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1.
The most diverse marine ecosystems, coral reefs, depend upon a functional symbiosis between a cnidarian animal host (the coral) and intracellular photosynthetic dinoflagellate algae. The molecular and cellular mechanisms underlying this endosymbiosis are not well understood, in part because of the difficulties of experimental work with corals. The small sea anemone Aiptasia provides a tractable laboratory model for investigating these mechanisms. Here we report on the assembly and analysis of the Aiptasia genome, which will provide a foundation for future studies and has revealed several features that may be key to understanding the evolution and function of the endosymbiosis. These features include genomic rearrangements and taxonomically restricted genes that may be functionally related to the symbiosis, aspects of host dependence on alga-derived nutrients, a novel and expanded cnidarian-specific family of putative pattern-recognition receptors that might be involved in the animal–algal interactions, and extensive lineage-specific horizontal gene transfer. Extensive integration of genes of prokaryotic origin, including genes for antimicrobial peptides, presumably reflects an intimate association of the animal–algal pair also with its prokaryotic microbiome.Coral reefs form marine-biodiversity hotspots that are of enormous ecological, economic, and aesthetic importance. Coral growth and reef deposition are based energetically on the endosymbiosis between the cnidarian animal hosts and photosynthetic dinoflagellate algae of the genus Symbiodinium, which live in vesicles within the gastrodermal (gut) cells of the animal and typically supply ≥90% of its total energy, while the host provides the algae with a sheltered environment and the inorganic nutrients needed for photosynthesis and growth (1). This tight metabolic coupling allows the holobiont (i.e., the animal host and its microbial symbionts) to thrive in nutrient-poor waters. Although the ecology of coral reefs has been studied intensively, the molecular and cellular mechanisms underlying the critical endosymbiosis remain poorly understood (2). As coral reefs face an ongoing and increasing threat from anthropogenic environmental change (3), new insights into these mechanisms are of critical importance to understanding the resilience and adaptability of coral reefs and thus to the planning of conservation strategies (4).Aiptasia is a globally distributed sea anemone that harbors endosymbiotic Symbiodinium like its Class Anthozoa relatives the stony corals (Fig. 1 and SI Appendix, Fig. S1A) (4, 5). Aiptasia has a range of polyp sizes convenient for experimentation and is easily grown in laboratory culture, where it reproduces both asexually (so that large clonal populations can be obtained) and sexually (allowing experiments on larvae and potentially genetic studies), and it can be maintained indefinitely in an aposymbiotic (dinoflagellate-free) state and reinfected by a variety of Symbiodinium strains (6, 7). These characteristics make Aiptasia a highly attractive model system for studies of the molecular and cellular basis of the cnidarian–dinoflagellate endosymbiosis (2, 4). To provide a solid platform for research on Aiptasia, we have sequenced and analyzed its genome. The results have already provided important insights into several aspects of the evolution and function of the symbiotic system.Open in a separate windowFig. 1.Phylogenetic position and different symbiotic states of Aiptasia. (A) Partial phylogenetic tree (see SI Appendix, SI Materials and Methods and Fig. S1A for details) shows Aiptasia grouped with other anthozoans among the cnidarians. Numbers on nodes denote bootstrap values. (B–D) An aposymbiotic Aiptasia polyp (B) and symbiotic polyps viewed under white light (C) or by fluorescence microscopy to visualize the red chlorophyll autofluorescence of the endosymbiotic Symbiodinium algae (D).  相似文献   
2.
A key consideration in assessing impacts of climate change is the possibility of synergistic effects with other human-induced stressors. In the ocean realm, climate change and overfishing pose two of the greatest challenges to the structure and functioning of marine ecosystems. In eastern Tasmania, temperate coastal waters are warming at approximately four times the global ocean warming average, representing the fastest rate of warming in the Southern Hemisphere. This has driven range extension of the ecologically important long-spined sea urchin (Centrostephanus rodgersii), which has now commenced catastrophic overgrazing of productive Tasmanian kelp beds leading to loss of biodiversity and important rocky reef ecosystem services. Coincident with the overgrazing is heavy fishing of reef-based predators including the spiny lobster Jasus edwardsii. By conducting experiments inside and outside Marine Protected Areas we show that fishing, by removing large predatory lobsters, has reduced the resilience of kelp beds against the climate-driven threat of the sea urchin and thus increased risk of catastrophic shift to widespread sea urchin barrens. This shows that interactions between multiple human-induced stressors can exacerbate nonlinear responses of ecosystems to climate change and limit the adaptive capacity of these systems. Management actions focused on reducing the risk of catastrophic phase shift in ecosystems are particularly urgent in the face of ongoing warming and unprecedented levels of predator removal from the world''s oceans.  相似文献   
3.
Coral bleaching has been identified as one of the major contributors to coral reef decline, and the occurrence of different symbionts determined by broad genetic groupings (clades A–H) is commonly used to explain thermal responses of reef-building corals. By using Stylophora pistillata as a model, we monitored individual tagged colonies in situ over a two-year period and show that fine level genetic variability within clade C is correlated to differences in bleaching susceptibility. Based on denaturing gradient gel electrophoresis of the internal transcribed spacer region 2, visual bleaching assessments, symbiont densities, host protein, and pulse amplitude modulated fluorometry, we show that subcladal types C78 and C8/a are more thermally tolerant than C79 and C35/a, which suffered significant bleaching and postbleaching mortality. Although additional symbiont types were detected during bleaching in colonies harboring types C79 and C35/a, all colonies reverted back to their original symbionts postbleaching. Most importantly, the data propose that the differential mortality of hosts harboring thermally sensitive versus resistant symbionts rather than symbiont shuffling/switching within a single host is responsible for the observed symbiont composition changes of coral communities after bleaching. This study therefore highlights that the use of broad cladal designations may not be suitable to describe differences in bleaching susceptibility, and that differential mortality results in a loss of both symbiont and host genetic diversity and therefore represents an important mechanism in explaining how coral reef communities may respond to changing conditions.  相似文献   
4.
When tropical systems lose species, they are often assumed to be buffered against declines in functional diversity by the ability of the species-rich biota to display high functional redundancy: i.e., a high number of species performing similar functions. We tested this hypothesis using a ninefold richness gradient in global fish faunas on tropical reefs encompassing 6,316 species distributed among 646 functional entities (FEs): i.e., unique combinations of functional traits. We found that the highest functional redundancy is located in the Central Indo-Pacific with a mean of 7.9 species per FE. However, this overall level of redundancy is disproportionately packed into few FEs, a pattern termed functional over-redundancy (FOR). For instance, the most speciose FE in the Central Indo-Pacific contains 222 species (out of 3,689) whereas 38% of FEs (180 out of 468) have no functional insurance with only one species. Surprisingly, the level of FOR is consistent across the six fish faunas, meaning that, whatever the richness, over a third of the species may still be in overrepresented FEs whereas more than one third of the FEs are left without insurance, these levels all being significantly higher than expected by chance. Thus, our study shows that, even in high-diversity systems, such as tropical reefs, functional diversity remains highly vulnerable to species loss. Although further investigations are needed to specifically address the influence of redundant vs. vulnerable FEs on ecosystem functioning, our results suggest that the promised benefits from tropical biodiversity may not be as strong as previously thought.The human-induced collapse of species has triggered a sixth mass extinction crisis worldwide (1). This ongoing biotic impoverishment may, in turn, markedly alter key ecosystem processes, such as productivity, nutrient cycling, and bioerosion, with undisputed consequences on ecosystem services that humanity needs to prosper (24).Beyond the loss of species, the loss of particular functions appears to be the main threat imperiling ecosystem processes and services (4, 5). When several species perform similar functions, this functional redundancy may ensure against the loss of ecosystem functioning following declines in species diversity (6, 7). The critical issue is whether the extraordinary species diversity on Earth matters for ecosystem functioning or whether a smaller proportion of species is enough to perform most of the key functions (8).This debate, at the core of ecological science (5), is even more vigorous in species-rich ecosystems where high functional redundancy among species is likely and where it is thus often assumed that ecosystem functioning is buffered against species loss. For instance, 75% of species could be lost before any functional group would disappear in an Argentinean plant community (6). Such high functional redundancy may ensure the level of functional diversity—i.e., the breadth of functions—against species loss following disturbance (9, 10) or explain why the relationship between species richness and ecosystem functioning may be weak (11) and asymptotic (12).Some tropical ecosystems that hold many more species than their temperate counterparts do not show a higher functional diversity (13). This pattern suggests that functional redundancy may be comparatively higher in the tropics (14). In contrast, despite high levels of species richness, some tropical ecosystems show little functional redundancy among species (15, 16), thus revealing their functional vulnerability: i.e., a potential decrease of functional diversity following species loss (17).Beyond aesthetic and moral arguments, the importance of conserving the whole of tropical biodiversity for maintaining the breadth of potential functions performed in species assemblages is still under scrutiny. Indeed, local or regional assessments are often based on a limited number of species and have offered contradictory results depending on ecosystems, taxa, and functional traits considered (9, 15, 18). We therefore still lack a global study, along a steep gradient of species richness, investigating how species are distributed among functional groups and, more particularly, the extent of functional redundancy and vulnerability.In the marine realm, tropical reefs host a remarkable diversity of fishes that sustain essential ecosystem processes (e.g., trophic control, bioerosion, nutrient cycling) (18). Within the diverse array of species, some perform unique roles and appear to be irreplaceable (19). Moreover, tropical-reef fishes from the Indo-Pacific show a richness that declines with increasing distance from the Indo-Australian Archipelago (IAA) (20), and tropical-reef fish faunas from the Atlantic Ocean have a markedly lower diversity than their Indo-Pacific counterparts (21). Thus, tropical-reef fishes constitute an archetypal situation where we expect a gradient of functional richness, redundancy, and vulnerability, depending on the distribution of species among functional groups. Instead of functional groups, built a priori or after clustering species based on an arbitrary level of trait similarity, we identified 646 functional entities (FEs) based on unique combinations of six categorical functional traits to classify the 6,316 fish species of the global pool. We also built a functional space where FEs were placed according to their trait combinations (22). We then assessed the level of functional diversity, functional redundancy, and functional vulnerability for the tropical-reef fish faunas along a ninefold gradient of species richness. Because the identity, the number, and the categorization of functional traits may influence the results (16), we also performed a series of sensitivity analyses to test the robustness of the findings when decreasing the number of FEs by up to one order of magnitude.  相似文献   
5.
6.
驻礁人员体能状况对比分析   总被引:8,自引:1,他引:7  
目的 :分析驻礁人员体能状况 ,为有针对性地制订干预措施提供依据。方法 :对 1 5 3名驻礁人员进行上礁前和下礁时VO2 max、肺活量、反应时、台阶试验等 1 0项指标检测、综合评分、对比分析。结果 :VO2 max上礁前为 ( 5 9.33± 6 .79)ml/(kg·min) ,下礁时为 ( 5 9.2 4± 7.2 6 )ml/(kg·min)。根据体能有关项目测定的总分评定 ,上礁前 ,优秀 76人 ,占 4 9.6 7% ;良好6 2人 ,占 4 0 .5 2 % ;合格 1 5人 ,占 9.81 %。下礁时 ,优秀 79人 ,占 5 1 .6 3% ;良好 5 6人 ,占 36 .6 0 % ;合格 1 8人 ,占 1 1 .77%。闭眼单腿站立 ,下礁时较上礁前站立时间短 (P <0 .0 1 )。体重、肺活量下礁时较上礁前增加 (P <0 .0 1 )。体重正常人员下礁时体脂率增加 ,与上礁前相比差异有显著性 (P <0 .0 5 )。下礁时体重增加 90人 ,占 5 8.82 %。因体重增加导致综合评分降低 (P <0 .0 1 ) ,肺活量降低 4 7人 ,占 30 .72 % ;综合评分也降低 (P <0 .0 1 )。结论 :驻礁人员体重增加 ,体能评分降低 ,肺活量降低 ,综合评分亦降低。有关部门应采取相应的干预措施 ,可在小礁添设适当的体育训练器材 ,以加强体育锻炼 ,避免体脂堆积  相似文献   
7.
The Great Barrier Reef (GBR) provides a globally significant demonstration of the effectiveness of large-scale networks of marine reserves in contributing to integrated, adaptive management. Comprehensive review of available evidence shows major, rapid benefits of no-take areas for targeted fish and sharks, in both reef and nonreef habitats, with potential benefits for fisheries as well as biodiversity conservation. Large, mobile species like sharks benefit less than smaller, site-attached fish. Critically, reserves also appear to benefit overall ecosystem health and resilience: outbreaks of coral-eating, crown-of-thorns starfish appear less frequent on no-take reefs, which consequently have higher abundance of coral, the very foundation of reef ecosystems. Effective marine reserves require regular review of compliance: fish abundances in no-entry zones suggest that even no-take zones may be significantly depleted due to poaching. Spatial analyses comparing zoning with seabed biodiversity or dugong distributions illustrate significant benefits from application of best-practice conservation principles in data-poor situations. Increases in the marine reserve network in 2004 affected fishers, but preliminary economic analysis suggests considerable net benefits, in terms of protecting environmental and tourism values. Relative to the revenue generated by reef tourism, current expenditure on protection is minor. Recent implementation of an Outlook Report provides regular, formal review of environmental condition and management and links to policy responses, key aspects of adaptive management. Given the major threat posed by climate change, the expanded network of marine reserves provides a critical and cost-effective contribution to enhancing the resilience of the Great Barrier Reef.  相似文献   
8.
During the last several decades corals have been in decline and at least one-third of all coral species are now threatened with extinction. Coral disease has been a major contributor to this threat, but little is known about the responsible pathogens. To date most research has focused on bacterial and fungal diseases; however, viruses may also be important for coral health. Using a combination of empirical viral metagenomics and real-time PCR, we show that Porites compressa corals contain a suite of eukaryotic viruses, many related to the Herpesviridae. This coral-associated viral consortium was found to shift in response to abiotic stressors. In particular, when exposed to reduced pH, elevated nutrients, and thermal stress, the abundance of herpes-like viral sequences rapidly increased in 2 separate experiments. Herpes-like viral sequences were rarely detected in apparently healthy corals, but were abundant in a majority of stressed samples. In addition, surveys of the Nematostella and Hydra genomic projects demonstrate that even distantly related Cnidarians contain numerous herpes-like viral genes, likely as a result of latent or endogenous viral infection. These data support the hypotheses that corals experience viral infections, which are exacerbated by stress, and that herpes-like viruses are common in Cnidarians.  相似文献   
9.
目的 研究远海驻礁部队战士的心理素质状况及其影响因素,分析其心理素质、健康主观评价、社会支持三者之间的关系。方法 使用军人心理素质量表、自测健康评定量表和领悟社会支持量表对驻某礁100名部队战士进行问卷调查。军人心理素质量表包括聪慧、忠诚、勇敢、自信和耐挫5个维度,自测健康评定量表包括生理健康、心理健康、社会健康3个维度,领悟社会支持量表包括家庭支持、朋友支持、其他支持3个维度。采用独立样本t检验对远海驻礁部队战士军人心理素质量表得分与总体军人心理素质常模进行比较,采用Pearson相关分析对3个量表中各维度得分及总分之间的相关性进行分析,采用多元线性回归分析探讨社会支持、健康主观评价和远海驻礁部队战士心理素质之间的相互影响。结果 远海驻礁部队战士军人心理素质量表自信维度(沉着+独立+乐群)得分优于总体常模(P=0.030),其余4个维度得分与常模相比差异均无统计学意义(P均>0.05)。Pearson相关分析显示,除远海驻礁部队战士军人心理素质量表忠诚维度得分与自测健康评定量表社会健康维度得分无相关性(P=0.366)外,军人心理素质量表、自测健康评定量表和领悟社会支持量表3个量表之间其余各维度得分及总分均呈正相关(P均<0.01)。多元线性回归分析结果显示,心理健康是耐挫的影响因素(P=0.006),家庭支持和生理健康是心理健康的影响因素(P=0.022,P<0.001),家庭支持是生理健康的影响因素(P=0.025)。结论 远海驻礁战士心理素质易受岛礁环境的影响,需要从加强社会支持、提高自身健康认识两方面入手改善远海驻礁战士的心理素质。  相似文献   
10.
Documenting the diversity of marine life is challenging because many species are cryptic, small, and rare, and belong to poorly known groups. New sequencing technologies, especially when combined with standardized sampling, promise to make comprehensive biodiversity assessments and monitoring feasible on a large scale. We used this approach to characterize patterns of diversity on oyster reefs across a range of geographic scales comprising a temperate location [Virginia (VA)] and a subtropical location [Florida (FL)]. Eukaryotic organisms that colonized multilayered settlement surfaces (autonomous reef monitoring structures) over a 6-mo period were identified by cytochrome c oxidase subunit I barcoding (>2-mm mobile organisms) and metabarcoding (sessile and smaller mobile organisms). In a total area of ∼15.64 m2 and volume of ∼0.09 m3, 2,179 operational taxonomic units (OTUs) were recorded from 983,056 sequences. However, only 10.9% could be matched to reference barcodes in public databases, with only 8.2% matching barcodes with both genus and species names. Taxonomic coverage was broad, particularly for animals (22 phyla recorded), but 35.6% of OTUs detected via metabarcoding could not be confidently assigned to a taxonomic group. The smallest size fraction (500 to 106 μm) was the most diverse (more than two-thirds of OTUs). There was little taxonomic overlap between VA and FL, and samples separated by ∼2 m were significantly more similar than samples separated by ∼100 m. Ground-truthing with independent assessments of taxonomic composition indicated that both presence–absence information and relative abundance information are captured by metabarcoding data, suggesting considerable potential for ecological studies and environmental monitoring.Understanding the diversity of life in the sea continues to challenge marine scientists because samples typically contain many rare species, most of them small and difficult to identify (1). Moreover, recent estimates suggest that between 33% and 91% of all marine species have never been named (2, 3). These constraints have limited our ability to investigate patterns of diversity beyond a few indicator groups (4), most often conspicuous macroinvertebrates and fish. For this reason, molecular methods, particularly high-throughput sequencing (HTS) approaches, hold considerable promise not only for fundamental understanding of diversity but also for biodiversity monitoring in the context of global change (5).Molecular methods are particularly powerful when combined with standardized sampling, allowing for direct comparisons across space and through time. In the ocean, analyzing standard volumes of readily sampled material (e.g., seawater, sediments) has a long tradition, and, increasingly, HTS approaches are being applied to these samples (6). Complex hard substrates provide greater challenges for consistent sampling, which can be met either by collecting approximately standard volumes (e.g., of rubble) or by deploying settlement structures (e.g., ref. 7).Here, we combine standardized sampling with molecular diversity assessments for samples from oyster reefs from one temperate location and one subtropical location on the US Atlantic Coast. In addition to their commercial value and their role in maintaining water quality, oyster beds shelter considerable diversity because of their 3D complexity, essentially the nontropical equivalent of coral reefs. They are also, like coral reefs, highly threatened, with up to 85% having been lost due to anthropogenic impacts (8).We report analyses of a nested set of autonomous reef monitoring structures (ARMS), which provide surfaces and spaces for mobile and sessile organisms to settle on or shelter within (SI Text, section I and Fig. S1). ARMS were deployed for about 6 mo on the ocean side of the Eastern Shore of Virginia (VA) and in the Indian River Lagoon in Florida (FL). At each location, there were three replicates ∼2 m apart at each of three sites ∼100 m apart (total of 18 ARMS; Fig. S1A). Four fractions were analyzed separately: sessile organisms growing on the plates and three fractions of organisms retained by 2-mm, 500-μm, and 106-μm sieves. We sequenced the cytochrome c oxidase subunit I (COI) gene for each specimen of the >2-mm animals (barcoding). The remaining fractions were homogenized, and COI amplicons were analyzed from bulk samples using HTS (metabarcoding). Sequences were clustered in operational taxonomic units (OTUs) and identified to the lowest possible taxonomic level using nucleotide BLAST (BLASTn) searches against public databases or by phylogenetic assignment when no direct match could be found. The effectiveness of the metabarcoding approach was assessed for the sessile and 2-mm to 500-μm fractions by comparing numbers of sequences with point counts and estimates of total DNA per OTU, respectively. Noneukaryotic sequences were not analyzed.  相似文献   
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