物在碳循环中的作用

于2004年2月在厦门港宝珠屿利用稀释法和饵料浓度差减法培养实验,同步研究了微型浮游动物对浮游植物的摄食压力和对一种优势桡足类瘦尾胸刺水蚤(C en tropages tenuirem isThompson et Scott)的饵料贡献.结果表明,微型浮游动物对浮游植物现存量的摄食压力为38%,对初级生产力的摄食压力为63%;瘦尾胸刺水蚤对微型浮游动物纤毛虫和对浮游植物的清滤率分别为3.08 mL.ind-1.h-1和0.31mL.ind-1.h-1,摄食率分别为0.44μg.ind-1.d-1和0.24μg.ind-1.d-1.纤毛虫对此种桡足类的饵料贡献比为65%~95%.由此可见,微型浮游动物在冬季厦门海域的海洋生态系统中,对浮游植物的生产和归宿起着十分重要的调控作用,在浮游植物和桡足类之间起着重要的营养连接作用.     

内源硫影响污染河湖磷营养盐环境行为的研究进展

硫和磷都是生物地球化学循环中重要的生源要素,两者的环境行为和耦合机制共同影响着污染河湖内源污染的释放.本文总结了污染河湖沉积物中硫与磷的环境行为以及它们之间耦合机制的最新研究进展,指出硫驱动的磷释放进而造成的水体富营养化是污染河湖中值得重视的环境问题,并同时对硫循环与其他生物地球化学循环耦合过程的研究提出展望,以期为治理污染河湖中的内源污染提供借鉴.     

黄海氮磷营养盐时空特征及影响过程分析

利用物理-生物地球化学耦合模型,模拟了黄海氮磷营养盐浓度及其结构的季节变化特征,并量化分析了不同过程对该海域营养盐结构的影响。氮磷营养盐浓度春夏低、秋冬高,近岸高外海低,底层高于表层;氮磷比春夏高于秋冬季;根据营养盐季节收支计算,发现黄海内部生物过程在营养盐浓度及其结构的季节变化过程中起着至关重要的作用。河流、大气、沉积物-水界面的营养盐输入是营养盐的重要补充过程,不超过总氮、磷补充量的33%。黄海氮磷比由冬季到春季升高是由于磷含量的下降幅度大于氮的下降幅度;夏季由于氮含量的上升幅度大于磷的上升幅度而继续升高;秋季由于氮含量下降,磷含量上升而下降。     

厌氧甲烷氧化及其影响因子的研究进展

厌氧甲烷氧化(anaerobic oxidation methane, AOM)对降低全球甲烷排放具有重要意义，是当前生物地球化学循环的研究热点之一。基于此，综述了以不同电子受体参与的AOM反应，包括硫酸盐还原型厌氧甲烷氧化、反硝化型厌氧甲烷氧化和金属离子型厌氧甲烷氧化，对参与不同类型AOM的相关微生物种类及代谢途径进行梳理，重点总结影响因子包括甲烷浓度、氧化还原电位、温度、pH值及盐度对AOM的影响，最后展望了应拓宽研究区域，探寻更多参与AOM的电子受体及其他反应耦合体系，以期为进一步研究甲烷氧化过程在碳、氮、硫及金属离子生物地球化学循环中的重要意义提供参考。     

木麻黄林生态系统营养元素的地球化学循环

以福建惠安１５年生木麻黄林为试材的定位观测结果表明：每年降水输入的营养物质为４９．２８５ｋｇ·ｈｍ－２,径流输出养分量１５．５０７ｋｇ·ｈｍ－２,养分净积累量３３．７７８ｋｇ·ｈｍ－２表明生态系统处于进展的变化过程中。养分地球化学循环的净变化值比生物循环减小７５．６％,这说明生物循环比地球化学循环强度大且速度快。     

Climate-driven trends in contemporary ocean productivity

Contributing roughly half of the biosphere's net primary production (NPP), photosynthesis by oceanic phytoplankton is a vital link in the cycling of carbon between living and inorganic stocks. Each day, more than a hundred million tons of carbon in the form of CO2 are fixed into organic material by these ubiquitous, microscopic plants of the upper ocean, and each day a similar amount of organic carbon is transferred into marine ecosystems by sinking and grazing. The distribution of phytoplankton biomass and NPP is defined by the availability of light and nutrients (nitrogen, phosphate, iron). These growth-limiting factors are in turn regulated by physical processes of ocean circulation, mixed-layer dynamics, upwelling, atmospheric dust deposition, and the solar cycle. Satellite measurements of ocean colour provide a means of quantifying ocean productivity on a global scale and linking its variability to environmental factors. Here we describe global ocean NPP changes detected from space over the past decade. The period is dominated by an initial increase in NPP of 1,930 teragrams of carbon a year (Tg C yr(-1)), followed by a prolonged decrease averaging 190 Tg C yr(-1). These trends are driven by changes occurring in the expansive stratified low-latitude oceans and are tightly coupled to coincident climate variability. This link between the physical environment and ocean biology functions through changes in upper-ocean temperature and stratification, which influence the availability of nutrients for phytoplankton growth. The observed reductions in ocean productivity during the recent post-1999 warming period provide insight on how future climate change can alter marine food webs.     

Polysaccharide aggregation as a potential sink of marine dissolved organic carbon

The formation and sinking of biogenic particles mediate vertical mass fluxes and drive elemental cycling in the ocean. Whereas marine sciences have focused primarily on particle production by phytoplankton growth, particle formation by the assembly of organic macromolecules has almost been neglected. Here we show, by means of a combined experimental and modelling study, that the formation of polysaccharide particles is an important pathway to convert dissolved into particulate organic carbon during phytoplankton blooms, and can be described in terms of aggregation kinetics. Our findings suggest that aggregation processes in the ocean cascade from the molecular scale up to the size of fast-settling particles, and give new insights into the cycling and export of biogeochemical key elements such as carbon, iron and thorium.     

Unsaturated fatty acid content in seston and tropho-dynamic coupling in lakes

Determining the factors that control food web interactions is a key issue in ecology. The empirical relationship between nutrient loading (total phosphorus) and phytoplankton standing stock (chlorophyll a) in lakes was described about 30 years ago and is central for managing surface water quality. The efficiency with which biomass and energy are transferred through the food web and sustain the production of higher trophic levels (such as fish) declines with nutrient loading and system productivity, but the underlying mechanisms are poorly understood. Here we show that in seston (fine particles in water) during summer, specific omega3-polyunsaturated fatty acids (omega3-PUFAs), which are important for zooplankton, are significantly correlated to the trophic status of the lake. The omega3-PUFAs octadecatetraenoic acid, eicosapentaenoic acid (EPA) and docosahexaenoic acid, but not alpha-linolenic acid, decrease on a double-logarithmic scale with increasing total phosphorus. By combining the empirical relationship between EPA-to-carbon content and total phosphorus with functional models relating EPA-to-carbon content to the growth and egg production of daphnids, we predict secondary production for this key consumer. Thus, the decreasing efficiency in energy transfer with increasing lake productivity can be explained by differences in omega3-PUFA-associated food quality at the plant-animal interface.     

Evolution and metabolic significance of the urea cycle in photosynthetic diatoms

Diatoms dominate the biomass of phytoplankton in nutrient-rich conditions and form the basis of some of the world's most productive marine food webs. The diatom nuclear genome contains genes with bacterial and plastid origins as well as genes of the secondary endosymbiotic host (the exosymbiont), yet little is known about the relative contribution of each gene group to diatom metabolism. Here we show that the exosymbiont-derived ornithine-urea cycle, which is similar to that of metazoans but is absent in green algae and plants, facilitates rapid recovery from prolonged nitrogen limitation. RNA-interference-mediated knockdown of a mitochondrial carbamoyl phosphate synthase impairs the response of nitrogen-limited diatoms to nitrogen addition. Metabolomic analyses indicate that intermediates in the ornithine-urea cycle are particularly depleted and that both the tricarboxylic acid cycle and the glutamine synthetase/glutamate synthase cycles are linked directly with the ornithine-urea cycle. Several other depleted metabolites are generated from ornithine-urea cycle intermediates by the products of genes laterally acquired from bacteria. This metabolic coupling of bacterial- and exosymbiont-derived proteins seems to be fundamental to diatom physiology because the compounds affected include the major diatom osmolyte proline and the precursors for long-chain polyamines required for silica precipitation during cell wall formation. So far, the ornithine-urea cycle is only known for its essential role in the removal of fixed nitrogen in metazoans. In diatoms, this cycle serves as a distribution and repackaging hub for inorganic carbon and nitrogen and contributes significantly to the metabolic response of diatoms to episodic nitrogen availability. The diatom ornithine-urea cycle therefore represents a key pathway for anaplerotic carbon fixation into nitrogenous compounds that are essential for diatom growth and for the contribution of diatoms to marine productivity.     

Pseudomonas sp. QG6降解喹啉过程中除磷特性及影响因素研究

从工业废水处理系统中分离出一株以喹啉为唯一碳源和氮源的假单胞菌QG6 (Pseudomonas sp. QG6), 用于喹啉降解同步除磷, 并采用正交实验设计优化出最佳条件。菌株QG6具有较好的喹啉降解能力, 12小时内能将96~144 mg/L的喹啉完全降解。菌株QG6在好氧条件下具有除磷能力, 不存在喹啉的条件下, 以有机碳为碳源、无机氮为氮源、初始磷酸盐浓度为8.69~19.41 mg/L时, 20小时内能去除磷酸盐86%以上。初始喹啉浓度为144 mg/L (其自身的碳氮比约7:1)、磷酸盐浓度为10 mg/L时, 若不外加有机碳源, 喹啉在12小时内被降解完全, 同一时段内除磷率仅为33%。外加有机碳源至碳氮比20:1且其他条件都相同时, 喹啉降解 效果不受影响, 且同步除磷率提高到 86%。正交实验表明, 外加碳源条件下喹啉降解的最佳条件按影响大小排列为: 初始喹啉浓度200 mg/L, 温度25°C, pH 8, 摇床转速120 rpm; 除磷最佳条件为: 摇床转速100 rpm, 温度为25°C, 初始喹啉浓度150 mg/L, pH 9。     

Uptake of dissolved organic carbon and trace elements by zebra mussels

Zebra mussels (Dreissena polymorpha) are widespread and abundant in major freshwater ecosystems in North America, even though the phytoplankton food resources in some of these systems seem to be too low to sustain them. Because phytoplankton biomass is greatly depleted in ecosystems with large D. polymorpha populations and bacteria do not seem to be an important food source for this species, exploitation of alternative carbon sources may explain the unexpected success of D. polymorpha in such environments. Here we examine the possibility that absorption of dissolved organic carbon (DOC) from water could provide a nutritional supplement to zebra mussels. We find that mussels absorb 14C-labelled DOC produced by cultured diatoms with an efficiency of 0.23%; this indicates that DOC in natural waters could contribute up to 50% of the carbon demand of zebra mussels. We also find that zebra mussels absorb some dissolved metals that have been complexed by the DOM; although absorption of dissolved selenium was unaffected by DOC, absorption of dissolved cadmium, silver and mercury by the mussels increased 32-, 8.7- and 3.6-fold, respectively, in the presence of high-molecular-weight DOC.     

Biological productivity and carbon cycling in the Arctic Ocean

Primary production, bacterial production, particulate organic carbon fluxes and organic carbon burial rates were quantified during the summer period of 1999 in the Arctic Ocean via 14C uptake, 3H uptake, 234Th/238U disequilibrium and 210Pbex dating, respectively. The integrated primary production in the water column was as high as 197 mmolC/(m2@d) in the Chukchi shelf and was 3.8 mmolC/(m2@d) in the Canada Basin. These rates are higher than those reported previously. The ratios of bacterial production to primary production in the study region were higher than 0.5, indicating that microbial activity is not depressed but important in cold Arctic waters. 234Th/238U disequilibria were evident at the station in the Canada Basin. The presence of significant 234Th deficiency suggested that scavenging and removal processes are also important to biogeochemical cycles of trace elements in the Arctic Ocean. Particulate organic carbon export flux was estimated to be 1.0 mmolC/(m2@d). Measurements of sediment excess 210Pb profile in the Chukchi shelf allowed us to estimate the amount of organic carbon buried in the bottom sediment, which ranged from 25 to 35 mmolC/(m2@d) and represented about 59%-82% of the mean primary production in the euphotic zone. Overall, our results indicated that the Arctic Ocean has active carbon cycling and is not a biological desert as previously believed. Therefore, the Arctic Ocean may play an important role in the global carbon cycle and climate change.     

长春南湖水生生态系统中浮游动物群落特征

研究了2001～2002年长春南湖生态系统中的浮游动物群落特征． 发现浮游动物94种， 其中51种为轮虫． 浮游动物优势种存在明显的季节变化, 浮游动物的个体数量在夏季和秋季各 出现一次高峰． 浮游动物年净产量为704.45 kJ·m^-2， 年总产量为1 642.50 kJ·m^-2; 全年浮游动物群落的P/B系数为41.4（以年净产量计）或96.4（以年总产量计）． 浮游动物群落对水柱原位浮游植物和浮游细菌的牧食力分别为2.57 kJ·m^-2·h^-1 和1.47 μg C·L^-1·h^-1， 是浮游植物和细菌同期净生产力的51.7%和32.9%．形成浮游动物净生产力的碳量是浮游植物总碳固定的8.2%． 浮游动物群落在一定程度上体现了南湖为温带富营养化湖泊的特征．     

基于改进TVGM的水–碳耦合机制研究

提高植被的水分利用效率（water use efficiency, WUE）可以在一定程度上缓解水资源短缺，如何提高WUE依赖于对生态系统水–碳循环耦合机制的深入理解. 以北京森林站为例，基于时变增益模型（times variant gain model，TVGM)耦合光合作用–气孔导度模型与双源蒸散发模型，从WUE系数及气孔导度2方面研究水–碳耦合机制. 研究结果表明:不考虑水–碳耦合关系导致模拟蒸散发偏高、模拟总初级生产力偏大，气孔导度的增加抑制水分利用效率的提高，其抑制效应随气孔导度的增加趋于平稳；日退耦系数在夏季达到最大，年平均退耦系数为0.1左右. 在北京森林站群体水平上，相对于光合速率，蒸腾速率对气孔导度的下降较为敏感，导致WUE随气孔导度的下降而降低. 对北京森林站地区水–碳耦合机制的研究，可为其生态系统管理与调控提供依据.