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1.
Understanding how communities respond to natural disturbances is fundamental to assess the mechanisms of ecosystem resistance and resilience. However, ecosystem responses to natural disturbances are rarely monitored both through space and time, while the factors promoting ecosystem stability act at various temporal and spatial scales. Hence, assessing both the spatial and temporal variations in species composition is important to comprehensively explore the effects of natural disturbances. Here, we suggest a framework to better scrutinize the mechanisms underlying community responses to disturbances through both time and space. Our analytical approach is based on beta diversity decomposition into two components, replacement and biomass difference. We illustrate this approach using a 9-year monitoring of coral reef fish communities off Moorea Island (French Polynesia), which encompassed two severe natural disturbances: a crown-of-thorns starfish outbreak and a hurricane. These disturbances triggered a fast logistic decline in coral cover, which suffered a 90% decrease on all reefs. However, we found that the coral reef fish composition remained largely stable through time and space whereas compensatory changes in biomass among species were responsible for most of the temporal fluctuations, as outlined by the overall high contribution of the replacement component to total beta diversity. This suggests that, despite the severity of the two disturbances, fish communities exhibited high resistance and the ability to reorganize their compositions to maintain the same level of total community biomass as before the disturbances. We further investigated the spatial congruence of this pattern and showed that temporal dynamics involved different species across sites; yet, herbivores controlling the proliferation of algae that compete with coral communities were consistently favored. These results suggest that compensatory changes in biomass among species and spatial heterogeneity in species responses can provide further insurance against natural disturbances in coral reef ecosystems by promoting high levels of key species (herbivores). They can also allow the ecosystem to recover more quickly.  相似文献   

2.
Mexico harbors more than 10% of the planet’s endemic species. However, the integrity and biodiversity of many ecosystems is experiencing rapid transformation under the influence of a wide array of human and natural disturbances. In order to disentangle the effects of human and natural disturbance regimes at different spatial and temporal scales, we selected six terrestrial (temperate montane forests, montane cloud forests, tropical rain forests, tropical semi-deciduous forests, tropical dry forests, and deserts) and four aquatic (coral reefs, mangrove forests, kelp forests and saline lakes) ecosystems. We used semi-quantitative statistical methods to assess (1) the most important agents of disturbance affecting the ecosystems, (2) the vulnerability of each ecosystem to anthropogenic and natural disturbance, and (3) the differences in ecosystem disturbance regimes and their resilience. Our analysis indicates a significant variation in ecological responses, recovery capacity, and resilience among ecosystems. The constant and widespread presence of human impacts on both terrestrial and aquatic ecosystems is reflected either in reduced area coverage for most systems, or reduced productivity and biodiversity, particularly in the case of fragile ecosystems (e.g., rain forests, coral reefs). In all cases, the interaction between historical human impacts and episodic high intensity natural disturbance (e.g., hurricanes, fires) has triggered a reduction in species diversity and induced significant changes in habitat distribution or species dominance. The lack of monitoring programs assessing before/after effects of major disturbances in Mexico is one of the major limitations to quantifying the commonalities and differences of disturbance effects on ecosystem properties.  相似文献   

3.
Facing a human-dominated world, ecologists are now reconsidering the role of disturbance for coral reef ecosystem dynamics. Human activities alter the natural disturbance regimes of coral reefs by transforming pulse events into persistent disturbance or even chronic stress, by introducing new disturbance, or by suppressing or removing disturbance. Adding these alterations to natural disturbance regimes will probably result in unknown synergistic effects. Simultaneously, humans are altering the capacity of reefs to cope with disturbance (e.g. by habitat fragmentation and reduction of functional diversity), which further exacerbates the effects of altered disturbance regimes. A disturbance that previously triggered the renewal and development of reefs might, under such circumstances, become an obstacle to development. The implications of these changes for reef-associated human activities, such as fishing and tourism, can be substantial.  相似文献   

4.
Coral reefs can undergo unexpected and dramatic changes in community composition, so called phase shifts. This can have profound consequences for ecosystem services upon which human welfare depends. Understanding of this behavior is in many aspects still in its infancy. Resilience has been argued to provide insurance against unforeseen ecosystem responses in the face of environmental change, and has become a prime goal for the management of coral reefs. However, diverse definitions of resilience can be found in the literature, making its meaning ambiguous. Several studies have used the term as a theoretical framework and concern regarding its practical applicability has been raised. Consequently, operationalizing theory to make resilience observable is an important task, particularly for policy makers and managers dealing with pressing environmental problems. Ultimately this requires some type of empirical assessments, something that has proven difficult due to the multidimensional nature of the concept. Biodiversity, spatial heterogeneity, and connectivity have been proposed as cornerstones of resilience as they may provide insurance against ecological uncertainty. The aim of this article is to provide an overview of the divergent uses of the concept and to propose empirical indicators of the cornerstones of coral reef resilience. These indicators include functional group approaches, the ratios of “good” and “bad” colonizers of space, measurements of spatial heterogeneity, and estimates of potential space availability against grazing capacity. The essence of these operational indicators of resilience is to use them as predictive tools to recognize vulnerability before disturbance occurs that may lead to abrupt phase shifts. Moving toward operationalizing resilience theory is imperative to the successful management of coral reefs in an increasingly disturbed and human-dominated environment. Communicating by Ecology Editor Professor Peter Mumby Order of authors 2–3 is alphabetic  相似文献   

5.
Ocean warming and acidification from increasing levels of atmospheric CO2 represent major global threats to coral reefs, and are in many regions exacerbated by local‐scale disturbances such as overfishing and nutrient enrichment. Our understanding of global threats and local‐scale disturbances on reefs is growing, but their relative contribution to reef resilience and vulnerability in the future is unclear. Here, we analyse quantitatively how different combinations of CO2 and fishing pressure on herbivores will affect the ecological resilience of a simplified benthic reef community, as defined by its capacity to maintain and recover to coral‐dominated states. We use a dynamic community model integrated with the growth and mortality responses for branching corals (Acropora) and fleshy macroalgae (Lobophora). We operationalize the resilience framework by parameterizing the response function for coral growth (calcification) by ocean acidification and warming, coral bleaching and mortality by warming, macroalgal mortality by herbivore grazing and macroalgal growth via nutrient loading. The model was run for changes in sea surface temperature and water chemistry predicted by the rise in atmospheric CO2 projected from the IPCC's fossil‐fuel intensive A1FI scenario during this century. Results demonstrated that severe acidification and warming alone can lower reef resilience (via impairment of coral growth and increased coral mortality) even under high grazing intensity and low nutrients. Further, the threshold at which herbivore overfishing (reduced grazing) leads to a coral–algal phase shift was lowered by acidification and warming. These analyses support two important conclusions: Firstly, reefs already subjected to herbivore overfishing and nutrification are likely to be more vulnerable to increasing CO2. Secondly, under CO2 regimes above 450–500 ppm, management of local‐scale disturbances will become critical to keeping reefs within an Acropora‐rich domain.  相似文献   

6.
Marine reserves help coastal ecosystems cope with extreme weather   总被引:1,自引:0,他引:1  
Natural ecosystems have experienced widespread degradation due to human activities. Consequently, enhancing resilience has become a primary objective for conservation. Nature reserves are a favored management tool, but we need clearer empirical tests of whether they can impart resilience. Catastrophic flooding in early 2011 impacted coastal ecosystems across eastern Australia. We demonstrate that marine reserves enhanced the capacity of coral reefs to withstand flood impacts. Reserve reefs resisted the impact of perturbation, whilst fished reefs did not. Changes on fished reefs were correlated with the magnitude of flood impact, whereas variation on reserve reefs was related to ecological variables. Herbivory and coral recruitment are critical ecological processes that underpin reef resilience, and were greater in reserves and further enhanced on reserve reefs near mangroves. The capacity of reserves to mitigate external disturbances and promote ecological resilience will be critical to resisting an increased frequency of climate‐related disturbance.  相似文献   

7.
Mumby  Peter J. 《Coral reefs (Online)》2017,36(3):1003-1011

Climate change will homogenise the environment and generate a preponderance of mediocre reefs. Managing seascapes of mediocrity will be challenging because our science is ill prepared to deal with the ‘shades of grey’ of reef health; we tend to study natural processes in the healthiest reefs available. Yet much can be gained by examining the drivers and implications of even subtle changes in reef state. Where strong ecological interactions are discovered, even small changes in abundance can have profound impacts on coral resilience. Indeed, if we are to develop effective early warnings of critical losses of resilience, then monitoring must place greater emphasis on measuring and interpreting changes in reef recovery rates. In terms of mechanism, a more nuanced approach is needed to explore the generality of what might be considered ‘dogma’. A more nuanced approach to science will serve managers needs well and help minimise the rise of mediocrity in coral reef ecosystems.

  相似文献   

8.
Cumulative pressures from global climate and ocean change combined with multiple regional and local‐scale stressors pose fundamental challenges to coral reef managers worldwide. Understanding how cumulative stressors affect coral reef vulnerability is critical for successful reef conservation now and in the future. In this review, we present the case that strategically managing for increased ecological resilience (capacity for stress resistance and recovery) can reduce coral reef vulnerability (risk of net decline) up to a point. Specifically, we propose an operational framework for identifying effective management levers to enhance resilience and support management decisions that reduce reef vulnerability. Building on a system understanding of biological and ecological processes that drive resilience of coral reefs in different environmental and socio‐economic settings, we present an Adaptive Resilience‐Based management (ARBM) framework and suggest a set of guidelines for how and where resilience can be enhanced via management interventions. We argue that press‐type stressors (pollution, sedimentation, overfishing, ocean warming and acidification) are key threats to coral reef resilience by affecting processes underpinning resistance and recovery, while pulse‐type (acute) stressors (e.g. storms, bleaching events, crown‐of‐thorns starfish outbreaks) increase the demand for resilience. We apply the framework to a set of example problems for Caribbean and Indo‐Pacific reefs. A combined strategy of active risk reduction and resilience support is needed, informed by key management objectives, knowledge of reef ecosystem processes and consideration of environmental and social drivers. As climate change and ocean acidification erode the resilience and increase the vulnerability of coral reefs globally, successful adaptive management of coral reefs will become increasingly difficult. Given limited resources, on‐the‐ground solutions are likely to focus increasingly on actions that support resilience at finer spatial scales, and that are tightly linked to ecosystem goods and services.  相似文献   

9.
Coral reef ecosystems are declining worldwide, yet regional differences in the trajectories, timing and extent of degradation highlight the need for in-depth regional case studies to understand the factors that contribute to either ecosystem sustainability or decline. We reconstructed social-ecological interactions in Hawaiian coral reef environments over 700 years using detailed datasets on ecological conditions, proximate anthropogenic stressor regimes and social change. Here we report previously undetected recovery periods in Hawaiian coral reefs, including a historical recovery in the MHI (~AD 1400-1820) and an ongoing recovery in the NWHI (~AD 1950-2009+). These recovery periods appear to be attributed to a complex set of changes in underlying social systems, which served to release reefs from direct anthropogenic stressor regimes. Recovery at the ecosystem level is associated with reductions in stressors over long time periods (decades+) and large spatial scales (>10(3) km(2)). Our results challenge conventional assumptions and reported findings that human impacts to ecosystems are cumulative and lead only to long-term trajectories of environmental decline. In contrast, recovery periods reveal that human societies have interacted sustainably with coral reef environments over long time periods, and that degraded ecosystems may still retain the adaptive capacity and resilience to recover from human impacts.  相似文献   

10.
The 1998 global coral bleaching event was the largest recorded historical disturbance of coral reefs and resulted in extensive habitat loss. Annual censuses of reef fish community structure over a 12-year period spanning the bleaching event revealed a marked phase shift from a prebleach to postbleach assemblage. Surprisingly, we found that the bleaching event had no detectable effect on the abundance, diversity or species richness of a local cryptobenthic reef fish community. Furthermore, there is no evidence of regeneration even after 5–35 generations of these short-lived species. These results have significant implications for our understanding of the response of coral reef ecosystems to global warming and highlight the importance of selecting appropriate criteria for evaluating reef resilience.  相似文献   

11.
Coral reefs in shallow-water environments (<30 m) are in decline due to local and global anthropogenic stresses. This has led to renewed interest in the ‘deep reef refugia’ hypothesis (DRRH), which stipulates that deep reef areas (1) are protected or dampened from disturbances that affect shallow reef areas and (2) can provide a viable reproductive source for shallow reef areas following disturbance. Using the Caribbean as an example, the assumptions of this hypothesis were explored by reviewing the literature for scleractinian corals—the reef framework builders on tropical reefs. Although there is evidence to support that deep reefs (>30 m) can escape the direct effects of storm-induced waves and thermal bleaching events, deep reefs are certainly not immune to disturbance. Additionally, the potential of deep reefs to provide propagules for shallow reef areas seems limited to ‘depth-generalist’ coral species, which constitute only ~25% of the total coral biodiversity. Larval connectivity between shallow and deep populations of these species may be further limited due to specific life history traits (e.g., brooding reproductive strategy and vertical symbiont acquisition mode). This review exposes how little is known about deep reefs and coral reproduction over depth. Hence, a series of urgent research priorities are proposed to determine the extent to which deep reefs may act as a refuge in the face of global reef decline.  相似文献   

12.
In the face of increasing cumulative effects from human and natural disturbances, sustaining coral reefs will require a deeper understanding of the drivers of coral resilience in space and time. Here we develop a high‐resolution, spatially explicit model of coral dynamics on Australia's Great Barrier Reef (GBR). Our model accounts for biological, ecological and environmental processes, as well as spatial variation in water quality and the cumulative effects of coral diseases, bleaching, outbreaks of crown‐of‐thorns starfish (Acanthaster cf. solaris), and tropical cyclones. Our projections reconstruct coral cover trajectories between 1996 and 2017 over a total reef area of 14,780 km2, predicting a mean annual coral loss of ?0.67%/year mostly due to the impact of cyclones, followed by starfish outbreaks and coral bleaching. Coral growth rate was the highest for outer shelf coral communities characterized by digitate and tabulate Acropora spp. and exposed to low seasonal variations in salinity and sea surface temperature, and the lowest for inner‐shelf communities exposed to reduced water quality. We show that coral resilience (defined as the net effect of resistance and recovery following disturbance) was negatively related to the frequency of river plume conditions, and to reef accessibility to a lesser extent. Surprisingly, reef resilience was substantially lower within no‐take marine protected areas, however this difference was mostly driven by the effect of water quality. Our model provides a new validated, spatially explicit platform for identifying the reefs that face the greatest risk of biodiversity loss, and those that have the highest chances to persist under increasing disturbance regimes.  相似文献   

13.
Coral reefs have been more severely impacted by recent climate instability than any other ecosystem on Earth. Corals tolerate a narrow range of physical environmental stress, and increases in sea temperature of just 1 °C over several weeks can result in mass coral mortality, often exceeding 95% of individuals over hundreds of square kilometres. Even conservative climate models predict that mass coral bleaching events could occur annually by 2050. Unfortunately, managers of coral‐reef resources have few options available to meet this challenge. Here, we investigate the role that fisheries conservation tools, including the designation of marine reserves, can play in altering future trajectories of Caribbean coral reefs. We use an individual‐based model of the ecological dynamics to test the influence of spatially realistic regimes of disturbance on coral populations. Two major sources of disturbance, hurricanes and coral bleaching, are simulated in contrasting regions of the Caribbean: Belize, Bonaire, and the Bahamas. Simulations are extended to 2099 using the HadGEM1 climate model. We find that coral populations can maintain themselves under all levels of hurricane disturbance providing that grazing levels are high. Regional differences in hurricane frequency are found to cause strikingly different spatial patterns of reef health with greater patchiness occurring in Belize, which has less frequent disturbance, than the Bahamas. The addition of coral bleaching led to a much more homogenous reef state over the seascape. Moreover, in the presence of bleaching, all reefs exhibited a decline in health over time, though with substantial variation among regions. Although the protection of herbivores does not prevent reef degradation it does delay rates of coral loss even under the most severe thermal and hurricane regimes. Thus, we can estimate the degree to which local conservation can help buy time for reefs with values ranging between 18 years in the Bahamas and over 50 years in Bonaire, compared with heavily fished systems. Ultimately, we demonstrate that local conservation measures can benefit reef ecosystem services but that their impact will vary spatially and temporally. Recognizing where such management interventions will either help or fail is an important step towards both achieving sustainable use of coral‐reef resources and maximizing resource management investments.  相似文献   

14.
Disturbance,coral reef communities,and changing ecological paradigms   总被引:4,自引:0,他引:4  
We examine changing ecological theory regarding the role of disturbance in natural communities and relate past and emerging paradigms to coral reefs. We explore the elements of this theory, including patterns (diversity, distribution, and abundance) and processes (competition, succession, and disturbance), using currently evolving notions concerning matters of scale (temporal and spatial), local versus regional species richness, and the equilibrium versus nonequilibrium controversy. We conclude that any attempt to categorize coral reef communities with respect to disturbance regimes will depend on the question being asked and the desired level of resolution: local assemblage versus regional species pool, successional versus geological time, and on the taxonomic and tropic affinities of species included in the study. As with many communities in nature, coral reefs will prove to be mosaics of species assemblages with equilibrial and nonequilibrial dynamics.  相似文献   

15.
Migrating species are common within seascapes, but the potential for these movements to alter the populations and functional roles of non‐migrating species (e.g. by increasing predation) is rarely investigated. This study considers whether the presence of nursery habitats (mangroves and seagrass) simply enhances the abundance of nursery‐using parrotfishes and piscivores on nearby coral reefs, or also affects other parrotfishes. Data from 131 reef sites and multiple seascape configurations across 13 degrees of latitude were used to model correlations between biophysical variables, including nursery habitat connectivity, and the abundance and grazing pressure of both nursery‐using species and other parrotfishes and piscivore biomass. Connectivity to mangroves and dense seagrass was positively correlated with the biomass of nursery‐using species, but was also negatively correlated with non‐nursery parrotfish populations. This reduction may be caused indirectly by nursery habitats increasing confamilial competition and predation by nursery‐using piscivores, particularly affecting small parrotfishes settling directly onto reefs. As key reef grazers, parrotfishes affect coral demographics. Consequently, a spatial simulation model predicted the impacts after five years of changes in grazing pressure because of nursery habitat connectivity. The model demonstrated that high nursery connectivity was correlated to changes in grazing pressure on nearby reefs that could potentially lead to differences in coral cover of ~3–4% when compared to low connectivity reefs. However, the direction of this change depended on the seascapes’ characteristics. Historically, large‐bodied, nursery‐using parrotfish would have increased grazing in all nursery‐rich seascapes. Overfishing means that nursery availability may have spatially variable impacts on coral cover, influencing reserve design. This study suggests that nursery availability may directly and indirectly modify an ecological process, and alter an ecological cascade (migrating species increase predator and competitor abundances, affecting other grazers and consequently corals). Therefore, elucidating the multi‐species impacts of animal movements is required to better understand ecosystem functioning.  相似文献   

16.
Coral reefs have emerged as one of the ecosystems most vulnerable to climate variation and change. While the contribution of a warming climate to the loss of live coral cover has been well documented across large spatial and temporal scales, the associated effects on fish have not. Here, we respond to recent and repeated calls to assess the importance of local management in conserving coral reefs in the context of global climate change. Such information is important, as coral reef fish assemblages are the most species dense vertebrate communities on earth, contributing critical ecosystem functions and providing crucial ecosystem services to human societies in tropical countries. Our assessment of the impacts of the 1998 mass bleaching event on coral cover, reef structural complexity, and reef associated fishes spans 7 countries, 66 sites and 26 degrees of latitude in the Indian Ocean. Using Bayesian meta-analysis we show that changes in the size structure, diversity and trophic composition of the reef fish community have followed coral declines. Although the ocean scale integrity of these coral reef ecosystems has been lost, it is positive to see the effects are spatially variable at multiple scales, with impacts and vulnerability affected by geography but not management regime. Existing no-take marine protected areas still support high biomass of fish, however they had no positive affect on the ecosystem response to large-scale disturbance. This suggests a need for future conservation and management efforts to identify and protect regional refugia, which should be integrated into existing management frameworks and combined with policies to improve system-wide resilience to climate variation and change.  相似文献   

17.
Loss of coral reef resilience can lead to dramatic changes in benthic structure, often called regime shifts, which significantly alter ecosystem processes and functioning. In the face of global change and increasing direct human impacts, there is an urgent need to anticipate and prevent undesirable regime shifts and, conversely, to reverse shifts in already degraded reef systems. Such challenges require a better understanding of the human and natural drivers that support or undermine different reef regimes. The Hawaiian archipelago extends across a wide gradient of natural and anthropogenic conditions and provides us a unique opportunity to investigate the relationships between multiple reef regimes, their dynamics and potential drivers. We applied a combination of exploratory ordination methods and inferential statistics to one of the most comprehensive coral reef datasets available in order to detect, visualize and define potential multiple ecosystem regimes. This study demonstrates the existence of three distinct reef regimes dominated by hard corals, turf algae or macroalgae. Results from boosted regression trees show nonlinear patterns among predictors that help to explain the occurrence of these regimes, and highlight herbivore biomass as the key driver in addition to effluent, latitude and depth.  相似文献   

18.
Relatively little is known about how the future effects of climatic change, including increases in sea level, temperature and storm severity and frequency, will impact on patterns of biodiversity on coral reefs, with the notable exception of recent work on corals and fish in tropical reef ecosystems. Sessile invertebrates such as ascidians, sponges and bryozoans occupying intertidal rubble habitats on coral reefs contribute significantly to the overall biodiversity and ecosystem function, but there is little or no information available on the likely impacts on these species from climate change. The existing strong physical gradients in these intertidal habitats will be exacerbated under predicted climatic change. By examining the distribution and abundance of nonscleractinian, sessile invertebrate assemblages exposed to different levels of wave action and at different heights on the shore around a coral reef, we show that coral reef intertidal biodiversity is particularly sensitive to physical disturbance. As physical disturbance regimes increase due to more intense storms and wave action associated with global warming, we can expect to see a corresponding decrease in the diversity of these cryptic sessile assemblages. This could impact negatively on the future health and productivity of coral reef ecosystems, given the ecosystem services these organisms provide.  相似文献   

19.
Tropical coral reefs feature extraordinary biodiversity and high productivity rates in oligotrophic waters. Due to increasing frequencies of perturbations – anthropogenic and natural – many reefs are under threat. Such perturbations often have devastating effects on these unique ecosystems and especially if they occur simultaneously and amplify each other''s impact, they might trigger a phase shift and create irreversible conditions.We developed a generic, spatially explicit, individual-based model in which competition drives the dynamics of a virtual benthic reef community – comprised of scleractinian corals and algae – under different environmental settings. Higher system properties, like population dynamics or community composition arise through self-organization as emergent properties. The model was parameterized for a typical coral reef site at Zanzibar, Tanzania and features coral bleaching and physical disturbance regimes as major sources of perturbations. Our results show that various types and modes (intensities and frequencies) of perturbations create diverse outcomes and that the switch from high diversity to single species dominance can be evoked by small changes in a key parameter.Here we extend the understanding of coral reef resilience and the identification of key processes, drivers and respective thresholds, responsible for changes in local situations. One future goal is to provide a tool which may aid decision making processes in management of coral reefs.  相似文献   

20.
Coral reefs provide food and livelihoods for hundreds of millions of people as well as harbour some of the highest regions of biodiversity in the ocean. However, overexploitation, land‐use change and other local anthropogenic threats to coral reefs have left many degraded. Additionally, coral reefs are faced with the dual emerging threats of ocean warming and acidification due to rising CO2 emissions, with dire predictions that they will not survive the century. This review evaluates the impacts of climate change on coral reef organisms, communities and ecosystems, focusing on the interactions between climate change factors and local anthropogenic stressors. It then explores the shortcomings of existing management and the move towards ecosystem‐based management and resilience thinking, before highlighting the need for climate change‐ready marine protected areas (MPAs), reduction in local anthropogenic stressors, novel approaches such as human‐assisted evolution and the importance of sustainable socialecological systems. It concludes that designation of climate change‐ready MPAs, integrated with other management strategies involving stakeholders and participation at multiple scales such as marine spatial planning, will be required to maximise coral reef resilience under climate change. However, efforts to reduce carbon emissions are critical if the long‐term efficacy of local management actions is to be maintained and coral reefs are to survive.  相似文献   

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