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1.
Monitoring coral reef communities at a decadal scale is necessary to understand and project their dynamics to provide a basis for reef management in light of disturbances and climate change. Complementing infrequent and localised in situ observations, time-series of aerial photographs and remotely sensed satellite images provide a means of monitoring the position and extent of reef-top coral communities, vegetation and abiotic substrata at the whole reef scale. The aim of the present study was to map such changes on Saint-Leu Reef (La Réunion) between 1973 and 2007. The period included two cyclones (1989, 2002) and one severe bleaching event (2002). Vertical images of the reef were recorded in five aerial photographs (1973, 1978, 1989, 1997, and 2003) and two Quickbird satellite images (2002, 2006) during that time. Quantitative in situ observations of parts of the reef-top were also available both to document ecological and substratum characteristics that produce the color and texture observable in the photos and satellite images. Coral communities were mapped on all images using manual delineation of polygons identified according to color and texture contrast. The 2006 Quickbird image was used as the mapping base and 15 types of coral communities were identified from a reef survey conducted in 2007. This hierarchical typology used coral growth forms, live and dead coral cover, macro-algae, substratum (sand, rubble and platform) and, to a lesser extent, coral taxonomy. The polygons at date t were over-laid onto image t − 1 across the whole series and their boundaries were manually edited to match the pattern on the earlier image. Labelling of polygons was guided by field-survey data and maps. For coral-dominated patches, six successive pairs of maps from 1973 to 2006 were compared to produce ‘coral community change maps’ for that period. Despite the multiple disturbance events, the coral community distribution and composition in 2006 on Saint-Leu Reef did not display major differences compared to 1973. This suggests a high degree of coral resilience at the site, led by rapid recovery of compact branching corals. The mapping techniques overcame challenges due to different image quality and the sparsity of in situ observations in time and space. Our results demonstrate the potential for further application of reef monitoring protocols based on complementary in situ and remote-sensing data to help understand the dynamics of reef-top coral reef communities and geomorphology over years to decades.  相似文献   

2.
In consideration of the rapid degradation of coral reef ecosystems, the establishment of models is helpful to comprehend the degradation mechanism of coral reef ecosystems and predict the development process of coral reef communities. According to the characteristics of complex ecosystem of tropical coral reefs in China, the coral reef functional group is the core level variable; combined with the multiple feedback effects of coral reef functional groups and environmental changes, the study presents a coral reef ecosystem dynamics model with hermatypic corals as the core. Based on the simulation of the assumed initial value and the internal feedback of the system, the results show that in the basic simulation(relative health conditions), the coverage area of live corals and coral reefs generally decreased first and then increased, and increased by 4.67% and 6.38% between2010 and 2050, respectively. Based on the calibration model and the current situation of the studied area, the multi-factor disturbance effects of coral reef communities were simulated and explored by setting up three scenarios involving fishing policy, terrestrial deposition, and inorganic nitrogen emissions. Among them, in the single factor disturbance, the fishing policy exerts the most direct impact on the community decline; and the succession phenomenon is obvious; the terrestrial sedimentation has a faster and more integrated effect on the community decline; the effect of inorganic nitrogen emission on the community decline is relatively slow. In the double/multi-factor disturbance, the superimposed disturbance will aggravate the multi-source feedback effect of the coral reef communities development, accelerate the community decay rate, and make its development trajectory more complicated and diverse. This method provides a scientific and feasible method for simulating the damage of long-term coral reef community and exploring the development law and adaptive management of coral reef ecosystems. In the future, it can be further studied in the ecological restoration process and decisionmaking direction of coral reefs.  相似文献   

3.
Coral mortality may result in macroalgal proliferation or a phase shift into an alga-dominated state. Subtidal, high-latitude western Indian Ocean coral communities at Sodwana Bay on the KwaZulu-Natal coast, South Africa, have experienced some mortality because of warm-water anomalies, storms and other causes, but the response of the macroalgae is unknown. We investigated the abundance and diversity of benthic algae on different hard natural substrata (dead digitate, brain and plate corals and beach rock) on Two-Mile Reef, Sodwana Bay. We also compared algal communities colonising ceramic, marble and pretreated ceramic tiles placed on the reef for six months. We identified 95 algae (14 Chlorophyta, 11 Phaeophyceae, 69 Rhodophyta and one cyanobacterium). Assemblages on natural and artificial substrata were dominated by the brown alga Lobophora variegata (Lamouroux) Womersley ex Oliveira and non-geniculate corallines (Rhodophyta, Corallinaceae). Cluster and ordination analyses revealed that the algae showed no affinity for particular substrata, whether natural or artificial. Algal cover was occasionally higher on rougher tiles and crustose corallines were significantly more abundant on marble than ceramic tiles. Two-Mile Reef had 23.1% dead and 48.4% live scleractinian coral cover, where dead corals were colonised indiscriminately by many small algal species, but there was no evidence of algal proliferation. The results provide a baseline for monitoring this high-latitude reef system.  相似文献   

4.
The abundance and health of scleractinian coral communities of Hormuz Island were investigated. For this purpose, we employed 20 m line intercept transects—12 in the intertidal zone and 15 subtidally to evaluate coral cover and community composition. The estimated dead coral coverage was 6.21%±0.81%, while live coral coverage was 16.93%±1.81%, considered as very poor. Totally, 12 genera were recorded, of which Porites with 11.9%±1.4% live cover was the dominant, while Goniopora had the least cover (0.07%±0.08%). Based on Mann-Whitney U-test, live coral coverage, dead coral coverage, algal coverage, cover of other benthic organisms and abiotic components showed significant univariate differences between zones (p<0.05). The Spearman correlation test between the abundance of biotic and abiotic components indicated significant negative correlation of live coral and sand with zoantharian and significant positive correlation of algae and other benthic organisms with rubble. The reef health indices used for the corals indicated that, in general, the environmental conditions were not suitable, which could be attributed to both natural and anthropogenic factors, the most important of which was zoantharian’ overgrowth on the scleractinian corals in this region.  相似文献   

5.
基于Ecopath模型的七连屿礁栖性生物的生态承载力分析   总被引：1，自引：0，他引：1  
生态承载力评估是开展生物资源增殖放流, 维持珊瑚礁生态系统健康的基础和前提。本文基于2019年渔业资源和生态环境的综合调查数据, 构建了七连屿珊瑚礁海域生态系统的生态通道(Ecopath)模型, 分析和探讨了相关功能组增殖放流的生态承载力。结果显示, 七连屿珊瑚礁海域生态系统各功能群营养级范围为1.00~3.81; 生态系统的总能量转化效率为13.45%; 生态系统以牧食食物链占据主导地位, 直接来源于初级生产者的能流占比为57%。系统总初级生产量/总呼吸量为2.54; 总初级生产量/总生物量为19.07; 系统连接指数和系统杂食性指数分别为0.36和0.22, 表明当前七连屿珊瑚礁海域生态系统的成熟度和稳定性偏低, 系统对于外界的干扰抵抗能力较弱。在未改变七连屿珊瑚礁生态系统结构和功能的前提下, 各功能组中珊瑚、双壳类和植食性鱼类的生态承载力分别为25.09~53.77t•km-2、2.55~39.95t•km-2和4.89~17.94t•km-2, 因此仍具有较大的增殖空间。珊瑚礁鱼类群落的最大生态承载力同珊瑚礁无脊椎动物群落的增殖密切相关, 在未来的珊瑚礁渔业管理中应从生态系统整体结构的角度综合考虑增殖放流的方法设计。  相似文献   

6.
雷州半岛珊瑚幼虫补充来源初步研究   总被引：2，自引：0，他引：2  
通过对中国南海北部珊瑚礁资源的调查,系统分析不同区域珊瑚礁群落的相近性.结合不同珊瑚的区域性和繁殖特点,推测雷州半岛珊瑚幼虫的外部来源主要是海南岛沿岸、越南沿岸以及广西沿岸的珊瑚群落.通过设定数值模型,跟踪拉格朗日轨迹方程,追踪到每年3-6月份从中国西沙群岛到雷州半岛的珊瑚幼虫扩散路径,验证了对外来幼虫的推测.通过对珊瑚幼虫扩散路径的初步研究,很好地揭示了我国珊瑚源的问题,揭示了雷州半岛珊瑚礁资源由于外部幼虫来源不足而减少的原因,同时也提出了保护珊瑚幼虫来源、保护输运路径的新的珊瑚礁保护区管理理念,以更好地保护珊瑚礁资源.  相似文献   

7.

Coral reef ecosystems worldwide are now being harmed by various stresses accompanying the degradation of fish habitats and thus knowledge of fish-habitat relationships is urgently required. Because conventional research methods were not practical for this purpose due to the lack of a geospatial perspective, we attempted to develop a research method integrating visual fish observation with a seabed habitat map and to expand knowledge to a two-dimensional scale. WorldView-2 satellite imagery of Spermonde Archipelago, Indonesia obtained in September 2012 was analyzed and classified into four typical substrates: live coral, dead coral, seagrass and sand. Overall classification accuracy of this map was 81.3% and considered precise enough for subsequent analyses. Three sub-areas (CC: continuous coral reef, BC: boundary of coral reef and FC: few live coral zone) around reef slopes were extracted from the map. Visual transect surveys for several fish species were conducted within each sub-area in June 2013. As a result, Mean density (Ind. / 300 m2) of Chaetodon octofasciatus, known as an obligate feeder of corals, was significantly higher at BC than at the others (p < 0.05), implying that this species’ density is strongly influenced by spatial configuration of its habitat, like the “edge effect.” This indicates that future conservation procedures for coral reef fishes should consider not only coral cover but also its spatial configuration. The present study also indicates that the introduction of a geospatial perspective derived from remote sensing has great potential to progress conventional ecological studies on coral reef fishes.

  相似文献   

8.
The widespread occurrence of microbialites in the last deglacial reef frameworks (16–6 Ka BP) implies that the accurate study of their development patterns is of prime importance to unravel the evolution of reef architecture through time and to reconstruct the reef response to sea-level variations and environmental changes.The present study is based on the sedimentological and chronological analysis (14C AMS dating) of drill cores obtained during the IODP Expedition #310 “Tahiti Sea Level” on the successive terraces which typify the modern reef slopes from Tahiti. It provides a comprehensive data base to investigate the microbialite growth patterns (i.e. growth rates and habitats), to analyze their roles in reef frameworks and to reconstruct the evolution of the reef framework architecture during sea-level rise.The last deglacial reefs from Tahiti are composed of two distinctive biological communities: (1) the coralgal communities including seven assemblages characterized by various growth forms (branching, robust branching, massive, tabular and encrusting) that form the initial frameworks and (2) the microbial communities developed in the primary cavities of those frameworks, a few meters (1.5 to 6 m) below the living coral reef surface, where they heavily encrusted the coralgal assemblages to form microbialite crusts. The dating results demonstrate the occurrence of two distinctive generations of microbialites: the “reefal microbialites” which developed a few hundred years after coralgal communities in shallow-water environments, whereas the “slope microbialites” grew a few thousands of years later in significantly deeper water conditions after the demise of coralgal communities.The development of microbialites was controlled by the volume and the shape of the primary cavities of the initial reef frameworks determined by the morphology and the packing of coral colonies. The most widespread microbialite development occurred in frameworks dominated by branching, thin encrusting, tabular and robust branching coral colonies which built loose and open frameworks typified by a high porosity (> 50%). In contrast, their growth was minimal in compact coral frameworks formed by massive and thick encrusting corals where primary cavities yielded a low porosity (~ 30%) and could not host a significant microbialite expansion.  相似文献   

9.
全球变暖引起的珊瑚白化和珊瑚钙化能力减弱,对全球珊瑚礁生态系统构成了严重威胁.在这样的背景下,相对高纬度海域石珊瑚(Scleractinia)群落被认为是珊瑚物种延续的最后避难所.通过分析大亚湾海域持续生长46年(1962-2007年)的滨珊瑚Porites骨骼参数(生长率、密度和钙化率),研究相对高纬度海域石珊瑚钙化对全球变暖以及人为热排放的响应模式.结果显示,滨珊瑚平均生长率、密度和钙化率分别为0.97cm·a-1(0.41-1.32cm·a-1)、1.45g·cm-3(1.17-1.65g·cm-3)和1.40g·(cm2·a)-1[0.59-1.93g·(cm2·a)-1].海表温度(SST)是该海域石珊瑚钙化的主导控制因素.1962-1993年,全球变暖、SST上升对大亚湾滨珊瑚生长有缓解冬季低温胁迫、促进骨骼钙化的作用.然而,随着SST持续上升以及大亚湾核电站的运行,全球变暖与核电站温排水对滨珊瑚骨骼形成高密度带造成抑制作用,导致自1993年以后滨珊瑚骨骼生长率和钙化率呈下降趋势,并出现1997-2001年和2006年的低谷.因此,全球变暖,至少是初期,对相对高纬度海域石珊瑚钙化乃至珊瑚礁发育是有促进作用的.但随着SST持续上升,加上ENSO等极端高温事件以及人类活动的影响,可能在未来会出现相对高纬度海域的大面积石珊瑚白化.  相似文献   

10.
Coral reefs are vital to the livelihood of coastal communities in Quintana Roo, México and the preservation of these ecosystems relies on the establishment of protected areas. Education should be one of the most important management tools in coral reef preservation. Surveys were made among primary and secondary school students of Quintana Roo to determine the level of education regarding coral reefs and their importance. Students had little awareness about reefs. Coverage of coral reef issues is insufficient in school curricula and information media. Many students will leave school and become users of the reef with little understanding of it and of the consequences of exploitation of the reef. Creation of marine parks has not increased education and public awareness. There is an immediate need to establish appropriate and continuously available educational programs in order to preserve coral reefs. Education should encourage codes of behavior and community support to management issues.  相似文献   

11.
Coral mining for use as construction material is a major cause of reef degradation in several coastal nations. We studied the long-term impact of coral mining at the Wakatobi marine park, Indonesia, where a substantial mining event was undertaken two decades ago in order to supply building material for a jetty. The mined area shows significant differences in reef viability compared to a control reef 1000 m away: the percentage of dead coral in the substrate, the percentage of live coral coverage, the species richness and abundance of hard corals are all greatly reduced. For the most part, soft corals and other (non-coral) invertebrates do not show significant differences in richness, abundance or diversity, but their species composition differs greatly: the control site abounds giant clams, whereas these are absent at the mined site; instead, the dominant species there is Strombus, an algae-grazing gastropod associated with stressed reefs. We conclude that the mined reef flat failed to recover from the severe mining event, despite being un-mined for over 20 years. Our results demonstrate that without effective management and enforcement, coral mining may cause a long-term, destructive impact on the coral reef ecosystem. We propose the following management steps: first, law enforcement measures must become more stringent; second, alternative income sources such as aquaculture, ecotourism, or even land-based alternatives need to be actively promoted and financed; third, alternative building materials such as landrock and concrete should become more accessible and affordable; and fourth, education and awareness regarding both the MPA regulations and the environmental impact of coral mining have to be strengthened.  相似文献   

12.
This paper reviews the socio-economic and ecological context of Fijian reef fisheries. This review is deemed necessary because improved understanding of the state and trends of Fiji's coral reef fisheries on a national level is required for designing an effective management plan for Fiji's inshore reef fisheries. The most important point that emerges from our review is that despite numerous studies of Fiji's reef fisheries, the current status of reef-associated fisheries at the national level is still uncertain due, mainly, to the lack of dependable data on the subsistence fisheries. This in turn leads to uncertainty about how the continuation of fishing, in particular, fishing focused on target species for the coral reef resources trade, will affect fishing communities and the ecosystem.  相似文献   

13.
Anthropogenic impacts and natural disturbances have been intense recently in the global scale, affecting the composition of coral reef benthic communities from coral to algal dominated reefs. However, this condition does not always occur considering corals are able to recover when the stressors falter. This study aims to investigate the change in coral reef benthic communities and the relationship among benthic categories. The study was carried out in 2014 and 2016 at five sites, three sites in the Lembeh Strait and two sites in Likupang, North Sulawesi Province. Underwater Photo Transect(UPT) was used at depth of around 4–6 m in slope areas. The result indicated that the benthic communities were slightly changing: the percent covers of hard corals, sponges, soft corals, macroalgae and substrate categories were not significantly different between the years but category of others, particularly seasonally growing hydroid, increased significantly, occupying the available substrates and overtopping other benthos surrounding. The study also found that there was a significant relationship between the change in benthic gradient and the number of hard coral colonies: when the composition becomes less complex, the number of colony declines. In contrast, the hard coral diversity remained unchanged, suggesting the coral reefs apparently have an ecological resilience(sustainable species diversity) against the change although ecological complexity declines. In addition, the hard coral cover was significantly correlated with soft coral and sponge covers, which did not change significantly among the years. In general, the coral reefs in North Sulawesi might experience a temporary blip due to the increasing percent cover of others, and be predicted to recover as there was no indication of soft corals and sponges to increase significantly. However, it is necessary to investigate the dynamic of benthic communities in different depth gradients to gain a comprehensive understanding as the communities respond differently to the light intensity.  相似文献   

14.
Recent studies suggest a future increase in sponge bioerosion as an outcome of coral reef decline around the world. However, the factors that shape boring sponge assemblages in coral reefs are not currently well understood. This work presents the results of a 17‐month assessment of the presence and species richness of boring sponges in fragments collected from living corals, dead coral reef matrix and coral rubble from Punta de Mita and Isabel Island, two coral reefs from the central coast of the Mexican Pacific Ocean. Both localities have a high cover of dead corals generated by past El Niño Southern Oscillation events, but Punta de Mita was also highly exposed to anthropogenic impacts. Additionally, environmental factors (water transparency, water movement, temperature, sediment deposition, SST, and chlorophyll concentration) were assessed to test the hypothesis that environmental conditions which are potentially harmful for corals can enhance sponge bioerosion. Isabel Island and Punta de Mita showed a similar species richness (13 and 11 species, respectively) but boring sponge presence in both live and dead corals was higher at Isabel Island (57.6%) than at Punta de Mita (35.7%). The same result was obtained when each type of substrate was analysed separately: dead coral reef matrix (81.3% versus 55.5%), coral rubble (47.7% versus 20.0%) and living corals (43.7% versus 31.7%). A principal components analysis showed a higher environmental heterogeneity at Punta de Mita, as well as important environmental differences between Punta de Mita and Isabel Island, due to sediment deposition (2.0 versus 0.2 kg·m?2·d?1) and water movement (24.5% versus 20.5% plaster dissolution day?1), that were also negatively correlated with boring sponge presence (r = ?0.7). By analysing the boring sponge assemblage, we found that environmental settings, together with habitat availability (i.e., dead coral substrate) differentiated assemblage structure at both localities. Major structural differences were largely due to species such as Cliona vermifera, Cliona tropicalis and Aka cryptica. In conclusion, factors such as habitat availability favored the presence of boring sponges but some environmental factors such as abrasion resulting from moving sediment acted restrictively, and exerted a major role in structuring boring sponge assemblages in the Mexican Pacific.  相似文献   

15.
Most artificial reef (AR) studies have examined the early colonization stages of benthic communities, while only a few have monitored the development of AR communities beyond the initial successional phases and evaluated the time scale needed for such development. In addition, despite the proliferation of AR studies, comparative studies between artificial and natural reefs (NRs) are scarce. We present here the monitoring results of initial (1-2 year) and progressed (10 year) stages of the developing benthic communities of a purpose-planned AR submerged at Eilat, Israel (Red Sea), and compare them to its adjacent NR. Visual surveys of macro-invertebrates were conducted on the initial stages and coral communities were characterized at the progressed stage, using belt transects. The results demonstrate a distinct shift in species composition of the AR communities along the monitoring periods: from a soft coral dominated community, comprised mainly of Dendronephthya hemprichi, in initial developmental stages of up to two years post-deployment, to a community dominated by the sponge Crella cyatophora at year 10. Distinct differences in coral species count, living cover and diversity were found between the AR and its neighboring NR. We estimate the time frame required to develop a progressed diverse AR community to be well over a decade, even in tropical ecosystems. The factors shaping the species composition of purpose-designed ARs in a coral reef environment, including structural design, spatial orientation, depth and age, are discussed.  相似文献   

16.
Abstract. Around the Biological Reserve of Caño Island, Pacific Costa Rica, there are five large coral reef flats (with size ranges of 0.8–4.2 ha) built mainly of dead Pocillopora spp. At present, they are covered mainly by crustose coralline algae and microatolls of Porites lobata . From the upper reef slope to the reef base several corals grow in small patches (e. g., Pavona clavus, Pavona varians, Pavona gigantea, Gardineroseris planulata, Psammocora superficialis, Pocillopora elegans, Pocillopora damicornis); the massive coral Porites Iobata is predominant. Pocilloporid species are predominant on most other eastern Pacific reefs.
The Caño Island reef is typical of a community whose structure has been controlled by both physical (in shallow water) and biological (in deeper water) factors. Shallow reef areas are influenced by strong wave action and extreme low tides. The distribution, abundance, and feeding preferences of corallivorous organisms (e. g., Acanthaster planci, Arothron meleagris, Pseudobalistes naufragium, Quoyula monodonta) on the deeper reef suggest that most pocilloporids are affected and limited by them. Although there is no evidence of any predator on Porites lobata at Caño Island, the triggerfish Pseudobalistes naufragium breaks off fragments of the coral while searching for food. These fragments often survive to form new colonies. Together, this dispersal mechanism, rapid injury recovery, and high resistance to environmental stress seem to enhance the distribution and dominance of the massive coral Porites lobata at Caño Island.  相似文献   

17.
Human activities in the watersheds surrounding Maunalua Bay, Oahu, Hawaii, have lead to the degradation of coastal coral reefs affecting populations of marine organisms of ecological, economic and cultural value. Urbanization, stream channelization, breaching of a peninsula, seawalls, and dredging on the east side of the bay have resulted in increased volumes and residence time of polluted runoff waters, eutrophication, trapping of terrigenous sediments, and the formation of a permanent nepheloid layer. The ecosystem collapse on the east side of the bay and the prevailing westward longshore current have resulted in the collapse of the coral and coralline algae population on the west side of the bay. In turn this has lead to a decrease in carbonate sediment production through bio-erosion as well as a disintegration of the dead coral and coralline algae, leading to sediment starvation and increased wave breaking on the coast and thus increased coastal erosion. The field data and resulting coral reef ecohydrology model presented in this paper demonstrate and quantify the importance of biophysical processes leading to coral reef degradation as the result of urbanization. Coral restoration in Maunalua Bay will require an integrated ecosystem approach.  相似文献   

18.
Since the early 1980s, episodes of coral reef bleaching and mortality, due primarily to climate-induced ocean warming, have occurred almost annually in one or more of the world's tropical or subtropical seas. Bleaching is episodic, with the most severe events typically accompanying coupled ocean–atmosphere phenomena, such as the El Niño-Southern Oscillation (ENSO), which result in sustained regional elevations of ocean temperature. Using this extended dataset (25+ years), we review the short- and long-term ecological impacts of coral bleaching on reef ecosystems, and quantitatively synthesize recovery data worldwide. Bleaching episodes have resulted in catastrophic loss of coral cover in some locations, and have changed coral community structure in many others, with a potentially critical influence on the maintenance of biodiversity in the marine tropics. Bleaching has also set the stage for other declines in reef health, such as increases in coral diseases, the breakdown of reef framework by bioeroders, and the loss of critical habitat for associated reef fishes and other biota. Secondary ecological effects, such as the concentration of predators on remnant surviving coral populations, have also accelerated the pace of decline in some areas. Although bleaching severity and recovery have been variable across all spatial scales, some reefs have experienced relatively rapid recovery from severe bleaching impacts. There has been a significant overall recovery of coral cover in the Indian Ocean, where many reefs were devastated by a single large bleaching event in 1998. In contrast, coral cover on western Atlantic reefs has generally continued to decline in response to multiple smaller bleaching events and a diverse set of chronic secondary stressors. No clear trends are apparent in the eastern Pacific, the central-southern-western Pacific or the Arabian Gulf, where some reefs are recovering and others are not. The majority of survivors and new recruits on regenerating and recovering coral reefs have originated from broadcast spawning taxa with a potential for asexual growth, relatively long distance dispersal, successful settlement, rapid growth and a capacity for framework construction. Whether or not affected reefs can continue to function as before will depend on: (1) how much coral cover is lost, and which species are locally extirpated; (2) the ability of remnant and recovering coral communities to adapt or acclimatize to higher temperatures and other climatic factors such as reductions in aragonite saturation state; (3) the changing balance between reef accumulation and bioerosion; and (4) our ability to maintain ecosystem resilience by restoring healthy levels of herbivory, macroalgal cover, and coral recruitment. Bleaching disturbances are likely to become a chronic stress in many reef areas in the coming decades, and coral communities, if they cannot recover quickly enough, are likely to be reduced to their most hardy or adaptable constituents. Some degraded reefs may already be approaching this ecological asymptote, although to date there have not been any global extinctions of individual coral species as a result of bleaching events. Since human populations inhabiting tropical coastal areas derive great value from coral reefs, the degradation of these ecosystems as a result of coral bleaching and its associated impacts is of considerable societal, as well as biological concern. Coral reef conservation strategies now recognize climate change as a principal threat, and are engaged in efforts to allocate conservation activity according to geographic-, taxonomic-, and habitat-specific priorities to maximize coral reef survival. Efforts to forecast and monitor bleaching, involving both remote sensed observations and coupled ocean–atmosphere climate models, are also underway. In addition to these efforts, attempts to minimize and mitigate bleaching impacts on reefs are immediately required. If significant reductions in greenhouse gas emissions can be achieved within the next two to three decades, maximizing coral survivorship during this time may be critical to ensuring healthy reefs can recover in the long term.  相似文献   

19.
根据2007年5月的调查资料,对南沙群岛渚碧礁海域造礁石珊瑚的群落结构、种类组成、覆盖率和死亡率等进行了分析研究.鉴定出的造礁石珊瑚有74种,其中鹿角珊瑚科(Acroporidae)种类最多.渚碧礁海域造礁石珊瑚群落澙湖内外差别较大,澙湖内造礁石珊瑚覆盖率和健康状况明显优于澙湖外,但是两者的死亡率都较高.礁坪和澙湖的优势种不同且优势度较高(优势度>40%),其中细柱滨珊瑚(Porites cylindrica)在澙湖内占主导地位(优势度:47.20%),而澙湖外以疣状杯形珊瑚(Pocillopora verrucosa)为主导(优势度:54.88%).造礁石珊瑚大量死亡的原因可能是自然因素和人类活动共同造成的,必须加以关注.  相似文献   

20.
Caribbean coral reefs are under strong natural and human pressures and many have undergone phase shifts as a result of local and global change. However few studies have quantified the extent of these phase shifts and the potential impacts that they have on coral reef communities. A temporal comparative analysis of several coral reefscape and landscape metrics was conducted for data from Mahahual, Quintana Roo, Mexico, between the years 2000 and 2006, when a phase shift occurred. Landscape metrics were calculated from coral reef and coastal cover maps obtained by multispectral satellite image classification using IKONOS satellite imagery. These metrics showed that the coastal landscape and reefscape of Mahahual lost 85 ha of vegetation cover and 43 ha of coral cover over 6 years, respectively. Coastal landscape transformation was induced by the construction of a cruise ship pier and multiple associated tourist developments along the coast, such as hotels and restaurants, meanwhile alteration of the reefscape may be associated with potential stressors such as coastal development, bleaching events and hurricanes.  相似文献   

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