Coral Reefs最新文献

Coral reef declines have been documented since the 1980's from a variety of global and local stressors. Management resource tools are needed to preserve these fragile ecosystems from stressors, both known and unknown. Laboratory studies have shown microplastics (MP) to have negative effects on coral physiology, but their effects in a natural environment are not well understood. Thus, our primary objectives were to explore associations between MPs and coral reef attributes. We measured MP concentrations from sub-surface water and coral tissue samples from two Caribbean/Atlantic scleractinian coral species, Montastraea cavernosa and Orbicella faveolata, from St. John, U.S. Virgin Islands and Florida's Coral Reef in 2017 and 2018, respectively. Polymer identification yielded mostly cotton or polyester fibers for both water and coral tissue samples. This study is the first to document MPs in coral tissues from either the U.S. Virgin Islands or Florida's Coral Reef and is the first to explore how MPs relate to coral reef attributes. Significant, positive relationships were seen between MPs in coral tissue and coral density, rugosity, and percent coral cover, indicating MPs may not have immediate adverse effects on coral reef health.

As coral reefs face increasingly frequent and severe disturbances, their condition relies more heavily on recovery dynamics. Understanding reef recovery is essential for assessing the long-term ecological integrity and functioning of these ecosystems. In this study, we used structure-from-motion photogrammetry to map reefs at Peros Banhos atoll (Chagos Archipelago) in the three years following the 2015-2016 mass coral bleaching event. This approach enabled us to detect and track individual post-bleaching coral recruits underpinning natural recovery (n = 1,074 across 72 m²), and investigate their early survival and growth. In 2017, one year after the bleaching, new recruit density was highest, largely due to comparatively high recruitment in sheltered sites. However, 2018 recruits had higher first-year survival and growth than the 2017 cohort, suggesting a negative legacy effect of high temperatures on reef recovery. Branching coral taxa showed both the highest first-year survival and growth. Interestingly, fine-scale substrate complexity at the onset of recovery was negatively associated with the density of recruits 1-2 years later. Despite favourable conditions that allowed the majority of recruits to survive and grow rapidly, all recruits combined accounted for only 2.39% coral cover three years after the bleaching event. Our results document vital rates during early natural recovery at a remote protected atoll and shed light on the dynamics of coral recruits immediately following mass bleaching. Further, we demonstrate the insight that photogrammetric approaches can provide to reef demographic studies.

Supplementary information: The online version contains supplementary material available at 10.1007/s00338-025-02732-8.

The coral skeletons that contribute to tropical reef structures are biominerals, composed of inorganic aragonite and organic biomolecules. The biomolecules influence the aragonite structure and material properties of the skeleton. We collected massive Porites lutea skeletons from Phuket, Thailand, in 1991, approximately one month into a temperature-induced bleaching event. Some specimens had expelled their Symbiodiniaceae in response to the increased water temperatures (bleached), while other corals appeared unaffected (unbleached). We investigate the effect of Symbiodiniaceae loss on the amino acid composition, aragonite structure, and Vickers hardness of the coral skeletons. We observe no significant difference in the amino acid content or composition of the outermost 1 mm of skeleton (representing 0.5 to 2 months growth) between bleached and unbleached specimens. The full width half maximum of the Raman spectrum ʋ₁ band, an indicator of disorder around the CO₃ group in the aragonite lattice, varies significantly between some corals in the outermost 200 µm of skeleton, but these differences are not attributable to the bleaching status of the coral colonies. Similarly, Vickers hardness varies significantly between some colonies, but this is not related to coral bleaching. This is a positive finding, suggesting that bleaching, from which corals recover, does not adversely affect the coral skeletal structure.

Supplementary information: The online version contains supplementary material available at 10.1007/s00338-025-02735-5.

Reef halos are circular patterns of bare sand surrounding patch reefs, formed by herbivorous fish grazing near their reef refuges. These formations serve as indicators of ecological processes, providing insights into interactions among herbivores, vegetation, and predators. Their size and prevalence are influenced by predator and herbivore densities, fishing pressure, and temperature, making them valuable proxies for assessing the impact of anthropogenic stressors on reef ecosystems. Halos can also be monitored using satellite imagery and artificial intelligence tools, offering a scalable method for evaluating ecosystem health. In this study, we present the first spatially explicit agent-based model to explore reef halo formation. By integrating seagrass growth models with herbivorous fish behavior, we capture the spatial complexity of halo dynamics. Our model reproduces observed field patterns, including halo size variability driven by temperature. In addition, the model uncovers new insights into the mechanisms behind the formation of sand corridors-vegetation-free pathways that link isolated halos-an aspect of halo dynamics that was previously unresolved. We propose that these corridors are shaped by limitations in rhizome growth rather than shifts in herbivore foraging behavior. These findings advance our understanding of the ecological processes driving halo formation and enhance the predictive value of halos as indicators of coral reef ecosystem health. The model offers a deeper insight into how reef systems respond to environmental pressures, providing a powerful tool for monitoring and managing reefs amid climate change and anthropogenic impacts.

Supplementary information: The online version contains supplementary material available at 10.1007/s00338-025-02729-3.

Regularly patterned reef ridges develop in the lagoons of at least one-third of Earth's coral reefs. The interactions between corals and their environment, occurring at scales from millimeters to meters, can lead to self-organized spatial patterns spanning hundreds of meters to kilometers. To understand the mechanism behind pattern formation, we first characterize these spatial patterns using satellite imagery from 63 sites across the Atlantic, Pacific, and Indian Oceans. Next, we develop a generalized Turing morphogenesis model. Corroborated by observed spatial patterns, results from our numerical model suggest that patterned ridges develop through a four-phase trajectory, dictated by changes in the lagoon's hydrodynamic regime. Initially, after an atoll lagoon forms, the first colonizing reefs establish as isolated pinnacles. These pinnacles then evolve into low-relief ridges and eventually form semi-enclosed inter-ridge ponds. In the terminal phase, a dense interconnected, branching, and rejoining ("anastomosing") pattern of reef ridges develop into a network, fully enclosing the ponds. Once enclosed, wind- and tide-induced currents are significantly reduced. Since corals rely on flow for feeding and shedding metabolites, ridge development stalls, and the pattern stabilizes. By combining empirical observations from around the world with a theoretical model, our study reveals the mechanism of reef pattern formation. Such a mechanistic understanding enables the use of emergent reef patterns to identify reef stress at the coral colony scale.

For sessile broadcast spawning marine invertebrates, such as corals, successful sexual reproduction depends on conspecifics spawning synchronously. The precise monthly, lunar, and diel timing and the extent of synchrony, i.e., proportion of population reproducing at the same time, are likely to play a key role in coral population recovery, persistence, and adaptation. Despite its importance, the mechanisms by which different environmental factors trigger corals to spawn on specific dates within the lunar cycle remain poorly understood. Periods of darkness post-sunset around full moon of the spawning month have been shown to induce spawning in merulinid corals, whereas for Acropora, moonlight is considered the main determinant driver of night of spawning. Here, we conducted two manipulative field experiments around full moon in Palau using the common table coral Acropora aff. hyacinthus to disentangle the role of moonlight and darkness post-sunset as proximate cues. Coral fragments were assigned to three treatments providing different post-sunset darkness conditions, versus control and procedural control fragments exposed to natural conditions. In contrast to previous studies on Acropora, we found that Acropora aff. hyacinthus can spawn synchronously in the absence of moonlight during the nights leading to spawning. Corals exposed to darkness post-sunset for at least two to three consecutive nights advanced their spawning compared to controls. This finding indicates that periods of darkness post-sunset can act as an inducer for spawning in Acropora as well as in merulinid corals, suggesting that this mechanism may be more widespread than previously thought.

Supplementary information: The online version contains supplementary material available at 10.1007/s00338-025-02618-9.

High mortality of juvenile corals hinder both the natural recovery of populations and the successful implementation of restoration efforts. Grazing is a significant cause of juvenile coral mortality, and grazer exclusion devices have been shown to increase juvenile coral survivorship. However, most experiments have used cages that typically alter water flow and light conditions, making it difficult to separate abiotic effects from those of grazing. Here, we test whether grazing deterrents can increase the survival and growth of six-month-old Acropora digitifera juveniles outplanted to a shallow reef crest, using arrangements of two or four long or short masonry nails designed to physically exclude larger grazers (e.g., parrotfish) while minimising abiotic changes. By the end of our study, colonies with deterrents had significantly larger planar area (almost tenfold for the most effective treatment), more branches, greater height, and higher survival than those without deterrents. A critical period in this study was the first week after outplanting when colonies with deterrents had significantly less tissue area loss from grazing than those without. Lower area loss in the first week was associated with significantly higher survival over the following 14 months, with an almost threefold improvement for the most effective treatment. For heavily grazed systems, our study highlights the importance of incorporating grazing deterrents into outplant devices to counteract the negative impact of large grazers on newly outplanted juvenile corals and boost restoration success.

Supplementary information: The online version contains supplementary material available at 10.1007/s00338-025-02703-z.

Scleractinian corals, the principal architects of coral reefs, face substantial threats from ongoing and anticipated climate change and other anthropogenic disturbances. This underscores the significance of investigating alternative reef-building organisms and their contribution to reefs’ resilience. Among these alternatives, colonial hydrozoans of the genus Millepora, commonly called ‘fire corals’, play substantial roles in contributing to coral reef structure and functionality by depositing calcareous exoskeletons. Despite the ecological importance of fire corals, fundamental knowledge gaps remain regarding their biology and reproductive ecology. Here, we present a comprehensive study on the population dynamics, reproductive ecology, phenology, and sex ratio of the three Red Sea fire corals—Millepora dichotoma, M. exaesa, and M. platyphylla—in the Gulf of Aqaba and Eilat. The abundance of M. dichotoma and M. exaesa seems to have remained consistent over the last 50 years across two of the three depth zones surveyed, indicating their potential resistance or resilience. However, at the third depth surveyed, their abundance appears to have decreased. Our extensive in-situ monitoring of breeding events over six consecutive years has revealed a previously undetected relationship between Millepora species breeding events and the lunar cycle. Histological analyses indicated remarkably short reproductive cycles of only 2–3 weeks, recurring multiple times within a single season, in both M. dichotoma and M. exaesa, which is a unique reproductive aspect compared to other reef-building corals. These results highlight the high reproductive and resilience potential of Millepora species. Consequently, fire corals could assume a more substantial role as keystone species in changing environments and future reefs, emphasizing their importance in reef conservation and management.

Climate-driven species range expansions are underway with more tropically affiliated species, including Scleractinian corals, becoming increasingly abundant at higher latitudes. However, uncertainty remains on how these range shifts will affect reef-scale ecosystem processes, which will ultimately depend on the traits of the taxa that dominate these assemblages. Here, we quantified spatiotemporal patterns in the taxonomic and trait structure of coral assemblages along the subtropical-temperate coast of Western Australia (27°–34°S). Coral abundance was generally low and coral cover < 5% across our study sites. Coral assemblages shared similarities in morphological trait structures across the latitudinal gradient, mostly characterised by taxa with simple morphologies; yet subtle differences were also observed across latitudes, with high-latitude corals characterised by slower growth rates and reduced maximum colony sizes. We found a 3.4-fold increase (from 1 to 3.4 individuals m⁻²) in coral abundance at one heavily disturbed location, where canopy-forming seaweeds were replaced by turfing algae, a pattern that was partly driven by an increase in the relative contribution of warm affinity taxa, such as Acropora spp. We predicted these changes would be reflected in different components of functional diversity; yet, despite a localised signal of tropicalisation, we only observed subtle changes in the functional identity, richness, evenness, and divergence. The spatially invariant trait structure of coral assemblages suggests that the nature of ecosystem functions will likely remain unchanged during early stages of tropicalisation, and hence their contribution to temperate reef-scale ecological processes will depend on dominance over other benthic foundational species.

Coral reefs are known to be one of the most diverse marine ecosystems on earth. However, these important ecosystems are heavily stressed by natural and anthropogenic activities. Environmental DNA (eDNA) metabarcoding is an innovative approach that can provide a greater diversity of taxonomic detections, non-invasive sampling, and a lower field component cost than traditional biomonitoring methods. Taiping Island (Itu Aba Island) is one of the major coral reef islands situated in the South China Sea where underwater visual surveys documented an outbreak of Crown-of-Thorns starfish (COTS) in 2021. In our study, we used eDNA metabarcoding to investigate whether there were shifts in coral communities by comparing pre- and post-COTS outbreak communities. One metabarcoding assay targeting the 18S gene and two assays targeting the ITS2 region (one of these assays specifically targeting Acroporid corals) were applied to 42 seawater samples collected in 2019 and 2021 from 12 sites around Taiping Island. Based on these three metabarcoding assays, 52 unique hard coral species were identified, corresponding to a total of 51 species in 2019 and 26 species in 2021. Our results indicated a significant decline in coral diversity but an increase in sponge diversity from the phylum porifera at Taiping Island in 2021. We suggest that these faunal shifts may be due to active feeding and disturbance of COTS at outbreak proportions that result in habitat changes. Our findings also suggest that eDNA can continue to serve as a promising tool to monitor the change in coral as well as reef-associated taxa during devastating outbreak events.