Context-dependent corallivory by parrotfishes in a Caribbean reef ecosystem

This study assesses the patterns of corallivory by parrotfishes across reefs of the Florida Keys, USA. These reefs represent a relatively unique combination within the wider Caribbean of low coral cover and high parrotfish abundance suggesting that predation pressure could be intense. Surveys across eight shallow forereefs documented the abundance of corals, corallivorous parrotfishes, and predation scars on corals. The corals Porites porites and Porites astreoides were preyed on most frequently with the rates of predation an order of magnitude greater than has been documented for other areas of the Caribbean. In fact, parrotfish bite density on these preferred corals was up to 34 times greater than reported for corals on other reefs worldwide. On reefs where coral cover was low and corals such as Montastraea faveolata, often preferred prey for parrotfishes, were rare, predation rates on P. porites and P. astreoides, and other less common corals, intensified further. The intensity of parrotfish predation increased significantly as coral cover decreased. However, parrotfish abundance showed only a marginal positive relationship with predation pressure on corals, likely because corallivorous parrotfish were abundant across all reefs. Parrotfishes often have significant positive impacts on coral cover by facilitating coral recruitment, survival, and growth via their grazing of algae. However, abundant corallivorous parrotfishes combined with low coral cover may result in higher predation on corals and intensify the negative impact that parrotfishes have on remaining corals.     

Patterns of Coral Recruitment and Post-settlement Mortality on Bermuda's Reefs: Comparisons to Caribbean and Pacific Reefs

The recruitment of juvenile corals and post-settlement mortalityare important processes for coral population dynamics and reefcommunity ecology. I monitored juvenile coral recruitment andsurvival on a severely disturbed reef in Bermuda from 1981 to1989 and on adjacent healthy reefs from 1986 to 1990. Poritesastreoides was the dominant recruiting species at all sites,due to the release of brooded planulae that may settle rapidly.The dominant corals on Bermuda's reef, Diploria spp., were poorrecruiters, perhaps due to the broadcast mode of reproductionof these species. However, Diploria spp. have lower juvenilemortality rates compared to P. astreoides, which may explaintheir abundance on Bermuda's reefs. Brooding corals, primarily agariciids, were the dominant recruitson Atlantic reefs compared to high recruitment rates by spawningacroporids in the Pacific, which may be the result of differentenvironmental conditions and/or evolutionary trends in the twooceans. The latter group also suffered high post-settlementmortality compared to brooding coralsin both the Atlantic andthe Pacific. Massive corals in both oceans had generally lowrecruitment rates, related to their spawning mode of reproduction,and low rates of post-settlement mortality. The dominant roleof long-lived massive corals on the Atlantic and Pacific reefscan be understood in terms of their life-history strategy incomparison to the relatively short-lived Pacific acroporidsand Atlantic agariciids that rely on different strategies tomaintain their populations.     

Behavioural and developmental responses of predatory coral reef fish to variation in the abundance of prey

Ecological theory suggests that the behaviour, growth and abundance of predators will be strongly influenced by the abundance of prey. Predators may in turn play an important role in structuring prey populations and communities. Responses of predators to variation in prey abundance have most commonly been demonstrated in low-diversity communities where food webs are relatively simple. How predators respond in highly diverse assemblages such as in coral reef habitats is largely unknown. This study describes an experiment that examined how the movement, diet and growth of the coral reef piscivore, Cephalopholis boenak (Serranidae) responded to variation in the abundance of its prey. Predator densities were standardised on small patch reefs made from the lagoonal reef-building coral, Porites cylindrica. These patch reefs exhibited natural variation in the abundance and community structure of multiple species of prey. However, our experiment generated a relatively simple predator–prey relationship, with C. boenak primarily responding to the most abundant species of prey. Three responses of predators were observed: aggregative, functional and developmental. Thirty-one per cent of individuals moved between patch reefs during the experiment, all from areas of relatively low to high prey density. Feeding rates were higher on patch reefs of high prey density, while growth rates of fish that remained on low prey density reefs throughout the experiment were lower. Growth rates of C. boenak on the experimental reefs were also much higher than for those living on natural patch reefs over the same time period, corresponding with overall differences in prey abundance. These results suggest that local abundance, feeding rate and growth of C. boenak were closely linked to the abundance of their main prey. This combination of predatory responses is a potential mechanism behind recent observations of density-dependent mortality and population regulation of prey in coral reef fish communities.     

Small-scale variability in the size structure of scleractinian corals around Moorea, French Polynesia: patterns across depths and locations

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. Handling editor: I. Nagelkerken     

Recruitment hotspots and bottlenecks mediate the distribution of corals on a Caribbean reef

Recruitment hotspots are locations where organisms are added to populations at high rates. On tropical reefs where coral abundance has declined, recruitment hotspots are important because they have the potential to promote population recovery. Around St. John, US Virgin Islands, coral recruitment at five sites revealed a hotspot that has persistent for 14 years. Recruitment created a hotspot in density of juvenile corals that was 600 m southeast of the recruitment hotspot. Neither hotspot led to increased coral cover, thus revealing the stringency of the demographic bottleneck impeding progression of recruits to adult sizes and preventing population growth. Recruitment hotspots in low-density coral populations are valuable targets for conservation and sources of corals for restoration.     

Habitat-dependent growth in a Caribbean sea urchin <Emphasis Type="Italic">Tripneustes ventricosus</Emphasis>: the importance of food type

The sea urchin Tripneustes ventricosus is a common, yet relatively poorly known, grazer of seagrass beds and coral reefs throughout the Caribbean. We compared the size and abundance of urchins between adjacent seagrass and coral reef habitats (where macroalgae are the dominant primary producers). We also conducted a laboratory experiment comparing the growth rate of juvenile urchins fed a diet of either macroalgae or seagrass. Reef urchins had significantly larger test diameter than those in the seagrass on some sampling dates. This size difference may be at least partially explained by diet, because laboratory-reared urchins fed macroalgae grew significantly faster than those fed seagrass. The seagrass population, however, was stable over time, whereas the reef population exhibited strong fluctuations in abundance. Overall, our study indicates that both the seagrass and coral reef habitats are capable of supporting healthy, reproductive populations of T. ventricosus. Each, however, appears to offer a distinct advantage: faster growth on the reef and greater population stability in the seagrass.     

The non-linear relationship between body size and function in parrotfishes

Parrotfishes are a group of herbivores that play an important functional role in structuring benthic communities on coral reefs. Increasingly, these fish are being targeted by fishermen, and resultant declines in biomass and abundance may have severe consequences for the dynamics and regeneration of coral reefs. However, the impact of overfishing extends beyond declining fish stocks. It can also lead to demographic changes within species populations where mean body size is reduced. The effect of reduced mean body size on population dynamics is well described in literature but virtually no information exists on how this may influence important ecological functions. The study investigated how one important function, scraping (i.e., the capacity to remove algae and open up bare substratum for coral larval settlement), by three common species of parrotfishes (Scarus niger, Chlorurus sordidus, and Chlorurus strongylocephalus) on coral reefs at Zanzibar (Tanzania) was influenced by the size of individual fishes. There was a non-linear relationship between body size and scraping function for all species examined, and impact through scraping was also found to increase markedly when fish reached a size of 15–20 cm. Thus, coral reefs which have a high abundance and biomass of parrotfish may nonetheless be functionally impaired if dominated by small-sized individuals. Reductions in mean body size within parrotfish populations could, therefore, have functional impacts on coral reefs that previously have been overlooked.     

Are artificial reefs surrogates of natural habitats for corals and fish in Dubai,United Arab Emirates?

Artificial reefs are often promoted as mitigating human impacts in coastal ecosystems and enhancing fisheries; however, evidence supporting their benefits is equivocal. Such structures must be compared with natural reefs in order to assess their performance, but past comparisons typically examined artificial structures that were too small, or were immature, relative to the natural reefs. We compared coral and fish communities on two large (>400,000 m³) and mature (>25 year) artificial reefs with six natural coral patches. Coral cover was higher on artificial reefs (50%) than in natural habitats (31%), but natural coral patches contained higher species richness (29 vs. 20) and coral diversity (H′ = 2.3 vs. 1.8). Multivariate analyses indicated strong differences between coral communities in natural and artificial habitats. Fish communities were sampled seasonally for 1 year. Multivariate fish communities differed significantly among habitat types in the summer and fall, but converged in the winter and spring. Univariate analysis indicated that species richness and abundance were stable throughout the year on natural coral patches but increased significantly in the summer on artificial reefs compared with the winter and spring, explaining the multivariate changes in community structure. The increased summer abundance on artificial reefs was mainly due to adult immigration. Piscivores were much more abundant in the fall than in the winter or spring on artificial reefs, but had low and stable abundance throughout the year in natural habitats. It is likely that the decreased winter and spring abundance of fish on the artificial reefs resulted from both predation and emigration. These results indicate that large artificial reefs can support diverse and abundant coral and fish communities. However, these communities differ structurally and functionally from those in natural habitats, and they should not be considered as replacements for natural coral and fish communities.     

Modeling vertical coral connectivity and mesophotic refugia

Whether mesophotic reefs will behave as refugia for corals threatened by global climate change and coastal development depends on vertical exchange of larvae between diverse habitats. Here we use a biophysical model of larval dispersal to estimate vertical connectivity of a broadcasting (Orbicella faveolata) and a brooding (Porites astreoides) species of coral in the US Virgin Islands. Modeling predicts subsidy to shallow areas by mesophotic larvae of both species based on local hydrology, adult reproductive characteristics, larval traits, and a wide range of scenarios developed to test depth-sensitive factors, such as fertilization rates and post-settlement survivorship. In extreme model scenarios of reduced fertilization and post-settlement survivorship of mesophotic larvae, 1–10 % local mesophotic subsidy to shallow recruitment is predicted for both species, which are demographically significant. Although direct vertical connectivity is higher for the broadcaster, the brooder demonstrates higher local multigenerational vertical connectivity, which suggests that local P. astreoides populations are more resilient than those of O. faveolata, and corroborates field studies. As shallow habitat degrades, mesophotic–shallow subsidy is predicted to increase for both species. This study is the first of its kind to simulate larval dispersal and settlement between habitats of different depths, and these findings have local, regional, and global implications for predicting and managing coral reef persistence in a changing climate.     

Coral reefs in the Southern Barents Sea: habitat description and the effects of bottom fishing

Fifteen Lophelia reefs from offshore to coastal areas off northern Norway were studied using video. Health status of the coral habitat (degree of physical impact, % cover of living tissue, colony size), occurrence of trawl marks and lost fishing gear, height of coral colonies and associated fauna were analysed from 44 video-lines. Fishing impact was more frequent on the offshore reefs (36.5% of the observed areas) than those in the coastal reefs (0.6%). The most visible effects of fishing were broken and displaced coral colonies. At some sites only small scattered fragments of live corals were observed, indicating recent impact. The mean colony height of Lophelia and gorgonian corals at impacted sites was around half the size of those at non-impacted sites. Both species richness and abundance was higher at non-impacted coral habitats compared to impacted. The actinarian Protanthea simplex and unidentified brittlestars were the only taxa with higher abundance on impacted compared with non-impacted habitats. The reefs at the offshore location were protected against bottom trawling in 2009 through the establishment of a marine protected area (MPA), but a general ban against trawling on known coral reefs had already been implemented in 1999. In the MPA, signs of regrowth were observed. Most of the observed damage probably occurred over 10 years earlier. Results show that live and non-impacted cold water coral reefs have an important ecological function by enhancing the local biodiversity and fish abundance. Preventing further damage to impacted reefs may lead to full recovery within a few decades.     

Differential survival of nursery‐reared Acropora cervicornis outplants along the Florida reef tract

In recent decades, the Florida reef tract has lost over 95% of its coral cover. Although isolated coral assemblages persist, coral restoration programs are attempting to recover local coral populations. Listed as threatened under the Endangered Species Act, Acropora cervicornis is the most widely targeted coral species for restoration in Florida. Yet strategies are still maturing to enhance the survival of nursery‐reared outplants of A. cervicornis colonies on natural reefs. This study examined the survival of 22,634 A. cervicornis colonies raised in nurseries along the Florida reef tract and outplanted to six reef habitats in seven geographical subregions between 2012 and 2018. A Cox proportional hazards regression was used within a Bayesian framework to examine the effects of seven variables: (1) coral‐colony size at outplanting, (2) coral‐colony attachment method, (3) genotypic diversity of outplanted A. cervicornis clusters, (4) reef habitat, (5) geographical subregion, (6) latitude, and (7) the year of monitoring. The best models included coral‐colony size at outplanting, reef habitat, geographical subregion, and the year of monitoring. Survival was highest when colonies were larger than 15 cm (total linear extension), when outplanted to back‐reef and fore‐reef habitats, and when outplanted in Biscayne Bay and Broward–Miami subregions, in the higher latitudes of the Florida reef tract. This study points to several variables that influence the survival of outplanted A. cervicornis colonies and highlights a need to refine restoration strategies to help restore their population along the Florida reef tract.     

Coral recruitment: patterns and processes determining the dynamics of coral populations

Coral recruitment describes the addition of new individuals to populations, and it is one of the most fundamental demographic processes contributing to population size. As many coral reefs around the world have experienced large declines in coral cover and abundance, there has been great interest in understanding the factors causing coral recruitment to vary and the conditions under which it can support community resilience. While progress in these areas is being facilitated by technological and scientific advances, one of the best tools to quantify recruitment remains the humble settlement tile, variants of which have been in use for over a century. Here I review the biology and ecology of coral recruits and the recruitment process, largely as resolved through the use of settlement tiles, by: (i) defining how the terms ‘recruit’ and ‘recruitment’ have been used, and explaining why loose terminology has impeded scientific advancement; (ii) describing how coral recruitment is measured and why settlement tiles have value for this purpose; (iii) summarizing previous efforts to review quantitative analyses of coral recruitment; (iv) describing advances from hypothesis-driven studies in determining how refuges, seawater flow, and grazers can modulate coral recruitment; (v) reviewing the biology of small corals (i.e. recruits) to understand better how they respond to environmental conditions; and (vi) updating a quantitative compilation of coral recruitment studies extending from 1974 to present, thus revealing long-term global declines in density of recruits, juxtaposed with apparent resilience to coral bleaching. Finally, I review future directions in the study of coral recruitment, and highlight the need to expand studies to deliver taxonomic resolution, and explain why time series of settlement tile deployments are likely to remain pivotal in quantifying coral recruitment.     

Variable reproductive success in fragmented populations

Marine habitats are naturally patchy and anthropogenic disturbance can further fragment them. Many marine animals are sessile as adults or obligate inhabitants of particular habitats, so populations living in isolated patches of habitat are linked largely by dispersal of planktonic larvae. Theoretically, larvae are more likely to find and settle into large patches of habitat than small patches, thus small habitat patches may experience a more discontinuous supply of recruits resulting in small populations with unusual size- or age-structures or odd sex ratios — conditions where Allee effects on reproductive success are likely. We tested this hypothesis for the Caribbean spotted spiny lobster (Panulirus guttatus), an obligate inhabitant of coral patch reefs whose mating dynamics are size-dependent. We found that P. guttatus were less abundant on small reefs where their size structure and per capita reproductive success were significantly more variable, particularly among large females that are susceptible to sperm limitation that diminishes fertilization rates. These results are indicative of Allee effects and provide a mechanistic understanding of how size-dependent mating dynamics influence reproductive success in ways that alter population dynamics in patchy habitats.     

Evidence for a host role in thermotolerance divergence between populations of the mustard hill coral (Porites astreoides) from different reef environments

Studying the mechanisms that enable coral populations to inhabit spatially varying thermal environments can help evaluate how they will respond in time to the effects of global climate change and elucidate the evolutionary forces that enable or constrain adaptation. Inshore reefs in the Florida Keys experience higher temperatures than offshore reefs for prolonged periods during the summer. We conducted a common garden experiment with heat stress as our selective agent to test for local thermal adaptation in corals from inshore and offshore reefs. We show that inshore corals are more tolerant of a 6‐week temperature stress than offshore corals. Compared with inshore corals, offshore corals in the 31 °C treatment showed significantly elevated bleaching levels concomitant with a tendency towards reduced growth. In addition, dinoflagellate symbionts (Symbiodinium sp.) of offshore corals exhibited reduced photosynthetic efficiency. We did not detect differences in the frequencies of major (>5%) haplotypes comprising Symbiodinium communities hosted by inshore and offshore corals, nor did we observe frequency shifts (‘shuffling’) in response to thermal stress. Instead, coral host populations showed significant genetic divergence between inshore and offshore reefs, suggesting that in Porites astreoides, the coral host might play a prominent role in holobiont thermotolerance. Our results demonstrate that coral populations inhabiting reefs <10‐km apart can exhibit substantial differences in their physiological response to thermal stress, which could impact their population dynamics under climate change.     

Recruitment and larval connectivity of a remnant Acropora community in the Arabian Gulf,United Arab Emirates

Coral cover and community structure in the Arabian Gulf have changed considerably in recent decades. Recurrent bleaching events have dramatically reduced the abundance of previously dominant Acropora corals and have given space to other more thermally resistant coral taxa. The loss of Acropora spp. has reduced reef structural complexity and associated biodiversity. Sir Bu Nair Island (SBN) is a nature reserve in the United Arab Emirates that sustains some of the last dense and extensive Acropora stands in the southern Gulf. This study investigated coral recruitment at a southern coral reef on SBN and examined larval dispersal and reef connectivity between SBN and other local and regional reefs through an agent-based model coupled with a 3D hydrodynamic model. Recruitment was surveyed with settlement tiles deployed from April to September 2019. Contrary to other reefs in the Gulf, we found that Acropora is indeed the major coral recruiter settling at SBN reefs, followed by Porites. The models indicate that SBN reefs are mostly self-seeding but also connected to other reefs in the Gulf. SBN can supply coral larvae to the neighbouring islands Siri and Abu Musa, and nearby reefs along with the north-eastern Emirates, Iranian coast and Strait of Hormuz. Findings highlight the importance of SBN to protect remnant populations of the locally almost extinct Acropora in a region where natural coral recovery is increasingly sparse.

     

Distribution and abundance of fish in deep-sea coral habitats

Experimental fishing with long-lines and gillnets was conducted on the continental shelf off southwestern Norway between 150 and 350 m depth. Abundance and distribution of redfish (Sebastes marinus L., 1758), ling (Molva molva L., 1758), and tusk (Brosme brosme Ascanius, 1772) were quantified in Lophelia pertusa (L., 1758) coral reefs and in non-coral habitats. The largest catches of redfish were made with long-line fleets set in coral reef habitats. Ling and tusk were also most numerous in coral habitats, although not statistically significant. Fish caught in coral habitats tended to be larger in size than in non-coral habitats. The diet of redfish, tusk and ling included the same prey groups in all habitats, but they differed at the species level. Lophelia-reefs may provide a profitable feeding place for tusk. For the planktivorous Sebastes, on the other hand, their affinity to the reefs seems primarily to be related to the physical structure offered by the reefs.     

Simulation of the effects of Acanthaster planci on the population structure of massive corals in the genus Porites: evidence of population resilience?

Scleractinian corals in the genus Porites are slow growing, can live for centuries, and can attain great size. In these respects they differ from the majority of coral species, which grow faster and live for years to decades. The predatory starfish Acanthaster planci L. feeds on a wide range of coral species including Porites spp., and during outbreaks in its populations, causes high coral mortality and injury over much of the affected reefs. Because they are slow growing and because recent outbreaks of the starfish occurred only 15 years apart, it may be argued that the Porites populations on affected reefs will be sent into a period of prolonged decline. The present study uses a size stage model of the transition matrix type to predict effects of starfish outbreaks of various frequencies on Porites populations. A transition matrix characterizing the mortality and injury caused in different Porites size classes at John Brewer Reef during an outbreak year was determined from field data. Transition matrices for non-outbreak years were constructed on the basis of realistic growth rates and postulated survivorship and recruitment schedules. The medium term (100 years) effects of outbreaks were simulated by alternation of a single iteration of the outbreak matrix with many iterations of each non-outbreak matrix. By varying the interval between simulated outbreaks it was possible to define combinations of growth rate, survivorship and recruitment which were viable for various outbreak intervals. Simulations based on estimates of the initial size frequency distribution, recruitment rates and colony growth rates for the John Brewer Reef population predicted that the population would remain viable in the face of outbreaks every 15 years only if juvenile and adult survivorship were high. However, within the range of colony growth rates known to occur throughout the Great Barrier Reef and at recruitment rates of the same order as those estimated in the field population, it appears that a much wider range of survivorship schedules could lead to parity or even sustained growth in the face of outbreaks recurring at intervals of from 1 to 3 decades. It is suggested that because the key measurable parameters (initial size structure, damage characteristics, recruitment rate and growth rate) are likely to be very patchy at the scale of whole reefs, no general statement concerning the prognosis for Porites would be meaningful. However the model provides a tool by which a standardized evaluation of this type of field data may be made on a reef by reef basis.     

Indirect consequences of fishing: reduction of coralline algae suppresses juvenile coral abundance

Removing predatory fishes has effects that cascade through ecosystems via interactions between species and functional groups. In Kenyan reef lagoons, fishing-induced trophic cascades produce sea urchin-dominated grazing communities that greatly reduce the overall cover of crustose coralline algae (CCA). Certain species of CCA enhance coral recruitment by chemically inducing coral settlement. If sea urchin grazing reduces cover of settlement-inducing CCA, coral recruitment and hence juvenile coral abundance may also decline on fished reefs. To determine whether fishing-induced changes in CCA influence coral recruitment and abundance, we compared (1) CCA taxonomic compositions and (2) taxon-specific associations between CCA and juvenile corals under three fisheries management systems: closed, gear-restricted, and open-access. On fished reefs (gear-restricted and open-access), abundances of two species of settlement-inducing CCA, Hydrolithon reinboldii and H. onkodes, were half those on closed reefs. On both closed and fished reefs, juveniles of four common coral families (Poritidae, Pocilloporidae, Agariciidae, and Faviidae) were more abundant on Hydrolithon than on any other settlement substrate. Coral densities were positively correlated with Hydrolithon spp. cover and were significantly lower on fished than on closed reefs, suggesting that fishing indirectly reduces coral recruitment or juvenile success over large spatial scales via reduction in settlement-inducing CCA. Therefore, managing reefs for higher cover of settlement-inducing CCA may enhance coral recruitment or juvenile survival and help to maintain the ecological and structural stability of reefs.     

Impact of cyclones on hard coral and metapopulation structure,connectivity and genetic diversity of coral reef fish

Cyclones have one of the greatest effects on the biodiversity of coral reefs and the associated species. But it is unknown how stochastic alterations in habitat structure influence metapopulation structure, connectivity and genetic diversity. From 1993 to 2018, the reefs of the Capricorn Bunker Reef group in the southern part of the Great Barrier Reef were impacted by three tropical cyclones including cyclone Hamish (2009, category 5). This resulted in substantial loss of live habitat-forming coral and coral reef fish communities. Within 6–8 years after cyclones had devastated, live hard corals recovered by 50–60%. We show the relationship between hard coral cover and the abundance of the neon damselfish (Pomacentrus coelestis), the first fish colonizing destroyed reefs. We present the first long-term (2008–2015 years corresponding to 16–24 generations of P. coelestis) population genetic study to understand the impact of cyclones on the meta-population structure, connectivity and genetic diversity of the neon damselfish. After the cyclone, we observed the largest change in the genetic structure at reef populations compared to other years. Simultaneously, allelic richness of genetic microsatellite markers dropped indicating a great loss of genetic diversity, which increased again in subsequent years. Over years, metapopulation dynamics were characterized by high connectivity among fish populations associated with the Capricorn Bunker reefs (2200 km²); however, despite high exchange, genetic patchiness was observed with annual strong genetic divergence between populations among reefs. Some broad similarities in the genetic structure in 2015 could be explained by dispersal from a source reef and the related expansion of local populations. This study has shown that alternating cyclone-driven changes and subsequent recovery phases of coral habitat can greatly influence patterns of reef fish connectivity. The frequency of disturbances determines abundance of fish and genetic diversity within species.

     

Resilience of corals to hurricanes: a simulation model

This study tested how the frequency and intensity of hurricanes, and the size and growth rate of coral colonies influence the resilience of coral populations to disturbance by severe storms. A simulation modelling approach was used to examine the resilience of four coral species with differing life history characteristics: Agaricia agaricites, A. lamarcki, Helioseris cucullata, and Porites astreoides. Resilience, defined as the rate of area (coral cover) gain, was greater for three of the species when storms were less frequent or more intense. Resilience for all species increased with colony growth rates and with increasing proportion of small and medium-sized colonies. We conclude that (1) coral populations composed of intermediate-size, fast-growing colonies the most resilient following one or more storm disturbances, and (2) that resilience of anthropogenically stressed corals depends, in part, on population size structure.