A study on the recovery of Tobago's coral reefs following the 2010 mass bleaching event.
TL;DR: The juvenile distribution and the response of individual species to the bleaching event support the notion that Caribbean reefs are becoming dominated by weedy non-framework building taxa which are more resilient to disturbances.
About: This article is published in Marine Pollution Bulletin.The article was published on 2016-03-15 and is currently open access. It has received 17 citations till now. The article focuses on the topics: Resilience of coral reefs & Environmental issues with coral reefs.
Summary (1 min read)
Jump to: [2.2.4 Statistical analysis ] – [2.3.1 Juvenile density and composition ] and [3.4 Discussion ]
2.2.4 Statistical analysis
- All juvenile and sediment data were tested for normality using the Shapiro-‐Wilk test and homogeneity of variance using graphical methods.
- Sedimentation rate data were found to be normally distributed, although juvenile data did not follow a normal destruction.
2.3.1 Juvenile density and composition
- Broadcasting juvenile taxa represented the minority (27.1 %) such as Siderastrea, Diploria, Montastrea and Colpophyllia.
- The small-‐sized brooding Scolymia spp., had moderate abundances of juveniles, mainly at Culloden sites.
3.4 Discussion
- Many species experienced a decline in colony abundance; percent cover and mean colony size by 2011, symptomatic of corals having suffered complete mortality and/or partial mortality.
- This study indicates that across Tobago’s different reef sites, the bleaching disturbance can lead to a dominance of smaller size coral colonies, which could negatively affect the reproductive output.
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TL;DR: How coral communities have changed in the northern sector of the Mexican Caribbean between 1985 and 2016 is evaluated, and the implications for the maintenance of physical reef functions in the back- and fore-reef zones are evaluated.
Abstract: Functional integrity on coral reefs is strongly dependent upon coral cover and coral carbonate production rate being sufficient to maintain three-dimensional reef structures. Increasing environmental and anthropogenic pressures in recent decades have reduced the cover of key reef-building species, producing a shift towards the relative dominance of more stress-tolerant taxa and leading to a reduction in the physical functional integrity. Understanding how changes in coral community composition influence the potential of reefs to maintain their physical reef functioning is a priority for their conservation and management. Here, we evaluate how coral communities have changed in the northern sector of the Mexican Caribbean between 1985 and 2016, and the implications for the maintenance of physical reef functions in the back- and fore-reef zones. We used the cover of coral species to explore changes in four morpho-functional groups, coral community composition, coral community calcification, the reef functional index and the reef carbonate budget. Over a period of 31 years, ecological homogenization occurred between the two reef zones mostly due to a reduction in the cover of framework-building branching (Acropora spp.) and foliose-digitiform (Porites porites and Agaricia tenuifolia) coral species in the back-reef, and a relative increase in non-framework species in the fore-reef (Agaricia agaricites and Porites astreoides). This resulted in a significant decrease in the physical functionality of the back-reef zone. At present, both reef zones have negative carbonate budgets, and thus limited capacity to sustain reef accretion, compromising the existing reef structure and its future capacity to provide habitat and environmental services.
40 citations
TL;DR: Investigating coral community composition across three different temperature and productivity regimes along a nearshore-offshore gradient on lagoonal reefs of the Belize Mesoamerican Barrier Reef System suggests that corals utilizing these two life history strategies may be better suited to cope with warmer oceans and thus may warrant protective status under climate change.
Abstract: Coral reefs are increasingly threatened by global and local anthropogenic stressors such as rising seawater temperature, nutrient enrichment, sedimentation, and overfishing. Although many studies have investigated the impacts of local and global stressors on coral reefs, we still do not fully understand how these stressors influence coral community structure, particularly across environmental gradients on a reef system. Here, we investigate coral community composition across three different temperature and productivity regimes along a nearshore-offshore gradient on lagoonal reefs of the Belize Mesoamerican Barrier Reef System (MBRS). A novel metric was developed using ultra-high-resolution satellite-derived estimates of sea surface temperatures (SST) to classify reefs as exposed to low (lowTP), moderate (modTP), or high (highTP) temperature parameters over 10 years (2003 to 2012). Coral species richness, abundance, diversity, density, and percent cover were lower at highTP sites relative to lowTP and modTP sites, but these coral community traits did not differ significantly between lowTP and modTP sites. Analysis of coral life history strategies revealed that highTP sites were dominated by hardy stress-tolerant and fast-growing weedy coral species, while lowTP and modTP sites consisted of competitive, generalist, weedy, and stress-tolerant coral species. Satellite-derived estimates of Chlorophyll-a (chl-a) were obtained for 13-years (2003–2015) as a proxy for primary production. Chl-a concentrations were highest at highTP sites, medial at modTP sites, and lowest at lowTP sites. Notably, thermal parameters correlated better with coral community traits between site types than productivity, suggesting that temperature (specifically number of days above the thermal bleaching threshold) played a greater role in defining coral community structure than productivity on the MBRS. Dominance of weedy and stress-tolerant genera at highTP sites suggests that corals utilizing these two life history strategies may be better suited to cope with warmer oceans and thus may warrant protective status under climate change.
26 citations
Cites background from "A study on the recovery of Tobago's..."
...in the Caribbean [25] and continued decline is expected as temperature stress increases [6, 26, 27], leading to a decline in reef complexity [28] Temperature Regimes Impact Coral Assemblages of Lagoonal Reefs...
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...A shift from dominance of competitive and generalist species to weedy and stress tolerant species occurred on Okinawan reefs following the 1998 El Niño bleaching event [29, 30] and an overall decline in coral cover and abundance currently occurring in the Caribbean has been coupled with an increase in abundance of weedy species [27, 31]....
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TL;DR: The results reinforce the notion that corals are sensitive to anthropogenic changes and reveal the scarcity of information on coral responses to pollution, tourism, overfishing and acidification, particularly in mesophotic ecosystems and in ecoregions outside the Indo-Pacific and Caribbean.
23 citations
TL;DR: It is postulate that the decline in skeletal extension rates for nearshore corals is driven primarily by the combined effects of long-term ocean warming and increasing exposure to higher levels of land-based anthropogenic stressors, with acute thermally induced bleaching events playing a lesser role.
Abstract: Anthropogenic global change and local stressors are impacting coral growth and survival worldwide, altering the structure and function of coral reef ecosystems. Here, we show that skeletal extension rates of nearshore colonies of two abundant and widespread Caribbean corals (Siderastrea siderea, Pseudodiploria strigosa) declined across the Belize Mesoamerican Barrier Reef System (MBRS) over the past century, while offshore coral conspecifics exhibited relatively stable extension rates over the same temporal interval. This decline has caused nearshore coral extension rates to converge with those of their historically slower growing offshore coral counterparts. For both species, individual mass coral bleaching events were correlated with low rates of skeletal extension within specific reef environments, but no single bleaching event was correlated with low skeletal extension rates across all reef environments. We postulate that the decline in skeletal extension rates for nearshore corals is driven primarily by the combined effects of long-term ocean warming and increasing exposure to higher levels of land-based anthropogenic stressors, with acute thermally induced bleaching events playing a lesser role. If these declining trends in skeletal growth of nearshore S. siderea and P. strigosa continue into the future, the structure and function of these critical nearshore MBRS coral reef systems is likely to be severely impaired.
21 citations
TL;DR: This article examined differences in coral and algal community compositions and their response to human disturbance and past heat stress, by analyzing 25 sites along a gradient of human disturbance in Majuro and Arno Atolls of the Republic of the Marshall Islands.
11 citations
References
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National Oceanic and Atmospheric Administration1, Silver Spring Networks2, James Cook University3, University of the Virgin Islands4, University of East Anglia5, Mote Marine Laboratory6, Simón Bolívar University7, University of the French West Indies and Guiana8, University of Puerto Rico at Mayagüez9, University of North Carolina at Wilmington10, University of Bedfordshire11, University of Havana12, University of Magdalena13, Griffith University14, University of Miami15, Spanish National Research Council16, Nova Southeastern University17, Smithsonian Tropical Research Institute18, Atlantic Oceanographic and Meteorological Laboratory19, University of Puerto Rico20, University of Exeter21, Bermuda Institute of Ocean Sciences22, National Autonomous University of Mexico23, Boston University24, University of Queensland25, The Nature Conservancy26, University of the West Indies27, Australian National University28, Marine Institute of Memorial University of Newfoundland29, Florida Institute of Technology30, University of California, Los Angeles31, University of Los Andes32, Central University of Venezuela33, Brown University34, Universiti Malaysia Terengganu35
TL;DR: Comparison of satellite data against field surveys demonstrated a significant predictive relationship between accumulated heat stress (measured using NOAA Coral Reef Watch's Degree Heating Weeks) and bleaching intensity.
Abstract: Background: The rising temperature of the world's oceans has become a major threat to coral reefs globally as the severity and frequency of mass coral bleaching and mortality events increase. In 2005, high ocean temperatures in the tropical Atlantic and Caribbean resulted in the most severe bleaching event ever recorded in the basin. Methodology/Principal Findings: Satellite-based tools provided warnings for coral reef managers and scientists, guiding both the iming and location of researchers' field observations as anomalously warm conditions developed and spread across the greater Caribbean region from June to October 2005. Field surveys of bleaching and mortality exceeded prior efforts in detail and extent, and provided a new standard for documenting the effects of bleaching and for testing nowcast and forecast products. Collaborators from 22 countries undertook the most comprehensive documentation of basin-scale bleaching to date and found that over 80% of corals bleached and over 40% died at many sites. The most severe bleaching coincided with waters nearest a western Atlantic warm pool that was centered off the northern end of the Lesser Antilles. Conclusions/Significance: Thermal stress during the 2005 event exceeded any observed from the Caribbean in the prior 20 years, and regionally-averaged temperatures were the warmest in over 150 years. Comparison of satellite data against field surveys demonstrated a significant predictive relationship between accumulated heat stress (measured using NOAA Coral Reef Watch's Degree Heating Weeks) and bleaching intensity. This severe, widespread bleaching and mortality will undoubtedly have long-term consequences for reef ecosystems and suggests a troubled future for tropical marine ecosystems under a warming climate.
755 citations
"A study on the recovery of Tobago's..." refers background in this paper
...Coral reefs in Tobago have experienced many of the same stressors asmany other Caribbean coral reefs like sedimentation, nutrient runoff, and the thermal stress events of 1998, 2005 and 2010 (Eakin et al., 2010; Lapointe et al., 2010;Mallela et al., 2010)....
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...Furthermore, ocean warming has led to episodes of mass coral bleaching and related coral mortality, which have contributed to the overall decline in coral cover (Eakin et al., 2010)....
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TL;DR: The demographic processes underlying a slow decline of corals on Jamaican reefs are examined, finding that rates of survival, population growth, and recruitment declined substantially over time for all species and the stable size structures became increasingly dominated by small colonies.
Abstract: Population decline, local extinction, and recovery are profoundly influenced by variation in demography and life-history traits. In open populations, changes in patterns of recruitment may also have a major influence on the size of local populations, particularly for short-lived organisms. We examine here the demographic processes underlying a slow decline of corals on Jamaican reefs, where coral cover has decreased by fourfold over a 16-yr period. We divided the study into three approximately equal intervals (1977–1982, 1982–1987, and 1987–1993) and constructed size-based transition matrices for each of three abundant species of corals (Montastrea annularis, Agaricia agaricites, and Leptoseris cucullata) that differ substantially in life history: Montastrea is slower-growing, longer-lived, and has lower rates of recruitment than the other two species. Rates of survival, population growth (λ), and recruitment declined substantially over time for all species and the stable size structures became increasingly dominated by small colonies. Elasticity and life table response analysis showed that changes in the persistence of large colonies had the biggest impact on population growth in all species. Simulations indicated that the levels of larval recruitment required to maintain populations at 1977 levels increased sharply over time, even as the actual recruitment rate declined. Recruitment failure was much more important to A. agaricites and L. cucullata than to M. annularis, which could survive long periods with minimal larval input. Recovery of these populations will require an increase in both survival and recruitment. The likelihood of the latter will depend on the scale of larval dispersal, and on the impact of large-scale mortality of adults on stock-recruitment relationships. Differences in connectivity and life histories of corals will determine future patterns of recovery or further decline.
540 citations
"A study on the recovery of Tobago's..." refers background in this paper
...Low numbers of Orbicella recruits have been well documented across Caribbean reefs (Hughes and Tanner, 2000; Irizarry-soto and Weil, 2009; Vermeij et al., 2011)....
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TL;DR: This report presents the reproductive patterns of eleven Caribbean coral species and attempts to explain the adaptive features and selective pressures that have led to the evolution of the four reproductive patterns described to date: (a) hermaphroditic broadcasters; (b) gonochoric broadcasters;
Abstract: The last decade has seen a resurgence of interest in the processes of sexual reproduction by scleractinian reef corals. Earlier investigations had focused fortuitously on brooding (planulating) species, which resulted in the general misconception that brooding was the main form of larval development of reef corals. More recent work on Indo-Pacific species has shown broadcast spawning and short annual reproductive periods to predominate. This report presents the reproductive patterns of eleven Caribbean coral species and attempts to explain the adaptive features and selective pressures that have led to the evolution of the four reproductive patterns described to date: (a) hermaphroditic broadcasters; (b) gonochoric broadcasters; (c) hermaphroditic broadcasters; (b) gonochoric brooders. Both (a) and (b) correlate with large colony size and short annual spawning periods; and (c) and (d) correlate with small colony size, multiple planulating cycles per year, and occupation of unstable habitats. Selection for outcrossing between long-lived individuals is proposed as the reason for gonochorism and for synchronous spawning of hermaphroditic broadcasters, and also for the large amount of sperm produced by hermaphroditic brooders. Selection for high rates of local recruitment is proposed as the force behind the evolution of brooding by species inhabiting unstable habitats and suffering high rates of adult mortality.
490 citations
"A study on the recovery of Tobago's..." refers result in this paper
..., 2008), andmay also be less fecund than larger colonies (Szmant, 1986), although not all experimental studies support this notion (GrahamandvanWoesik, 2013)....
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...Smaller colonies are more likely to succumb to stressors (Hughes, 1984; McClanahan et al., 2008), andmay also be less fecund than larger colonies (Szmant, 1986), although not all experimental studies support this notion (GrahamandvanWoesik, 2013)....
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TL;DR: It appears that bleached corals were able to survive the prolonged period without nutritional contribution from their zooxanthellae by consuming their own structural materials for maintenance, but then, did not have the resources necessary for reproduction.
Abstract: Colonies of Montastrea annularis from Carysfort Reef, Florida, that remained bleached seven months after the 1987 Caribbean bleaching event were studied to determine the long term effects of bleaching on coral physiology. Two types of bleached colonies were found: colonies with low numbers of zooxanthellae with normal pigment content, and a colony with high densities of lowpigment zooxanthellae. In both types, the zooxanthellae had an abnormal distribution within polyp tissues: highest densities were observed in basal endoderm and in mesenteries where zooxanthellae are not normally found. Bleached corals had 30% less tissue carbon and 44% less tissue nitrogen biomass per skeletal surface area, but the same tissue C:N ratio as other colonies that either did not bleach (normal) or that bleached and regained their zooxanthellae (recovered). Bleached corals were not able to complete gametogenesis during the reproductive season following the bleaching, while recovered corals were able to follow a normal gametogenic cycle. It appears that bleached corals were able to survive the prolonged period without nutritional contribution from their zooxanthellae by consuming their own structural materials for maintenance, but then, did not have the resources necessary for reproduction. The recovered corals, on the other hand, must have regained their zooxanthellae soon after the bleaching event since neither their tissue biomass nor their ability to reproduce were impaired.
470 citations
"A study on the recovery of Tobago's..." refers background or result in this paper
...Consequently, it is possible that the juvenile densities reported in this study were even lower than usual, due to the impact of the earlier 2005 bleaching event (Szmant and Gassman, 1990)....
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...Broadcasting taxa in the Caribbean are especially vulnerable as most bleaching events tend to occur during their yearly spawning period between August and October (Szmant and Gassman, 1990)....
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TL;DR: In this paper, loss on ignition (LOI) has been widely used as a method to estimate the amount of organic matter and carbonate mineral content (and indirectly of organic and inorganic carbon) in sediments.
Abstract: Since the publication of the paper of Dean (1974), loss on ignition (LOI) has been widely used as a method
to estimate the amount of organic matter and carbonate mineral content (and indirectly of organic and
inorganic carbon) in sediments. The relationships between LOI at 550 oC (LOI550) and organic carbon
(OC) content and between LOI at 950 oC (LOI950) and inorganic carbon (IC) content are currently accepted
as a standard. However, the comparison of 150 analyses of samples of diverse lithologies, collected
from a single core, reveals that these relationships are affected by sediment composition (presence of clays,
salts, and the variable content of organic carbon). This results in an incremental error on the estimation of
carbon content from LOI values that invalidates the use of LOI values as a quantitative method for
estimating carbon content. Conversely, the general trends of LOI550 and LOI950 show a good correlation
with carbon content (both organic and inorganic) allowing use of LOI as a qualitative test for carbon
content. Similarly, in our case, LOI at 105 oC (LOI105) is a good qualitative proxy for the trends in gypsum
content.
393 citations