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A study on the recovery of Tobago's coral reefs following the 2010 mass bleaching event
... The coral communities that surround Tobago are distinguished from other Caribbean coral reefs by thriving in waters characterized by high turbidity (Muller-Karger et al., 1988), as well as elevated nutrients and reduced salinity (Hu et al., 2004). Owing to large differences in the hydro-geomorphology between the east and west sides of the island, due to water movement (Chollett et al., 2012), siltation (Buglass et al., 2016;Mallela et al., 2010), elevation and geology (Snoke et al., 2001), one can also presume that reef habitats may also differ between hydro-geomorphic settings. Elucidating this difference may to help focus important conservation considerations and strategies at the scales which may differ between hydro-geomorphic settings. ...
... Firstly, CTB (crustose coralline algae, algal turf and bare substrate) is a major contributor to benthic cover. This generalized condition is consistent with the historical record for Tobago from the 1980s to present (Alemu I and Clement, 2014;Buglass et al., 2016;Laydoo, 1985a,b;Mallela et al., 2010), which may be the result of storm damages, coastal dredging, destructive fishing or other suppressed ecological processes experienced in past decades (Bruno et al., 2014). Secondly, while some reefs experience high levels of hard coral cover (>30%), others have very low hard coral cover (<5%), but, macroalgal cover remained low and a high abundance of CTB was observed instead. ...
... That is, mean hard coral cover did not change significantly between the two survey periods for corresponding sites (2007: 15.84% and 2016: 14.13%), despite significant post-bleaching mortality in the years following the 2010 mass bleaching event. However, species-specific losses in coral populations following successive mass bleaching events may be driving site-specific shifts toward increase in small low-relief corals (Buglass et al., 2016), characterised by lower rates of carbonate production and reef growth (Perry et al., 2015). These changes become more obvious when we consider the large-scale shift on Caribbean reefs over the last 40 years (Jackson et al., 2014), from large branching corals and subsequent dominance of massive growth forms (Gardner et al., 2003;Pandolfi and Jackson, 2007). ...
We detail the spatial variability of coral reefs benthic composition in 2016 and use long-term monitoring data to examine the influence of mass coral bleaching on the spatio-temporal dynamics of turbid-water coral reef communities in Tobago, across distinct hydro-geomorphic settings (sheltered vs. wave exposed). Our results show distinct spatial variability in major benthic components. Mean hard coral cover (14.83 ± 0.85) ranged from 2% to 37% with few sites exceeding 20%. Macroalgae cover was low (6.04 ± 0.61) with most sites experiencing <8% cover. Differences in benthic cover between hydro-geomorphic setting was driven by contrasts in proportions of sponge, macroalgae and Orbicella faveolata. Spatio-temporal analyses using linear mixed modelling suggests overall relative stability of hard coral and decline in macroalgae against the 2007 baseline. The important interaction between time and location was only identified for soft coral and CTB (crustose coralline algae, turf algae and bare substrate). Overall, hard coral cover appears to have declined at some sites and macroalgae to have increased at other, but there is no evidence of widespread regime shift. While hydro-geomorphic setting produced significant but weak effects (R>0.3) on spatial and temporal patterns, our findings suggest that sheltered hydro-geomorphic settings are less predisposed to macroalgal overgrowth. In the era of climate change, targeted management should focus on strategies that mitigate macroalgal overgrowth, promote hard coral stability (or resilience) while preventing further loss.
... Bleaching events can have catastrophic impacts on the coral community depending on the extent and severity of the event, although impacts vary greatly among taxa (Darling et al. 2013). For taxa that survive bleaching, colony size structures often become truncated due to high mortality in large colonies (McClanahan et al. 2008;Buglass et al. 2016;Hughes et al. 2019). This loss of largesized adult brood-stock can reduce fecundity, dampen larval recruitment, and impair community reassembly to the same pre-disturbance assemblage (Buglass et al. 2016;Hughes et al. 2019). ...
... For taxa that survive bleaching, colony size structures often become truncated due to high mortality in large colonies (McClanahan et al. 2008;Buglass et al. 2016;Hughes et al. 2019). This loss of largesized adult brood-stock can reduce fecundity, dampen larval recruitment, and impair community reassembly to the same pre-disturbance assemblage (Buglass et al. 2016;Hughes et al. 2019). Hence, tracking changes in the relative abundance and sizes of colonies post-disturbance can offer meaningful insights into the trajectory of coral community recovery (Johns et al. 2014). ...
Severe thermal stress events occurring on the backdrop of globally warming oceans can result in mass coral mortality. Tracking the ability of a reef community to return to pre-disturbance composition is important to inform the likelihood of recovery or the need for active management to conserve these ecosystems. Here, we quantified annual, temporal changes in the benthic communities for the three years following mass coral mortality at Jarvis Island—an uninhabited island in the Pacific Remote Islands Marine National Monument. While Jarvis experienced catastrophic coral mortality in 2015 due to heat stress resulting from the 2015/16 El Niño, significant annual shifts were documented in the benthic community in the three years post-disturbance. Macroalgal and turf dominance of the benthos was temporary—likely reflecting the high biomass of herbivorous reef fishes post-bleaching—giving way to calcifiers such as crustose coralline algae and Halimeda, which may facilitate rather than impede coral recovery. By 2018, indications of recovery were detectable in the coral community itself as juvenile densities increased and stress-tolerant genera, such as Pavona, exceeded their pre-disturbance densities. However, densities of Montipora and Pocillopora remain low, suggesting recovery will be slow for these formerly dominant taxa. Collectively, the assemblage and taxon-specific shifts observed in the benthic and coral community support cautious optimism for the potential recovery of Jarvis Island’s coral reefs to their pre-disturbance state. Continued monitoring will be essential to assess whether reassembly is achieved before further climate-related disturbance events affect this reef system.
... Corresponding with a significant drop in coral cover, other benthic community types such as macroalgae have showed an increase in dominance in the following years (IMA, 2016). Since the 2010 bleaching event, hard coral cover appears to have remained stable or shown minor declines at some survey sites, but no recovery (Buglass et al 2016, Amoroso, 2017. (Beijbom et al., 2015). ...
... However, the results highlighted that there has been little to no recovery of hard coral cover over the last ten years. Sites need to continue to be assessed individually to determine why hard coral cover recovery is being inhibitedbe it competition with algae or limited coral recruitment, or nutrient pollution (Buglass et al 2016). Restoration methods can then focus on improving the environmental conditions to support hard coral recruitment and survival. ...
In 2019, ten coral reefs sites in Tobago were surveyed as part of the Baseline Assessment of Tobago’s Coral Reefs Project carried out by the Institute of Marine Affairs (IMA) and compared to the IMA’s long-term coral reef monitoring dataset (2010 - 2018). The aim of long-term monitoring is to provide data to observe spatial and temporal trends in coral reef composition and to advise on specific efforts, such as marine spatial planning and ecosystem based management to conserve marine biodiversity. The ten sites were surveyed and analysed for spatial trends in benthic cover, as well as assessed for temporal changes in the benthic composition. Collected images were analysed using a deep-learning framework, which allowed annotators to carry out coral point count analyses guided by machines trained to identify benthic categories using manually analysed datasets. While turf algae dominated all monitoring sites, some sites continued to show prevalence in hard coral cover including Angel Reef and Buccoo Outer Reef. Octocoral communities were more prominent at Buccoo West Reef, Culloden East and Castara, and sponge communities were prominent on Blackjack Hole and Flying Reef. There were significant spatial differences among reef sites with Blackjack Hole being the most dissimilar reef community with regard to benthic composition. Conversely, neighbouring Caribbean reef sites – Castara, Culloden East and West, and Plymouth reefs were the most similar with regard to community composition. Long-term trends show a decline in hard coral cover across sites because of the 2010 coral-bleaching event, with no significant change, further degradation or recovery in the following nine years.
... Brooding corals such as P. astreoides and Agaricia sp. are often the most abundant following disturbance; they were found to compose 30-80% of juveniles in Tobago after a large-scale bleaching event in 2010 [74]. Porites astreoides is often able to persist in these environments, and therefore, its abundance is frequently used to differentiate high stress sites with those that have more optimal conditions [75]. ...
Coral reefs are the most diverse habitat per unit area in the world’s oceans, supporting an estimated 1–3 million species in only 0.2% of its area. These ecosystems have suffered severe declines since the 1970s, largely as a result of climate change, ocean acidification, pollution, disease, and overfishing. Porites astreoides is a shallow species that is able to thrive in a variety of environmental conditions and has been a clear ‘winner’ on Atlantic reefs in the last decades. This, coupled with its ease of identification and wide distribution, has caused P. astreoides to become a focal species in many scientific studies. Given the current and increasing significance of P. astreoides, this review sought to (i) identify the key life history traits that allowed this species to thrive under stressful conditions; (ii) compile aspects of its biology and ecology to understand its future contribution to Atlantic reefs, and (iii) identify knowledge gaps. To date, no comprehensive overview of the literature exists for P. astreoides. All articles available on Google Scholar up to the time of submission containing the terms ‘Mustard Hill Coral’, ‘Porites astreoides’, or ‘P. astreoides’ were examined for potential inclusion in this review. Papers were assessed based on whether they captured the most influential or widespread theories, represented an important trend in the research, or contained novel findings relevant to the understanding of this species. This review provides a scholarly resource and wide-ranging synthesis of P. astreoides on Atlantic reefs of today and the future.
... Perhaps, P. americana was an earlier colonizer than T. coccinea. The three colonies of P. strigosa were 41-70 mm in diameter, which is small, considering that colonies ≤50 mm are not always documented in population studies (Buglass et al., 2016) and that the maximum size of this species exceeds 100 cm (Camacho-Vite et al., 2022). The other two species cannot reach such large sizes. ...
Little is known about early coral settlement on shipwrecks with regard to their species and size compositions. Hurricanes in the Caribbean have a long history of sinking ships but a link with new coral settlement is understudied. In 2017, Hurricane Irma caused the sinking of over 300 vessels in the coastal waters of Saint Martin, eastern Caribbean. In 2021, coral settlement was studied on one of them, which included two native, one non-native, and two cryptogenic species. The corals were smaller than 8 cm in diameter. The invasive Tubastraea coccinea was the most abundant scleractinian and was predominantly represented by juveniles. A cryptogenic species, Stragulum bicolor, new for the Caribbean, was the most common octocoral. Because they can be harmful to the environment, shipwrecks should be monitored frequently for the occurrence of non-native species, especially when they are only a few years old.
... The abundance of MHCs has been found to be positively correlated with higher abundances of these urchins, but their grazing is more damaging to young recruits than that of herbivorous fishes . Brooding corals such as the MHC and Agaricia sp. are often the most abundant following disturbance events; they were found to compose 30-80% of juveniles in Tobago after a large scale bleaching event in 2010 (Buglass et al. 2016). The establishment of MPAs increases the success and abundance of MHC recruits, with this species, Agaricia sp., and Montastrea sp. ...
The objectives of this research were: 1) create a benthic map of the Sandy Island-Oyster Bed MPA (SIOBMPA); and 2) study populations of Porites astreoides (pa) in the Caribbean/Grenada. A benthic map was created using 127 truthing points and eCognition software. Mapped habitats in the SIOBMPA were: dense seagrass (25.74%); sand (23.32%); coral framework (5.88%); and others. Compiled survey data in the Caribbean revealed regional success of pa. Temporal changes in size, abundance and coverage and the relationship between benthic components, MPAs, and river outflows on pa coverage in Grenada was assessed. The abundance of pa fell (p<0.05), and colony size/coverage increased (p<0.05). Coverage of pa was negatively correlated with MPA status, rubble, sand, macroalgae, gorgonians, and weedy corals and positively with pavement, coralline algae, and stress-tolerant/generalist corals. This study for the first time has documented the distribution of benthic habitats in the SIOBMPA and population dynamics of pa.
... Although recovery of coral abundance, diversity and reef ecological functioning is conceivable in certain cases (Buglass et al., 2016;Cunning et al., 2016;Gilmour et al., 2013;Pisapia et al., 2016), successful recruitment of coral larvae from less impacted reef areas is key (Holbrook et al., 2018). However, larval dispersal capacities of corals at and surrounding affected sites are often unknown or not prioritized by resource managers during conservation planning (Balbar & Metaxas, 2019;McCook et al., 2009). ...
Information about the distribution of alleles among marine populations is critical for determining patterns of genetic connectivity that are essential in modern conservation planning. To estimate population connectivity in Singapore’s urbanised equatorial reef system, we analysed single nucleotide polymorphisms (SNPs) from two species of reef‐building corals with distinct life histories. For Porites sp., a broadcast‐spawning coral, we found cryptic lineages which were differentially distributed at inshore and central‐offshore sites that could be attributed to contemporary surface current regimes. Near panmixia was observed for Pocillopora acuta with differentiation of colonies at the farthest site from mainland Singapore, a possible consequence of the brooding nature and relatively long pelagic larval duration of the species. Furthermore, analysis of recent gene flow showed that 60‐80% of colonies in each population were non‐migrants, underscoring self‐recruitment as an important demographic process in this reef system. Apart from helping to enhance the management of Singapore’s coral reef ecosystems, findings here pave the way for better understanding of the evolution of marine populations in Southeast Asia.
... Donner et al., 2007;Eakin et al., 2010;LaJeunesse, Smith, Finney, & Oxenford, 2009);(Alemu & Clement, 2014Buglass, Donner, & Alemu, 2016;Kemp, Hernandez-Pech, Iglesias-Prieto, Fitt, & Schmidt, 2014); and 2014-2016(Eakin et al., 2016). Years that directly preceded or followed a reported bleaching event, years containing bleaching events (DHW ≥ 4), and other years that had high number of cores exhibiting low extension were noted and included as explanatory variables in least squares regression, thereby identifying which years contained significantly higher fractions of cores exhibiting low extension within each reef environment. ...
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.
... The comparison of 2014 pre-thermal stress benthic cover data and our 2016 data suggest that any bleaching which may have occurred in 2014 had a limited effect on total coral cover. While bleaching did not appear to alter overall coral cover, it is possible that past disturbances such as bleaching or disease outbreaks may have caused some fragmentation, which would cause the sizefrequency distributions to shift towards smaller corals (Buglass et al., 2014). Unfortunately, this could not be tested because the earlier data did not include size-frequency measurements. ...
Climate change and human disturbance threatens coral reefs across the Pacific, yet there is little consensus on what characterizes a "healthy" reef. Benthic cover, particularly low coral cover and high macroalgae cover, are often used as an indicator of reef degradation, despite uncertainty about the typical algal community compositions associated with either near-pristine or damaged reefs. In this study, we examine differences in coral and algal community compositions and their response to human disturbance and past heat stress, by analysing 25 sites along a gradient of human disturbance in Majuro and Arno Atolls of the Republic of the Marshall Islands. Our results show that total macroalgae cover indicators of reef degradation may mask the influence of local human disturbance, with different taxa responding to disturbance differently. Identifying macroalgae to a lower taxonomic level (e.g. the genus level) is critical for a more accurate measure of Pacific coral reef health.
... Depending on the severity, coral bleaching phenomena result in depressed growth and increased mass mortality of coral reef areas [8,10] and permanent damage [11,15,16]. Severe coral bleaching phenomena often lead to significant reductions in coral cover, abundance of the majority of dominant coral species and changes in coral community composition [42]. When corals are exposed to temperatures one or two degrees Celsius higher than average mean surface water temperatures can cause substantial mortality when linked with increased pressure from the solar intensity. ...
Satellite monitoring thermal stress on the coral reef is of fundamental importance to understand coral bleaching phenomenon. The new phenomenon of global coral bleaching events is caused highly visual indicator of ocean warming. The rise in global ocean warming generated by climate change and satellite provides an important role in the detection of reef scale thermal stress and changing significant shifts in ocean temperature that cause coral bleaching phenomenon. Surveys conducted at four Island in Western Indonesia region (Bintan Island, Batam Island, Lingga Island and Natuna Island). Satellite data from Aqua and Terra MODIS were used to evaluate the relative importance of bleaching pattern from 2015 to 2016 during the incidence of coral bleaching. Ncdf4 R-analysis and Ocean Data View (ODV) were used to comparison analysis SST anomaly dataset from Aqua and Terra MODIS. To assess the impact of bleaching phenomena on coral communities using photo quadrats with 50 meters transect line at 1 m intervals in sixty-three sampling site (14 sites in Bintan Island, 11 sites in Lingga Island, 19 sites in Natuna Island and 19 Site in Batam Island). Each photograph was analysed in Coral Point Count program with Excel extensions (CPCe). The raw point data from all photographs on a transect line were combined to calculate the percent cover of bleaching phenomena. The percent bleaching incidence during 2015 - 2016 event resulted in positive temperature anomalies above the warmest monthly climatology value of currently increasing Sea Surface Temperature (SST) at 1°C - 2°C on bleaching phenomenon site. Thermal satellite data from Aqua and Terra Modis showed significant related increasing anomaly SST from 2015 and 2016 where coral bleaching occur 34.57% in Bintan Island, 6.56% in Lingga Island, 0,95% in Natuna Island and 10,07% in Batam island, respectively.
... Tobago is surrounded by ~30km2 of coral reef, but here we focused on coral reef habitats located at 21 sites in the study area (Figure 2.1 Goreau 1967;Kenny 1976;Laydoo 1985;Laydoo and Heileman 1987;Laydoo 1991;IMA 1996;O'Farrell and Day 2006;Lapointe et al. 2010;Mallela, Parkinson, and Day 2010;Alemu I 2016), few have attempted to integrate findings into coastal and marine ecosystem management decision support systems. ...
Coral reefs are important to the socio-economic and cultural development of Tobago, where they contribute significantly to the gross domestic product and support livelihoods. However, the increasing demand for multiple ecosystem services, a sectorial approach to coral reef management and poor governance, characterised by short term planning has engendered a number of conflicts and trade-offs among stakeholders and services. In order to optimise the long-term delivery of multiple ecosystem services, a holistic approach to coral reef management is recommended such that considers not only nature’s benefits but the flow of ecosystem services from supply to benefit areas and the influence of ecological stressors on ecosystem services production. However given limited management resources and capacity, innovative ways must be found to adapt existing methods to achieve ecosystem services goals, especially among developing island nations. Using the island of Tobago as a case study, we quantified and mapped the production and interactions (trade-offs, synergies and bundling) of the supply and benefits sides of shoreline protection, fisheries production and recreational opportunity across southwest Tobago (21 sites). We also assessed the impact of ecological pressures on ecosystem service production. By linking ecological integrity and ecological pressures to ecosystem services we demonstrated i) a strong positive service-integrity relationships, ii) a strong negative service-pressure relationships, iii) the positive influence of human interventions on ecosystem services and iv) a number of utility thresholds that might inform trade-off decision making. Further, we note that for some ecosystem services, the production even among degraded reefs can produce equivalent or near-equivalent levels of benefit and support livelihood opportunity. Finally, by linking ecosystem services to the economy, we were able to demonstrate a preference of recreational users for improved coral reef management expressed as willingness-to-pay.
... As a consequence, most disease events are identified during or after bleaching (Cantin and Lough, 2014), although they may partially or fully recover from bleaching events (Depczynski et al., 2013). Examples of mass mortality associated with bleaching have been documented, reducing coral cover and modifying the structure and function of the entire benthic community (Buglass et al., 2015;Burt et al., 2011;Guest et al., 2016;Marimuthu et al., 2013;Swain et al., 2016;Thompson and Dolman, 2010;Wild et al., 2011). Actually, the consequences of bleaching may be classified into two broad categories: immediate and longer term effects (Baker et al., 2008). ...
Coral reefs have long inspired marine ecologists and conservationists around the world due to their ecological and socioeconomic importance. Much knowledge on the anthropogenic impacts on coral species has been accumulated, but relevant research gaps on coral ecology remain underappreciated in human-modified seascapes. In this review we assessed 110 studies on coral responses to five major human disturbances- acidification, climate change, overfishing, pollution and non-regulated tourism -to identify geographic and theoretical gaps in coral ecology and help to guide further researches on the topic. We searched for papers in Web of Science published from 2000 to 2016 and classified them according to the ocean, ecoregion, human threat, level of biological organization, study approach, method of data collection, depth of data collected, and type of coral response. Most studies were carried out in the Indo-Pacific and Caribbean (36.3 and 31.9%, respectively) and used observational approach (60%) with scuba diving (36.3%) to assess the impact of ocean warming (55.4%) on coral communities (58.2%). Only 37 of the 141 global ecoregions that contain coral reefs were studied. All studies were restricted to shallow waters (0.5-27 m depth) and reported negative responses of corals to human disturbance. Our results reinforce the notion that corals are sensitive to anthropogenic changes. They reveal the scarcity of information on coral responses to pollution, tourism, overfishing and acidification, particularly in mesophotic ecosystems (>30 m depth) and in ecoregions outside the Indo-Pacific and Caribbean. Experimental studies at the individual and population levels should be also encouraged.
... The IPCC Fifth Assessment Report (Field et al. 2014) and several regional studies document climate change impacts on coasts, marine biophysical systems (Forster et al. 2014), terrestrial systems, water resources (Boger et al. 2014), human settlements, tourism, agriculture, health, sea levels (which affects ground water quality), coastal fisheries, shoreline erosion, and the destruction of coastal properties and infrastructure (Reguero et al. 2015). Climate change is tied to ocean acidification, coral bleaching and drought (which negatively affects biodiversity) (Oxenford and Valles 2016;Buglass et al. 2016;Gomar 2014), and an increase in vector climateinduced diseases such as Zika and dengue (Field et al. 2014). In recent times, climate change has been attributed to extreme drought in Jamaica, flooding in Guyana and Belize in 2010 (most of Guyana's built areas are below sea level), and an increase in the incidence of dengue and Zika in Trinidad and Tobago. ...
... Weedy and stress tolerant corals have been shown to be more resilient than competitive and generalist species [22,24], and are hypothesized to dominate warmer and more impacted reefs (e.g., reefs closer to the shore). 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]. Interestingly, fossil assemblages from excavated pits on reefs in Panama reveal that mortality and changes in reef communities caused by anthropogenic impact (such as land clearing and overfishing) predate mass bleaching events, indicating that other sub-lethal stressors can impact coral community structure [32][33][34]. ...
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.
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 (low TP ), moderate (mod TP ), or high (high TP ) temperature parameters over 10 years (2003 to 2012). Coral species richness, abundance, diversity, density, and percent cover were lower at high TP sites relative to low TP and mod TP sites, but these coral community traits did not differ significantly between low TP and mod TP sites. Analysis of coral life history strategies revealed that high TP sites were dominated by hardy stress tolerant and fast-growing weedy coral species, while low TP and mod TP 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 high TP sites, medial at mod TP sites, and lowest at low TP 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 high TP 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.
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.
Juvenile coral survivorship (the proportion of juvenile colonies surviving from t 1 to t 2) was assessed by counting, photographing and mapping all juveniles found in 2003 within random permanent 0.25m 2 quadrats at four depth intervals at each of four inshore and mid-shelf reefs and at deeper habitats (>18m) in two shelf-edge reefs (N=96/reef) in La Parguera, southwest coast of Puerto Rico. Quadrats were resurveyed and photographed in 2005 to evaluate surviving juveniles, mortality and new recruits. Total number of juveniles dropped from 718 in 31 scleractinian species in 2003 to 396 in 28 species in 2005, an average juvenile survivorship of 54.8%. Mean juvenile density decreased from 1.2 (± 0.06) colonies/0.25 m 2 in 2003 to 0.7 (± 0.05) colonies/0.25 m 2 in 2005. Juvenile coral composition, relative abundances, survivorship and recruitment varied significantly across depth intervals within reefs and among reefs. Some species with high relative abundances in 2003 showed high survivorship in 2005 [Siderastrea siderea (28.3% and 65% respectively), Porites astreoides (15.1% and 55.6%), and Diploria strigosa (7.5% and 45.2%)]. Other taxa had relative low abundances but high survivorship [Montastraea cavernosa (4.6% and 66.7%) and Stephanocoenia intersepta (4.6% and 48.3%)]. Survivorship was significantly higher in deeper habitats at three of the four fringing reefs. Furthermore, the semi-exposed inshore, highly sedimented reefs, showed higher juvenile survivorship than the mid-shelf and shelf-edge reefs. There was no clear relationship between survivorship and reproductive mode (brooding vs. broadcast spawning) of sexual reproduction. Overall, only 78 new recruits were found in 2005.
Rising sea temperatures are likely to increase the frequency of disease outbreaks affecting reef-building corals through impacts on coral hosts and pathogens. We present and compare climate model projections of temperature conditions that will increase coral susceptibility to disease, pathogen abundance and pathogen virulence. Both moderate (RCP 4.5) and fossil fuel aggressive (RCP 8.5) emissions scenarios are examined. We also compare projections for the onset of disease-conducive conditions and severe annual coral bleaching, and produce a disease risk summary that combines climate stress with stress caused by local human activities. There is great spatial variation in the projections, both among and within the major ocean basins, in conditions favouring disease development. Our results indicate that disease is as likely to cause coral mortality as bleaching in the coming decades. These projections identify priority locations to reduce stress caused by local human activities and test management interventions to reduce disease impacts.
Rising sea temperatures are likely to increase the frequency of disease outbreaks affecting reef-building corals through impacts on coral hosts and pathogens. We present and compare climate model projections of temperature conditions that will increase coral susceptibility to disease, pathogen abundance and pathogen virulence. Both moderate (RCP 4.5) and fossil fuel aggressive (RCP 8.5) emissions scenarios are examined. We also compare projections for the onset of disease-conducive conditions and severe annual coral bleaching, and produce a disease risk summary that combines climate stress with stress caused by local human activities. There is great spatial variation in the projections, both among and within the major ocean basins, in conditions favouring disease development. Our results indicate that disease is as likely to cause coral mortality as bleaching in the coming decades. These projections identify priority locations to reduce stress caused by local human activities and test management interventions to reduce disease impacts.
Tanjung Rhu, Pulau Langkawi, which is located in the northwest of Peninsular Malaysia. The objective of this study was to measure and compare the sediment fallout rates of Teluk Dedap in Tanjung Rhu with its control site in Teluk Datai during the wet and dry seasons to shed light on the sedimentation problem faced by the coral reefs of north Pulau Langkawi. Sediment fallouts were collected from the spring tidal periods of both the wet and dry seasons. Results showed that sediment fallout rates in Tanjung Rhu were 1,403.48 ± 125.60 g/m 2 /day (dry season) and 6,550.77 ± 641.43 g/m 2 /day (wet season). In Teluk Datai the sediment fallout rates were 1,532.99 ± 201.81 g/m 2 /day (dry season) and 12,446.45 ± 237.81 g/m2/day (wet season). Sediment fallout rate is typically lower during the dry season compared to the wet season, and it is lower on the reef flats than the reef slopes. Paired sample t-tests revealed that there were significant differences in the sediment fallout on the reef flats and reef slopes. Sediment fallout was significantly higher on the reef flat than the reef slopes for both sampling locations during both the dry and wet seasons. However, based on a single-factor ANOVA (p = 0.05), no significant difference was observed between the overall sediment fallout and fallout rates between the two sampling locations during the dry and wet seasons. Microscopic analysis was also performed to examine the possible composition of the analysed sediment fractions. Results showed that the main components of the coarser sediment fractions were biogenic materials and lithified sediments, while for the finer sediment fractions, the main components were feldspar and siliceous and quartz materials.
Presents the results of a world calibration experiment for particle size analyzers, together with overviews on automated instruments and the theory of particle size characterization. The 24 chapters that comprise the text are organized into five parts. The three introductory chapters (part I) discuss the basic principles behind particle size analysis. The ten chapters of part II present the theory, methods and calibration of the principal methods employed in particle size analyzers. Part III covers in situ methods (two chapters) whilst part IV (four chapters) discusses the way in which particle size data are interpreted and manipulated. Finally, part V provides examples of how grain size data can be applied in the earth sciences. -after Editor
Ocean temperatures are increasing globally and the Caribbean is no exception. An extreme ocean warming event in 2010 placed Tobago's coral reefs under severe stress resulting in widespread coral bleaching and threatening the livelihoods that rely on them. The bleaching response of four reef building taxa was monitored over a six month period across three major reefs systems in Tobago. By identifying taxa resilient to bleaching we propose to assist local coral reef managers in the decision making process to cope with mass bleaching events. The bleaching signal (length of exposure to high ocean temperatures) varied widely between the Atlantic and Caribbean reefs, but regardless of this variation most taxa bleached. Colpophyllia natans, Montastraea faveolata and Siderastrea siderea were considered the most bleaching vulnerable taxa. Interestingly, reefs with the highest coral cover showed the greatest decline reef building taxa, and conversely, reefs with the lowest coral cover showed the most bleaching but lowest change in coral cover with little algal overgrowth post-bleaching.
Coral communities are changing rapidly worldwide through loss of coral cover and shifts in species composition. Although many reef-building corals are likely to decline, some weedy opportunistic species might increase in abundance. Here we explore whether the reshuffling of species can maintain ecosystem integrity and functioning. Using four common Caribbean reef-building coral genera we modeled rates of reef construction and complexity. We show that shifting coral assemblages result in rapid losses in coral-community calcification and reef rugosity that are independent of changes in the total abundance of reef corals. These losses are considerably higher than those recently attributed to climate change. Dominance patterns of coral assemblages seem to be the most important driver of the functioning of coral reefs and thus, the future of these ecosystems might depend not only on reductions of local and global stressors, but also on the maintenance of keystone coral species.
Coral reefs are damaged by natural disturbances and local and global anthropogenic stresses. As stresses intensify, so do debates about whether reefs will recover after significant damage. True headway in this debate requires documented temporal trajectories for coral assemblages subjected to various combinations of stresses; therefore, we report relevant changes in coral assemblages at Little Cayman Island. Between 1999 and 2012, spatiotemporal patterns in cover, densities of juveniles and size structure of assemblages were documented inside and outside marine protected areas using transects, quadrats and measurements of maximum diameters. Over five years, bleaching and disease caused live cover to decrease from 26% to 14%, with full recovery seven years later. Juvenile densities varied, reaching a maximum in 2010. Both patterns were consistent within and outside protected areas. In addition, dominant coral species persisted within and outside protected areas although their size frequency distributions varied temporally and spatially. The health of the coral assemblage and the similarity of responses across levels of protection suggested that negligible anthropogenic disturbance at the local scale was a key factor underlying the observed resilience.
The recent intensification of human disturbances in the Caribbean has increased the prevalence of partial mortality on coral colonies. Partial mortality can change colony size by directly shrinking colonies or by splitting colonies into fragments. A reduction in colony size can also adversely affect fecundity and fitness as internal resources shift away from reproduction toward colony maintenance. This study aimed to determine whether three Caribbean coral species, Siderastrea siderea, Montastraea faveolata, and Diploria strigosa, along the reef tract in Puerto Morelos, Mexico (20o52′N, 86o51′W), continued to dedicate resources to reproduction when colonies were fragmented to pre-maturation size. Contrary to expectations, eggs were found in colonies that were smaller than the maturation size and had been subjected to partial mortality. The continued dedication of resources toward reproduction, even in the smallest colonies, suggests that resource trade-offs away from reproduction are not as rigid as previously suggested in stressed corals.
A comparison of the community structure of juvenile hermatypic corals of 2 to 37 m depth at the fringing reefs of Curaçao between 1975 and 2005 shows a decline of 54.7% in juvenile coral abundance and a shift in species composition. Agaricia species and Helioseris cucullata, the most common juveniles in 1975, showed the largest decline in juvenile abundance (a 9 and 120 fold decrease in density respectively) with Helioseris cucullata being nearly extirpated locally. In 2005, Porites astreoides contributed most colonies to the juvenile coral community, increasing from 8.2% (in 1975) to 19.9% of the total juvenile community. Between 1975 and 2005, juveniles of brooding species decreased in relative abundance while the abundance of juveniles of broadcast spawning species increased or remained the same. These data illustrate the magnitude of the changes that have occurred in only three decades in the composition of juvenile coral communities.
Montastrea annularis is hermaphroditic, with an annual gametogenic cycle that begins in May and ends with spawning in August and/or September. M. cavernosa is dioecious, with a prolonged oogenic cycle that begins in November, a briefer spermatogenic cycle that begins in May, and spawning events during July, August and/or September. Spawning for both species appears to occur c1wk after the full moon. Both species delay reproduction until colony size reaches c100cm2 in surface area. In M. annularis, but not in M. cavernosa, polyps in the middle of the colony have greater reproductive activity than those near edges of the colony. Ripe gonads of M. annularis account for 30-40% of the biomass of sexually mature polyps. Assuming 10-50% bottom cover by this species, spawning releases 8.4-44g C m-2 and 0.9-4.7g N m-2 to the reef water column on one or two nights yr-1. The failure of sexual recruits of M. annularis to appear on Caribbean coral reefs cannot be attributed to lack of reproductive effort. -from Author
Although hermatypic coral recruits grow faster on the upper surfaces of artificial substrata on coral reefs, survival is greater in the shade on vertical and under surfaces. Growth of recruits is faster in shallow waters but survival increases with depth, at least to 20 m, as the light decreases. Adult corals can survive and grow in cool nutrient-rich waters, but survival of recruits is more successful in nutrient-poor waters. Nutrients and light are beneficial to coral growth, but faster- growing fouling organisms respond more directly to a rich supply of nutrients and light. As levels of light and nutrient input decrease, the rate of biomass accumulation of the benthic community decreases, and hermatypic corals have a greater chance of reaching a refuge in size from being overgrown. Between geographic locations, the difference in rate of biomass accumulation at comparable depths is influenced by nutrient input. At a given locality, the rate of biomass accumulation of algae is related to light which decreases with shading and depth.
In 1998, coral populations in Belize were disturbed simultaneously by a severe coral bleaching event and Hurricane Mitch. The impact of these disturbances was assessed for naturally occurring populations of coral recruits (2 to 20 mm diameter), at a depth of 8 to 10 m on the forereef of Clovers Atoll. Bleaching took place at all 4 study sites but the hurricane only affected 2 sites, enabling the effects of bleaching to be compared to those arising from bleaching plus hurricane damage. Predisturbance recruit density, size-frequency distribution, and community structure were similar between sites (at kilometre scales). The bleaching event lasted ca 3.5 mo. From 70 to 90% of adult colonies bleached and at least 25% of recruits exhibited signs of bleaching. A month after adult colonies had regained usual colouration, only 1% of recruits showed even partial bleaching. Surprisingly, coral bleaching alone had no measurable effect on either recruit density or community structure. The combination of bleaching and hurricane disturbance reduced total recruit densities to 20% of pre-disturbance levels. Effects of bleaching/hurricane disturbance on community structure were spatially patchy, and I suggest that such patchiness may arise from variable cover of protective microhabitat and/or different storm conditions mediated by proximity to reef cuts (breaks in the reef crest).
A 2-yr continuous photographic monitoring of a tagged population of the encrusting coral Oculina patagonica in the Mediterranean was conducted to study intra-colonial bleaching dynamics and the relationship between bleaching, mortality, and colony size. Surveys of non-tagged colonies showed that during the peak bleaching season (August, sea surface temperature = 31 degrees C), non-bleached colonies were frequently found to be small colonies averaging 4.6 +/- 2.3 cm in diameter. Within tagged colonies, percent bleached surface area was correlated to water temperature. In colonies that underwent bleaching, the perimeter of the colony was affected first, and, as water temperatures increased, bleaching progressed toward the colony center, During the summer months, partial mortality occurred in the perimeter region of bleached colonies in 22% of the tagged colonies and 25% of the tagged colonies died; 40% of the colonies that died belonged to the largest size group. This partial mortality caused an average decline of 46 +/- 27% in the average colony size, resulting in a shift to a smaller size group within the monitored population. Since in this species, colonies as small as 2 cm in diameter are reproductive, bleaching may have a less significant effect on the reproductive fitness of the small size groups in the population. The high mortality of large colonies, high survivorship of the small colonies, and the decline in colony size, due to partial mortality, suggest that, in the case of bleaching in populations of O. patagonica, small colony size is advantageous.
The coral reefs of Tobago represent some of the southernmost reefs in the Caribbean and have developed under the influence of runoff (e.g. terrestrial sediment and nutrients) from South American rivers. Local terrestrial runoff resulting from poor land management practices have also impacted reef development. Benthic surveys were conducted at 11 sites around the island in order to assess reef status. Mean (±SD) coral cover across Tobago was 14.9 (±7.6) % and macroalgae cover was highly variable ranging between 65 % at Bulldog Reef (Atlantic Coast), to 1.2 % at Mt Irvine (Caribbean coast). Montastrea faveolata (Ellis) and Diploria strigosa (Dana) dominated scleractinian coral communities and gorgonians accounted for 12.3 (±7.1) % of total benthic cover. Yellow band disease was observed on the major reef builders, M. faveolata, at most sites. The grazing urchin, Diadema antillarum (Philippi), have not recovered since their demise in the 1980’s. However despite limited grazing, the majority of monitoring sites were still dominated by coral communities.
For species with complex life histories such as scleractinian corals, processes occurring early in life can greatly influence the number of individuals entering the adult population. A plethora of studies have examined settlement patterns of coral larvae, mostly on artificial substrata, and the composition of adult corals across multiple spatial and temporal scales. However, relatively few studies have examined the spatial distribution of small (≤50 mm diameter) sexually immature corals on natural reef substrata. We, therefore, quantified the variation in the abundance, composition and size of juvenile corals (≤50 mm diameter) among 27 sites, nine reefs, and three latitudes spanning over 1000 km on Australia's Great Barrier Reef. Overall, 2801 juveniles were recorded with a mean density of 6.9 (±0.3 SE) ind.m, with , and accounting for 84.1% of all juvenile corals surveyed. Size-class structure, orientation on the substrate and taxonomic composition of juvenile corals varied significantly among latitudinal sectors. The abundance of juvenile corals varied both within (6-13 ind.m) and among reefs (2.8-11.1 ind.m) but was fairly similar among latitudes (6.1-8.2 ind.m), despite marked latitudinal variation in larval supply and settlement rates previously found at this scale. Furthermore, the density of juvenile corals was negatively correlated with the biomass of scraping and excavating parrotfishes across all sites, revealing a potentially important role of parrotfishes in determining distribution patterns of juvenile corals on the Great Barrier Reef. While numerous studies have advocated the importance of parrotfishes for clearing space on the substrate to facilitate coral settlement, our results suggest that at high biomass they may have a detrimental effect on juvenile coral assemblages. There is, however, a clear need to directly quantify rates of mortality and growth of juvenile corals to understand the relative importance of these mechanisms in shaping juvenile, and consequently adult, coral assemblages.
Coral mortality has increased in recent decades, making coral recruitment
more important than ever in sustaining coral reef ecosystems and contributing to their
resilience. This review summarizes existing information on ecological factors affecting
scleractinian coral recruitment. Successful recruitment requires the survival of coral offspring
through sequential life history stages. Larval availability, successful settlement,
and post-settlement survival and growth are all necessary for the addition of new coral
individuals to a reef and ultimately maintenance or recovery of coral reef ecosystems. As
environmental conditions continue to become more hostile to corals on a global scale,
further research on fertilization ecology, connectivity, larval condition, positive and negative
cues infl uencing substrate selection, and post-settlement ecology will be critical to
our ability to manage these diverse ecosystems for recovery. A better understanding of
the ecological factors infl uencing coral recruitment is fundamental to coral reef ecology
and management.
The density of juvenile scleratinian corals was quantified in shallow-water (4-18 m) sites representing three common reef types of the Florida Reef Tract: high-relief spur and groove, relict reef flat, and relict spur and groove. Reef types were chosen to encompass differences in depth, physical relief, and coral abundance. The purpose of this study was to 1) determine the density of juveniles in relation to non-juvenile corals and depth; and 2) evaluate correlations between juveniles and non-juvenile density in relation to larval dispersal strategies. Juvenile corals were identified and enumerated in random l-m2 quadrat surveys and compared to density and cover of non-juveniles. Juveniles of 16 species were identified among the study sites. The number of species observed as juveniles was significantly greater in deeper (> 10 m), relict spur and groove sites. Juvenile density differed significantly among sites and reef types, ranging from 1.18 to 3.74 colonies m-2. Juvenile density was greatest in relict spur and groove sites and was weakly correlated (r = 0.581) with depth. Juveniles comprised from 20.6 to 51.5% of the total coral assemblage in study sites. The majority of juveniles in high-relief spur and groove and relict reef flat communities were Agaricia agaricites, Porites astreoides, and P. porites. The majority of juveniles in relict spur and groove sites were P. astreoides, P. porites, and Montastraea cavernosa. Non-juvenile density and cover were significantly different among the study sites. Non-juvenile density (r = 0.577) was weakly correlated with depth. Coral cover ranged from 0.4 to 13 percent throughout the study area and was greatest in high-relief spur and groove communities. Life history strategies of juveniles in high-relief spur and groove and relict reef flat communities were generally characterized by species that brood larvae and attain a small colony size. Juveniles of three dominant brooding species (A. agaricites, P. astreoides, and P. porites) were significantly correlated to parental abundance across sites, suggesting that either self-seeding may occur for some species or that some recruits have been able to grow and survive. Density of juvenile A. agaricites was inversely related to depth (r = -0.326). Juveniles of three broadcasting species (M. annularis. M. cavernosa, Siderastrea siderea) were significantly correlated to parental abundance and increased in abundance with depth (r > 0.450). In contrast to some previous studies of juvenile coral assemblages in Caribbean reefs, the results suggest that parental abundance and composition may be a direct function of juvenile abundance in reef communities of the Florida Keys.
Coral bleaching reports have increased in the past few decades and coral bleaching is now among the primary disturbances to
coral reefs. Warm-water anomalies affect and kill a large variety of organisms, including scleractinian corals, octocorals,
hydrocorals, zoanthids, anemones, sponges, and green calcareous algae. Immediate effects are evident in the physiology and
condition of the organism; and delayed effects on size, growth, reproduction, recruitment, and disease are also evident. Both
influence ecological processes of productivity and calcification. There are examples of both short- and long-term changes
in community structure and losses in diversity. Good examples of local management reducing bleaching effects are few and there
is little comprehensive evidence that either resistance to bleaching or recovery is higher in highly managed reefs.
This 14-year study (1989–2003) develops recovery benchmarks based on a period of very strong coral recovery in Acropora-dominated assemblages on the Great Barrier Reef (GBR) following major setbacks from the predatory sea-star Acanthaster planci in the early 1980s. A space for time approach was used in developing the benchmarks, made possible by the choice of three
study reefs (Green Island, Feather Reef and Rib Reef), spread along 3 degrees of latitude (300km) of the GBR. The sea-star
outbreaks progressed north to south, causing death of corals that reached maximum levels in the years 1980 (Green), 1982 (Feather)
and 1984 (Rib). The reefs were initially surveyed in 1989, 1990, 1993 and 1994, which represent recovery years 5–14 in the
space for time protocol. Benchmark trajectories for coral abundance, colony sizes, coral cover and diversity were plotted
against nominal recovery time (years 5–14) and defined as non-linear functions. A single survey of the same three reefs was
conducted in 2003, when the reefs were nominally 1, 3 and 5years into a second recovery period, following further Acanthaster impacts and coincident coral bleaching events around the turn of the century. The 2003 coral cover was marginally above the
benchmark trajectory, but colony density (colonies.m−2) was an order of magnitude lower than the benchmark, and size structure was biased toward larger colonies that survived the
turn of the century disturbances. The under-representation of small size classes in 2003 suggests that mass recruitment of
corals had been suppressed, reflecting low regional coral abundance and depression of coral fecundity by recent bleaching
events. The marginally higher cover and large colonies of 2003 were thus indicative of a depleted and aging assemblage not
yet rejuvenated by a strong cohort of recruits.
KeywordsClimate change-Resilience-Benchmarks-Diversity-
Acropora
-Recovery
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.
The size structure of coral populations is influenced by biotic and physical factors, as well as species-specific demographic
rates (recruitment, colony growth, mortality). Coral reefs surrounding Moorea Island are characterized by strong environmental
gradients at small spatial scales, and therefore, we expected that the size structure of coral populations would vary greatly
at this scale. This study aimed at determining the degree of spatial heterogeneity in the population size structure of two
coral taxa, Pocillopora meandrina and massive Porites spp., among depths (6, 12, and 18 m) and among locations (Vaipahu, Tiahura and Haapiti) representing different exposure to
hydrodynamic forces. Our results clearly underlined the strong heterogeneity in the size structure of both P. meandrina and massive Porites spp., with marked variation among depths and among locations. However, the lack of any consistent and regular trends in the
size structure along depths or among locations, and the lack of correlation between size structure and mean recruitment rates
may suggest that other factors (e.g., stochastic life history processes, biotic interactions, and disturbances) further modify
the structure of coral populations. We found that the size structure of P. meandrina was fundamentally different to that of massive Porites spp., reflecting the importance of life history characteristics in population dynamics.
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.
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±0.2m−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.
In late summer 2005 a mass coral bleaching event occurred in the Caribbean. Here we quantify coral bleaching in Barbados at
six sites on the island’s sheltered west and exposed southwest coasts, including nearshore fringing and patch reefs and offshore
bank reef habitats. Onset of coral bleaching occurred in late August 2005 and persisted for many months after temperatures
cooled. All reef habitats and virtually all coral taxa were affected, with an average of 70.6% of all colonies bleaching.
Nearshore reefs (<10m depth) were affected more severely than offshore deeper reefs (>15m) with an average of 80.6% of all
coral colonies bleaching compared with 60.5% on the latter. Inter-species variation in susceptibility to bleaching was marked
with >90% of colonies bleaching in some species whilst <10% bleached in others. Follow-up surveys revealed low coral mortality,
with an overall mean of 3.8% partial colony death across all species and reefs by February 2006. However, bleached condition
has persisted with a mean of 37.7% of all coral colonies still bleached after 5 1/2months, indicating that loss of live coral
is likely to continue for some time. This event represents the most severe bleaching episode ever witnessed on Barbados’ reefs
and emphasises the vulnerability of small island states, with a high reliance on healthy coral reef ecosystem services, to
elevated sea water temperatures associated with climate variability and global climate change.
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.
Since the early 1980s, episodes of coral reef bleaching and mortality, due primarily to climate-induced ocean warming, have occurred almost annually in one or more of the world's tropical or subtropical seas. Bleaching is episodic, with the most severe events typically accompanying coupled ocean–atmosphere phenomena, such as the El Niño-Southern Oscillation (ENSO), which result in sustained regional elevations of ocean temperature. Using this extended dataset (25+ years), we review the short- and long-term ecological impacts of coral bleaching on reef ecosystems, and quantitatively synthesize recovery data worldwide. Bleaching episodes have resulted in catastrophic loss of coral cover in some locations, and have changed coral community structure in many others, with a potentially critical influence on the maintenance of biodiversity in the marine tropics. Bleaching has also set the stage for other declines in reef health, such as increases in coral diseases, the breakdown of reef framework by bioeroders, and the loss of critical habitat for associated reef fishes and other biota. Secondary ecological effects, such as the concentration of predators on remnant surviving coral populations, have also accelerated the pace of decline in some areas. Although bleaching severity and recovery have been variable across all spatial scales, some reefs have experienced relatively rapid recovery from severe bleaching impacts. There has been a significant overall recovery of coral cover in the Indian Ocean, where many reefs were devastated by a single large bleaching event in 1998. In contrast, coral cover on western Atlantic reefs has generally continued to decline in response to multiple smaller bleaching events and a diverse set of chronic secondary stressors. No clear trends are apparent in the eastern Pacific, the central-southern-western Pacific or the Arabian Gulf, where some reefs are recovering and others are not. The majority of survivors and new recruits on regenerating and recovering coral reefs have originated from broadcast spawning taxa with a potential for asexual growth, relatively long distance dispersal, successful settlement, rapid growth and a capacity for framework construction. Whether or not affected reefs can continue to function as before will depend on: (1) how much coral cover is lost, and which species are locally extirpated; (2) the ability of remnant and recovering coral communities to adapt or acclimatize to higher temperatures and other climatic factors such as reductions in aragonite saturation state; (3) the changing balance between reef accumulation and bioerosion; and (4) our ability to maintain ecosystem resilience by restoring healthy levels of herbivory, macroalgal cover, and coral recruitment. Bleaching disturbances are likely to become a chronic stress in many reef areas in the coming decades, and coral communities, if they cannot recover quickly enough, are likely to be reduced to their most hardy or adaptable constituents. Some degraded reefs may already be approaching this ecological asymptote, although to date there have not been any global extinctions of individual coral species as a result of bleaching events. Since human populations inhabiting tropical coastal areas derive great value from coral reefs, the degradation of these ecosystems as a result of coral bleaching and its associated impacts is of considerable societal, as well as biological concern. Coral reef conservation strategies now recognize climate change as a principal threat, and are engaged in efforts to allocate conservation activity according to geographic-, taxonomic-, and habitat-specific priorities to maximize coral reef survival. Efforts to forecast and monitor bleaching, involving both remote sensed observations and coupled ocean–atmosphere climate models, are also underway. In addition to these efforts, attempts to minimize and mitigate bleaching impacts on reefs are immediately required. If significant reductions in greenhouse gas emissions can be achieved within the next two to three decades, maximizing coral survivorship during this time may be critical to ensuring healthy reefs can recover in the long term.
The abundance of juvenile corals was quantified by visual and photographic methods to determine whether photography could be used as a rapid census technique in reef monitoring projects. Between 9 and 17 0.25-m(2) quadrats were positioned randomly along replicate 25-m transects on reefs in St. John (U.S. Virgin Islands), the Florida Keys, and Belize. In the visual method, all juvenile corals (0.4 cm less than or equal to diameter less than or equal to 5.0 cm) in both open and cryptic locations within the quadrats were identified to genus and counted. A close-up photograph of a 0.039-m(2) planar area was then taken in the center of each quadrat for subsequent analysis. Plots of the running mean and standard error of juvenile density against the number of transects produced asymptotes after approximately three transects at each site, suggesting that sample sizes were sufficient for both methods. However, juvenile densities estimated by the visual method were not correlated with values obtained by the photographic method at any site. These discrepancies cannot be attributed to dissimilar sampling areas, because analysis of variance demonstrated that the difference between methods varied among sites, and because similar variation was apparent when visual and photographic surveys were compared for similar sample areas. Rather, the discrepancies are a consequence of juvenile corals growing in microhabitats where they cannot be quantified in planar photographs. We recommend the visual technique to quantify juvenile corals; at four sites we found that adequate estimates of juvenile density can be obtained from surveys of 0.5 x 0.5 m quadrats, randomly positioned at 17 locations along each of four 25-m transect lines.
The past few decades have seen an increase in the frequency and intensity of disturbance on coral reefs, resulting in shifts in size and composition of coral populations. These changes have lead to a renewed focus on processes that influence demographic rates in corals, such as corallivory. While previous research indicates selective corallivory among coral taxa, the importance of coral size and the density of coral colonies in influencing corallivory are unknown. We surveyed the size, taxonomy and number of bites by parrotfish per colony of corals and the abundance of three main corallivorous parrotfish (Sparisoma viride, Sparisoma aurofrenatum, Scarus vetula) at multiple spatial scales (reefs within islands: 1-100 km, and between islands: >100 km) within the Bahamas Archipelago. We used a linear mixed model to determine the influence of coral taxa, colony size, colony density, and parrotfish abundance on the intensity of corallivory (bites per m(2) of coral tissue). While the effect of colony density was significant in determining the intensity of corallivory, we found no significant influence of colony size or parrotfish abundance (density, biomass or community structure). Parrotfish bites were most frequently observed on the dominant species of reef building corals (Montastraea annularis, Montastraea faveolata and Porites astreoides), yet our results indicate that when the confounding effects of colony density and size were removed, selective corallivory existed only for the less dominant Porites porites. As changes in disturbance regimes result in the decline of dominant frame-work building corals such as Montastraea spp., the projected success of P. porites on Caribbean reefs through high reproductive output, resistance to disease and rapid growth rates may be attenuated through selective corallivory by parrotfish.
Free space is necessary for larval recruitment in all marine benthic communities. Settling corals, with limited energy to invest in competitive interactions, are particularly vulnerable during settlement into well-developed coral reef communities. This situation may be exacerbated for corals settling into coral-depauperate reefs where succession in nursery microhabitats moves rapidly toward heterotrophic organisms inhospitable to settling corals. To study effects of benthic organisms (at millimeter to centimeter scales) on newly settled corals and their survivorship we deployed terra-cotta coral settlement plates at 10 m depth on the Mesoamerican Barrier Reef in Belize and monitored them for 38 mo. During the second and third years, annual recruitment rates declined by over 50% from the previous year. Invertebrate crusts (primarily sponges) were absent at the start of the experiment but increased in abundance annually from 39, 60, to 73% of the plate undersides by year three. Subsequently, substrates hospitable to coral recruitment, including crustose coralline algae, biofilmed terra-cotta and polychaete tubes, declined. With succession, substrates upon which spat settled shifted toward organisms inimical to survivorship. Over 50% of spat mortality was due to overgrowth by sponges alone. This result suggests that when a disturbance creates primary substrate a "recruitment window" for settling corals exists from approximately 9 to 14 mo following the disturbance. During the window, early-succession, facilitating species are most abundant. The window closes as organisms hostile to coral settlement and survivorship overgrow nursery microhabitats.
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.
Satellite-based tools provided warnings for coral reef managers and scientists, guiding both the timing 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.
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.
Coral cover on Caribbean reefs has declined rapidly since the early 1980's. Diseases have been a major driver, decimating communities of framework building Acropora and Orbicella coral species, and reportedly leading to the emergence of novel coral assemblages often dominated by domed and plating species of the genera Agaricia, Porites and Siderastrea. These corals were not historically important Caribbean framework builders, and typically have much smaller stature and lower calcification rates, fuelling concerns over reef carbonate production and growth potential. Using data from 75 reefs from across the Caribbean we quantify: (i) the magnitude of non-framework building coral dominance throughout the region and (ii) the contribution of these corals to contemporary carbonate production. Our data show that live coral cover averages 18.2% across our sites and coral carbonate production 4.1 kg CaCO3 m−2 yr−1. However, non-framework building coral species dominate and are major carbonate producers at a high proportion of sites; they are more abundant than Acropora and Orbicella at 73% of sites; contribute an average 68% of the carbonate produced; and produce more than half the carbonate at 79% of sites. Coral cover and carbonate production rate are strongly correlated but, as relative abundance of non-framework building corals increases, average carbonate production rates decline. Consequently, the use of coral cover as a predictor of carbonate budget status, without species level production rate data, needs to be treated with caution. Our findings provide compelling evidence for the Caribbean-wide dominance of non-framework building coral taxa, and that these species are now major regional carbonate producers. However, because these species typically have lower calcification rates, continued transitions to states dominated by non-framework building coral species will further reduce carbonate production rates below ‘predecline’ levels, resulting in shifts towards negative carbonate budget states and reducing reef growth potential.
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.
Models of population dynamics based on age-related parameters do not provide accurate predictions if within-age-class variance in those parameters is high. Often the demographic fate of an individual or population may be predicted more accurately using size rather than age classifications. A general model of size-related population dynamics is here designed to include processes, such as fragmentation and shrinkage, which are excluded from conventional age-related demographic analysis. The parameters of the model were measured in a study of a colonial, sessile coral. Differences in individual rates of growth and shrinkage resulted in huge long- term variations in calculated colony size, fecundity and mortality rates between corals of equal age. Individuals of the same age thus have widely differing probabilities of obtaining representation in subsequent generations. Population growth was simulated by adding a constant number of juvenile corals every year to the smallest size class. Although the model has no density-dependent parameters, population growth stops. The population size attained depends on the number of settling juveniles. Local populations of sessile organisms may be regulated by larval input, as well as by recurring disturbances or density-dependent interactions.-from Author
On Caribbean reefs, a striking trend of the last 25 years has been the decline in cover of the framework-building coral Montastraea annularis, a species that has dominated reefs throughout the region for millennia. Clearly, such losses are important ecologically, but to evaluate their significance fully, they need to be placed in the context of the proximal causes and balanced against the potential for gains in cover through growth and recruitment. In this study, a population of M. annularis in St. John, U. S. Virgin Islands, was censused annually from 1988 to 2003 to quantify coral cover and construct a size-based demographic model. The model was developed to explore the mechanisms of change in coral cover and to ascertain likely trajectories for future population growth. Over the study period, the cover of M. annularis declined from 41% in 1988, to; 12% by 1999 (a 72% decline) but remained unchanged statistically for the last five years of the study. Between 1988 and 2003, colony abundances declined by 57% (from 47 colonies/m(2) to 20 colonies/m(2)), and the losses were driven mostly by the death and fission of medium to large colonies (i.e., >= 151 cm(2)). By 2003, the population had proportionally more small colonies (70% were <= 50 cm(2)) and fewer large colonies (3% were > 250 cm(2)) than in 1988 (60% and 6%, respectively), and the changes in population structure had accelerated >= 14% in terms of the rate of change in population size and the time necessary to attain equilibrium of colony size structure. Importantly, this analysis revealed an ongoing and imminent population decline coincident with the recent period of apparently stable coral cover. Fifty-year projections indicate the strong likelihood of extirpation of M. annularis at this particular site in St. John (in contrast to a continuation of constant low cover) and suggest that the 1988 population structure cannot be restored by recruitment. It is unlikely that the population decline will reverse until there is an amelioration of the conditions that kill individual colonies.
On most coral reefs, the percentage cover of scleractinian corals has declined greatly over the last 30 yr; some species that are more resistant to mortality have been less affected than others. Porites astreoides is one species that has become a more prominent com- ponent of coral reef communities throughout the Caribbean. Analyses of coral reefs in shallow water (5 to 6 m depth) at 6 locations spanning a 4100 km arc of the Caribbean were used to evaluate the contri- bution of P. astreoides to contemporary reefs. Photo- quadrats recorded in 2003/2004 were used to esti- mate the percentage cover and colony density of P. astreoides, and colony size-frequency structure was analyzed to gain insight into demographic processes. At all locations, reefs were characterized by
Episodes of mass coral bleaching in recent decades have been attributed
to periods of anomalously warm ocean temperatures. In 2005, the sea
surface temperature (SST) anomaly in the tropical North Atlantic that
contributed to the strong hurricane season caused widespread coral
bleaching in the eastern Caribbean. In this study, we used the GFDL
global climate models to evaluate the contribution of natural climate
variability and anthropogenic forcing to the thermal stress that caused
the 2005 coral bleaching event. Historical temperature data and
simulations for the 1870-2000 period show that the observed warming in
the region is unlikely to be due to unforced climate variability alone.
Simulation of background climate variability suggests that anthropogenic
warming may have increased the probability of occurrence of significant
thermal stress events for corals in this region by an order of
magnitude. Under scenarios of future greenhouse gas emissions, mass
coral bleaching in the eastern Caribbean may become a biannual event in
20-30 years. However, if corals and their symbionts can adapt by 1 -
1.5°C, such mass bleaching events may not begin to recur at
potentially harmful intervals until the latter half of the century. The
delay could enable more time to alter the path of greenhouse gas
emissions, although long-term "committed warming" even after
stabilization of atmospheric CO2 levels may still represent an
additional long-term threat to corals. These results suggest that
protecting coral reefs from climate change will require both managing
local pressures on reefs, in order to increase resilience to committed
warming, and reducing greenhouse gas emissions.
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.
Colony size is an important life-history characteristic of corals and changes in colony size will have significant effects
on coral populations. This study summarizes ∼21,000 haphazard colony size measurements of 26 common coral taxa (mostly coral
genera) collected annually between 1992 and 2006 in seven Kenyan reef lagoons. There was a major coral bleaching and mortality
event in early 1998 and all seven reefs were affected. The seven locations include two long-protected Marine National Parks
(Malindi and Watamu), one relatively recently established park (Mombasa), and four unprotected locations (Vipingo, Kanamai,
Ras Iwatine, and Diani). They span about 150km and represent three distinct fishery management regimes: old protected (OP),
newly protected (NP), and unprotected (UP). Seventeen taxa had statistically significant different sizes for comparisons of
the management regimes, with only one genus, Pavona, having larger sizes in the unprotected reefs. The size of eight coral genera showed a significant time and management interaction,
and size frequency differences that existed in management areas prior to 1998 were further increased after the bleaching event.
Time alone was a significant factor for eleven genera, and in all cases colonies were smaller after 1998. For most taxa, colony
size distributions were significantly skewed and had right-tailed distributions. After 1998, the right-tailed distributions
of Acropora, Hydnophora, and Montipora were significantly reduced. Most taxa had peaky distributions and only Acropora experienced a statistically significant change from peaky to flat. The mean sizes of taxa were not related to their mortality
across 1998, which indicates that the size effect was within rather than between taxa. Astreopora and Platygyra were well-sampled taxa that did not show an effect of management, but had reduced median sizes across 1998. Consequently,
no taxa were tolerant of both fishing and bleaching disturbances and the combined effect was to reduce the size of all corals.
Oceanographic measurements and sediment samples were collected during the summer of 2006 as part of a multi-year study of coastal circulation and the fate of terrigenous sediment on coral reefs in Hanalei Bay, Kauai. The goal of this study was to better understand sediment dynamics in a coral reef-lined embayment where winds, ocean surface waves, and river floods are important processes. During a summer period that was marked by two wave events and one river flood, we documented significant differences in sediment trap collection rates and the composition, grain size, and magnitude of sediment transported in the bay. Sediment trap collection rates were well correlated with combined wave-current near-bed shear stresses during the non-flood periods but were not correlated during the flood. The flood's delivery of fine-grained sediment to the bay initially caused high turbidity and sediment collection rates off the river mouth but the plume dispersed relatively quickly. Over the next month, the flood deposit was reworked by mild waves and currents and the fine-grained terrestrial sediment was advected around the bay and collected in sediment traps away from the river mouth, long after the turbid surface plume was gone. The reworked flood deposits, due to their longer duration of influence and proximity to the seabed, appear to pose a greater long-term impact to benthic coral reef communities than the flood plumes themselves. The results presented here display how spatial and temporal differences in hydrodynamic processes, which result from variations in reef morphology and orientation, cause substantial variations in the deposition, residence time, resuspension, and advection of both reef-derived and fluvial sediment over relatively short spatial scales in a coral reef embayment.
Although multivariate analysis of ecological data already existed and was being actively developed in the 1960s, it really flourished in the years 1970 and later. Many textbooks were published during these years; among them were the seminal Écologie numérique (Legendre and Legendre 1979) and its English translation Numerical Ecology (Legendre and Legendre 1983). The authors of these books unified, under one single roof, a very wide array of statistical and other numerical techniques and presented them in a comprehensive way, not only to help researchers understand the available methods of analyses, but also to explain how to choose and apply them in an ordered, logical way to reach their research goals. Mathematical explanations are not absent from these books, and they provide a precious insider look into the various techniques, which is appealing to readers wishing to go beyond the simple user level.