Current Ecological Status of Remote Coral Reefs of Clipperton Island, Tropical Eastern Pacific

Clipperton, an uninhabited and remote coral atoll from the Eastern Pacific, is an important steppingstone area that harbors a high marine biodiversity. Despite its biogeographic importance, little information on the ecological status of its coral reefs is available from the last decade. Herein, we characterized the benthic coral community and health status among four different shallow reef-zones (North to South) of Clipperton during the Tara Pacific expedition in 2018. The benthic composition and coverage percentage, as well as occurrence of a pink-spotted coral phenotype (trematodiasis infection) was assessed. Total live coral cover on Clipperton reefs was 66% (55-85%), differing between sites, with massive Porites and branching Pocillopora corals dominating the benthic community with an average 48% (32-66%), and 15% (3-21%), respectively. While Clipperton reefs exhibited significant live coral cover overall, the trematode infection was commonly observed, with a higher occurrence in massive corals (Porites 27%, and Pavona 31%). This observation is possibly related to the combined effects of previously heatwaves, and local inputs of guano-derived nutrients discharged during storms and hurricanes. These results demonstrates that even highly remote reefs supporting high coral cover can be subjected to local and global threats, including but not limited to parasite prevalence, likely in relation to natural disturbances such as thermal stress and tropical cyclones.

Reef location has a greater impact than coral bleaching severity on the microbiome of Pocillopora acuta

Coral reefs are increasingly threatened by heat stress events leading to coral bleaching. In 2016, a mass bleaching event affected large parts of the Great Barrier Reef (GBR). Whilst bleaching severity and coral mortality are usually monitored throughout major bleaching events, other health indicators, such as changes in microbial partners, are rarely assessed. We examined the impact of the 2016 bleaching event on the composition of the microbial communities in the coral Pocillopora acuta at Havannah Island Pandora reef, separated by 12 km on the inshore central GBR. Corals experienced moderate heat stress (3.6 and 5.3 degree heating weeks), inducing major bleaching (30–60%) at the coral community level. Samples were partitioned according to Symbiodiniaceae densities into three bleaching severity categories (mild, moderate, and severe). Whilst Symbiodiniaceae densities were similar at both reef locations, sequencing of the Symbiodiniaceae ITS2 and prokaryotic 16S rRNA genes revealed that microbial communities were significantly different between reefs, but not according to bleaching severity. Symbiodiniaceae composition was dominated by the genus Cladocopium with low abundances of Durusdinium detected in moderately and severely bleached colonies at both sites, despite site-specific ITS2 profiles. Bacterial communities were dominated by Proteobacteria and were almost entirely lacking the common Pocilloporid associate Endozoicomonas regardless of bleaching severity. Strikingly, only 11.2% of the bacterial Amplicon Sequencing Variants (ASVs) were shared between sites. This reef specificity was driven by 165 ASVs, mainly from the family Rhodobacteraceae. Comparison with previous studies suggests that the moderate heat stress experienced on the central GBR in 2016 caused the near-complete absence of Endozoicomonas. Symbiodiniaceae and bacteria (particularly Rhodobacteraceae) can be vertically transmitted in P. acuta, and larval propagation can be spatially restricted for this brooding species. Our results demonstrate that, unlike bleaching severity, location-specific factors and species-specific life history traits might have been paramount in shaping the P. acuta microbiome.

Comparison of Standard Caribbean Coral Reef Monitoring Protocols and Underwater Digital Photogrammetry to Characterize Hard Coral Species Composition, Abundance and Cover

The precise assessing and monitoring of coral reefs are necessary to address and understand the threats and changes in coral communities. With the development of new technologies and algorithms for image processing, new protocols like underwater photogrammetry are implemented to study these ecosystems. This study compares the main ecological metrics for reef condition assessment, obtained with an underwater digital photogrammetry protocol (UWP) and traditional sampling design simulations in coral reefs of the Cozumel Reefs National Park. Three orthomosaics (380 m2) per reef on six fringing reefs were constructed, and the hard coral community characterized using a Geographic Information System (GIS). The orthomosaics were also used as a basis to simulate transect lines and obtain data on the hard coral community according to the video transect (VT) protocol, point intercept (PIT) protocol, and the Atlantic and Gulf Rapid Reef Assessment (AGRRA) protocol. Higher colony abundance, species richness, and lower coral cover estimates (p < 0.05) were obtained with the UWP. This protocol was also sensitive to small sized species. All the sampling designs showed similar capability to identify dominant species in terms of colony abundance and coral cover. The VT, PIT, and AGGRA showed similar coral cover values (p > 0.05), which seems to indicate that these sampling designs overestimate this important metric. Our results will help to understand and integrate the observations obtained with UWP with long-term data obtained with commonly used monitoring protocols in the Caribbean region.

Abundance and Characteristics of Microplastics in Seawater and Corals From Reef Region of Sanya Bay, China

Microplastics (MPs) contamination is widespread in the coral reef ecosystems leading to the exposure of both corals and other biotas. Knowledge gaps still exist concerning patterns in MPs abundance spatially. This work quantified the MPs abundance and characteristics in the seawater and corals in the Sanya Bay, Hainan Island. MPs abundance was detected in the seawater and coral samples ranging from 15.50 to 22.14 items L–1, and 0.01 to 3.60 items polyp–1, respectively. We found the predominant size and type of MPs in seawater and corals were smaller than 2 mm and fiber. Further analysis revealed that the characteristics of MPs in the corals were significantly different from those in the seawater environment, indicating that the MPs are selectively enriched in corals. Furthermore, the MPs particles ingested and retained in coral tissue may be related to the polyp size. This study shows that MPs are present in the whole coral reef region and the coral community structure would be potentially harmed by these contaminants.

Spatial Patterns of Coral Community Structure in the Toliara Region of Southwest Madagascar and Implications for Conservation and Management

The Great Reef of Toliara, on the southwestern coast of Madagascar, has been documented as harbouring flourishing reef communities in the 1960s, but has since been affected by various threats, causing a coral decline last reported in 2008. In 2017, we examined the spatial heterogeneity in coral community structure in the region of Toliara. Coral assemblages were characterized by a marked spatial variability, with significant variation for most of the descriptors among the three major habitats and also among stations within habitats. We recorded high coral cover, with values >40% at six of the 10 stations, which was associated with high abundance of coral colonies. We also documented the return to an Acropora-dominated coral assemblage. While these positive results suggest a recent return to healthier coral assemblages, they must be tempered, as the diversity that we recorded was lower than in the 1960s. Moreover, we found a high cover of algae at several stations, suggesting that the ecosystem is likely close to the tipping point toward a phase shift. Finally, the population size-structure of major coral taxa was positively skewed, with few large colonies to ensure the replenishment of local populations. The marked spatial variation suggests that marine protected areas should integrate a sufficiently large area to capture the scale of this spatial heterogeneity.

Study on suitability of Derawan Island as marine tourism destination towards development of sustainable tourism in the new capital city candidate of Indonesia

Derawan Island is one of the leading tourist destinations in Kalimantan Timur Province which is a candidate for the new capital city of Indonesia. Marine tourism on Derawan Island relies on the potential of marine resources so that a suitability study is needed for the development of sustainable tourism. This study aims to determine the suitability of marine tourism, especially the interest in diving and snorkeling in sites of Derawan Island. Data collection was carried out by surveying in December 2020 at five snorkeling and six popular dive sites in Derawan Island. Data on coral community, the number of coral fish species, and the water quality parameters are used to analyze the suitability of marine tourism. Line Intercept Transect (LIT) method was used to collecting coral community data, Underwater Visual Census (UVC) method was used to collect data on the abundance of reef fish species, and in situ water quality parameters. Tourism suitability index formula (IKW) using the four classification marine tourism suitability matrix was used to analyze the data. The results of the analysis show the suitability index for diving tourism as a whole is in suitable to very suitable category, while the snorkeling tourism suitability index is in the suitable category.

Multi-Variate Analyses of Coral Mortality From the 2014–2015 Stony Coral Tissue Loss Disease Outbreak Off Miami-Dade County, Florida

Environmental compliance monitoring associated with the Port Miami dredging project (2013–2015), designed to assess the impact of project-generated sediments on the local coral community, fortuitously captured a thermal bleaching event and the first reports of an emergent, highly contagious, white-plague-like coral disease outbreak in the fall of 2014. The disease, now termed stony coral tissue loss disease (SCTLD), has decimated reefs throughout Florida and is now spreading across the Caribbean. The high prevalence of disease, the number of affected species, and the high mortality of corals affected suggests SCTLD may be the most lethal coral disease ever recorded. Previous analyses of the dredge monitoring data have reached mixed conclusions about the relative impact of dredging on coral mortality and has often parsed out disease susceptible individuals to isolate the impacts of dredging only. We use multi-variate analyses, including time-based survival analyses, to examine the timing and impacts of dredging, coral bleaching, and disease on local coral mortality. By examining the status of corals monthly from the October 2013 to July 2015 observational period, we found that coral mortality was not significantly affected by a coral’s proximity to the dredge site or sediment burial. Instead, coral mortality was most strongly impacted by disease and the emergence of SCTLD during the monitoring period. During the 2-year monitoring period, 26.3% of the monitored corals died, but the only conditions significantly affected by the dredge were partial burial and partial mortality. The strongest link to mortality was due to disease, which impacted coral species differently depending on their susceptibility to SCTLD. The focus on disturbances associated with dredging created a circumstance where the greater impacts of this emergent disease were downplayed, leading to a false narrative of the resulting mortality on the local coral communities. The results of this study reveal that while local events such as a dredging project do have quantifiable effects and can be harmful to corals, regional and global threats that result in mass coral mortality such as thermal stress and disease represent an existential threat to coral reefs and must be urgently addressed.

More than local adaptation: high diversity of response to seawater acidification in seven coral species from the same assemblage in French Polynesia

Responses of corals to seawater acidification have been extensively studied. Sensitivity varies widely between species, highlighting the need to avoid extrapolation from one to another to get an accurate understanding of coral community responses. We tested the responses of seven coral species (Acropora cytherea, Acropora hyacinthus, Acropora pulchra, Leptastrea pruinosa, Montipora grisea, Pavona cactus, Pocillopora verrucosa) from the Mo'orea lagoon to a 48-day exposure to three pH scenarios (pH 7.95, 7.7 and 7.3). Tissue necrosis, mortality, growth rates, photophysiological performances and colour index were recorded. Few significant differences were noted between pH 7.95 and 7.7, but species-specific responses were observed at pH 7.3. While our data do not allow identification of the mechanisms behind this diversity in response between species inhabiting the same environment, it can exclude several hypotheses such as local adaptation, skeletal type, corallum morphology or calcification rate as sole factors determining coral sensitivity to pH.

Impacts of Stony Coral Tissue Loss Disease (SCTLD) on Coral Community Structure at an Inshore Patch Reef of the Upper Florida Keys Using Photomosaics

Since the appearance of stony coral tissue loss disease (SCTLD) on reefs off Miami in 2014, this unprecedented outbreak has spread across the entirety of Florida’s coral reef tract, as well as to many territories throughout the Caribbean. The endemic zone reached the upper Florida Keys by 2016, resulting in partial or complete mortality of coral colonies across numerous species. Disease was first observed at Cheeca Rocks (Islamorada, Florida) in the beginning of 2018, with reports of coral mortality peaking mid-year. The disease was still present at Cheeca Rocks as of March 2020, however, to a lesser degree compared to the initial outbreak. Annual monitoring efforts have been ongoing at Cheeca Rocks since 2012, including repeated benthic photomosaics of a 330 m2 survey zone, spanning six replicate sites. As such, a repository of coral community composition data exists for before and after the disease outbreak that was analyzed to assess the impacts of SCTLD on reef communities at an upper Florida Keys inshore reef. Cheeca Rocks is hypothesized to be a resilient reef due to its persistent high coral cover despite its inshore location, which subjects corals to fluctuating water quality and marginal environmental conditions. Coral populations here have been shown to recover from bleaching events and heat stress with minimal coral mortality. Though colonies of coral species characterized as highly and moderately susceptible to SCTLD (e.g., Colpophyllia natans, Diploria labyrinthiformis, Pseudodiploria strigosa, Orbicella annularis, and O. faveolata) suffered mortality as a result of the outbreak with an average loss of 16.42% relative cover by species, the overall impacts on coral cover and community structure were relatively low, contributing to a loss of total coral cover of only 1.65%. Comparison of photomosaic data to other studies indicate Cheeca Rocks may not have been affected as severely as other sites on Florida’s coral reef tract, underlying this site’s potential role in coral resilience to stressors including bleaching events, land-based pollution, and disease epizootics.