Coral Reef Resilience And Resistance To Bleaching Pdf

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Coral Health and Disease pp Cite as. Most of this destruction occurred in the Indian Ocean, where prolonged elevations of sea surface temperature were maintained by prevailing currents that pooled warm water in the western Indo-Pacific. In most cases, coral reef destruction equated to a dramatic reduction in live coral cover on these reefs e.

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Coral reef resilience and resistance to bleaching

Globally increasing sea surface temperatures threaten coral reefs, both directly and through interactions with local stressors. More resilient reefs have a higher likelihood of returning to a coral-dominated state following a disturbance, such as a mass bleaching event. We calculated relative resilience scores for sites from an existing commonwealth-wide survey using eight resilience indicators—such as coral diversity, macroalgae percent cover, and herbivorous fish biomass—and assessed which indicators most drove resilience.

We found that sites of very different relative resilience were generally highly spatially intermixed, underscoring the importance and necessity of decision making and management at fine scales. In combination with information on levels of two localized stressors fishing pressure and pollution exposure , we used the resilience indicators to assess which of seven potential management actions could be used at each site to maintain or improve resilience.

Fishery management was the management action that applied to the most sites. Island-wide or community-level managers can use the actions and vulnerability information as a starting point for resilience-based management of their reefs. The available data still permitted analyses comparable to previous assessments, demonstrating that desktop resilience assessments can substitute for assessments with field components under some circumstances.

This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.

Data Availability: All relevant data are within the manuscript and its Supporting Information files. Funding: This research was funded by U. Competing interests: The authors have declared that no competing interests exist. Although resilience is relevant with respect to any kind of environmental disturbance, for coral reefs a major concern is resilience to rising SST and its interaction with local stressors [ 4 ]. Prolonged elevated SST can disturb reefs by causing corals to bleach lose the symbiotic dinoflagellates that provide a large share of their nutrients , potentially leading to coral mortality.

Resilience-based management has become an important principle for managing reefs with respect to multiple stressors at multiple spatial scales. However, to manage reefs based on resilience, managers must know which reefs or areas tend to be more resilient and which tend to be less [ 3 ]. The resilience of reefs can be identified by conducting a resilience assessment, the goal of which is to inform reef management at one or more spatial scales [ 5 ].

Resilience is generally defined relative to a pool of sites or an area of interest, rather than in absolute terms. There are two main reasons to conduct resilience assessments: 1 to help target where to engage in various environmental management actions, and 2 to evaluate the effectiveness of reef management and conservation actions taken to increase resilience [ 6 ]. Potential outputs of resilience assessments include the spatial distribution of sites of varying resilience, the range in relative resilience, drivers of resilience [ 7 ], and management actions that can be informed by resilience [ 8 ].

These can be highly localized actions, like selecting sites where outplanting corals will be most beneficial and likely to succeed, or broader-scale actions, like designing marine protected areas to include sites with a range of resilience [ 9 ]. Resilience assessments are based on identification of measurable properties i. Resilience indicators can be used to help identify which properties of reefs drive high resilience in an area, which is important for understanding how reefs respond to the stressor of interest.

Ideally, resilience indicators capture reef state pattern and function process , both of which contribute to sensitivity and adaptive capacity [ 6 ]. It should then follow that management actions that increase these indicators such as the creation of herbivore management areas to increase herbivore biomass [ 10 ] will increase reef resilience. Methods for reef resilience assessments were formalized by [ 6 ].

Croix, U. In addition to mapping resilience by survey site, assessments have generally included management recommendations, such as where coral restoration is most likely to be effective and where protected areas should be enforced or established. We assessed the resilience of coral reefs to ocean warming around the U. Caribbean commonwealth of Puerto Rico using the methods of [ 7 ] and [ 2 ]. The assessment encompasses the entire island, as well as the outlying islands.

Unlike some previous resilience assessments, this assessment is not based on a field survey designed specifically to measure resilience because we wanted to explore the feasibility of the approach using only readily available data. We therefore limited ourselves to using existing commonwealth-wide data. Because field surveys tailored to resilience assessments are not feasible in all situations, this serves as a test of what can be done using desktop methods alone. This survey used a probabilistic design in which sampling location was stratified by depth, habitat, region of Puerto Rico, and presence of a marine protected area.

The survey included sites at which were conducted 25x4 m fish belt transects [ 17 ]; topographic complexity surveys using 24 vertical relief measurements in the same transects [ 18 ]; and 20 m line-point intercept LPI benthic surveys [ 19 ].

In addition, 10x1 m coral colony demographic surveys were conducted at of the sites using the same stratification system [ 20 ]; these recorded species, dimensions, and health status for all colonies greater than 4 cm diameter.

Indicators for resilience to increasing SST may not be the same as indicators of resilience to other large-scale climate stressors, such as ocean acidification OA or changing storm patterns. For example, the dozens of indicators of [ 12 ] and [ 6 ] focused on resilience to warmer oceans, rather than on other consequences of planet-scale changes. We intended our indicators to do likewise. We first narrowed the universe of potential resilience indicators by comparing those used in assessments in other locations with reef biocriteria metrics for Puerto Rico that were developed for a biological condition gradient BCG project [ 22 ] S1 Table.

The BCG is an approach for assessing the condition of an ecosystem on an absolute scale using a suite of indicators selected by experts. We determined which previously used resilience indicators and which Puerto Rico biocriteria metrics we could calculate from the available data. Because NCRMP was not designed for a resilience assessment, not all the data included in other resilience assessments were available for Puerto Rico, primarily coral recruitment. The experts recommended that all of the indicators used in previous assessments except for one should be included in the Puerto Rico assessment.

The recommended indicators were: Simpson diversity of scleractinian corals, fraction of scleractinian colonies without disease, percent cover of scleractinian corals, percent cover of macroalgae, total herbivorous fish biomass, and the average thermal tolerance of scleractinian corals. SST variation was deemed unlikely to be an important resilience indicator in Puerto Rico because of the relatively consistent variation across the study area, making it the only indicator with available data used in previous assessments to not be recommended as an indicator for this assessment.

For consistency with previous assessments and because of evidence for the role of temperature variability in bleaching response e. The panel also recommended that rugosity be included as an indicator. This list of indicators is more ecologically focused than some other resilience assessments that used different methods e. Because Simpson diversity, fraction of corals without disease, and average coral thermal tolerance required colony-specific information from the demographic survey, we used only survey sites at which a demographic survey was conducted.

This left sites with adequate data for calculation of all indicators. We followed the methods of [ 7 ] and [ 2 ] to calculate resilience indicators. For all indicators, larger values mean greater resilience.

A brief description of the calculation of each indicator is below:. After we calculated the raw indicator values, we rescaled each indicator to 1, with 1 being the highest value of that indicator found at any of the sites. Finally, we averaged the rescaled indicators with and without the temperature variation indicator to obtain a composite relative resilience score for each site.

We rescaled those values to 1, so that the site with the highest resilience among those surveyed had a value of 1. Rescaling individual indicators and the resilience score to 1 emphasizes that they are relative to the surveyed sites. We ranked the composite resilience scores between 1 and and divided them into quartiles. Our use of quartiles differs from some previous resilience assessments [ 8 , 14 , 15 ], which categorized sites based on the average and standard deviation of the resilience scores or divided sites into resilience and stressor categories based on fixed numeric cutoffs [ 13 ].

We used quartiles to assign sites to resilience categories because of the skewed distribution of resilience scores. Our use of quartile-based resilience categories instead of resilience scores or standard deviation-based resilience categories further emphasizes the relative nature of the resilience assessment. This emphasis on relativity is similar to that of [ 26 ], who identified oases of healthy reefs within degraded areas using distributions of surveyed sites.

We examined the spatial distribution of resilience scores in two ways. We did this using both inverse distance and inverse distance squared for the spatial relationship conceptualization the rate at which sites near each other are expected to be similar because neither one is obviously more conceptually applicable, and with an infinite distance threshold i. This create a resilience surface using the resilience scores of nearby sites. Note that this analysis interpolates resilience scores for areas with non-reef habitat, like soft bottom habitat.

Looking only at composite resilience scores masks the variation behind those scores, as well as important information from the indicators themselves.

Indeed, knowing the relative influence of different indicators on resilience scores can help with designing monitoring programs and management actions [ 8 ].

Therefore, we examined the contribution of individual indicators to the composite resilience scores in three ways. First, we created box plots of rescaled indicators to visualize how much each indicator varied.

The more variable an indicator is, the more useful it is for distinguishing resilience between sites [ 2 ]. Second, we created a matrix of Spearman rank-correlation coefficients between all indicators. We used Spearman correlation coefficients because the distributions of several of the indicators were heavily skewed.

Third, we performed an exploratory factor analysis EFA with a varimax rotation on all the indicators to identify latent variables in the resilience assessment. All calculations and statistical analyses were performed in R [ 27 ].

In the above calculation of resilience scores, all indicators were equally weighted. In other words, we assumed they contribute equally to reef resilience. Because this is probably an unrealistic assumption, but the actual importance of each indicator is unknown [ 7 , 11 ], we assessed to what extent the weighting of indicators affected resilience rankings and quartiles.

In addition to the unweighted resilience scores, we calculated resilience scores using nine different indicator weighting systems Table 1. This is not an exhaustive list of weighting options, nor do we think that any one of them is correct, just as we do not propose that all indicators equally measure reef resilience.

Rather, the weighting systems are supposed to show to what extent the resilience scores are robust to the null model that each indicator equally represents reef resilience.

To calculate the weighted resilience scores, we multiplied each indicator by its weight and averaged those weighted values for each site, then rescaled to 1 as with the unweighted indicators. A larger value means the indicator is given more weight in calculation of the resilience score. Weighting systems 3—9 are based on Table 2 in [ 12 ]. Root mean square errors RMSE are from the comparison of weighted indicator resilience ranks against unweighted indicator resilience ranks.

Weighting systems 1 and 2 randomly assigned weights within specified ranges to indicators while systems 3—9 were based on Table 2 in [ 12 ], which provides relative importance values for reef resilience indicators based on a review of literature and expert opinion.

Systems 4 through 6 are essentially less extreme versions of system 3. Thus, systems 7 through 9 are the most ecologically grounded of all the scaling systems. After we applied the weighting systems, we calculated by how much the resilience rank of each site changed under each weighting system and how many sites changed their resilience quartile. We used these to assess how much the various weighting systems affected resilience scores. Increasing SST interacts with and compounds the effects of localized stressors [ 28 ].

Previous resilience assessments, such as [ 29 ] and [ 9 ], have recognized these localized stressors as important moderators of resilience. Thus, in addition to the above resilience indicators, we also calculated two stressors that can be used to inform reef management: potential fishing pressure, relative land-based pollution loads a combination of nitrogen and sediment loads.

Potential fishing pressure : [ 30 ] created a grid of estimated potential line, net, trap, and dive fishing pressure around Puerto Rico by surveying fishermen see also [ 31 ].

We assigned the total fishing pressure of each grid cell to the survey stations. Nine stations around Vieques and Culebra islands were so close to shore that they were not in the fishing grid; we assigned those stations the total fishing pressure of the nearest grid cell.

Symbiont Diversity on Coral Reefs and Its Relationship to Bleaching Resistance and Resilience

Coral bleaching occurs when coral polyps expel algae that live inside their tissues. Normally, coral polyps live in an endosymbiotic relationship with these algae, which are crucial for the health of the coral and the reef. Bleached corals continue to live but begin to starve after bleaching. The leading cause of coral bleaching is rising water temperatures. In , bleaching of coral on the Great Barrier Reef killed between 29 and 50 percent of the reef's coral. The corals that form the great reef ecosystems of tropical seas depend upon a symbiotic relationship with algae-like single-celled flagellate protozoa called zooxanthellae that live within their tissues and give the coral its coloration.

Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. Grimsditch and R. Grimsditch , R. Salm Published Environmental Science. Burgeoning populations, destructive fishing practices, coastal development, sedimentation from forest clearing and unsound agricultural practices, expanding tourism, and increasing pollution are the primary agents of human impact. Save to Library.

The concept of resilience is long established across a wide-range of disciplines, but its evaluation in many ecosystems has been challenging due to the complexities involved in quantifying a somewhat abstract dynamical phenomenon. We develop a framework of resilience-related concepts and describe their methodological approaches. Seven broad approaches were identified under the three principle concepts of 1 ecological resilience ecological resilience, precariousness and current attractor , 2 engineering resilience short-term recovery rate and long-term reef performance , and 3 vulnerability absolute and relative vulnerability respectively. Using specific examples, we assess the strengths and limitations of each approach and their capacity to answer common management questions. The current synthesis provides new directions for resilience assessments to be incorporated into management decisions and has implications on the research agenda for advances in resilience assessments.


Conservation Biology 17(4): Resistance And Resilience To Coral Blea​ching: Implications For Coral Reef. Conservation And.


Ocean acidification and warming will lower coral reef resilience

Coral reefs are a globally threatened ecosystem due to a range of anthropogenic impacts. Increasing sea surface temperatures associated with global warming are a particular threat, as corals grow close to their upper thermal limit. When this limit is exceeded for a sufficient length of time during thermal stress events, corals lose their algal symbionts, resulting in coral bleaching and possible mortality. Coral reefs have experienced the most severe and extended global bleaching event to date from to

Globally increasing sea surface temperatures threaten coral reefs, both directly and through interactions with local stressors. More resilient reefs have a higher likelihood of returning to a coral-dominated state following a disturbance, such as a mass bleaching event. We calculated relative resilience scores for sites from an existing commonwealth-wide survey using eight resilience indicators—such as coral diversity, macroalgae percent cover, and herbivorous fish biomass—and assessed which indicators most drove resilience.

Coral Reef Resilience through Biodiversity

Caroline S. Ideally, global action to reduce emission of carbon dioxide and other greenhouse gases will be accompanied by local action. Effective management requires reduction of local stressors, identification of the characteristics of resilient reefs, and design of marine protected area networks that include potentially resilient reefs. Future research is needed on how stressors interact, on how climate change will affect corals, fish, and other reef organisms as well as overall biodiversity, and on basic ecological processes such as connectivity. Not all reef species and reefs will respond similarly to local and global stressors. Because reef-building corals and other organisms have some potential to adapt to environmental changes, coral reefs will likely persist in spite of the unprecedented combination of stressors currently affecting them. The biodiversity of coral reefs is the basis for their remarkable beauty and for the benefits they provide to society.

Grimsditch and Rodney V. Resistance , Free , Resilience , Oracl , Bleaching , Coral reef resilience and resistance to bleaching. Link to this page:. Moringa oleifera: a natural gift -A review. Khawaja Tahir Mahmood. Tahira Mugal.

Coral Reef Resilience through Biodiversity

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Ocean warming and acidification from increasing levels of atmospheric CO 2 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 CO 2 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 CO 2 projected from the IPCC's fossil-fuel intensive A1FI scenario during this century.

Coral Bleaching pp Cite as. At the heart of these complex ecosystems is an obligate symbiosis between the coral animal and single-celled photosynthetic algae. This mutually beneficial relationship provides the coral host with sufficient cheap energy to form the massive reef structures that create diverse habitats for many other organisms. Aside from their natural beauty, many millions of people depend on healthy coral reefs for their livelihoods. Human activities, through increased greenhouse gases, are now imposing a compounding threat to maintenance of these charismatic ecosystems -- mass coral bleaching events where the coral--algal symbiosis breaks down due to thermal stress. This book brings together current scientific information on coral bleaching at different space and time scales, from deep geological time to future projections and its consequences for the many associated coral reef organisms. Unable to display preview.

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Resilience Concepts and Their Application to Coral Reefs

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2 Response
  1. Fong G.

    Foreword. Vast changes in the seas are destroying the world's precious coral reefs at an coral bleaching and what is meant by resistance 8th_ann_rept.​pdf.

  2. Gail B.

    PDF | On Jan 1, , Gabriel D. Grimsditch and others published Coral Reef Resilience and Resistance to Bleaching | Find, read and cite all the research you​.

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