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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TL;DR: Investigation of effects of eutrophication and sedimentation on juvenile abundance, juvenile mortality and community structure of scleractinian corals on fringing reefs on the west coast of Barbados, West Indies, in 1989 suggests that juvenile mortality rates of different species are similar on eutrophic reefs, and that differences in adult community structure between eUTrophic and less eutrophe reefs may be largely explained by interspecific differences in juvenile mortality becoming smaller.
Abstract: This study investigated effects of eutrophication and sedimentation on juvenile abundance, juvenile mortality and community structure of scleractinian corals on fringing reefs on the west coast of Barbados, West Indies, in 1989. Juvenile abundance was lower on cutrophic/high-sediment reefs than less eutrophic/lowsediment reefs, but juvenile size was larger on the former. The larger size could result from size-selective mortality against smaller juveniles on the eutrophic reefs, from lower recruitment to the eutrophic reefs, or from faster growth on the eutrophic reefs. Juvenile mortality was higher on the eutrophic reefs than the less eutrophic reefs and may result from increased smothering of corals by algae and sediment. Algae were more abundant on the eutrophic reefs, probably in response to elevated nutrients and/or because grazers (Diadema antillarum; herbivorous fish) were less common on eutrophic reefs. Juvenile community structure on all reefs was dominated by Type 1 corals (high recruitment, high natural mortality), but Type 2 corals (low recruitment, low natural mortality) became more common in adult communities on the less eutrophic reefs. This transition in community structure did not occur on the eutrophic reefs, adult community structure continuing to be dominated by Type 1 corals. The fact that the pattern of relative abundance of species in the juvenile community is maintained in the adult community on the eutrophic reefs suggests that juvenile mortality rates of different species are similar on eutrophic reefs, and hence that differences in adult community structure between eutrophic and less eutrophic reefs may be largely explained by interspecific differences in juvenile mortality becoming smaller on eutrophic reefs.
138 citations
"A study on the recovery of Tobago's..." refers background in this paper
...Third, we assess the rate and composition of sedimentation at each site, as high levels of sedimentation are known to affect the growth stages of coral lifecycle (Wittenberg and Hunte, 1992; Miller et al., 2000; Fabricius, 2005)....
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01 Jan 2002
TL;DR: It is suggested that bleaching has adverse and long-lasting effects on coral reproduction and that previously bleached colonies may be more susceptible to future stress.
Abstract: Extensive bleaching of corals occurred at Heron Island Reef during the 1998 mass bleaching event on the Great Barrier Reef, Australia. Two hundred coral colonies were labelled and sampled on the reef flat at Heron Island in March 1998 (when approximately 80% of corals growing in the intertidal reef flat were bleached). These included both bleached and unbleached colonies of many species. Bleached colonies of all sampled species had lower densities of symbiotic dinoflagellates and lower chlorophyll a concentrations per surface area of coral tissue than unbleached colonies. Samples of the colonies were decalcified and polyps dissected to determine fecundity. There were significantly fewer eggs present in the bleached than unbleached colonies in all sampled species. In many species, no eggs were present in the bleached colonies. Eggs that were present were also significantly smaller in the bleached than the unbleached colonies of the majority of species sampled. There were also significantly fewer polyps containing eggs and testes in the bleached than the unbleached colonies. The percentage of tissue made up by lipids in the bleached colonies was significantly lower than that of the unbleached colonies in some species. By July 1998, 23% of the sampled colonies had died and many of the previously bleached colonies had regained their colour, suggesting visually that they had recovered. However, previously bleached colonies in November .1998 still had fewer eggs and reproductive polyps than colonies that had been previously unbleached. In July of the following year, in the middle of the Australian winter, many of the corals that had. bleached the year before bleached again and more colonies had died. In contrast, none of the previously unbleached colonies bleached at this time. In November 1999, just prior to the spawning period, there were large areas of coral on the reef slope that were noticeably pale. These pale colonies were sampled along with adjacent normally pigmented corals and the pale colonies were almost entirely devoid of eggs. During the 1998 bleaching event approximately 80% of the reef slope colonies were bleached, so it is likely that these pale colonies were previously bleached colonies. These data suggest that bleaching has adverse and long-lasting effects on coral reproduction and that previously bleached colonies may be more susceptible to future stress.
136 citations
"A study on the recovery of Tobago's..." refers background in this paper
..., 2005), the bleaching of adult colonies is known to reduce the reproductive output of corals in the years following the thermal stress (Ritson-williams et al., 2009;Ward et al., 2000;Mallela and Crabbe, 2009)....
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...…tend not to suffer greatly from bleaching-induced mortality (Mumby, 1999; Shenkar et al., 2005), the bleaching of adult colonies is known to reduce the reproductive output of corals in the years following the thermal stress (Ritson-williams et al., 2009;Ward et al., 2000;Mallela and Crabbe, 2009)....
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...Bleaching, the paling of corals due to the loss of the symbiotic microalgae Symbiodinium, makes coral colonies vulnerable to complete or partial mortality and susceptible to infectious diseases (Ward et al., 2000)....
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TL;DR: In this paper, the authors investigated the differences in rates of coral recruitment and/or coral survivorship in Biscayne National Park (BNP) by measuring: (1) juvenile and adult coral densities, and (2) size-frequency distributions of smaller coral size classes.
Abstract: Coral communities of Biscayne National Park (BNP) on offshore linear bank-barrier reefs are depauperate of reef corals and have little topographic relief, while those on lagoonal patch reefs have greater coral cover and species richness despite presumably more stressful environmental regimes closer to shore. We hypothesized that differences in rates of coral recruitment and/or of coral survivorship were responsible for these differences in community structure. These processes were investigated by measuring: (1) juvenile and adult coral densities, and (2) size-frequency distributions of smaller coral size classes, at three pairs of bank- and patch-reefs distributed along the north-south range of coral reefs within the Park. In addition, small quadrats (0.25 m2) were censused for colonies <2 cm in size on three reefs (one offshore and one patch reef in the central park, and one intermediate reef at the southern end), and re-surveyed after 1 year. Density and size frequency data confirmed that large coral colonies were virtually absent from the offshore reefs, but showed that juvenile corals were common and had similar densities to those of adjacent bank and patch reefs. Large coral colonies were more common on inshore patch reefs, suggesting lower survivorship (higher mortality) of small and intermediate sized colonies on the offshore reefs. The more limited small-quadrat data showed similar survivorship rates and initial and final juvenile densities at all three sites, but a higher influx of new recruits to the patch reef site during the single annual study period. We consider the size-frequency data to be a better indicator of juvenile coral dynamics, since it is a more time-integrated measurement and was replicated at more sites. We conclude that lack of recruitment does not appear to explain the impoverished coral communities on offshore bank reefs in BNP. Instead, higher juvenile coral mortality appears to be a dominant factor structuring these communities.
134 citations
"A study on the recovery of Tobago's..." refers background or methods in this paper
...Third, we assess the rate and composition of sedimentation at each site, as high levels of sedimentation are known to affect the growth stages of coral lifecycle (Wittenberg and Hunte, 1992; Miller et al., 2000; Fabricius, 2005)....
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...A low juvenile population dominated by brooding taxa with weedy life history strategies is common across Caribbean reefs (Miller et al., 2000; Moulding, 2005; Irizarry-soto and Weil, 2009; Manfrino et al., 2013)....
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...Differences in juvenile densities between sites were tested employing Kruskal– Wallis test by Dunn's post-hoc pairwise test (using packagesmultcomp 1.2.17 and coin 1.0-23) (Miller et al., 2000)....
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...This distinction was made as small-sized corals tend to be sexually mature adults once larger than 2 cm (Chiappone and Sullivan, 1996;Miller et al., 2000; Irizarry-soto and Weil, 2009)....
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130 citations
"A study on the recovery of Tobago's..." refers methods in this paper
...Particle size analysis of sediments per trap set was conducted using the wet sieving method (Syvitski, 2007), using ~0....
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...Particle size analysis of sediments per trap set was conducted using the wet sieving method (Syvitski, 2007), using ~0.5 g from each composite sediment sample separated into five fractions according to the Wentworth size class system....
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TL;DR: Despite strong recovery of several dominant Acropora species, five formerly common species from this area were not observed suggesting local extinction, and conservation of these patch reefs is warranted given the predicted increase in bleaching events, and the role that these communities may play in regional recovery.
Abstract: Elevated sea surface temperatures in the late 1990s were associated with widespread coral mortality in the Arabian Gulf, particularly in Acropora dominated areas. This study investigates the composition, condition, and recruitment patterns of coral communities in Saih Al-Shaib, Dubai, United Arab Emirates, a decade after mass bleaching. Five statistically distinct communities were identified by cluster analysis, with grouping optimized from 17 significant indicator species. Overall, 25 species of scleractinian coral were observed, representing 35 ± 1.6% coral cover. Densities of recruits were low (0.8 ± 0.2 m−2), and composition generally reflected that of the surrounding adult community. Ten years after mass mortality, Acropora dominated assemblages were observed in three of the six sites examined and coral cover (41.9 ± 2.5%) was double post-bleaching cover. One shallow near-shore site appears to have had recovery of Acropora reset by a further bleaching event in 2002. However, the prevalence of young Acropora colonies here indicates that recovery may recur in several years. One area formerly dominated by Acropora is now dominated by faviids and poritids, with adult and juvenile composition suggesting this dominance shift is likely to persist. Porites lutea and Porites harrisoni dominated communities were negligibly impacted by the bleaching events, and the limited change in coral cover and composition in intervening years likely results from slow growth and low recruitment. Despite strong recovery of several dominant Acropora species, five formerly common species from this area were not observed suggesting local extinction. Dubai coral communities exhibit both resistance and resilience to elevated sea temperatures. The conservation of these patch reefs is warranted given the predicted increase in bleaching events, and the role that these communities may play in regional recovery.
115 citations
"A study on the recovery of Tobago's..." refers background in this paper
...Other environmental disturbances such as terrestrial runoff or fishing pressure may further undermine the recovery process (Burt et al., 2008)....
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