Ocean acidification from increasing atmospheric CO2 is progressively affecting seawater chemistry, but predicting ongoing and near-future consequences for marine ecosystems is challenging without empirical field data. Here we quantify tropical coral reef benthic communities at 37 stations with varying exposure to submarine volcanic CO2 seeping, and determine the aragonite saturation state (ΩAr) where significant changes occur in situ. With declining ΩAr, reef communities displayed progressive retractions of most reef-building taxa and a proliferation in the biomass and cover of non-calcareous brown and red algae, without clear tipping points. The percent cover of all complex habitat-forming corals, crustose coralline algae (CCA) and articulate coralline Rhodophyta declined by over 50% as ΩAr levels declined from present-day to 2, and importantly, the cover of some of these groups was already significantly altered at an ΩAr of 3.2. The diversity of adult and juvenile coral also rapidly declined. We further quantitatively predict coral reef community metrics for the year 2100 for a range of emissions scenarios, especially shared socio-economic pathways SSP2-4.5 and SSP3-7.0. The response curves show that due to ocean acidification alone, reef states will directly depend on CO2 emissions, with higher emissions causing larger deviations from the reefs of today.
Continue reading ‘Progressive changes in coral reef communities with increasing ocean acidification’Posts Tagged 'corals'
Progressive changes in coral reef communities with increasing ocean acidification
Published 8 December 2025 Science ClosedTags: algae, BRcommunity, chemistry, community composition, corals, field, otherprocess, vents
Resistance of the cold-water coral Dendrophyllia cornigera to single and combined global change stressors
Published 28 November 2025 Science ClosedTags: biological response, corals, growth, laboratory, morphology, mortality, multiple factors, North Atlantic, oxygen, respiration, temperature
Current knowledge of the consequences on global change in deep marine ecosystems is still limited, especially since environmental pressures do not act separately, and their potential interactions are mostly unknown. Cold-water corals (CWC) play a significant role in the deep sea, being ecosystem engineers supporting high biodiversity. However, global change may impact CWCs, compromising their integrity and survival. In this study, a nine-month aquaria experiment was conducted on the CWC Dendrophyllia cornigera from the NW Iberian Shelf (NE Atlantic Ocean). The aim was to assess the individual and combined effects of elevated temperature (12 vs. 15 °C), low pH (~ 7.99 vs. 7.69 pHT) and low oxygen (~ 6.4 vs. 4.7 mL L−1), based on the IPCC RCP 8.5 scenario. During the experiment, coral survival, skeletal growth, tissue cover and respiration were monitored as response variables. No significant effects were found on any of the response variables for either individual or combined stressors, pointing to the resistance of D. cornigera to different global change scenarios. Such a physiological resistance may support D. cornigera persistence under future conditions where other CWCs with narrower tolerance ranges may face greater limitations. However, further research is needed to assess potential trade-offs to cope with environmental change, which might impact the long-term survival capacity of this species.
Continue reading ‘Resistance of the cold-water coral Dendrophyllia cornigera to single and combined global change stressors’Dynamics of a coral reef system under climate change
Published 28 November 2025 Science ClosedTags: biological response, BRcommunity, communitymodeling, corals, echinoderms, modeling, multiple factors, temperature
Highlights
- It is established that a new a stochastic coral-starfish model with global warming and ocean acidification.
- It is revealed that the change in global warming has a decisive impact on the dominant position of corals and starfish.
- It is found that the variation of pH is able to destabilize coral-starfish interactions.
Abstract
The intensification of global warming and ocean acidification are important factors affecting coral reef degradation, however, their impact mechanisms on coral reef system are still unclear. In this paper, we study the dynamics of a stochastic coral-starfish model considering the factors of global warming and ocean acidification, where the stochastic environmental fluctuation is characterized by mean-reverting Ornstein-Uhlenbeck (OU) process. A key advantage of considering global warming and ocean acidification in coral reef systems is that it can accurately describe the dynamic mechanisms of coral-starfish interactions, providing a scientifically reliable theoretical basis for exploring the evolutionary succession of coral reef systems. The main purpose of this paper is to investigate how global warming and ocean acidification affect the dynamic mechanisms of coral reef systems in the presence and absence of stochastic disturbances. Mathematically, we mainly study the critical threshold conditions for the transcritical bifurcation, saddle-node bifurcation, and Hopf bifurcation of deterministic coral reef system, as well as the existence of ergodic stationary distribution, precise expressions of probability density function, persistent in the mean, and stochastic extinction dynamics in stochastic coral reef system, which in turn provide a theoretical basis for numerical simulations. Numerical analysis indicates that the variations of global warming and ocean acidification can generate a great influence on the coral-starfish dynamics with and without OU process. Significantly, it is found that coral growth dominates under the increasing global warming effect, while starfish growth dominates under the decreasing global warming effect in a randomly perturbed environment. Furthermore, the change of pH has capacity to destabilize coral-starfish interactions, while the intensified global warming can lead to the extinction of starfish. These findings may contribute to the studies of potential strategies for protecting coral reef ecosystems under the impact of climate change.
Continue reading ‘Dynamics of a coral reef system under climate change’Acidic oceans are forcing corals to build weaker skeletons
Published 26 November 2025 Press releases ClosedTags: corals
When scientists raised baby reef-building corals in acidic seawater pushed toward about pH 7.6, the youngsters still built skeletons.
The tiny skeletons were denser yet less stable, so the corals were more likely to snap when waves or animals pushed on them.
Across tropical oceans, reefs depend on countless such skeletons growing, thickening, and locking together.
As ocean acidification deepens, scientists are racing to understand whether coral skeletons can keep pace.
Inside a coral’s first skeleton
The work was led by Dr. Federica Scucchia, a postdoctoral associate at the University of Rhode Island (URI). Her research focuses on biomineralization, the way living organisms build hard mineral structures, in young reef building corals.
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The team combined three-dimensional X-ray scanning with short growth intervals. They also used electron microscopes to see features smaller than a micrometer and to trace tiny crystals.
These tools let them map mineral density, crystal size, and growth zone shapes in Stylophora pistillata, a common Red Sea stony coral.
Under normal pH, the thickening deposits made up most of the skeleton and wrapped around a web of rapid accretion deposits.
Inside those fibers, much of the mineral turned out to be amorphous calcium carbonate, a disordered mineral form that later transforms into crystals. Only a smaller share had already organized into dense calcium carbonate crystals that pack tightly together.
In more acidic water, the pattern shifted in several important ways. Both growth zones became denser overall, and the crystals inside them grew larger, even though the total skeleton volume shrank.
Continue reading ‘Acidic oceans are forcing corals to build weaker skeletons’The larva-Symbiodiniaceae association at risk: putative impacts of climate change on reproduction, dispersal, and recruitment in coral reefs
Published 24 November 2025 Science ClosedTags: biological response, BRcommunity, cnidaria, corals, mollusks, physiology, phytoplankton, porifera, reproduction, review
The relationship between invertebrates and Symbiodiniaceae dinoflagellates is the ecological foundation of diverse and productive coral reef ecosystems. Climate change-induced breakdown of this partnership, i.e., bleaching, is repeatedly driving widespread reef degradation. Thus, the future trajectory of this ecosystem depends on the reproduction and dispersal capacity of invertebrate-Symbiodiniaceae symbiosis. This review examines how climate change affects the biology of larvae from three invertebrate phyla—Porifera, Cnidaria, and Mollusca—that host Symbiodiniaceae, focusing on differences in symbiont transmission mode, symbiont location, and the larvae´s reliance on these associations. Due to limited research on Porifera and Mollusca hosts, most knowledge of larvae-Symbiodiniaceae associations stems from coral larvae patterns. The myriads of combinations of genetic and ecophysiologically distinct hosts and symbionts result in highly context-dependent responses to warming, but symbiotic larvae tend to be more susceptible to oxidative stress and show higher mortality than aposymbiotic larvae. While ocean acidification has little direct effect on the algal symbionts, it impacts larvae variably, especially calcifying larvae (e.g., mollusks), which suffer from impaired calcification and higher mortality. Climate change also impairs the reproductive processes of Symbiodiniaceae-bearing invertebrates, reducing gamete output, causing asynchronous spawning, and lowering larval survival. These effects will result in a persistent decline in recruitment with increased larval retention, consequently reducing reef connectivity and genetic diversity, thus weakening ecosystem resilience. This underscores the urgent need to hasten knowledge on larval ecology under climate change and the functional role of symbionts to better inform marine conservation planning and to incorporate larval ecology in the future predictions.
Continue reading ‘The larva-Symbiodiniaceae association at risk: putative impacts of climate change on reproduction, dispersal, and recruitment in coral reefs’A century of change in the California Current: upwelling system amplifies acidification
Published 19 November 2025 Science ClosedTags: biological response, chemistry, corals, field, modeling, North Atlantic, paleo, regionalmodeling
Predicting the pace of acidification in the California Current System (CCS), a productive upwelling system that borders the west coast of North America, is complex because the anthropogenic contribution is intertwined with other natural sources. A central question is whether acidification in the CCS will follow the pace of increasing atmospheric CO2, or if climate effects and other biogeochemical processes will either amplify or attenuate acidification. Here, we apply the boron isotope pH proxy to cold-water orange cup corals to establish a historic level of acidification in the CCS and the Salish Sea, an associated marginal sea. Through a combination of complementary modeling and geochemical approaches, we show that the CCS and Salish Sea have experienced amplified acidification over the industrial era, driven by the interaction between anthropogenic CO2 and a thermodynamic buffering effect. From this foundation, we project future acidification in the CCS under elevated CO2 emissions. The projected change in pCO2 over the 21st century will continue to outpace atmospheric CO2, posing challenges to marine ecosystems of biological, cultural, and economic importance.
Continue reading ‘A century of change in the California Current: upwelling system amplifies acidification’Newly discovered CO2 (carbon dioxide) vent cave drives r-strategy shift in a Mediterranean aphotoendosymbiotic coral
Published 14 November 2025 Science ClosedTags: abundance, biological response, chemistry, corals, field, growth, Mediterranean, morphology, reproduction, vents
Highlights
- Characterization of an unexplored CO2 vent cave
- CO2 vents chemical-physical parameters affect ecological traits of calcifiers
- Aphotoendosymbiotic solitary coral naturally inhabiting a CO2-rich gas environment.
- Prolonged acidified conditions did not affect C. inornata growth rate
- Shift towards an r-demographic strategy in response to acidified conditions
Abstract
Submarine CO2 volcanic vents represent peculiar environments with varying seawater chemical-physical parameters that may affect the ecological traits of calcifying organisms, such as growth and demographic characteristics. The present study focused on exploring the growth and population dynamics of a temperate, solitary and aphotoendosymbiotic coral Caryophyllia inornata (Duncan, 1878) living in a CO2 vent cave at 14 m depth. The volcanic emissions in and around the cave led high levels of pCO2, resulting in lower calcium carbonate saturation state (Ωa: 2.1–2.2) values compared to those observed in the ambient seawater of the Mediterranean Sea, not affected by venting activity. Prolonged acidified conditions (pHT: 7.5) did not affect C. inornata growth rate but resulted in a population with higher percentage of juvenile individuals, lower average ages and a lower age at maximum biomass percentage, thus suggesting a transition in its population dynamics towards an r-demographic strategy. This study provides a detailed characterization of a previously unexplored CO2 vent cave, highlighting the importance of these sites as natural laboratories to offer valuable insights into understanding the full ecological impact of aphotoendosymbiotic corals under ocean acidification.
Continue reading ‘Newly discovered CO2 (carbon dioxide) vent cave drives r-strategy shift in a Mediterranean aphotoendosymbiotic coral’Integrative analysis of coral plasticity and adaptations reveals key proteins driving resilience to changes in ocean carbonate chemistry
Published 14 November 2025 Science ClosedTags: adaptation, biological response, calcification, corals, laboratory, molecular biology, otherprocess, physiology
Understanding how corals adapt to changes in seawater carbonate chemistry is crucial for developing effective coral conservation strategies. Research to date has mostly focused on short-term experiments, overlooking long-term evolutionary effects. Here, we investigated the link between short-term stress responses and long-term genetic adaptations in the coral species Porites pukoensis through experiments under varying CO2 and alkalinity conditions. Our results showed that alkalinity enrichment significantly increased coral calcification rates by 35%-45% compared to high CO2 treatment, highlighting the potential of alkalinity enrichment to mitigate acidification impacts. Corals modulated relative expression levels of basic and acidic proteins in response to changes in seawater carbonate chemistry in the stress experiments. Genomic data revealed that this mechanism has been evolutionarily fixed in various organisms adapting to seawater carbonate chemistry. Additionally, both experimental and genomic results showed that extracellular matrix proteins, like collagen with von Willebrand factor type A domain, were modified in response to distinct carbonate environments. Molecular dynamics simulations and in-vitro experiments demonstrated that the structural stability of these proteins contributes to coral resilience under acidified conditions. This study established an integrated framework combining stress experiments, multi-omics analyses, molecular simulations, and in-vitro validation to identify key proteins involved in coral adaptation to acidification.
Continue reading ‘Integrative analysis of coral plasticity and adaptations reveals key proteins driving resilience to changes in ocean carbonate chemistry’Rapid ocean acidification and coral calcification response in the northern South China Sea: insights from δ11B and B/Ca records in Porites coral
Published 30 October 2025 Science ClosedTags: biological response, chemistry, corals, field, North Pacific, physiology
Abstract
Ocean acidification (OA) threatens coral calcification by reducing the carbonate ion concentration that corals need to build their skeletons. However, assessments of the impacts of long-term OA are scarce, limiting our understanding of the response and acclimatization of corals to high pCO2 levels. Here we present a 42-year (1968–2010) seasonal δ11B and B/Ca records from Porites corals at Dongsha Atoll, located in the northern South China Sea. Our results reveal a rapid decline in seawater pH over this period, at a rate of −0.0021 ± 0.0008 pH units per year. Of special interest is that the interannual variability in seawater pH appears to be primarily co-regulated by hydrological changes in the Pearl River and fluctuations in the strength of Kuroshio intrusion. These factors are linked to large-scale climate systems and interannual-to-decadal variability, including the Pacific Decadal Oscillation, El Nino-Southern Oscillation, and East Asian Winter Monsoon. Meanwhile, reconstructed carbonate chemistry from the coral calcifying fluid suggests that Porites corals at Dongsha Atoll are able to physiologically modulate their internal pH. This up-regulation of internal pH not only buffers seasonal fluctuations in the aragonite saturation state and sustains stable calcification rates year-round, but also aids in long-term resistance to the detrimental effects of OA.
Plain Language Summary
Ocean acidification poses a major threat to coral reefs by reducing the concentration of carbonate ions essential for coral skeleton formation. However, long-term assessments of ocean acidification impacts on coral calcification are scarce, limiting our understanding of coral resilience and their potential for acclimation to ocean acidification. Using a 42-year Porites coral δ11B and B/Ca records, we investigated long-term variability in pHsw and the carbonate chemistry of the coral calcifying fluid (e.g., pHcf and Ωcf) in the northern South China Sea. Our results reveal a significant decline in pHsw over the past four decades. The interannual variability in pHsw is primarily co-modulated by hydrological changes in the Pearl River system and variations in the strength of Kuroshio intrusion. Physiological modulation of pHcf up-regulation in Dongsha corals plays a key role in minimizing seasonal fluctuations in Ωcf, maintaining stable year-round calcification rates, and contributing to their long-term resistance to the adverse effects of ocean acidification over the past 42 years.
Key Points
- A 42-year δ11B and B/Ca records from Dongsha corals reveals rapid OA and physiological adjustment of calcifying fluid carbonate chemistry
- Interannual pHsw variability is primarily co-modulated by hydrological changes in the Pearl River and variations in the Kuroshio intrusion
- Under a rapid OA rate (−0.0021 ± 0.0008 pHsw yr−1), calcifying fluid Ωcf remains constant, suggesting that DSA corals are resistant to OA
Will coral reefs be gone by 2050? How bleaching, acidification, and ocean heating are killing coral reefs (podcast)
Published 21 October 2025 Web sites and blogs ClosedTags: corals, podcast
Twenty-five years ago, a landmark paper warned that the world’s coral reefs could vanish by 2050. Now, halfway to that projected date (and amid ever more frequent coral bleaching events), that grim prediction feels increasingly close to reality. What is the current state of Earth’s coral reefs, and what would happen to our planetary home without them?
In this episode, Nate is joined by Ove Hoegh-Guldberg, the marine biologist who made this landmark prediction, for an update on the health of coral reefs and the primary ecological stressors driving their decline. Drawing on decades of research, he explains the mechanisms of coral bleaching, the critical biodiversity hotspots that reefs create, and the implications for human populations that depend on these ecosystems. Ove also touches on the emotional impact of witnessing the loss of reefs for the scientists who have dedicated their lives to studying them.
How are human actions increasingly putting pressure on the very ecosystems that support more than one billion people? What would happen to the broader health of the oceans if reefs were to disappear entirely? And most of all, what changes can both individuals and institutions make today to support the health of these vital ecosystems – and in-turn, the well-being of the entire Earth?
Continue reading ‘Will coral reefs be gone by 2050? How bleaching, acidification, and ocean heating are killing coral reefs (podcast)’Oxidative stress and histological alterations in coral Briareum violacea co-exposed to ocean acidification and microplastic stressors
Published 17 October 2025 Science ClosedTags: biological response, BRcommunity, corals, laboratory, morphology, multiple factors, North Pacific, performance, physiology, phytoplankton, plastics
Ocean acidification and microplastic pollution are two major stressors threatening coral health, yet their combined impacts and underlying mechanisms remain poorly understood. This study investigated the combined effects of ocean acidification and microplastics exposure to coral health. Briareum violacea was exposed to pH at 7.7, 7.5, and 7.3 combined with polyethylene microplastic (PE-MP; 50 mg/L) for 21 days. Polyp length and behavioral adaptability were monitored daily, while coral was collected on days 14 and 21 to assess Symbiodiniaceae density, antioxidant enzyme activity, and histopathological alterations. Results showed that combined exposure to different pH (7.7, 7.5, and 7.3) and PE-MP significantly impaired coral condition, reduced polyp length and Symbiodiniaceae density, along with intensified oxidative stress and tissue damage compared to single stressors. These findings underscore coral vulnerability under combined stressors, emphasizing the necessity for future research to address long-term ecological consequences and resilience mechanisms in coral reef ecosystems.
Continue reading ‘Oxidative stress and histological alterations in coral Briareum violacea co-exposed to ocean acidification and microplastic stressors’Corals fine-tune their chemistry to survive in today’s acidic seas
Published 13 October 2025 Press releases ClosedTags: corals
Some reef-building corals seem to keep making sturdy skeletons even as the ocean grows more acidic. New evidence from long-lived corals suggests they can tweak the chemistry at the site where their skeleton forms, helping them push through conditions that should, in theory, slow them down.
The work, led by CU Boulder researchers and collaborators, looks back over roughly two centuries of rising acidity and finds corals adjusting their internal calcification engine to stay in the game.
Corals adapt to harsh chemistry
“We found that corals were able to regulate the mechanism they use to build and maintain their skeletons despite the ocean becoming more acidic,” said Jessica Hankins, the paper’s first author and a Ph.D. student in the Department of Geological Sciences.
“It’s an unexpected and hopeful signal; however, we need more long-term data to know what it really means.”
Continue reading ‘Corals fine-tune their chemistry to survive in today’s acidic seas’Environmental conditions and carbonate chemistry variability influencing coral reef composition along the Pacific coast of Costa Rica
Published 10 October 2025 Science ClosedTags: biogeochemistry, BRcommunity, chemistry, community composition, corals, field, North Pacific, otherprocess
Coral reef development is influenced by a wide variety of factors, including temperature, salinity, nutrient concentrations, and carbonate chemistry. Studies focusing on physicochemical drivers of coral reef distribution and composition in the Eastern Tropical Pacific (ETP) are scarce, and carbonate chemistry and nutrient data for this region are limited. This study measured coral reef composition and physicochemical parameters along the Pacific coast of Costa Rica, over a one-year period at three locations: Santa Elena and Matapalo in the north, and Parque Nacional Marino Ballena in the south. Our results show high seasonal and spatial variability of physicochemical conditions with significant differences mainly explained by inorganic nutrient concentrations, with driving processes also having a strong influence on the variability of carbonate chemistry parameters. Coastal upwelling is the main driver of the seasonal variability in Santa Elena. Comparison of seasonal dissimilarity within locations confirms the presence of a geographical gradient, with stronger influence of the upwelling in Santa Elena relative to Matapalo, where several parameters displayed a lower seasonality and a carbonate system that supports reef development throughout the year. Conversely, in Marino Ballena the river discharges during rainy season exerted a strong control on the seasonal variability. The integrated analysis of coral reef composition and physicochemical parameters suggests that in addition to inorganic nutrients carbonate chemistry also plays a key role in coral distribution. Analyzing the spatial distribution of the main reef builders provides insights into the species-specific tolerance to varying conditions. Pavona clavus is widely distributed in both the northern and southern locations, suggesting that this massive coral is very tolerant to the high variability of physicochemical conditions. The dominant corals in the north (Pavona gigantea and Pocillopora spp.) are highly tolerant to nutrient-enriched cold waters with low aragonite saturation, while one of the main reef-builders in southern locations (Porites cf. lobata) cope better with low salinity, low aragonite saturation and low light intensity caused by river discharges. Understanding the preferences of individual coral species at our study locations can shed light on the environmental factors driving coral reef distribution in other locations of the ETP.
Continue reading ‘Environmental conditions and carbonate chemistry variability influencing coral reef composition along the Pacific coast of Costa Rica’Coral calcification resistance to acidification is physiologically linked with complex intracellular calcium ion dynamics between host and symbiont cells
Published 8 October 2025 Science ClosedTags: biological response, BRcommunity, calcification, corals, laboratory, molecular biology, North Pacific, phytoplankton
Coral calcification is a highly complex process with numerous caveats regarding the mechanisms that dictate productivity and function. Ion homeostasis, however, is the foremost physiological process unanimously shared among Scleractinia and essential for calcification. Consequently, changes to the seawater environment may elicit adverse effects on ion homeostasis. With increasing climate shifts, the physicochemical regime of our global ocean is changing rapidly. Responses of coral calcification to physicochemical change prevail in having little uniformity on an unambiguous mechanism of resistance. Therefore, this study chose a relatively tolerant Hawaiian coral, Montipora capitata to focus efforts on understanding ion homeostasis under chemical seawater manipulation designed to limit calcification. Results indicate a physiological hormesis (two-phase adaptive response) of overall coral host gene expression that was not shared with algal symbionts and decoupled from calcification rates. The sole ion homeostatic mechanism shown was calcium ion regulation by both the host and symbiont cells. Calcium ion homeostasis was also found to be mechanistically different between winter and summer seasons. Thus, potentially indicating complex interactions between host and symbiont cells, as well as the ability for M. capitata to promote calcification under stress. Putatively synthesized here are the physiological cascades and mechanisms of resistance to environmental triggers of acidosis and seasonal change. This work provides insight into linking calcium ion homeostasis with coral resistance and aims to suggest this mechanism as biomolecular indicator used in future assessments to compare tolerance.
Continue reading ‘Coral calcification resistance to acidification is physiologically linked with complex intracellular calcium ion dynamics between host and symbiont cells’Thermal and acidification gradients reveal tolerance thresholds in Pocillopora acuta recruits
Published 1 October 2025 Science ClosedTags: biological response, corals, laboratory, molecular biology, morphology, mortality, multiple factors, North Pacific, reproduction, temperature
Ocean warming and acidification are among the biggest threats to the persistence of coral reefs. Organismal stress tolerance thresholds are life stage specific, can vary across levels of biological organisation and also depend on natural environmental variability. Here, we exposed the early life stages of Pocillopora acuta in Kāne‘ohe Bay, Hawai‘i, USA, a common reef-building coral throughout the Pacific, to projected ocean warming and acidification scenarios. We measured ecological, physiological, biomineralisation and molecular responses across the critical transition from larvae to newly settled recruits following 6 days of exposure to diel fluctuations in temperature and pH in Control (26.8°C–27.9°C, 7.82–7.96 pHTotal), Mid (28.4°C–29.5°C, 7.65–7.79 pHTotal) and High conditions (30.2°C–31.5°C, 7.44–7.59 pHTotal). We found that P. acuta early life stages are capable of survival, settlement and calcification under all scenarios. The High conditions, however, caused a significant reduction in survival and settlement capacity, with changes in the skeletal fibre deposition patterns. Although there was limited impact on the expression of biomineralisation genes, exposure to High conditions resulted in strong transcriptomic responses including depressed metabolism, reduced ATP production and increased activity of DNA damage-repair processes, indicative of a compromised metabolic state. Collectively, our findings demonstrate that coral juveniles living in environments with large diurnal fluctuations in seawater temperature and pH, such as Kāne‘ohe Bay, can tolerate exposure to moderate projected increased temperature and reduced pH. However, under more severe environmental conditions, significant negative effects on coral cellular metabolism and overall organismal survival jeopardise species fitness and recruitment.
Continue reading ‘Thermal and acidification gradients reveal tolerance thresholds in Pocillopora acuta recruits’4D insights into coral biomineralization: effects of ocean acidification on the early skeleton development of a stony coral
Published 24 September 2025 Science ClosedTags: biological response, corals, laboratory, morphology, Red Sea, reproduction
Coral biomineralization drives the formation of reef structures, but ocean acidification (OA) threatens this process. Coral survival requires effective skeletogenesis in early life stages, through the formation of co joined growth zones: rapid accretion deposits (RADs) and thickening deposits (TDs). Contrasting theories and lack of data on how these zones form hamper our understanding of normal coral growth and under future OA. This study describes growth patterns of RADs and TDs during the early stages of coral calcification under both normal and OA conditions. The work reveals geometric characteristics of RADs and TDs at micro- and sub-micrometer scales, as a basis for learning how OA impacts the early-formed skeletons. By combining material science approaches and Monte-Carlo simulations to model electron interactions that probe mineral phase composition, we show how TDs and RADs form simultaneously, challenging the classical “step-by-step” growth hypothesis. Unexpectedly, under normal pH, TDs comprise ≈65% amorphous calcium carbonate (ACC) and only 35% crystalline aragonite. Under OA, skeletons exhibit higher densities, with only 50% ACC. RADs are underdeveloped under OA, reducing skeletal bending resistance and increasing fracture risk. These findings reveal that the effect of OA on coral skeletogenesis is more complex than previously understood.
Continue reading ‘4D insights into coral biomineralization: effects of ocean acidification on the early skeleton development of a stony coral’Microplastic exposure under future oceanic conditions further threatens an endangered coral, Acropora cervicornis
Published 22 September 2025 Science ClosedTags: biological response, BRcommunity, corals, laboratory, morphology, multiple factors, photosynthesis, physiology, phytoplankton, plastics, South Atlantic, temperature
Microplastic pollution is ubiquitous in the oceans. However, little is known about the physiological impact of microplastics on corals, particularly under predicted future ocean conditions. This study investigated the individual impacts of microplastic exposure (MP) and predicted future ocean conditions [ocean acidification and warming (OAW)] as well as the combination of these stressors (OAW+MP) on the growth and physiology of Acropora cervicornis, a threatened Caribbean coral and its associated symbiont, Symbiodiniaceae. After 22 days, the OAW+MP treatment resulted in more pronounced physiological changes than either stressor individually or the control. OAW conditions alone had minimal impacts, despite A. cervicornis generally being sensitive to thermal stress. The OAW+MP treatment and the MP treatment also disrupted the host-symbiont relationship evidenced by the higher symbiont densities relative to the control and the OAW treatments. Additionally, the OAW+MP treatment resulted in lower chlorophyll a per symbiont cell. Microplastic handling is energetically costly, possibly leading to changes in host-symbiont signaling. Photosynthetic efficiency was only marginally lower in the OAW+MP treatment, and values did not indicate photosystem damage. Negative host health impacts were found with the OAW+MP treatment exhibiting lower skeletal growth compared to the control and lower host protein concentrations compared to the OAW treatment. These results indicate that although short term microplastic exposure alone may not pose a significant threat to coral health, when adding additional stressors, it can further threaten the health and recovery of this already vulnerable species.
Continue reading ‘Microplastic exposure under future oceanic conditions further threatens an endangered coral, Acropora cervicornis’The impacts of ocean acidification on coral reefs in the Red Sea and ways to address it – a review
Published 17 September 2025 Science ClosedTags: biological response, BRcommunity, corals, mitigation, physiology, Red Sea, review
Ocean acidification (OA) is an escalating environmental challenge that poses significant threats to marine ecosystems, especially coral reefs. The Red Sea, characterized by its distinct marine biodiversity and climatic conditions, is becoming increasingly susceptible to the effects of (OA). This review investigates the impact of ocean acidification on coral reefs in the Red Sea, emphasizing physiological, ecological, and socio-economic consequences. Alterations in seawater chemistry, notably a reduction in pH and the availability of carbonate ions, impede coral calcification, disrupt symbiotic relationships, and contribute to coral bleaching. The review also highlights the vulnerability of coral species in the Red Sea, which is further exacerbated by local stressors such as temperature variations, pollution, and overfishing. Additionally, it examines various strategies to mitigate these impacts, including active coral reef restoration, genetic adaptation research, the creation of marine protected areas, and the mitigation of local environmental stressors. Addressing ocean acidification in the Red Sea necessitates a combination of global and regional initiatives aimed at reducing (CO2) emissions, alongside local conservation measures to enhance the resilience of coral reef ecosystems. This review highlights the critical need for interdisciplinary research and cooperative efforts to protect the future of coral reefs in the region.
Continue reading ‘The impacts of ocean acidification on coral reefs in the Red Sea and ways to address it – a review’Seasonal impacts of ocean acidification and warming on coral physiology from pre- and post-summer temperature and pCO2 conditions of Acropora digitifera and Montipora digitata
Published 17 September 2025 Science ClosedTags: biological response, corals, morphology, multiple factors, North Pacific, physiology, temperature
This study examines the impact of ocean acidification (OA), ocean warming (OW), and combination of OA + OW on the physiology of branching corals Acropora digitifera and Montipora digitata before and after a summer bleaching event. The experiments were conducted in pre- and post-summer of 2017 to evaluate changing coral calcification rates and the maximum quantum yield of PSII (Fv/Fm). Our finding showed that both species experience reduced calcification rates and Fv/Fm under these stress conditions. Notably, the most severe impacts were observed in the post-summer period, suggesting that the prior summer conditions, including bleaching stress, exacerbated the effects of additional stressors. The increased sensitivity observed post-summer highlights the potential for synergistic impacts of multiple stressors, with prior exposure to high temperatures and bleaching events contributing to diminished thermal tolerance. These findings underscore the importance of considering the timing and cumulative effects of climate stressors on coral physiology. Further research is needed to explore the physiological and ecological mechanisms driving these seasonal responses to better predict and mitigate the impacts of climate change on coral reef ecosystems.
Continue reading ‘Seasonal impacts of ocean acidification and warming on coral physiology from pre- and post-summer temperature and pCO2 conditions of Acropora digitifera and Montipora digitata’Mathematical analysis on the effects of microplastic pollution and ocean acidification on coral reefs in aquatic ecosystem
Published 10 September 2025 Science ClosedTags: biological response, BRcommunity, communitymodeling, corals, modeling, multiple factors, plastics
This study explores the complex interplay between microplastic contamination and ocean acidification in influencing coral reef ecosystems through the development of a mathematical model with time-varying parameters. The model ensures positivity and boundedness to accurately represent ecological dynamics, and stability analyses provide insights into system behavior under various environmental conditions. Numerical simulations validate the theoretical results and reveal that microplastic accumulation in marine environments significantly hinders coral reef establishment while contributing to elevated oceanic carbon dioxide levels. These rising CO2 levels, primarily driven by anthropogenic emissions, lead to accelerated ocean acidification, further degrading coral reefs. Model predictions indicate that, if unchecked, the current trends in microplastic pollution and ocean acidification will result in a 50% reduction in coral reef coverage within four decades. However, the findings suggest that limiting microplastic input into aquatic ecosystems could mitigate these adverse effects, preserving reef health and slowing acidification. By quantifying the relationship between microplastic pollution, ocean acidification, and coral reef dynamics, this study provides a robust framework for understanding and addressing critical threats to marine ecosystems.
Continue reading ‘Mathematical analysis on the effects of microplastic pollution and ocean acidification on coral reefs in aquatic ecosystem’
