This study evaluates the impacts of coral reef conservation and marine protected areas (MPAs) on the well-being of fishing communities in Central Vietnam. The Cu Lao Cham MPA is chosen as the case study. Coral reef health and four aspects of socioeconomic conditions (i.e., catch rate [also related to food security], access to the resource, employment, and income) are investigated. Data on the four different aspects were gathered from different sources. The results show that there is good evidence for how coral reef conservation can transfer the flow of benefits from the ecosystem to the local people. However, trade-offs also occur as a result of the development of tourism, including the degradation of fish resources and the environment. The managers of the MPA and the community should take into account trade-offs in resource management and should focus on appropriate MPA planning and fisheries management outside the MPA to achieve better outcomes for the local community from coral reef conservation
Heterotrophic feeding in newly-settled coral planulae can potentially improve survivorship and accelerate early development in some species; however, an optimal diet to facilitate this does not currently exist. This study evaluated the efficacy of three heterotrophic feeding regimes (enriched rotifers, unfiltered seawater, and a novel, particulate diet), against a wholly-phototrophic treatment on Acropora hyacinthus, A. loripes, A. millepora, and A. tenuis recruits, over 93 days post-settlement. The unfiltered seawater treatment recorded maximum survival for all species (A. hyacinthus 95.9±8.0%, A. loripes: 74.3±11.5%, A. millepora: 67±12.7%, A. tenuis: 53.2±11.3%), although not significant. Growth (% surface area gain) was also greatest in the unfiltered seawater, and this was significant for A. millepora (870±307%) and A. tenuis(693±91.8%) (p<0.05). Although total lipid concentration was relatively stable across treatments, the lipid class composition exhibited species-specific responses to each treatment. Lower saturated and higher polyunsaturated fatty acids appeared beneficial to recruit performance, particularly in the unfiltered seawater, which generally contained the highest levels of 20:5n-3 (EPA), 22:6n-3 (DHA), and 20:4n-6 (ARA). The present study demonstrates the capacity of a nutritionally adequate and readily accepted heterotrophic feeding regime to increase coral recruit survival, growth, and health, which can greatly reduce the time required in cost- and labour-intensive culture.
The degradation of coral reefs is widely reported, yet there is a poor understanding of the adaptability of reef fishes to cope with benthic change. We tested the effects of coral reef degradation on the feeding plasticity of four reef fish species. We used isotopic niche sizes and mean δ15N and δ13C values of each species in two coral reefs that differed in benthic condition. The species chosen have contrasting feeding strategies; Chaetodon lunulatus (corallivore), Chrysiptera rollandi (zooplanktivore), Halichoeres melanurus (invertivore) and Zebrasoma velifer (herbivore). We predicted that the corallivore would have a lower mean δ15N value and a smaller isotopic niche size in the degraded reef, that the herbivore and the invertivore might have a larger isotopic niche size and/or a different mean δ13C value, whereas the zooplanktivore might be indifferent since the species is not linked to coral degradation. Some results matched our predictions; C. lunulatus had a smaller niche size on the degraded reef, but no difference in mean δ15N and δ13C values, and H. melanurus displayed an increase in niche size and a lower mean δ15N value on the degraded reef. Some other results were contrary to our predictions; whereas Z. velifer and C. rollandi had smaller mean δ13C values but no difference in niche size. Our findings suggest there may be feeding plasticity to maintain a similar diet despite contrasting habitat characteristics, with different amplitude depending on species. Such findings suggest that certain species guilds would probably adapt to changes linked to habitat degradation.
Reef-building corals have essential roles in reef ecosystems but are highly susceptible to disturbances. Increasing anthropogenic disturbances are eroding coral community resilience, leading to declining reef ecosystem function and status globally. Successful reproduction and recruitment are essential for restoring coral populations but recruitment-limitation can constrain recovery. We supplied ~400,000 Acropora tenuis larvae in fine-mesh enclosures on each of four larval-enhancement plots, comprising natural reef substrata and ten settlement tiles, on degraded reef areas in the northwestern Philippines. Initial mean total settlement on tiles in larval-enhancement plots was high (255.3 ± 68.6), whereas no larvae settled in natural control plots. Recruit survivorship began stabilising after five months, with juveniles becoming visible by eye at nine months. After three years a mean of 2.3 m−2 colonies survived within each larval-enhancement plot. Most colonies grew rapidly (16.1 ± 0.7 cm mean diameter) and spawned successfully at three years, thereby quickly re-establishing a breeding population. In contrast, natural recruitment failed to produce any new visible A. tenuis colonies. These results demonstrate that mass larval settlement can rapidly enhance recruitment and coral recovery on degraded reef areas, and provides an important option for active reef restoration where larval supply and recruitment success are limiting.
Bio-constructions by Sabellaria worms play a key functional role in the coastal ecosystems being an engineer organism and for this reason are the object of protection. The most widespread reef building species along Atlantic and Mediterranean coasts is S. alveolata (L.), while the aggregations of S. spinulosa are typically limited to the North Sea coasts. This paper constitutes the first detailed description of unusual large S. spinulosareefs in the Mediterranean Sea. Defining current health status and evaluating the most important threats and impacts is essential to address conservation needs and design management plans for these large biogenic structures. Present knowledge on Mediterranean reefs of S. alveolata is fragmentary compared to Northeast Atlantic reefs, and concerning S. spinulosa, this paper represents a focal point in the knowledge on Mediterranean reefs of this species. A one-year study on temporal changes in reef structure and associated fauna is reported. The annual cycle of S. spinulosa reef shows a spawning event in winter-early spring, a period of growth and tubes aggregation from spring-early summer to autumn and a degeneration phase in winter. The variations exhibited in density of the worm aggregation and the changes in the reef elevation highlight a decline and regeneration of the structure over a year. The many ecological roles of the S. spinulosa reef were mainly in providing a diversity of microhabitats hosting hard and sandy bottom species, sheltering rare species, and producing biogenic structures able to provide coastal protection. The Mediterranean S. spinulosa reef does not shelter a distinctive associated fauna; however the richness in species composition underscores the importance of the reef as a biodiversity hot-spot. Finally, the roles of the biogenic formations and their important biotic and physical dynamics support the adoption of strategies for conservation of Mediterranean S.spinulosa reefs, according to the aims of the Habitat Directive.
For sessile organisms such as reef-building corals, differences in the degree of dispersion of individuals across a landscape may result from important differences in life-history strategies or may reflect patterns of habitat availability. Descriptions of spatial patterns can thus be useful not only for the identification of key biological and physical mechanisms structuring an ecosystem, but also by providing the data necessary to generate and test ecological theory. Here, we used an in situ imaging technique to create large-area photomosaics of 16 plots at Palmyra Atoll, central Pacific, each covering 100 m2 of benthic habitat. We mapped the location of 44,008 coral colonies and identified each to the lowest taxonomic level possible. Using metrics of spatial dispersion, we tested for departures from spatial randomness. We also used targeted model fitting to explore candidate processes leading to differences in spatial patterns among taxa. Most taxa were clustered and the degree of clustering varied by taxon. A small number of taxa did not significantly depart from randomness and none revealed evidence of spatial uniformity. Importantly, taxa that readily fragment or tolerate stress through partial mortality were more clustered. With little exception, clustering patterns were consistent with models of fragmentation and dispersal limitation. In some taxa, dispersion was linearly related to abundance, suggesting density dependence of spatial patterning. The spatial patterns of stony corals are non-random and reflect fundamental life-history characteristics of the taxa, suggesting that the reef landscape may, in many cases, have important elements of spatial predictability.
Modern reef-building corals sustain a wide range of ecosystem services because of their ability to build calcium carbonate reef systems. The influence of environmental variables on coral calcification rates has been extensively studied, but our understanding of their relative importance is limited by the absence of in situ observations and the ability to decouple the interactions between different properties. We show that temperature is the primary driver of coral colony (Porites astreoides and Diploria labyrinthiformis) and reef-scale calcification rates over a 2-year monitoring period from the Bermuda coral reef. On the basis of multimodel climate simulations (Coupled Model Intercomparison Project Phase 5) and assuming sufficient coral nutrition, our results suggest that P. astreoides and D. labyrinthiformis coral calcification rates in Bermuda could increase throughout the 21st century as a result of gradual warming predicted under a minimum CO2 emissions pathway [representative concentration pathway (RCP) 2.6] with positive 21st-century calcification rates potentially maintained under a reduced CO2 emissions pathway (RCP 4.5). These results highlight the potential benefits of rapid reductions in global anthropogenic CO2 emissions for 21st-century Bermuda coral reefs and the ecosystem services they provide.
The atolls and coral banks of the Chagos Archipelago (British Indian Ocean Territory) in the central Indian Ocean were badly affected by the warm water event that started in 2015 and lasted for nearly two years. On these reefs, coral mortality was very severe, reducing coral cover to <10% cover and usually about 5%, almost eliminating soft corals and reducing the 3-Dimensional structure of the reefs. Most atolls are not inhabited, so any changes are driven by climate changes rather than by any direct, local anthropogenic effect. Coral cover has been measured for 20 years using the same methods, while temperature loggers have recorded water temperature at various depths for over 10 years. Water temperatures have risen by one third of a degree on ocean reefs and over one half of a degree in lagoons over this period, causing the recent severe mortality. Juvenile corals have also been recorded at intervals during the last few years, and numbers severely declined following the mortality of the adults. Estimates of calcification suggest a marked reduction, from a state of vigorous reef growth that had not long recovered from the previous severe warming event of 1998, to one of net erosion. Predictions suggest that recurrences of mass mortalities will take place too frequently for any significant recovery of reef health in these atolls by the late 2020s.
Winnowing of poorly-adapted species from local communities causes shifts/declines in species richness, making ecosystems increasingly ecologically depauperate. Low diversity can be associated with marginality of environments, which is increasing as climate change impacts ecosystems globally. This paper demonstrates the demographic mechanisms (size-specific mortality, growth, fertility; and metapopulation connectivity) associated with population-level changes due to thermal stress extremes for five zooxanthellate reef-coral species. Effects vary among species, leading to predictable changes in population size and, consequently, community structure. The Persian/Arabian Gulf (PAG) is an ecologically marginal reef environment with a subset of Indo-Pacific species, plus endemics. Local heating correlates with changes in coral population dynamics and community structure. Recent population dynamics of PAG corals were quantified in two phases (medium disturbed MD 1998–2010 and 2013–2017, severely disturbed SD 1996/8, 2010/11/12) with two stable states of declining coral frequency and cover. The strongest changes in life-dynamics, as expressed by transition matrices solved for MD and SD periods were in Acropora downingiand Porites harrisoni, which showed significant partial and whole-colony mortality (termed “shrinkers”). But in Dipsastrea pallida, Platygyra daedalea, Cyphastraea microphthalma the changes to life dynamics were more subtle, with only partial tissue mortality (termed “persisters”). Metapopulation models suggested recovery predominantly in species experiencing partial rather than whole-colony mortality. Increased frequency of disturbance caused progressive reduction in coral size, cover, and population fecundity. Also, the greater the frequency of disturbance, the more larval connectivity is required to maintain the metapopulation. An oceanographic model revealed important local larval retention and connectivity primarily between adjacent populations, suggesting that correlated disturbances across populations will lead to winnowing of species due to colony, tissue, and fertility losses, with resultant insufficient dispersal potential to make up for losses—especially if disturbances increase under climate change. Variable extinction thresholds exist based on the susceptibility of species to disturbance (“shrinkers” vs. “persisters”), determining which species will be winnowed from the community. Besides projected changes in coral community and population structure, no species are projected to increase in cover. Increased marginality due to climate change will lead to a net loss of coral cover and novel communities in PAG.
Population genomic surveys suggest that climate-associated genetic variation occurs widely across species, but whether it is sufficient to allow population persistence via evolutionary adaptation has seldom been quantified. To ask whether rapid adaptation in reef-building corals can keep pace with future ocean warming, we measured genetic variation at predicted warm-adapted loci and simulated future evolution and persistence in a high-latitude population of corals from Rarotonga, Cook Islands. Alleles associated with thermal tolerance were present but at low frequencies in this cooler, southerly locality. Simulations based on predicted ocean warming in Rarotonga showed rapid evolution of heat tolerance resulting in population persistence under mild warming scenarios consistent with low CO2 emission plans, RCP2.6 and RCP4.5. Under more severe scenarios, RCP6.0 and RCP8.5, adaptation was not rapid enough to prevent extinction. Population adaptation was faster for models based on smaller numbers of additive loci that determine thermal tolerance and for higher population growth rates. Finally, accelerated migration via transplantation of thermally tolerant individuals (1 to 5%/year) sped adaptation. These results show that cool-water corals can adapt to warmer oceans but only under mild scenarios resulting from international emissions controls. Incorporation of genomic data into models of species response to climate change offers a promising method for estimating future adaptive processes.