Ocean acidification typically reduces coral calcification rates and can fundamentally alter skeletal morphology. We use atomic force microscopy (AFM) and microindentation to determine how seawater pCO2 affects skeletal structure and Vickers hardness in a Porites lutea coral. At 400 µatm, the skeletal fasciculi are composed of tightly packed bundles of acicular crystals composed of quadrilateral nanograins, approximately 80–300 nm in dimensions. We interpret high adhesion at the nanograin edges as an organic coating. At 750 µatm the crystals are less regular in width and orientation and composed of either smaller/more rounded nanograins than observed at 400 µatm or of larger areas with little variation in adhesion. Coral aragonite may form via ion-by-ion attachment to the existing skeleton or via conversion of amorphous calcium carbonate precursors. Changes in nanoparticle morphology could reflect variations in the sizes of nanoparticles produced by each crystallization pathway or in the contributions of each pathway to biomineralization. We observe no significant variation in Vickers hardness between skeletons cultured at different seawater pCO2. Either the nanograin size does not affect skeletal hardness or the effect is offset by other changes in the skeleton, e.g. increases in skeletal organic material as reported in previous studies.
Continue reading ‘The response of coral skeletal nano structure and hardness to ocean acidification conditions’Posts Tagged 'corals'
The response of coral skeletal nano structure and hardness to ocean acidification conditions
Published 9 August 2023 Science ClosedTags: biological response, corals, laboratory, morphology
Ontogenetic differences in the response of the cold-water coral Caryophyllia huinayensis to ocean acidification, warming and food availability
Published 1 August 2023 Science ClosedTags: biological response, calcification, corals, laboratory, morphology, mortality, multiple factors, nutrients, performance, respiration, South Pacific, temperature
Highlights
- Response to multiple stressors differs between cold-water coral life stages.
- Elevated temperature and reduced feeding have the strongest effect.
- Highest mortality occurs in adult corals.
- Calcification rates decrease the most in juvenile corals.
- Three-month delay in response to changing environmental conditions.
Abstract
Cold-water corals (CWCs) are considered vulnerable to environmental changes. However, previous studies have focused on adult CWCs and mainly investigated the short-term effects of single stressors. So far, the effects of environmental changes on different CWC life stages are unknown, both for single and multiple stressors and over long time periods. Therefore, we conducted a six-month aquarium experiment with three life stages of Caryophyllia huinayensis to study their physiological response (survival, somatic growth, calcification and respiration) to the interactive effects of aragonite saturation (0.8 and 2.5), temperature (11 and 15 °C) and food availability (8 and 87 μg C L−1). The response clearly differed between life stages and measured traits. Elevated temperature and reduced feeding had the greatest effects, pushing the corals to their physiological limits. Highest mortality was observed in adult corals, while calcification rates decreased the most in juveniles. We observed a three-month delay in response, presumably because energy reserves declined, suggesting that short-term experiments overestimate coral resilience. Elevated summer temperatures and reduced food supply are likely to have the greatest impact on live CWCs in the future, leading to reduced coral growth and population shifts due to delayed juvenile maturation and high adult mortality.
Continue reading ‘Ontogenetic differences in the response of the cold-water coral Caryophyllia huinayensis to ocean acidification, warming and food availability’Genomic signatures suggesting adaptation to ocean acidification in a coral holobiont from volcanic CO2 seeps
Published 25 July 2023 Science ClosedTags: adaptation, biological response, BRcommunity, corals, field, molecular biology, otherprocess, physiology, phytoplankton, prokaryotes, South Pacific, vents
Ocean acidification, caused by anthropogenic CO2 emissions, is predicted to have major consequences for reef-building corals, jeopardizing the scaffolding of the most biodiverse marine habitats. However, whether corals can adapt to ocean acidification and how remains unclear. We addressed these questions by re-examining transcriptome and genome data of Acropora millepora coral holobionts from volcanic CO2 seeps with end-of-century pH levels. We show that adaptation to ocean acidification is a wholistic process involving the three main compartments of the coral holobiont. We identified 441 coral host candidate adaptive genes involved in calcification, response to acidification, and symbiosis; population genetic differentiation in dinoflagellate photosymbionts; and consistent transcriptional microbiome activity despite microbial community shifts. Coral holobionts from natural analogues to future ocean conditions harbor beneficial genetic variants with far-reaching rapid adaptation potential. In the face of climate change, these populations require immediate conservation strategies as they could become key to coral reef survival.
Continue reading ‘Genomic signatures suggesting adaptation to ocean acidification in a coral holobiont from volcanic CO2 seeps’Differences in carbonate chemistry up-regulation of long-lived reef-building corals
Published 24 July 2023 Science ClosedTags: adaptation, biological response, calcification, chemistry, corals, field, morphology, otherprocess, physiology, South Pacific
With climate projections questioning the future survival of stony corals and their dominance as tropical reef builders, it is critical to understand the adaptive capacity of corals to ongoing climate change. Biological mediation of the carbonate chemistry of the coral calcifying fluid is a fundamental component for assessing the response of corals to global threats. The Tara Pacific expedition (2016–2018) provided an opportunity to investigate calcification patterns in extant corals throughout the Pacific Ocean. Cores from colonies of the massive Porites and Diploastrea genera were collected from different environments to assess calcification parameters of long-lived reef-building corals. At the basin scale of the Pacific Ocean, we show that both genera systematically up-regulate their calcifying fluid pH and dissolved inorganic carbon to achieve efficient skeletal precipitation. However, while Porites corals increase the aragonite saturation state of the calcifying fluid (Ωcf) at higher temperatures to enhance their calcification capacity, Diploastrea show a steady homeostatic Ωcf across the Pacific temperature gradient. Thus, the extent to which Diploastrea responds to ocean warming and/or acidification is unclear, and it deserves further attention whether this is beneficial or detrimental to future survival of this coral genus.
Continue reading ‘Differences in carbonate chemistry up-regulation of long-lived reef-building corals’Implementing a coral reef CaCO3 production module in the iLOVECLIM climate model
Published 20 July 2023 Science ClosedTags: biological response, corals, globalmodeling, methods, modeling
Coral reef development is intricately linked to both climate and the concentration of atmospheric CO2, specifically through temperature and carbonate chemistry in the upper ocean. In turn, the calcification of corals modifies the concentration of dissolved inorganic carbon and total alkalinity in the ocean, impacting air-sea gas exchange, atmospheric CO2 concentration, and ultimately the climate. This retroaction between atmospheric conditions and coral biogeochemistry can only be accounted for with a coupled coral-carbon-climate model. Here we present the implementation of a coral reef calcification module into an Earth System model. Simulated coral reef production of the calcium carbonate mineral aragonite depends on photosynthetically active radiation, nutrient concentrations, salinity, temperature and the aragonite saturation state. An ensemble of 210 parameter perturbation simulations was performed to identify carbonate production parameter values that optimise the simulated distribution of coral reefs and associated carbonate production. The tuned model simulates the presence of coral reefs and regional-to-global carbonate production values in good agreement with data-based estimates. The model enables assessment of past and future coral-climate coupling on seasonal to millennial timescales, highlighting how climatic trends and variability may affect reef development and the resulting climate-carbon feedback.
Continue reading ‘Implementing a coral reef CaCO3 production module in the iLOVECLIM climate model’A comparison of SNARF-1 and skeletal δ11B estimates of calcification media pH in tropical coral
Published 17 July 2023 Science ClosedTags: biological response, calcification, chemistry, corals, laboratory, Mediterranean, paleo
Coral skeletal boron geochemistry offers opportunities to probe the pH of the calcification media (pHCM) of modern and fossil specimens, to estimate past changes in seawater pH and to explore the biomineralisation response to future ocean acidification. In this research we grew 2 Stylophora pistillata coral microcolonies over glass coverslips to allow analysis of the pH sensitive dye SNARF-1, in the extracellular calcification medium at the growing edge of colonies where the first aragonite crystals are formed, under both light and dark conditions. We use secondary ion mass spectrometry (SIMS) to measure the boron isotopic composition (δ11B) of the skeleton close to the growth edge after 2 to 3 days of additional calcification had enlarged the crystals until they joined, generating a continuous sheet of aragonite. Mean skeletal δ11B-pHCM estimates are higher than those by SNARF-1 by 0.35–0.44 pH units. These differences either reflect real variations in the pH of the calcification media associated with each measurement technique or indicate other changes in the biomineralisation process which influence skeletal δ11B. SNARF-1 measures directly the pH of the extracellular calcification medium while skeletal δ11B analyses aragonite potentially formed via both extracellular and intracellular biomineralisation pathways. Analysis of a third coral specimen, also growing on a glass slide but with a 5 cm long branch, indicated good agreement between the δ11B value of the apex of the branch and the skeletal growth edge. The tissues overlying both these regions were transparent indicating they had low symbiont densities. This suggests that the biomineralisation process is broadly comparable between these sites and that studies growing corals over glass slides/coverslips provide representative data for the colony apex.
Continue reading ‘A comparison of SNARF-1 and skeletal δ11B estimates of calcification media pH in tropical coral’Succession of ocean acidification and its effects on reef-building corals
Published 7 July 2023 Science ClosedTags: biological response, calcification, corals, laboratory, methods, North Pacific, review
Since 2008, we have been conducting a series of coral-rearing experiments, mainly at the Sesoko Station of the Tropical Biosphere Research Center at the University of the Ryukyus, under an overarching project, called the Acidification Impact on Calcifiers project (AICAL project). The AICAL project integrates the efforts of several individual research programs, and project members employ a custom-made, high-precision pCO2-adjusted seawater generator (the AICAL apparatus) to study the effects of ocean acidification on marine calcifying organisms. With this system, rearing experiments can be conducted under conditions mimicking those in the preindustrial era, and the future. In this review, we summarize the results of ocean acidification experiments on corals and other organisms, with a focus on studies conducted by the AICAL project members. We examine the response of organisms to ocean acidification in a hierarchical fashion: differences among various groups of calcifying organisms, and interspecific and intraspecific variation in corals. In the case of corals, we consider not only the effects of ocean acidification, but also those caused by rising seawater temperatures and eutrophication. Our major findings are that coral calcification may have already decreased from a preindustrial level and that there are evident interspecific and intraspecific differences in tolerance against ocean acidification. These findings suggest future decrease of coral cover, accompanied by species compositional changes under climate change scenarios.
Continue reading ‘Succession of ocean acidification and its effects on reef-building corals’Adaptive mechanisms of the deep-sea coral Polymyces wellsi (Flabellidae, Scleractinia) illuminate strategies for global climate change
Published 29 June 2023 Science ClosedTags: adaptation, biological response, chemistry, corals, field, molecular biology, North Pacific, otherprocess
Highlights
- Adaptive mechanisms of deep-sea solitary coral are studied by comparative transcriptome.
- Solitary corals experienced at least three independent adaptations into deep sea.
- Potentially new calcification mechanisms are proposed for deep-sea solitary coral.
- pI values of skeleton organic matrix proteins in the coral are adaptively increased.
Abstract
An oxygen minimum zone (OMZ) typically occurs in the tropical western Pacific and is characterized by an unfavorably low pH, a rather low oxygen content and extreme food limitation. Understanding how deep-sea corals survive in these challenging conditions, especially how calcification occurs at depths near the aragonite saturation horizon, is anticipated to provide a strategy for stony corals to address global climate change. In this study, we collected the deep-sea solitary coral Polymyces wellsi living in the OMZ of the Caroline Ridge and analyzed its mitochondrial genome and transcriptome. Phylogenetic analysis based on mitochondrial genomes suggested that the solitary character and the deep-sea adaptations evolved at least three times in Scleractinia. In comparison to the transcriptomes of shallow-water counterparts, the genetic elements related to biomineralization, mitochondrial components, and ciliary motion underwent positive selection and expansion in P. wellsi, which suggested their significance in facilitating the adaptations to the stressors of low pH, insufficient oxygen content, scarce food resources, or the combined effects of these stressors within the OMZ. An interesting finding of this study was that the positively selected amino acids in P. wellsi increased the isoelectric points of its skeleton organic matrix proteins, which suggested a novel bio-indicator that may reflect the adaptive capacity to the external acidified seawater. Overall, this study not only provides insights into the adaptive mechanisms of deep-sea solitary corals but also illuminates strategies for global climate change.
Continue reading ‘Adaptive mechanisms of the deep-sea coral Polymyces wellsi (Flabellidae, Scleractinia) illuminate strategies for global climate change’Synergistic genomic mechanisms of adaptation to ocean acidification in a coral holobiont
Published 23 June 2023 Science ClosedTags: adaptation, biological response, corals, field, molecular biology, otherprocess, physiology, South Pacific
Ocean acidification, caused by anthropogenic CO2 emissions, is predicted to have major consequences for reef-building corals, jeopardizing the scaffolding of the most biodiverse marine habitats. However, whether corals can adapt to ocean acidification and how remains unclear. We addressed these questions by re-examining transcriptome and genome data of Acropora millepora coral holobionts from volcanic CO2 seeps with end-of-century pH levels. We show that adaptation to ocean acidification is a wholistic process involving the three main compartments of the coral holobiont. We identified 441 coral host candidate adaptive genes involved in calcification, response to acidification, and symbiosis; population genetic differentiation in dinoflagellate photosymbionts; and consistent transcriptional microbiome activity despite microbial community shifts. Coral holobionts from natural analogues to future ocean conditions harbor beneficial genetic variants with far-reaching rapid adaptation potential. In the face of climate change, these populations require immediate conservation strategies as they could become key to coral reef survival.
Continue reading ‘Synergistic genomic mechanisms of adaptation to ocean acidification in a coral holobiont’The impacts of ocean acidification, warming and their interactive effects on coral prokaryotic symbionts
Published 14 June 2023 Science ClosedTags: biological response, BRcommunity, community composition, corals, laboratory, molecular biology, multiple factors, North Pacific, otherprocess, physiology, primary production, prokaryotes, temperature
Reef-building corals, the foundation of tropical coral reefs, are vulnerable to climate change e.g. ocean acidification and elevated seawater temperature. Coral microbiome plays a key role in host acclimatization and maintenance of the coral holobiont’s homeostasis under different environmental conditions, however, the response patterns of coral prokaryotic symbionts to ocean acidification and/or warming are rarely known at the metatranscriptional level, particularly the knowledge of interactive and persistent effects is limited. Using branching Acropora valida and massive Galaxea fascicularis as models in a lab system simulating extreme ocean acidification (pH 7.7) and/or warming (32 °C) in the future, we investigated the changes of in situ active prokaryotic symbionts community and gene expression of corals under/after (6/9 d) acidification (A), warming (H) and acidification–warming (AH) by metatranscriptome analysis with pH8.1, 26 °C as the control.
Continue reading ‘The impacts of ocean acidification, warming and their interactive effects on coral prokaryotic symbionts’Separate and combined effects of elevated pCO2 and temperature on the branching reef corals Acropora digitifera and Montipora digitata
Published 31 May 2023 Science ClosedTags: abundance, algae, biological response, calcification, corals, laboratory, mortality, multiple factors, North Pacific, otherprocess, photosynthesis, temperature
Ocean acidification (OA) and warming (OW) are major global threats to coral reef ecosystems; however, studies on their combined effects (OA + OW) are scarce. Therefore, we evaluated the effects of OA, OW, and OA + OW in the branching reef corals Acropora digitifera and Montipora digitata, which have been found to respond differently to environmental changes. Our results indicate that OW has a greater impact on A. digitifera and M. digitata than OA and that the former species is more vulnerable to OW than the latter. OW was the main stressor for increased mortality and decreased calcification in the OA + OW group, and the effect of OA + OW was additive in both species. Our findings suggest that the relative abundance and cover of M. digitata are expected to increase whereas those of A. digitifera may decrease in the near future in Okinawa.
Continue reading ‘Separate and combined effects of elevated pCO2 and temperature on the branching reef corals Acropora digitifera and Montipora digitata’Acid times in physiology: a systematic review of the effects of ocean acidification on calcifying invertebrates
Published 5 May 2023 Science ClosedTags: biological response, calcification, corals, crustaceans, echinoderms, growth, mollusks, mortality, physiology, review
The reduction in seawater pH from rising levels of carbon dioxide (CO2) in the oceans has been recognized as an important force shaping the future of marine ecosystems. Therefore, numerous studies have reported the effects of ocean acidification (OA) in different compartments of important animal groups, based on field and/or laboratory observations. Calcifying invertebrates have received considerable attention in recent years. In the present systematic review, we have summarized the physiological responses to OA in coral, echinoderm, mollusk, and crustacean species exposed to predicted ocean acidification conditions in the near future. The Scopus, Web of Science, and PubMed databases were used for the literature search, and 75 articles were obtained based on the inclusion criteria. Six main physiological responses have been reported after exposure to low pH. Growth (21.6%), metabolism (20.8%), and acid-base balance (17.6%) were the most frequent among the phyla, while calcification and growth were the physiological responses most affected by OA (>40%). Studies show that the reduction of pH in the aquatic environment, in general, supports the maintenance of metabolic parameters in invertebrates, with redistribution of energy to biological functions, generating limitations to calcification, which can have severe consequences for the health and survival of these organisms. It should be noted that the OA results are variable, with inter and/or intraspecific differences. In summary, this systematic review offers important scientific evidence for establishing paradigms in the physiology of climate change in addition to gathering valuable information on the subject and future research perspectives.
Continue reading ‘Acid times in physiology: a systematic review of the effects of ocean acidification on calcifying invertebrates’Coral persistence despite marginal conditions in the Port of Miami
Published 4 May 2023 Science ClosedTags: abundance, algae, biological response, BRcommunity, chemistry, community composition, corals, field, fish, North Pacific, otherprocess
Coral cover has declined worldwide due to anthropogenic stressors that manifest on both global and local scales. Coral communities that exist in extreme conditions can provide information on how these stressors influence ecosystem structure, with implications for their persistence under future conditions. The Port of Miami is located within an urbanized environment, with active coastal development, as well as commercial shipping and recreational boating activity. Monitoring of sites throughout the Port since 2018 has revealed periodic extremes in temperature, seawater pH, and salinity, far in excess of what have been measured in most coral reef environments. Despite conditions that would kill many reef species, we have documented diverse coral communities growing on artificial substrates at these sites—reflecting remarkable tolerance to environmental stressors. Furthermore, many of the more prevalent species within these communities are now conspicuously absent or in low abundance on nearby reefs, owing to their susceptibility and exposure to stony coral tissue loss disease. Natural reef frameworks, however, are largely absent at the urban sites and while diverse fish communities are documented, it is unlikely that these communities provide the same goods and services as natural reef habitats. Regardless, the existence of these communities indicates unlikely persistence and highlights the potential for coexistence of threatened species in anthropogenic environments, provided that suitable stewardship strategies are in place.
Continue reading ‘Coral persistence despite marginal conditions in the Port of Miami’Short-term responses of Corallina officinalis (rhodophyta) to global-change drivers in a stressful environment of Patagonia, Argentina
Published 28 April 2023 Science ClosedTags: biological response, corals, laboratory, light, multiple factors, nutrients, physiology, primary production, South Atlantic
Over the last two decades, an increasing interest has arisen in the responses of primary producers to global-change drivers and, more recently, in the need to consider how those various drivers may interact. To understand how Corallina officinalis (hereafter Corallina) can be affected by future changing conditions, we investigated the short-term direct effects of co-occurring increased nutrient loads, solar radiation, and lower pH, assessing how these clustered drivers affected Corallina‘s overall physiological performance in a harsh Patagonian coastal environment. To describe the seasonal trend of the physiological parameters in the field, we sampled subtidal Corallina to determine their net oxygen production (NOP), pigments, and carbonate content (CC). Furthermore, we conducted seasonal 10-days experiments, simulating the conditions predicted for the year 2100 by the IPCC (RCP 8.5) —manipulating pH, nutrients, and irradiance—along with the current conditions. The pigments and carotenoids/chlorophyll-a ratio were, in general, constant in the field over the seasons; but the NOP and CC dropped in spring, when the carotenoids peaked. After the experiment, the highest carotenoid/chlorophyll-a ratio was registered in summer under both the currentand the predictedconditions and in winter under the predictedcondition. This lower physiological status was also reflected in almost all other variables. Thus, Corallina may display an acclimatation strategy to cope with high ultraviolet-radiation levels by adjusting its pigment composition to avoid photoinhibition. An understanding of how Corallina, as a habitat-forming species, will respond to future global-change may provide clues about the extent of effects on the ecosystem functions and services.
Continue reading ‘Short-term responses of Corallina officinalis (rhodophyta) to global-change drivers in a stressful environment of Patagonia, Argentina’Seasonal upwelling conditions modulate the calcification response of a tropical scleractinian coral
Published 26 April 2023 Science ClosedTags: biological response, calcification, chemistry, corals, field, North Atlantic
Natural processes such as upwelling of deeper-water masses change the physical-chemical conditions of the water column creating localized ocean acidification events that can have an impact on the natural communities. This study was performed in a coral reef system of an archetypical bay within the Tayrona National Natural Park (PNNT) (Colombia), and aimed to quantify net calcification rates of a foundational coral species within a temporal context (6 months) taking into account the dynamics of seasonal upwelling that influence the study area. Net calcification rates of coral fragments were obtained in situ by the alkalinity anomaly technique in short-term incubations (~2.5 h). We found a significant effect of the upwelling on net calcification rates (Gnet) (p < 0.05) with an 42% increase in CaCO3 accretion compared to non-upwelling season. We found an increase in total alkalinity (AT) and dissolved inorganic carbon (DIC) with decreased aragonite saturation (Ωara) for the upwelling months, indicating an influence of the Subtropical Under Water mass (SAW) in the PNNT coral community. Significant negative correlations between net calcification with temperature and Ωara, which indicates a positive response of M. auretenra with the upwelling conditions, thus, acting as “enhancer” of resilience for coral calcification.
Continue reading ‘Seasonal upwelling conditions modulate the calcification response of a tropical scleractinian coral’Adaptive governance of coral reefs: cases of Florida and the Caribbean
Published 25 April 2023 Science ClosedTags: biological response, BRcommunity, corals, mitigation, policy
Coral reefs are one of the most imperiled yet one of the most valuable ecosystems on the planet, providing food, medicine, and property protection to hundreds of millions of coastal people all over the world. Coral reefs are being lost at an unprecedented rate throughout their range. In the Florida Reef Tract alone, 98% of hard coral has died due to heat waves, disease, and poor water quality, making modern reefs almost unrecognizable. Given the stress that coral reefs are facing due to human and natural causes, there are two key knowledge gaps that are essential to address: the significance of the losses of culturally important benefits that coral reefs provide to people, and the ways that people are adapting to the rapid loss of coral reefs. This dissertation aims to address both gaps.
Continue reading ‘Adaptive governance of coral reefs: cases of Florida and the Caribbean’What conservation strategies support the adaptive capacity of coastal ecosystems in three island states facing a changing climate in Micronesia?
Published 20 April 2023 Science ClosedTags: biological response, BRcommunity, corals, mitigation, review, socio-economy, South Pacific
Coastal ecosystems, such as coral reefs, mangroves, and seagrass beds, are highly vulnerable to the impacts of climate change. The degradation and loss of these ecosystems, stemming from the increased impacts of climate change-related drivers, threaten the well-being of island communities in Micronesia, as they are very reliant on and connected with these coastal ecosystems. Supporting the adaptive capacity of ecosystems through climate adaptive conservation, and thus better equipping them to recover from and adapt to the potential impacts, in turn reduces the vulnerability of the social-ecological system. This thesis identified five main climate change-related drivers that impact coastal systems across three selected states in Micronesia. First, based on a conceptual social-ecological systems (SES) framework, a literature review and analysis were conducted to identify and select three ecosystem adaptive capacity (AC) elements: Heterogeneity, connectivity, and ecosystem functioning. Building on that, second, a literature review aided the identification of climate adaptive conservation strategies and related actions that can support the adaptive capacity of ecosystems. Following a qualitative content analysis, eight climate adaptive conservation strategies and 26 activities were selected and categorized. Third, the extent of (1) the strategy effectiveness, (2) their integration in conservation policy and planning documents, and (3) their implementation on a national scale were evaluated through a semi-quantitative expert consultation in each of the selected states, exemplified with coral reefs.
The findings from this research showed that while the climate adaptive strategies and activities were considered effective in supporting the adaptive capacity of coral reefs in Micronesia, the extent of their implementation ranked low. Strategies, such as “Addressing non-climatic drivers” were considered highly effective, however their implementation fell comparably short. Contrary, targeting heterogeneity was considered of least importance. Thus, as their regional implementation ranked low, the ability of the strategies to support coral adaptive capacity was limited for all three countries. Particularly, the upscaling and mainstreaming of these strategies was considered crucial by the experts. Therefore, this research proposed to prioritize addressing non-climatic drivers, supporting coral reef restoration, and recommended to integrate communities in the design of climate adaptive conservation. Further to apply actionable co-produced science to advance the evidence base and applicability of the strategies in supporting ecosystem AC.
Continue reading ‘What conservation strategies support the adaptive capacity of coastal ecosystems in three island states facing a changing climate in Micronesia?’Coral adaptive capacity insufficient to halt global transition of coral reefs into net erosion under climate change
Published 18 April 2023 Science ClosedTags: adaptation, biogeochemistry, biological response, BRcommunity, communitymodeling, corals, Indian, modeling, multiple factors, North Atlantic, North Pacific, otherprocess, primary production, regionalmodeling, South Pacific, temperature
Projecting the effects of climate change on net reef calcium carbonate production is critical to understanding the future impacts on ecosystem function, but prior estimates have not included corals’ natural adaptive capacity to such change. Here we estimate how the ability of symbionts to evolve tolerance to heat stress, or for coral hosts to shuffle to favourable symbionts, and their combination, may influence responses to the combined impacts of ocean warming and acidification under three representative concentration pathway (RCP) emissions scenarios (RCP2.6, RCP4.5 and RCP8.5). We show that symbiont evolution and shuffling, both individually and when combined, favours persistent positive net reef calcium carbonate production. However, our projections of future net calcium carbonate production (NCCP) under climate change vary both spatially and by RCP. For example, 19%–35% of modelled coral reefs are still projected to have net positive NCCP by 2050 if symbionts can evolve increased thermal tolerance, depending on the RCP. Without symbiont adaptive capacity, the number of coral reefs with positive NCCP drops to 9%–13% by 2050. Accounting for both symbiont evolution and shuffling, we project median positive NCPP of coral reefs will still occur under low greenhouse emissions (RCP2.6) in the Indian Ocean, and even under moderate emissions (RCP4.5) in the Pacific Ocean. However, adaptive capacity will be insufficient to halt the transition of coral reefs globally into erosion by 2050 under severe emissions scenarios (RCP8.5).
Continue reading ‘Coral adaptive capacity insufficient to halt global transition of coral reefs into net erosion under climate change’Projected effects of climate change on marine ecosystems in Southeast Asian seas
Published 17 April 2023 Science ClosedTags: biological response, BRcommunity, chemistry, corals, modeling, North Pacific, phytoplankton, primary production, regionalmodeling, South Pacific, zooplankton
The seas of Southeast Asia are home to some of the world’s most diverse ecosystems and resources that support the livelihoods of millions of people. Climate change will bring temperature changes, acidification and other environmental change, with uncertain consequences for human and natural systems, but there has been little regional-scale climate modelling of the marine ecosystem. We present initial dynamically downscaled projections using a biogeochemical model suitable for coastal and shelf seas. A coupled physical-biogeochemical model with a resolution of 0.1° (approximately 11 km) was used to create projections of future environmental conditions under moderate (RCP4.5) and high (RCP8.5) greenhouse gas scenarios. Changes for different parts of the region are presented, including four sensitive coastal sites of key importance for biodiversity and sustainable development: UNESCO Biosphere Reserves at Cu Lao Cham-Hoi An in Vietnam, Palawan in the Philippines and Taka Bonerate-Kepulauan Selayar in Indonesia, and coastal waters of Sabah, Malaysia, which include several marine parks. The projections show a sea that is warming by 1.1 to 2.9°C through the 21st century, with dissolved oxygen decreasing by 5 to 13 mmol m-3 and changes in many other environmental variables. The changes reach all parts of the water column and many places are projected to experience conditions well outside the range seen at the start of the century. The resulting damage to coral reefs and altered species distribution would have consequences for biodiversity, the livelihoods of small-scale fishers and the food security of coastal communities. Further work using a range of global models and regional models with different biogeochemical components is needed to provide confidence levels, and we suggest some ways forward. Projections of this type serve as a key tool for communities and policymakers as they plan how they will adapt to the challenge of climate change.
Continue reading ‘Projected effects of climate change on marine ecosystems in Southeast Asian seas’Macroalgal cover on coral reefs: spatial and environmental predictors, and decadal trends in the Great Barrier Reef
Published 14 April 2023 Science ClosedTags: abundance, algae, biological response, BRcommunity, corals, field, otherprocess, South Pacific
Macroalgae are an important component of coral reef ecosystems. We identified spatial patterns, environmental drivers and long-term trends of total cover of upright fleshy and calcareous coral reef inhabiting macroalgae in the Great Barrier Reef. The spatial study comprised of one-off surveys of 1257 sites (latitude 11–24°S, coastal to offshore, 0–18 m depth), while the temporal trends analysis was based on 26 years of long-term monitoring data from 93 reefs. Environmental predictors were obtained from in situ data and from the coupled hydrodynamic-biochemical model eReefs. Macroalgae dominated the benthos (≥50% cover) on at least one site of 40.4% of surveyed inshore reefs. Spatially, macroalgal cover increased steeply towards the coast, with latitude away from the equator, and towards shallow (≤3 m) depth. Environmental conditions associated with macroalgal dominance were: high tidal range, wave exposure and irradiance, and low aragonite saturation state, Secchi depth, total alkalinity and temperature. Evidence of space competition between macroalgal cover and hard coral cover was restricted to shallow inshore sites. Temporally, macroalgal cover on inshore and mid-shelf reefs showed some fluctuations, but unlike hard corals they showed no systematic trends. Our extensive empirical data may serve to parameterize ecosystem models, and to refine reef condition indices based on macroalgal data for Pacific coral reefs.
Continue reading ‘Macroalgal cover on coral reefs: spatial and environmental predictors, and decadal trends in the Great Barrier Reef’
