海南岛海菖蒲种群克隆多样性和遗传结构

海草是生长在潮间带和潮下带的单子叶植物,由海草植物组成的海草床是生态系统服务价值最高的生态系统之一.然而,近几十年人类活动干扰、全球气候变化等因素导致海草床衰退严重.海菖蒲是分布于热带、体型最大的雌雄异株海草,我国位于该物种的分布北缘,本文对其克隆多样性和遗传结构进行研究,以期为该海草的保护提供参考.采用4对多态微卫星标记对采自海南岛4个地点的现存海菖蒲种群的样品进行基因型分型.结果表明:海菖蒲种群克隆多样性和遗传多样性较低,这与所研究种群处于分布区北缘有关;种群间遗传分化值范围较大(0.073~0.309),这可能是由于分布于不同港湾的种群间距离范围较大以及局域绝灭/再拓殖的遗传漂变效应所致;各种群未发现近期经历种群瓶颈的信号,很可能是由于种群内遗传多样性已经很低,种群减小未能导致遗传多样性明显降低.根据种群遗传特征,提出了重点保护种群的建议,鉴于目前我国海菖蒲等海草快速衰退的局面,应强化海草保护并实施海草床生态恢复.     

广东沿海海草床的现状、面临的威胁与保护建议

海草床是地球上最具价值的生态系统之一,为人类提供广泛的生态系统服务。我国乃至全球范围内海草床面临着人类活动威胁,且呈退化趋势。广东海草研究起步较晚,近年来涌现的一些研究成果将广东海草分布特征清晰地呈现在世人面前,并发现海草床受到的威胁来源多样,但缺乏系统的总结。基于广东滨海地区未来一段时间将持续面临高强度人类活动压力的背景下,为有效保护海草床及其生物多样性,亟需进一步深入了解广东海草床存在的问题,从而提出针对性的保护建议。本文通过回顾21世纪以来广东海草床研究成果,汇总了广东海草分布信息,并结合现场调研和国内外海草床的研究报道,梳理了广东海草床面临的威胁。结果表明广东沿岸海草分布广泛,现有海草床面积约1,540ha。海草种类共5种,以卵叶喜盐草(Halophilaovalis)和贝克喜盐草(H.beccarii)为主,日本鳗草(Zosterajaponica)、单脉二药草(Haloduleuninervis)和短柄川蔓草(Ruppia brevipedunculata)分布较少。本文阐明了人为因素和自然因素如何影响海草的生长和分布,并指出了广东海草床主要面临着海水养殖、渔业捕捞、陆源污...     

微生物参与海草床元素循环及其生态修复功能

海草是分布在全球海岸带的沉水被子植物,与周围环境共同形成的海草床生态系统是三大典型海洋生态系统之一,具有十分重要的生态功能。20世纪以来,全球海草床衰退严重,研究海草床的生态修复迫在眉睫,现有修复方法未能足够重视微生物在海草床中的重要作用。本文综合阐述了微生物在海草床生态系统有机物矿化和营养流动过程中起到的作用,分析了微生物驱动下的海草床水体与沉积物之间的元素循环,提出了人类活动引起海草床退化的原因,总结了海草床微生物的系统研究方法,并在此基础上提出从微生物生态的角度修复海草床的新思路。     

海草生态学研究进展

海草床生态系统是生物圈中最具生产力的水生生态系统之一,具有重要的生态系统服务功能。作者根据海草生态学及相关领域的最新研究进展,对世界范围内海草床的空间分布、海草床的生态系统服务功能以及外界因素对海草床的影响等研究进展进行了综述。海草床生态系统服务功能主要包括净化水质、护堤减灾、提供栖息地和生态系统营养循环等。对海草床影响较大的外界环境因素包括盐度、温度、营养盐、光照、其他动物摄食、人类活动和气候变化等。海草普查、海草生态功能研究,影响海草床的主要环境因素,海草修复研究等将是我国海草研究的主要方向。     

生态系统修复国内外研究进展与展望

气候变化和人类活动的增加不仅导致生态系统退化、生物多样性丧失、生物圈资源供给能力降低, 而且极大地制约了社会经济的可持续发展。尽管在全世界范围内已实施了大量的保护工作, 但全球生态系统退化仍在继续, 逐渐成为备受关注的全球性问题。文章首先厘清生态系统修复的发展历程、相关概念与理论。其次, 归纳生态系统修复的全球议题, 涉及生态系统服务及其价值评估、生物多样性保护、应对气候变化与碳储存、自然保护地、监测体系与适应性管理、公平性与多主体参与等方面。然后, 总结我国森林、草原、河流与湿地、海洋与海岸带的生态系统退化问题与修复进展, 梳理生态保护红线、自然保护地生态系统修复和国土空间生态保护修复3种措施的进展与不足。最后, 对山水林田湖草沙一体化保护与系统治理、生态系统修复的多元融资政策与渠道、荒野生态保护修复的探索与实践、城镇生态系统修复的研究与应用以及生态系统修复对生物多样性的保护与维持等五个方面进行展望, 以期为我国进一步开展生态系统保护修复的相关研究与实践提供指导。     

自然衰退“史无前例”,物种灭绝率“加速”——IPBES全球评估报告简述

2019年4月29日至5月4日,生物多样性和生态系统服务政府间科学与政策平台（IPBES）第七届全体会议在法国巴黎召开,会议通过了IPBES全球评估报告,指出当前全球正面临自然衰退"史无前例"和物种灭绝率"加速"的局面,保护和恢复自然需要"变革性改变"。会议于2019年5月6日发布决策者摘要,核心内容包括：（1）自然及其对人类的重要贡献的评估;（2）直接和间接的驱动力分析;（3）全球目标和政策方案;（4）政策工具、选项和最佳实践等内容。IPBES全球评估报告为我国生态系统服务和可持续发展领域的研究带来如下启示：（1）系统评估我国生物多样性与生态系统保护现状;（2）探讨推动我国可持续发展的变革性方案;（3）加强可持续发展的高等教育与公众宣传。     

海草床育幼功能及其机理

海草床是近岸海域中生产力极高的生态系统,是许多海洋水生动物的重要育幼场所。从生物幼体的密度、生长率、存活率和生境迁移4个方面阐述海草床育幼功能,并从食源和捕食压力两个方面探讨海草床育幼功能机理。许多生物幼体在海草床都呈现出较高的密度、生长率和存活率,并且在个体发育到一定阶段从海草床向成体栖息环境迁移。丰富的食物来源或较低的捕食压力可能是海草床具有育幼功能的主要原因,但不同的生物幼体对海草床的利用有差异,海草床育幼功能的机理在不同环境条件下也存在差异。提出未来海草床育幼功能的重点研究方向:(1)量化海草床对成体栖息环境贡献量;(2)全球气候变化和人类活动对海草床育幼功能的影响;(3)海草床育幼功能对海草床斑块效应和边缘效应的响应,以期为促进我国海草床育幼研究和海草床生态系统保护提供依据。     

海草生态系统的固碳机理及贡献

由海草、红树林、盐沼草等植被组成的滨海和海洋生态系统是地球中高效的碳汇热点,它们所固定的碳被称为"蓝碳".作为全球生态服务功能价值最高的生态系统之一,海草生态系统所固定的碳是蓝碳里的重要组成部分.高生产力、高效过滤及高稳定性造就了海草生态系统巨大的固碳能力,进而对全球碳循环具有深刻影响.然而,人为影响以及全球气候变化使全球海草床加速衰退,成为地球生物圈中退化速度最快的生态系统之一.当前,国内外对海草床等滨海生态系统固碳能力的关注、研究深度与广度仍远远不足,对全球海草固碳的评估仍存在诸多不确定性.为了能更准确地评估全球海草床的碳埋存,一些基础性的科学问题应优先考虑:1)全国和全球海草的准确分布面积;2)不同海草优势种类或不同地域的海草床碳汇能力的差异;3)人为干扰和全球气候变化对海草生态系统碳捕获和碳埋存的影响.     

生态系统服务功能与可持续发展

本文阐述了生态系统服务功能,生态系统不仅为人类提供了食品、医药及其它生产生活原料,更重要的是维持了人类赖以生存的生命支持系统,维持物质的生物地化循环与水文循环,维持生物多样性,净化环境,维持大气化学的平衡与稳定;分析探讨了生态系统服务功能及其与可持续发展研究的关系,可持续发展要以保护生态环境为基础,与资源和环境的承载能力相协调,而人类活动对森林、湿地和其他生态系统的破坏,已严重危害了生态系统的服务功能,保护生态系统服务功能已刻不容缓;从而提出了保护生态服务功能的对策。     

生态系统的净化服务及其价值研究

生态系统对环境的净化服务是其向人类提供的重要服务功能之一,了解生态系统的净化机理及其价值,对自然资源的保护及其可持续利用有着十分重要的作用。本文讨论了生态系统的净化服务的机理,提出了生态系统净化类型,在此基础上,运用经济学和环境经济学原理,探讨了生态系统的净化价值评估方法,以我国森林生态系统为例,对生态系统的净化价值进行了估算。     

Seagrass Restoration Enhances “Blue Carbon” Sequestration in Coastal Waters

Seagrass meadows are highly productive habitats that provide important ecosystem services in the coastal zone, including carbon and nutrient sequestration. Organic carbon in seagrass sediment, known as “blue carbon,” accumulates from both in situ production and sedimentation of particulate carbon from the water column. Using a large-scale restoration (>1700 ha) in the Virginia coastal bays as a model system, we evaluated the role of seagrass, Zostera marina , restoration in carbon storage in sediments of shallow coastal ecosystems. Sediments of replicate seagrass meadows representing different age treatments (as time since seeding: 0, 4, and 10 years), were analyzed for % carbon, % nitrogen, bulk density, organic matter content, and ²¹⁰Pb for dating at 1-cm increments to a depth of 10 cm. Sediment nutrient and organic content, and carbon accumulation rates were higher in 10-year seagrass meadows relative to 4-year and bare sediment. These differences were consistent with higher shoot density in the older meadow. Carbon accumulation rates determined for the 10-year restored seagrass meadows were 36.68 g C m^-2 yr^-1. Within 12 years of seeding, the restored seagrass meadows are expected to accumulate carbon at a rate that is comparable to measured ranges in natural seagrass meadows. This the first study to provide evidence of the potential of seagrass habitat restoration to enhance carbon sequestration in the coastal zone.     

The fundamental role of ecological feedback mechanisms for the adaptive management of seagrass ecosystems – a review

Seagrass meadows are vital ecosystems in coastal zones worldwide, but are also under global threat. One of the major hurdles restricting the success of seagrass conservation and restoration is our limited understanding of ecological feedback mechanisms. In these ecosystems, multiple, self‐reinforcing feedbacks can undermine conservation efforts by masking environmental impacts until the decline is precipitous, or alternatively they can inhibit seagrass recovery in spite of restoration efforts. However, no clear framework yet exists for identifying or dealing with feedbacks to improve the management of seagrass ecosystems. Here we review the causes and consequences of multiple feedbacks between seagrass and biotic and/or abiotic processes. We demonstrate how feedbacks have the potential to impose or reinforce regimes of either seagrass dominance or unvegetated substrate, and how the strength and importance of these feedbacks vary across environmental gradients. Although a myriad of feedbacks have now been identified, the co‐occurrence and likely interaction among feedbacks has largely been overlooked to date due to difficulties in analysis and detection. Here we take a fundamental step forward by modelling the interactions among two distinct above‐ and belowground feedbacks to demonstrate that interacting feedbacks are likely to be important for ecosystem resilience. On this basis, we propose a five‐step adaptive management plan to address feedback dynamics for effective conservation and restoration strategies. The management plan provides guidance to aid in the identification and prioritisation of likely feedbacks in different seagrass ecosystems.     

Local Knowledge and Conservation of Seagrasses in the Tamil Nadu State of India

Local knowledge systems are not considered in the conservation of fragile seagrass marine ecosystems. In fact, little is known about the utility of seagrasses in local coastal communities. This is intriguing given that some local communities rely on seagrasses to sustain their livelihoods and have relocated their villages to areas with a rich diversity and abundance of seagrasses. The purpose of this study is to assist in conservation efforts regarding seagrasses through identifying Traditional Ecological Knowledge (TEK) from local knowledge systems of seagrasses from 40 coastal communities along the eastern coast of India. We explore the assemblage of scientific and local traditional knowledge concerning the 1. classification of seagrasses (comparing scientific and traditional classification systems), 2. utility of seagrasses, 3. Traditional Ecological Knowledge (TEK) of seagrasses, and 4. current conservation efforts for seagrass ecosystems. Our results indicate that local knowledge systems consist of a complex classification of seagrass diversity that considers the role of seagrasses in the marine ecosystem. This fine-scaled ethno-classification gives rise to five times the number of taxa (10 species = 50 local ethnotaxa), each with a unique role in the ecosystem and utility within coastal communities, including the use of seagrasses for medicine (e.g., treatment of heart conditions, seasickness, etc.), food (nutritious seeds), fertilizer (nutrient rich biomass) and livestock feed (goats and sheep). Local communities are concerned about the loss of seagrass diversity and have considerable local knowledge that is valuable for conservation and restoration plans. This study serves as a case study example of the depth and breadth of local knowledge systems for a particular ecosystem that is in peril.     

Global seagrass distribution and diversity: A bioregional model

Seagrasses, marine flowering plants, are widely distributed along temperate and tropical coastlines of the world. Seagrasses have key ecological roles in coastal ecosystems and can form extensive meadows supporting high biodiversity. The global species diversity of seagrasses is low (< 60 species), but species can have ranges that extend for thousands of kilometers of coastline. Seagrass bioregions are defined here, based on species assemblages, species distributional ranges, and tropical and temperate influences. Six global bioregions are presented: four temperate and two tropical. The temperate bioregions include the Temperate North Atlantic, the Temperate North Pacific, the Mediterranean, and the Temperate Southern Oceans. The Temperate North Atlantic has low seagrass diversity, the major species being Zostera marina, typically occurring in estuaries and lagoons. The Temperate North Pacific has high seagrass diversity with Zostera spp. in estuaries and lagoons as well as Phyllospadix spp. in the surf zone. The Mediterranean region has clear water with vast meadows of moderate diversity of both temperate and tropical seagrasses, dominated by deep-growing Posidonia oceanica. The Temperate Southern Oceans bioregion includes the temperate southern coastlines of Australia, Africa and South America. Extensive meadows of low-to-high diversity temperate seagrasses are found in this bioregion, dominated by various species of Posidonia and Zostera. The tropical bioregions are the Tropical Atlantic and the Tropical Indo-Pacific, both supporting mega-herbivore grazers, including sea turtles and sirenia. The Tropical Atlantic bioregion has clear water with a high diversity of seagrasses on reefs and shallow banks, dominated by Thalassia testudinum. The vast Tropical Indo-Pacific has the highest seagrass diversity in the world, with as many as 14 species growing together on reef flats although seagrasses also occur in very deep waters. The global distribution of seagrass genera is remarkably consistent north and south of the equator; the northern and southern hemispheres share ten seagrass genera and only have one unique genus each. Some genera are much more speciose than others, with the genus Halophila having the most seagrass species. There are roughly the same number of temperate and tropical seagrass genera as well as species. The most widely distributed seagrass is Ruppia maritima, which occurs in tropical and temperate zones in a wide variety of habitats. Seagrass bioregions at the scale of ocean basins are identified based on species distributions which are supported by genetic patterns of diversity. Seagrass bioregions provide a useful framework for interpreting ecological, physiological and genetic results collected in specific locations or from particular species.     

Predicting the cumulative effect of multiple disturbances on seagrass connectivity

The rate of exchange, or connectivity, among populations effects their ability to recover after disturbance events. However, there is limited information on the extent to which populations are connected or how multiple disturbances affect connectivity, especially in coastal and marine ecosystems. We used network analysis and the outputs of a biophysical model to measure potential functional connectivity and predict the impact of multiple disturbances on seagrasses in the central Great Barrier Reef World Heritage Area (GBRWHA), Australia. The seagrass networks were densely connected, indicating that seagrasses are resilient to the random loss of meadows. Our analysis identified discrete meadows that are important sources of seagrass propagules and that serve as stepping stones connecting various different parts of the network. Several of these meadows were close to urban areas or ports and likely to be at risk from coastal development. Deep water meadows were highly connected to coastal meadows and may function as a refuge, but only for non‐foundation species. We evaluated changes to the structure and functioning of the seagrass networks when one or more discrete meadows were removed due to multiple disturbance events. The scale of disturbance required to disconnect the seagrass networks into two or more components was on average >245 km, about half the length of the metapopulation. The densely connected seagrass meadows of the central GBRWHA are not limited by the supply of propagules; therefore, management should focus on improving environmental conditions that support natural seagrass recruitment and recovery processes. Our study provides a new framework for assessing the impact of global change on the connectivity and persistence of coastal and marine ecosystems. Without this knowledge, management actions, including coastal restoration, may prove unnecessary and be unsuccessful.     

Miniature baited remote underwater video (mini-BRUV) reveals the response of cryptic fishes to seagrass cover

Seagrass habitats worldwide are degrading and becoming fragmented, threatening the important ecosystem services they provide. Fauna associated with seagrasses, particularly cryptic species, are expected to respond to these changes, but are difficult to detect at ecologically meaningful scales using non-extractive techniques. We used a small, wide-angle camera (GoPro) and a small quantity of bait positioned within the canopy of Posidonia australis meadows in Jervis Bay, New South Wales to assess the response of fishes to seagrass cover. We saw a clear positive relationship with the condition of P. australis; a high cover of this seagrass had positive effects on the diversity and abundance of cryptic fauna. Our findings highlight ecosystem shifts associated with the loss and fragmentation of biogenic habitat. These changes are of particular relevance for P. australis meadows given their current status as an endangered ecological community in several locations in NSW and their slow rate of recovery from disturbance.     

Comparative Evidence that Salt Marshes and Mangroves May Protect Seagrass Meadows from Land-derived Nitrogen Loads

Seagrass meadows within estuaries are highly sensitive to increased supplies of nitrogen (N). The urbanization of coastal watersheds increases the delivery of N to estuaries, threatening seagrass habitats; both seagrass production per unit area and the area of seagrass meadows diminish as land-derived N loads increase. The damaging effects of land-derived N loads may be lessened where there are fringes of coastal wetlands interposed between land and seagrass meadows. Data compiled from the literature showed that production per unit area by seagrasses increased and losses of seagrass habitat were lower in estuaries with relatively larger areas of fringing wetlands. Denitrification and the burial of land-derived N within fringe wetlands may be sufficient to protect N-sensitive seagrass habitats from the detrimental effects of land-derived N. The protection furnished by fringing wetlands may be overwhelmed by increases in anthropogenic N loads in excess of 20–100 kg N ha⁻¹ y⁻¹. The relationships of land-derived N loadings, fringing coastal wetlands, and seagrass meadows demonstrate that different units of the landscape mosaic found in coastal zones do not exist as separate units, but instead are coupled and uncoupled by biogeochemical transformations and transport among environments. Received 12 December 2000; accepted 15 August 2001.     

Seagrasses and eutrophication

This review summarizes the historic, correlative field evidence and experimental research that implicate cultural eutrophication as a major cause of seagrass disappearance. We summarize the underlying physiological responses of seagrass species, the potential utility of various parameters as indicators of nutrient enrichment in seagrasses, the relatively sparse available information about environmental conditions that exacerbate eutrophication effects, and the better known array of indirect stressors imposed by nutrient over-enrichment that influence seagrass growth and survival. Seagrass recovery following nutrient reductions is examined, as well as the status of modeling efforts to predict seagrass response to changing nutrient regimes.The most common mechanism invoked or demonstrated for seagrass decline under nutrient over-enrichment is light reduction through stimulation of high-biomass algal overgrowth as epiphytes and macroalgae in shallow coastal areas, and as phytoplankton in deeper coastal waters. Direct physiological responses such as ammonium toxicity and water-column nitrate inhibition through internal carbon limitation may also contribute. Seagrass decline under nutrient enrichment appears to involve indirect and feedback mechanisms, and is manifested as sudden shifts in seagrass abundance rather than continuous, gradual changes in parallel with rates of increased nutrient additions. Depending on the species, interactions of high salinity, high temperature, and low light have been shown to exacerbate the adverse effects of nutrient over-enrichment. An array of indirect effects of nutrient enrichment can accelerate seagrass disappearance, including sediment re-suspension from seagrass loss, increased system respiration and resulting oxygen stress, depressed advective water exchange from thick macroalgal growth, biogeochemical alterations such as sediment anoxia with increased hydrogen sulfide concentrations, and internal nutrient loading via enhanced nutrient fluxes from sediments to the overlying water. Indirect effects on trophic structure can also be critically important, for example, the loss of herbivores, through increased hypoxia/anoxia and other habitat shifts, that would have acted as “ecological engineers” in promoting seagrass survival by controlling algal overgrowth; and shifts favoring exotic grazers that out-compete seagrasses for space. Evidence suggests that natural seagrass population shifts are disrupted, slowed or indefinitely blocked by cultural eutrophication, and there are relatively few known examples of seagrass meadow recovery following nutrient reductions.Reliable biomarkers as early indicators of nutrient over-enriched seagrass meadows would benefit coastal resource managers in improving protective measures. Seagrasses can be considered as “long-term" integrators (days to weeks) of nutrient availability, especially through analyses of their tissue content, and of activities of enzymes such as nitrate reductase and alkaline phosphatase. The ratio of leaf nitrogen content to leaf mass has also shown promise as a “nutrient pollution indicator” for the seagrass Zostera marina, with potential application to other species. In modeling efforts, seagrass response to nutrient loading has proven difficult to quantify beyond localized areas because long-term data consistent in quality are generally lacking, and high inter-annual variability in abundance and productivity depending upon stochastic meteorological and hydrographic conditions.Efforts to protect remaining seagrass meadows from damage and loss under eutrophication, within countries and across regions, are generally lacking or weak and ineffective. Research needs to further understand about seagrasses and eutrophication should emphasize experimental studies to assess the response of a wider range of species to chronic, low-level as well as acute, pulsed nutrient enrichment. These experiments should be conducted in the field or in large-scale mesocosms following appropriate acclimation, and should emphasize factor interactions (N, P, C; turbidity; temperature; herbivory) to more closely simulate reality in seagrass ecosystems. They should scale up to address processes that occur over larger scales, including food-web dynamics that involve highly mobile predators and herbivores. Without any further research, however, one point is presently very clear: Concerted local and national actions, thus far mostly lacking, are needed worldwide to protect remaining seagrass meadows from accelerating cultural eutrophication in rapidly urbanizing coastal zones.