Scleractinian Corals Research Articles

Reproductive characteristics and gametogenic cycle of the scleractinian coral Dendrophyllia ramea.

The present study marks a pioneering investigation into the reproductive cycle of the scleractinian coral Dendrophyllia ramea. This is one of the first reproduction studies conducted in the Mediterranean Sea for a colonial azooxanthellate coral. Coral samples were collected in 2017 (May and October) and 2018 (February and July) in the Alborán Sea (SW Mediterranean). This location was selected due to its rarity as one of the few sites where this species thrives at depths shallower than 40 m. These samples were used to study the sexual patterns, fertilization mechanisms and gametogenic cycles by means of histological techniques. To broaden the scope, Sea Surface Temperature (SST) and Chlorophyll-a (Chl-a) data from open access databases have been considered to explore the potential influence of these environmental factors as triggers for gamete development and spawning time. The findings cast D. ramea as a gonochoric species, since no hermaphroditic specimens were observed among the analysed samples. Additionally, the lack of larvae and embryos in any of the analysed polyps, suggest that this species is fertilised externally. Two oocyte cohorts have been detected simultaneously, hinting at a yearly reproductive cycle, characterised by a prolonged oocyte maturation and seasonal spawning period taking place between August and October. Nevertheless, D. ramea display a low fecundity compared to other scleractinians inhabiting deep waters. Lastly, the early stages of gametogenesis seem to be coupled with the highest Chl-a values (i.e., March and December), whereas spawning takes place throughout the warmest period of the year (August to October).

Novel marine metalloprotease—new approaches for inhibition of biofilm formation of Stenotrophomonas maltophilia

Many marine organisms produce bioactive molecules with unique characteristics to survive in their ecological niches. These enzymes can be applied in biotechnological processes and in the medical sector to replace aggressive chemicals that are harmful to the environment. Especially in the human health sector, there is a need for new approaches to fight against pathogens like Stenotrophomonas maltophilia which forms thick biofilms on artificial joints or catheters and causes serious diseases. Our approach was to use enrichment cultures of five marine resources that underwent sequence-based screenings in combination with deep omics analyses in order to identify enzymes with antibiofilm characteristics. Especially the supernatant of the enrichment culture of a stony coral caused a 40% reduction of S. maltophilia biofilm formation. In the presence of the supernatant, our transcriptome dataset showed a clear stress response (upregulation of transcripts for metal resistance, antitoxins, transporter, and iron acquisition) to the treatment. Further investigation of the enrichment culture metagenome and proteome indicated a series of potential antimicrobial enzymes. We found an impressive group of metalloproteases in the proteome of the supernatant that is responsible for the detected anti-biofilm effect against S. maltophilia.Key points• Omics-based discovery of novel marine-derived antimicrobials for human health management by inhibition of S. maltophilia• Up to 40% reduction of S. maltophilia biofilm formation by the use of marine-derived samples• Metalloprotease candidates prevent biofilm formation of S. maltophilia K279a by up to 20%

Reef structure of the Florida Reef Tract for the period 2005–2020

Shallow-water coral reefs of the Florida Reef Tract compose the third largest reef in the world, but during the last several decades, scleractinian (stony) corals have suffered unprecedented declines from global and local stressors. A program to evaluate the effects of high-temperature bleaching events was initiated by The Nature Conservancy’s Florida Reef Resilience Program in 2005 and surveys have been completed across at least some portion of the entire region every year since. The program adopted a demographic (colony-based) assessment approach, which records colony species, size (height and maximum diameter), and estimated partial mortality (percent barren skeleton). Because reef structure is critical to ecosystem functioning and services, data from 2005 to 2020 were analyzed to describe the abundance, size, and morphological complexity of stony coral colonies forming the biogenic reef. Colony height, footprint, surface area, and volume summed for 6016 transects were used to describe reef structure and averages were used to characterize the components that contributed to the structure. Nearly 150,000 colonies representing 49 species were reported during this period and results demonstrated both spatial and temporal changes for the region and for geographic subregions. Some subregions showed increasing colony density, especially for three small, hemispheric species, and declining average colony size.

Oxidative stress responses of the scleractinian coral Acropora digitifera from the tropical Bidong Island, Malaysia - focus on protein thiol groups' detection

Over the past 40 years, recurrent episodes of coral bleaching have been observed around the world, which have led to coral reef degradation. The investigation of several biomarkers' responses is essential to understand the phenomenon. The present field experiment study was conducted on nine healthy colonies of the scleractinian coral Acropora digitifera collected in Bidong Island (north-eastern Peninsular Malaysia) between 2019 and 2020 to evaluate their oxidative stress status through the assessment of Symbiodiniaceae (SD) density, antioxidant enzyme activities, lipid oxidation, and protein thiol, with special emphasis on temperature. This study revealed that the presence of the dominant SD ITS2 type C3 from 2019 to 2020 suggests that the relationship between A. digitifera and the genus Cladocopium remains unaffected by the temperature. Concomitantly, there was no significant increase in antioxidant enzyme activities (glutathione S-transferase and catalase) with temperature, indicating that A. digitifera was capable of managing oxidative stress even in a warm environment. The monthly mean antioxidant enzyme activities and malondialdehyde (MDA) levels were lowest in July 2020 and then increased significantly in the subsequent sampling month, indicating a biochemical regulation to maintain cellular homeostasis. Meanwhile, the level of sensitive protein thiol was highest at 30.8 °C and significantly reduced up to 60% as temperature fluctuated, showing that proteins undergo only a small range of oxidative modifications. In addition, we found a weak negative correlation between SD density and thiol content, which may indicate that (1) the presence of SD constantly causes subtle oxidative pressure on coral hosts and (2) the presence of high SD density increases the potential for thiol oxidation. We conclude that there is no direct evidence of A. digitifera experiencing considerable oxidative stress and cellular damage, provided the rate of disturbance remains low.

Branching Lithophyllum Coralline Algae: Dominant Reef Builders on Herbivory-Depressed Tropical Reefs after High Coral Mortality

A unique shift in benthic community composition, where scleractinian corals are replaced by coralline algae, has been observed on coral reefs in Guam in the western Pacific. Guam’s reefs have been subjected to intense fishing pressure and impaired water quality for decades. Since 2013, heat stress has emerged as an additional major threat to the island’s coral reefs. After a severe coral bleaching and mortality event in 2017, branching coralline algae of the genus Lithophyllum rapidly overgrew dead coral skeletons of the ecosystem engineer Acropora abrotanoides and have since become major components of forereef communities over a broad depth range. By now, the persistence of increased Lithophyllum cover meets the temporal criterium of phase shifts, but accurate estimates on the degree of dominance over appropriate spatial scales are lacking due to the absence of reliable baseline data. The ecological impacts of coral reef transitions towards increased coralline cover are unclear. Whereas carbonate budgets and reef growth could remain positive in the long term, the downstream effect of changes in structural complexity, (micro)habitat diversity, and benthic community composition on ecological processes and reef-associated faunal assemblages is unknown.

Newly deceased Caribbean reef-building corals experience rapid carbonate loss and colonization by endolithic organisms

Coral mortality triggers the loss of carbonates fixed within coral skeletons, compromising the reef matrix. Here, we estimate rates of carbonate loss in newly deceased colonies of four Caribbean reef-building corals. We use samples from living and recently deceased colonies following a stony coral tissue loss disease (SCTLD) outbreak. Optical densitometry and porosity analyses reveal a loss of up to 40% of the calcium carbonate (CaCO3) content in dead colonies. The metabolic activity of the endolithic organisms colonizing the dead skeletons is likely partially responsible for the observed dissolution. To test for the consequences of mass mortality events over larger spatial scales, we integrate our estimates of carbonate loss with field data of the composition and size structure of coral communities. The dissolution rate depends on the relative abundance of coral species and the structural properties of their skeletons, yet we estimate an average reduction of 1.33 kg CaCO3 m−2, nearly 7% of the total amount of CaCO3 sequestered in the entire system. Our findings highlight the importance of including biological and chemical processes of CaCO3 dissolution in reef carbonate budgets, particularly as the impacts of global warming, ocean acidification, and disease likely enhance dissolution processes.

Microorganisms and dissolved metabolites distinguish Florida's Coral Reef habitats.

As coral reef ecosystems experience unprecedented change, effective monitoring of reef features supports management, conservation, and intervention efforts. Omic techniques show promise in quantifying key components of reef ecosystems including dissolved metabolites and microorganisms that may serve as invisible sensors for reef ecosystem dynamics. Dissolved metabolites are released by reef organisms and transferred among microorganisms, acting as chemical currencies and contributing to nutrient cycling and signaling on reefs. Here, we applied four omic techniques (taxonomic microbiome via amplicon sequencing, functional microbiome via shotgun metagenomics, targeted metabolomics, and untargeted metabolomics) to waters overlying Florida's Coral Reef, as well as microbiome profiling on individual coral colonies from these reefs to understand how microbes and dissolved metabolites reflect biogeographical, benthic, and nutrient properties of this 500-km barrier reef. We show that the microbial and metabolite omic approaches each differentiated reef habitats based on geographic zone. Further, seawater microbiome profiling and targeted metabolomics were significantly related to more reef habitat characteristics, such as amount of hard and soft coral, compared to metagenomic sequencing and untargeted metabolomics. Across five coral species, microbiomes were also significantly related to reef zone, followed by species and disease status, suggesting that the geographic water circulation patterns in Florida also impact the microbiomes of reef builders. A combination of differential abundance and indicator species analyses revealed metabolite and microbial signatures of specific reef zones, which demonstrates the utility of these techniques to provide new insights into reef microbial and metabolite features that reflect broader ecosystem processes.

Changes in the community structure of stony corals in the southern Mexican Caribbean

The Mexican Caribbean coral reef ecosystem has endured the effects of global and regional stressors and, recently, the massive arrivals of the free-living, floating brown algae Sargassum spp. This study aimed to evaluate spatiotemporal changes in the stony coral community structure in the southern Mexican Caribbean by a temporal comparison of live coral cover and colony density using a data set collected in 2008–2009 and a recent survey in 2021 within a Protected Natural Area. A multivariate analysis approach was used to reveal spatiotemporal changes in coral cover and colony densities. Coral cover ranged from 6.9 to 8.9% in 2008–2009 to 6.5% in 2021, the lowest values recorded for the area. Coral colony density ranged from 0.68 to 0.78 colonies m−1 in 2008–2009 to 0.68 colonies m−1 in 2021. The present results appear to represent subtle changes during the last decade.

Environmental assessment of oyster beds in the northern Arabian Gulf Coast of the United Arab Emirates

The United Arab of Emirates (UAE) hosts valuable coastal and marine biodiversity, and oysters are one of the habitants of its marine ecosystem. Oysters play an essential role in the nearshore coasts where they work as an active filter. They filter nutrients, phytoplankton, sediments, heavy metals, and toxins out of the water, which improves the water quality. This is the first study that characterizes oyster bed habitats in the UAE by analyzing water quality parameters, polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs)and heavy metals in water, sediments and oyster samples collected from five locations along the coasts of Sharjah, Ajman, and Umm al Quwain. Oyster bed areas supported a diverse assemblage of benthic life including oysters, scallops, pen shells, hard corals, and macroalgae. Mobile species in these habitats included groupers, emperors, snappers, sea snakes, among others. The phytoplankton assemblages were dominated by diatoms, dinoflagellates, and small cryptophytes. Harmful diatom Pseudonitzschia was found in all locations. No detectable concentrations of PAHs and OCPs were reported in this study, and water quality parameters were within the acceptable levels for the region. On the other hand, water quality index was reported marginal, mostly due to the presence of higher than acceptable concentrations of chromium and mercury in all sites studied. Bioconcentration factors concluded that oysters were able to bioconcentrate metals such as arsenic, cadmium, chromium, and zinc, when compared to water. No detectable concentrations of lead and mercury were reported in oysters, suggesting higher depuration rates for those metals.

Characterizing Reef Net Metabolism Via the Diel Co‐Variation of pH and Dissolved Oxygen From High Resolution in Situ Sensors

AbstractCoral reefs are subject to degradation by multiple environmental stressors which are predicted to intensify. Stress can alter ecosystem composition, with shifts from hard coral to macroalgae dominated reefs often accompanied by an increase in soft corals and sponges. Such changes may alter net ecosystem metabolism and biogeochemistry by shifting the balance between photosynthesis, respiration, calcification and dissolution. We deployed high temporal resolution pH and dissolved oxygen (DO) sensors at four Caribbean reef sites with varying covers of hard and soft corals, sponges and macroalgae. The resultant data indicated that the strength of the “metabolic pulse”, specifically the co‐variation in daily pH and DO oscillations, was driven by the net balance of light ‐dependent and ‐independent metabolism. pH and DO were positively correlated over the diel cycle at coral dominated sites, suggesting that photosynthesis and respiration were the major controlling processes, and further indicated by agreement with a simple production:respiration model. Whereas, at a site with high macroalgal cover, pH and DO decoupling was observed during daylight hours. This indicates that an unidentified light‐driven process altered the expected pH:DO relationship. We hypothesize that this could be mediated by the higher levels of macroalgae, which either stimulated bacterial‐mediated carbonate dissolution via the production and release of allelopathic compounds or retained oxygen, evolved during photosynthesis, in the gaseous form in seawater (ebullition). Our work demonstrates that high resolution monitoring of pH and DO provides insight into coral reef biogeochemical functioning and can be key for understanding long‐term changes in coral reef metabolism.

Physiology of the widespread pulsating soft coral Xenia umbellata is affected by food sources, but not by water flow.

Coral energy and nutrient acquisition strategies are complex and sensitive to environmental conditions such as water flow. While high water flow can enhance feeding in hard corals, knowledge about the effects of water flow on the feeding of soft corals, particularly those pulsating, is still limited. In this study, we thus investigated the effects of feeding and water flow on the physiology of the pulsating soft coral Xenia umbellata. We crossed three feeding treatments: (i) no feeding, (ii) particulate organic matter (POM) in the form of phytoplanktonand (iii) dissolved organic carbon (DOC) in the form of glucose, with four water volume exchange rates (200, 350, 500 and 650 L h-1) over 15 days. Various ecophysiological parameters were assessed including pulsation rate, growth rate, isotopic and elemental ratios of carbon (C) and nitrogen (N) as well as photo-physiological parameters of the Symbiodiniaceae (cell density, chlorophyll-a and mitotic index). Water flow had no significant effect but feeding had a substantial impact on the physiology of the X. umbellata holobiont. In the absence of food, corals exhibited significantly lower pulsation rates, lower Symbiodiniaceae cell density and lower mitotic indices compared to the fed treatments, yet significantly higher chlorophyll-a per cell and total N content. Differences were also observed between the two feeding treatments, with significantly higher pulsation rates and lower chlorophyll-a per cell in the DOC treatment, but higher C and N content in the POM treatment. Our findings suggest that the X. umbellata holobiont can be viable under different trophic strategies, though favouring mixotrophy. Additionally, the physiology of the X. umbellata may be regulated through its own pulsating behaviour without any positive or negative effects from different water flow. Therefore, this study contributes to our understanding of soft coral ecology, particularly regarding the competitive success and widespread distribution of X. umbellata.

PLANNING ANALYSIS OF KALEDUPA PORT WHARF BY USING SAP2000 SOFTWARE

Kaledupa Port is a public port that serves a limited number of domestic sea transportation activities. With the growth of the tourism sector in Wakatobi Regency, especially at Kaledupa Island, the operational intensity of the Kaledupa port has also continued to increase. One of the efforts that can be made in the development of Kaledupa Port is to analyze the planning of the Kaledupa Port wharf for quality improvement and evaluation at the Kaledupa Port. This study aims to find out what kind of loads work on the wharf which can then be modeled for wharf planning in the SAP2000 software. Based on the planning analysis, the Kaledupa port wharf is planned to have a length of 82 m and a width of 10 m with a general cargo ship with a maximum weight of 1,000 DWT. The results of the wharf modeling in the SAP2000 software with steel piles with a diameter of 508 mm and a thickness of 14 mm with a carrying capacity is 86.31 tons and based on the carrying capacity of the soil at location BH-02 the soil carrying capacity is 158.88 tons at a depth of 23 m with hard soil or coral conditions.

Stony coral tissue loss disease intervention with amoxicillin leads to a reversal of disease-modulated gene expression pathways.

Stony coral tissue loss disease (SCTLD) remains an unprecedented disease outbreak due to its high mortality rate and rapid spread throughout Florida's Coral Reef and wider Caribbean. A collaborative effort is underway to evaluate strategies that mitigate the spread of SCTLD across coral colonies and reefs, including restoration of disease-resistant genotypes, genetic rescue, and disease intervention with therapeutics. We conducted an in-situ experiment in Southeast Florida to assess molecular responses among SCTLD-affected Montastraea cavernosa pre- and post-application of the most widely used intervention method, CoreRx Base 2B with amoxicillin. Through Tag-Seq gene expression profiling of apparently healthy, diseased, and treated corals, we identified modulation of metabolomic and immune gene pathways following antibiotic treatment. In a complementary ex-situ disease challenge experiment, we exposed nursery-cultured M. cavernosa and Orbicella faveolata fragments to SCTLD-affected donor corals to compare transcriptomic profiles among clonal individuals from unexposed controls, those exposed and displaying disease signs, and corals exposed and not displaying disease signs. Suppression of metabolic functional groups and activation of stress gene pathways as a result of SCTLD exposure were apparent in both species. Amoxicillin treatment led to a 'reversal' of the majority of gene pathways implicated in disease response, suggesting potential recovery of corals following antibiotic application. In addition to increasing our understanding of molecular responses to SCTLD, we provide resource managers with transcriptomic evidence that disease intervention with antibiotics appears to be successful and may help to modulate coral immune responses to SCTLD. These results contribute to feasibility assessments of intervention efforts following disease outbreaks and improved predictions of coral reef health across the wider Caribbean.

Alacranes reef: A refuge for structurally complex coral species from increasing stressors

Coral reefs worldwide are being exposed to an interconnected myriad of anthropogenic stressors degrading their structure and functions. Therefore, global coral cover and coral reef ecosystem services have declined by half since the 1950s. Yet, remote reefs represent a time capsule to study ecological processes on minimally disturbed reefs, and these findings can steer management decisions and actions to enhance resilience. Combining in situ and satellite-derived data from the remote Alacranes Reef system located in the Gulf of Mexico, we evaluated benthic cover data and coral structural complexity together with physical drivers and direct coral stressors to better understand the current reef conditions of this remote system. Our main results show that 57% of the reef sites have >10% hard coral cover and are dominated by structurally complex species. Moreover, sites with >20% coral cover were associated with significantly shallower depths, smaller wave significant height, fewer bleaching impacts, as well as fewer macroalgae and cyanobacteria cover. Despite cumulative stressors impacting the Alacranes reef system, coral species assemblages and conditions are still driven by natural physical gradients, and the system hosts potential refuges for structurally complex species in the wider Caribbean. However, not all these refuges are fully protected, and strategic local management is key to maintaining and enhancing coral resilience in the context of increasing global stressors.

Cryopreservation and revival of Hawaiian stony corals using isochoric vitrification

Corals are under siege by both local and global threats, creating a worldwide reef crisis. Cryopreservation is an important intervention measure and a vital component of the modern coral conservation toolkit, but preservation techniques are currently limited to sensitive reproductive materials that can only be obtained a few nights per year during spawning. Here, we report the successful cryopreservation and revival of cm-scale coral fragments via mL-scale isochoric vitrification. We demonstrate coral viability at 24 h post-thaw using a calibrated oxygen-uptake respirometry technique, and further show that the method can be applied in a passive, electronics-free configuration. Finally, we detail a complete prototype coral cryopreservation pipeline, which provides a platform for essential next steps in modulating post-thaw stress and initiating long-term growth. These findings pave the way towards an approach that can be rapidly deployed around the world to secure the biological genetic diversity of our vanishing coral reefs.

Investigating microbial size classes associated with the transmission of stony coral tissue loss disease (SCTLD).

Effective treatment and prevention of any disease necessitates knowledge of the causative agent, yet the causative agents of most coral diseases remain unknown, in part due to the difficulty of distinguishing the pathogenic microbe(s) among the complex microbial backdrop of coral hosts. Stony coral tissue loss disease (SCTLD) is a particularly destructive disease of unknown etiology, capable of transmitting through the water column and killing entire colonies within a matter of weeks. Here we used a previously described method to (i) isolate diseased and apparently healthy coral colonies within individual mesocosms containing filtered seawater with low microbial background levels; (ii) incubate for several days to enrich the water with coral-shed microbes; (iii) use tangential-flow filtration to concentrate the microbial community in the mesocosm water; and then (iv) filter the resulting concentrate through a sequential series of different pore-sized filters. To investigate the size class of microorganism(s) associated with SCTLD transmission, we used 0.8 µm pore size filters to capture microeukaryotes and expelled zooxanthellae, 0.22 µm pore size filters to capture bacteria and large viruses, and 0.025 µm pore size filters to capture smaller viruses. In an attempt to further refine which size fraction(s) contained the transmissible element of SCTLD, we then applied these filters to healthy "receiver" coral fragments and monitored them for the onset of SCTLD signs over three separate experimental runs. However, several factors outside of our control confounded the transmission results, rendering them inconclusive. As the bulk of prior studies of SCTLD in coral tissues have primarily investigated the associated bacterial community, we chose to characterize the prokaryotic community associated with all mesocosm 0.22 µm pore size filters using Illumina sequencing of the V4 region of the 16S rRNA gene. We identified overlaps with prior SCTLD studies, including the presence of numerous previously identified SCTLD bioindicators within our mesocosms. The identification in our mesocosms of specific bacterial amplicon sequence variants that also appear across prior studies spanning different collection years, geographic regions, source material, and coral species, suggests that bacteria may play some role in the disease.

Adaptation strategies of relatively high-latitude marginal reef corals in response to severe temperature fluctuations

The large seasonal temperature fluctuations caused by global warming and frequent marine heatwaves pose new challenges to survival of relatively high-latitude marginal reef corals. However, the adaptation strategies of high-latitude marginal corals are not fully understood. We employed integrated approach to investigate the response mechanism of hosts, Symbiodiniaceae, and symbiotic bacteria of marginal reef corals Acropora pruinosa and Pavona decussate in response to large seasonal temperature fluctuations. The coral holobiont maintained a high level of immunity to adapt to seasonal pressure by increasing Symbiodiniaceae energy supply. The symbiotic Symbiodiniaceae of two coral was dominated by C1 subgroup, and was stable across seasons. The α-diversity of symbiotic bacteria P. decussata and A. pruinosa in summer was higher than that in winter. The symbiotic bacterial community of two coral reorganized during different seasons. Scleractinian corals improve adaptability to seasonal stress by increasing energy supply to maintain high levels of immunity, increasing symbiotic bacterial α-diversity, and changing dominant bacteria. This study demonstrates the adaptation strategies of marginal reef corals to seasonal temperature fluctuations and provides novel insights into the study of the adaptation of corals and relatively high-latitude coral refuges in the context of global warming and intensified marine heatwaves.

Seasonal upwelling conditions promote growth and calcification in reef-building coralline algae.

Crustose coralline algae (CCA) are important components of reef ecology contributing to reef framework construction. However, little is known about how seasonal upwelling systems influence growth and calcification of tropical CCA. We assessed marginal and vertical growth and net calcification rates of two dominant but morphologically different reef-building CCA, Porolithon antillarum and Lithophyllum cf. kaiseri, in a shallow coral reef of the Colombian Caribbean during upwelling and non-upwelling seasons. Growth and calcification rates varied seasonally with higher values during the upwelling compared to the non-upwelling (rainy) season. Annual vertical growth showed rates of 4.48 ± 1.58 and 4.31 ± 2.17 mm · y-1 , net calcification using crust growth estimates of 0.75 ± 0.30 g and 0.68 ± 0.60 g CaCO3 · cm-2 · y-1 and net calcification using the buoyant weight method of 1.49 ± 0.57 and 0.52 ± 0.11 g CaCO3 · cm-2 · y-1 in P. antillarum and L. kaiseri, respectively. Seawater temperature was inversely related with growth and calcification; however, complex oceanographic interactions between temperature and resource availability (e.g., light, nutrients, and CO2 ) are proposed to modulate CCA vital rates. Although CCA calcification rates are comparable to hard corals, CCA vertical accretion is much lower, suggesting that the main contribution of CCA to reef construction is via cementation processes. These results provide baseline data on CCA in the region and generate useful information for monitoring the impacts of environmental changes on tropical upwelling environments.

The comparative effects of chronic microplastic and sediment deposition on the scleractinian coral Merulina ampliata

Despite increasing research into the effects of microplastics on corals, no study to date has compared this relatively novel pollutant with a well-established stressor such as downwelling sediments. Here, Merulina ampliata coral fragments were exposed to polyethylene terephthalate (PET) and calcium carbonate particles (200–300 μm) at two deposition levels, high (115.20 ± 5.83 mg cm−2 d−1, mean ± SE) and low (22.87 ± 1.90 mg cm−2 d−1) in specially-designed Flow-Through Resuspension (FloTR) chambers. After 28 d, there were no significant differences between fragments exposed to sediments and microplastics for coral skeletal growth, Symbiodiniaceae density, and areal or cellular chlorophyll a concentrations. There were also no significant differences between levels of treatments, or with the control fragments. More PET microplastic particles were incorporated into the coral skeletons of fragments exposed to microplastics compared to those exposed to sediment and the control fragments, but there was no difference between fragments exposed to high and low microplastic levels. Together, the results show that M. ampliata appears to be able to cope with both microplastic and sediment stress, and suggests that microplastics do not represent a more serious threat than downwelling sediments at the levels tested.

Differing lesion recovery rates of two Caribbean stony coral species across a shallow water to mesophotic depth gradient suggest different sensitivity to repeated disturbance

Differing lesion recovery rates of two Caribbean stony coral species across a shallow water to mesophotic depth gradient suggest different sensitivity to repeated disturbance