Ecological studies on Prochlorococcus in China seas

Prochlorococcus, a tiny oxygenic photosynthetic picoplankton with unique pigment composition, has been found to be ubiquitous and abundant in the world oceans, and has been recognized to be closely related to living resources and environmental issues. It has attracted the interest of marine biologists since its discovery, and field data on it over global oceans have accumulated rapidly in the past 10 years. In China, we have studied Prochlorococcus for 8 years, achieving a basic ecological understanding. The presence of Prochlorococcus in China seas, marginal seas of the west Pacific, was confirmed, and its distribution patterns were also brought to light. Prochlorococcus is very abundant in the South China Sea and the offshore regions of the East China Sea. It is seasonally present in the southeast part of the Yellow Sea and absent in the Bohai Sea. Temporal and spatial variations of the abundance of Prochlorococcus and their affecting factors, physiological and ecological characteristics of Prochlorococcus and their relationships to the other groups of picoplankton, and the importance of Prochlorococcus in total biomass and possible roles in living resources and environmental problems are discussed. In the future, isolation of different Prochlorococcus strains from the China seas and their physiological characteristics, genetic diversity, phylogenies and gene exploiture, etc. are important issues to be addressed.     

罗源湾及九龙江口美肩鳃鳚仔、稚鱼的新记录

研究了罗源湾和九龙江口美肩锶鲥仔、稚鱼的形态特征,时空分布及其与环境的关系,美肩锶鲥不仅分布在黄海和渤海,南海和东海也有分布。仔稚鱼的主要特征:眼大、吻短、稍突出、头高、体中等延长,左右侧肩,头顶包一骨质冠,头冠左右两侧及左右眼眶上有骨嵴,前锶盖骨隅角具一强棘,以上构造都着生小刺,前鳃盖骨后缘有4枚小棘突,腹囊大,背面具黑色素点,肌节37～45(8-12 28-32),背鳍一个,延长,胸鳍大,腹鳍喉位,背、臀鳍的两支鳍骨之间有尖三角形骨片。     

旧居住区生态节能系统研究

旧居住区环境景观改善的具体措施也必须按照“完善使用功能”、“美化环境面貌”、“营造社区精神”三个层面进行，这三个层面即密不可分，同为环境景观改善必须完成的目标，又在策略上呈现出基础、升级、最高的递进关系。我国居民对居住的需求已从有住房、住得好的个人生理需求，向具有良好的居住环境和社会文化整体环境的需求过度。我国城乡人居环境质量有了显著提高，在对生态环境的保护和利用、绿化配置与休闲娱乐、重视地域性文化的延续等景观建设方面取得了很大成就，但背后也存在一些问题有待进一步研究和解决。尤其旧居住区的环境景观改善都是些局部点缀性的绿化、环境设施的随意增加等方面着手，没有从根本上改善人居环境。     

热带岛礁型海洋牧场中珊瑚礁生境与资源的修复

我国南海的离岸岛礁以珊瑚礁生境为主。珊瑚礁在提升海洋生态资源和维护我国海洋国土权益上发挥了至关重要的作用。近年来,在全球气候变化以及人类活动的影响下,南海珊瑚礁生境和资源严重退化,威胁着渔业资源、海洋环境以及国土安全。现代化的海洋牧场被认为是实现南海资源可持续发展战略的新型海洋生物资源开发模式。珊瑚礁生境与资源的修复则是热带岛礁型海洋牧场建设的基础和关键。基于此,本文整理了珊瑚礁生境与资源修复的技术方法,详细介绍了珊瑚礁生境构建框架生物造礁石珊瑚的有性繁殖、断枝培育、底播移植等技术方法以及珊瑚礁其他特色生物资源人工放流技术,并提出了在珊瑚礁生境与资源修复中所面临的问题及相应对策。     

以长山列岛为例探讨我国渔业经济可持续发展

长山列岛(以下简称长岛)是我国八大群岛之一,地处黄海、渤海交汇处,作为渤海门户,其生态环境保护和渔业经济发展的双赢具有十分重要的战略意义.在全球气候变化和人类活动影响的大背景下,本综述以海洋环境保护与生态修复为出发点,围绕渔业资源管理与生态化水产养殖等问题,多层次、多维度探讨长岛渔业经济可持续发展的基本路径,并与全球其...     

Genome divergence in two Prochlorococcus ecotypes reflects oceanic niche differentiation

The marine unicellular cyanobacterium Prochlorococcus is the smallest-known oxygen-evolving autotroph. It numerically dominates the phytoplankton in the tropical and subtropical oceans, and is responsible for a significant fraction of global photosynthesis. Here we compare the genomes of two Prochlorococcus strains that span the largest evolutionary distance within the Prochlorococcus lineage and that have different minimum, maximum and optimal light intensities for growth. The high-light-adapted ecotype has the smallest genome (1,657,990 base pairs, 1,716 genes) of any known oxygenic phototroph, whereas the genome of its low-light-adapted counterpart is significantly larger, at 2,410,873 base pairs (2,275 genes). The comparative architectures of these two strains reveal dynamic genomes that are constantly changing in response to myriad selection pressures. Although the two strains have 1,350 genes in common, a significant number are not shared, and these have been differentially retained from the common ancestor, or acquired through duplication or lateral transfer. Some of these genes have obvious roles in determining the relative fitness of the ecotypes in response to key environmental variables, and hence in regulating their distribution and abundance in the oceans.     

Low-light-adapted Prochlorococcus species possess specific antennae for each photosystem

Prochlorococcus, the most abundant genus of photosynthetic organisms, owes its remarkably large depth distribution in the oceans to the occurrence of distinct genotypes adapted to either low- or high-light niches. The pcb genes, encoding the major chlorophyll-binding, light-harvesting antenna proteins in this genus, are present in multiple copies in low-light strains but as a single copy in high-light strains. The basis of this differentiation, however, has remained obscure. Here we show that the moderate low-light-adapted strain Prochlorococcus sp. MIT 9313 has one iron-stress-induced pcb gene encoding an antenna protein serving photosystem I (PSI)--comparable to isiA genes from cyanobacteria--and a constitutively expressed pcb gene encoding a photosystem II (PSII) antenna protein. By comparison, the very low-light-adapted strain SS120 has seven pcb genes encoding constitutive PSI and PSII antennae, plus one PSI iron-regulated pcb gene, whereas the high-light-adapted strain MED4 has only a constitutive PSII antenna. Thus, it seems that the adaptation of Prochlorococcus to low light environments has triggered a multiplication and specialization of Pcb proteins comparable to that found for Cab proteins in plants and green algae.     

Episodic fresh surface waters in the Eocene Arctic Ocean

It has been suggested, on the basis of modern hydrology and fully coupled palaeoclimate simulations, that the warm greenhouse conditions that characterized the early Palaeogene period (55-45 Myr ago) probably induced an intensified hydrological cycle with precipitation exceeding evaporation at high latitudes. Little field evidence, however, has been available to constrain oceanic conditions in the Arctic during this period. Here we analyse Palaeogene sediments obtained during the Arctic Coring Expedition, showing that large quantities of the free-floating fern Azolla grew and reproduced in the Arctic Ocean by the onset of the middle Eocene epoch (approximately 50 Myr ago). The Azolla and accompanying abundant freshwater organic and siliceous microfossils indicate an episodic freshening of Arctic surface waters during an approximately 800,000-year interval. The abundant remains of Azolla that characterize basal middle Eocene marine deposits of all Nordic seas probably represent transported assemblages resulting from freshwater spills from the Arctic Ocean that reached as far south as the North Sea. The termination of the Azolla phase in the Arctic coincides with a local sea surface temperature rise from approximately 10 degrees C to 13 degrees C, pointing to simultaneous increases in salt and heat supply owing to the influx of waters from adjacent oceans. We suggest that onset and termination of the Azolla phase depended on the degree of oceanic exchange between Arctic Ocean and adjacent seas.     

Deep convection in the Irminger Sea forced by the Greenland tip jet

Open-ocean deep convection, one of the processes by which deep waters of the world's oceans are formed, is restricted to a small number of locations (for example, the Mediterranean and Labrador seas). Recently, the southwest Irminger Sea has been suggested as an additional location for open-ocean deep convection. The deep water formed in the Irminger Sea has the characteristic temperature and salinity of the water mass that fills the mid-depth North Atlantic Ocean, which had been believed to be formed entirely in the Labrador basin. Here we show that the most likely cause of the convection in the Irminger Sea is a low-level atmospheric jet known as the Greenland tip jet, which forms periodically in the lee of Cape Farewell, Greenland, and is associated with elevated heat flux and strong wind stress curl. Using a history of tip-jet events derived from meteorological land station data and a regional oceanic numerical model, we demonstrate that deep convection can occur in this region when the North Atlantic Oscillation Index is high, which is consistent with observations. This mechanism of convection in the Irminger Sea differs significantly from those known to operate in the Labrador and Mediterranean seas.     

Evidence for low sulphate and anoxia in a mid-Proterozoic marine basin

Many independent lines of evidence document a large increase in the Earth's surface oxidation state 2,400 to 2,200 million years ago, and a second biospheric oxygenation 800 to 580 million years ago, just before large animals appear in the fossil record. Such a two-staged oxidation implies a unique ocean chemistry for much of the Proterozoic eon, which would have been neither completely anoxic and iron-rich as hypothesized for Archaean seas, nor fully oxic as supposed for most of the Phanerozoic eon. The redox chemistry of Proterozoic oceans has important implications for evolution, but empirical constraints on competing environmental models are scarce. Here we present an analysis of the iron chemistry of shales deposited in the marine Roper Basin, Australia, between about 1,500 and 1,400 million years ago, which record deep-water anoxia beneath oxidized surface water. The sulphur isotopic compositions of pyrites in the shales show strong variations along a palaeodepth gradient, indicating low sulphate concentrations in mid-Proterozoic oceans. Our data help to integrate a growing body of evidence favouring a long-lived intermediate state of the oceans, generated by the early Proterozoic oxygen revolution and terminated by the environmental transformation late in the Proterozoic eon.     

本国生态足迹指标的构建及其实证研究

基于生态足迹方法,提出并构建了度量国家环境压力总量的本国生态足迹指标,应用该指标对我国1961年~2003年的本国生态足迹、环境承载面积及本国生态赤字进行了计算,分析了中国环境压力的历史轨迹、发展趋势及其构成和主要矛盾,探讨了它们与经济发展的关系.结果表明我国的生态系统从20世纪70年代初就一直处于超载状态,本国生态足迹已达28亿多公顷.这表明我国经济的快速发展和工业化进程是以本国生态资源的大量消耗为基础的;而能源和农业问题是中国可持续发展需要解决的首要问题.     

论公路工程建设的环境保护

为了保护环境，构建节能环保社会，近年，我国政府出台了一系列的环境保护措施，倡导低碳生活。作为基础建设中重要组成部分的公路工程建设，也应重点考虑对环境的保护问题，本文重点阐述公路建设运营各个环节的环境保护措施。     

中国资源环境问题的发展态势及其演变阶段分析

资源环境保护是生态文明建设的核心和主线。研究中国资源环境问题的演变特征和趋势,对于制定新时期生态文明建设战略目标和推进生态文明建设实践具有重要的意义。本文在揭示中国资源环境问题的国际地位和作用基础上,对建国以来尤其是改革开放以来中国资源环境问题的发展态势进行了分析,借助3个“倒u型”理论对中国资源环境问题的演变阶段开展了实证研究,并提出了中国资源环境问题的未来趋势的综合判断。     

Temperature excludes N2-fixing heterocystous cyanobacteria in the tropical oceans

Whereas the non-heterocystous cyanobacteria Trichodesmium spp. are the dominant N2-fixing organisms in the tropical oceans, heterocystous species dominate N2 fixation in freshwater lakes and brackish environments such as the Baltic Sea. So far no satisfactory explanation for the absence of heterocystous cyanobacteria in the pelagic of the tropical oceans has been given, even though heterocysts would seem to represent an ideal strategy for protecting nitrogenase from being inactivated by O2, thereby enabling cyanobacteria to fix N2 and to perform photosynthesis simultaneously. Trichodesmium is capable of N2 fixation, apparently without needing to differentiate heterocysts. Here we show that differences in the temperature dependence of O2 flux, respiration and N2 fixation activity explain how Trichodesmium performs better than heterocystous species at higher temperatures. Our results also explain why Trichodesmium is not successful in temperate or cold seas. The absence of heterocystous cyanobacteria in the pelagic zone of temperate and cold seas, however, requires another explanation.     

Cyanophages infecting the oceanic cyanobacterium Prochlorococcus

Prochlorococcus is the numerically dominant phototroph in the tropical and subtropical oceans, accounting for half of the photosynthetic biomass in some areas. Here we report the isolation of cyanophages that infect Prochlorococcus, and show that although some are host-strain-specific, others cross-infect with closely related marine Synechococcus as well as between high-light- and low-light-adapted Prochlorococcus isolates, suggesting a mechanism for horizontal gene transfer. High-light-adapted Prochlorococcus hosts yielded Podoviridae exclusively, which were extremely host-specific, whereas low-light-adapted Prochlorococcus and all strains of Synechococcus yielded primarily Myoviridae, which has a broad host range. Finally, both Prochlorococcus and Synechococcus strain-specific cyanophage titres were low (< 10(3) ml(-1)) in stratified oligotrophic waters even where total cyanobacterial abundances were high (> 10(5) cells x ml(-1)). These low titres in areas of high total host cell abundance seem to be a feature of open ocean ecosystems. We hypothesize that gradients in cyanobacterial population diversity, growth rates, and/or the incidence of lysogeny underlie these trends.     

关于我国西北地区水资源开发利用的探讨

水资源短缺、生态脆弱是制约我国西北地区社会经济发展和生态改善的主要因素。本文综合分析了西北地区水资源的特征及其分布,对开发利用水资源中存在的问题提出了有效的解决途径。     

Genomic island variability facilitates Prochlorococcus-virus coexistence

Prochlorococcus cyanobacteria are extremely abundant in the oceans, as are the viruses that infect them. How hosts and viruses coexist in nature remains unclear, although the presence of both susceptible and resistant cells may allow this coexistence. Combined whole-genome sequencing and PCR screening technology now enables us to investigate the effect of resistance on genome evolution and the genomic mechanisms behind the long-term coexistence of Prochlorococcus and their viruses. Here we present a genome analysis of 77 substrains selected for resistance to ten viruses, revealing mutations primarily in non-conserved, horizontally transferred genes that localize to a single hypervariable genomic island. Mutations affected viral attachment to the cell surface and imposed a fitness cost to the host, manifested by significantly lower growth rates or a previously unknown mechanism of more rapid infection by other viruses. The mutant genes are generally uncommon in nature yet some carry polymorphisms matching those found experimentally. These data are empirical evidence indicating that viral-attachment genes are preferentially located in genomic islands and that viruses are a selective pressure enhancing the diversity of both island genes and island gene content. This diversity emerges as a genomic mechanism that reduces the effective host population size for infection by a given virus, thus facilitating long-term coexistence between viruses and their hosts in nature.     

东北民族森林生态文化论纲

历史上的东北少数民族生存于森林环境,森林环境培育了各民族森林生态文化。其基本特征是各民族对其森林生态环境的保护和适应,形成了与森林生态系统相协调的生计方式、社会规范、信仰体系和价值观念。提出传承森林生态文化,促进城市化发展与建立区域广大的森林自然保护区相结合,是东北各民族建设生态文明的制度途径。     

南海深水海山上的新发现

 在国家自然科学基金委重大研究计划“南海深部计划”指导下，于2013-2019年期间，分别运用载人或遥控深潜器，针对南海深海盆中的部分海山开展了4个科学探测航次，在南海首次发现了大面积的高丰度铁锰结核分布区、“南溟”古热液区和惊人的冷水珊瑚生态林。这些发现不仅为深入认识南海不同时空尺度演化的复杂过程及相互作用开辟了新的研究领域，还探索实践了中国海洋高新技术发展与前沿基础科学研究紧密结合并相互促进的高效创新研究模式。     

人类活动和生存环境

人与自然原本是一种辨证和谐的关系，相互依存，平等共处。19世纪以来，人口激增，尤其是近200年来，世界人口直线上升，加之世界经济迅速发展，对环境造成极大的冲击与压力，尤其是对生活资料来源的各种自然资源，以及对地球承载能力产生压力。人类正面临一个土地荒毁、环境污染、交通拥阻、水荒水污、能源危机、资源耗损、生态全面失衡的世界。惨重的代价已引起人类的高度警觉，科学发展观、和谐伦理学、低代价经济增长论、绿色GDP、环境人类学、生态伦理等等学说应运而生，其意义重大而深远。