Reef-building coral populations are at serious risk of collapse due to the combined effects of ocean warming and acidification. Nonetheless, many corals show potential to adapt to the changing ocean conditions. Here we examine the broad sense heritability (H2) of coral calcification rates across an ecologically and phylogenetically diverse sampling of eight of the primary reef-building corals across the Indo-Pacific. We show that all eight species exhibit relatively high heritability of calcification rates under combined warming and acidification (0.23–0.56). Furthermore, tolerance to each factor is positively correlated and the two factors do not interact in most of the species, contrary to the idea of trade-offs between temperature and pH sensitivity, and all eight species can co-evolve tolerance to elevated temperature and reduced pH. Using these values together with historical data, we estimate potential increases in thermal tolerance of 1.0–1.7°C over the next 50 years, depending on species. None of these species are probably capable of keeping up with a high global change scenario and climate change mitigation is essential if reefs are to persist. Such estimates are critical for our understanding of how corals may respond to global change, accurately parametrizing modelled responses, and predicting rapid evolution.
Continue reading ‘Widespread scope for coral adaptation under combined ocean warming and acidification’Posts Tagged 'calcification'
Widespread scope for coral adaptation under combined ocean warming and acidification
Published 27 September 2024 Science ClosedTags: biological response, BRcommunity, calcification, corals, mesocosms, molecular biology, mortality, multiple factors, North Pacific, temperature
Ocean acidification does not prolong recovery of coral holobionts from natural thermal stress in two consecutive years
Published 24 September 2024 Science ClosedTags: adaptation, biological response, BRcommunity, calcification, corals, laboratory, mortality, multiple factors, North Pacific, nutrients, otherprocess, physiology, protists, zooplankton
Under predicted future ocean conditions, corals will experience frequent and intense thermal stress events while simultaneously being exposed to chronic ocean acidification. Yet, some corals will likely be more resistant and/or resilient to these predicted conditions than others and may be critical to reef persistence in the future. Following natural thermal stress in two consecutive years (2014 and 2015), we evaluated the effects of feeding and simulated ocean acidification on the physiological recovery of Montipora capitata and Porites compressa sourced from Kāneʻohe Bay and Waimānalo Bay, Hawaiʻi. Following the 2014 thermal stress event, simulated ocean acidification did not slow recovery of the holobiont and feeding enhanced recovery. However, feeding did not decrease susceptibility to the 2015 thermal stress event, and simulated ocean acidification did not increase susceptibility. Recovery strategies employed between species and between sites clearly differed, highlighting that coral reef restoration and management should consider species-level and site-specific vulnerabilities. Overall, our findings call attention to the immediate threat which ocean warming presents, the lack of additional stress to the holobiont from ocean acidification, the importance of heterotrophy in coral resilience, and the potential significance of additional local biotic stressors (i.e., predator outbreaks) for coral resiliency under annual thermal stress.
Continue reading ‘Ocean acidification does not prolong recovery of coral holobionts from natural thermal stress in two consecutive years’Carbon budgets of coral reef ecosystems in the South China Sea
Published 20 September 2024 Science ClosedTags: biological response, calcification, corals, North Pacific, primary production
The coral reef ecosystem is one of the most productive ecosystems in the ocean, and is also an important calcium carbonate deposition region. Because excess production is very low in coral reefs, organic carbon reservoirs are very limited. During the calcification process, each mole of CaCO3 will produce 1 mol of CO2, approximately 60% of which will be released into the atmosphere through the sea-air interface. This causes coral reefs to be large inorganic carbon reservoirs, but at the same time, most coral reefs act as atmospheric CO2 sources (which also act as sinks in some coral reefs). Therefore, clarifying the sea-air CO2 exchange flux and carbon storage is critical for understanding the carbon cycle in coral reef ecosystems. In this paper, we summarize the carbon cycle processes in the coral reefs of the South China Sea (SCS) and estimate the total CO2 budget and carbon reserves. According to current research, the coral reefs in this area act as a source of atmospheric CO2, releasing 0.37−1.59 × 1011 g C a-1 into the atmosphere. Owing to their extremely high biological productivity and carbonate productivity, the carbon reserves of coral reefs in the SCS range from 1.66–3.78 × 1012 g C a-1, which is an order of magnitude greater than the CO2 emissions at the sea–air interface. Overall, coral reefs in the SCS are important carbon storage areas. As the current results are still approximate, a more comprehensive and in-depth investigation is needed to clarify the carbon source/sink processes, regulatory mechanisms, and carbon storage capacity of SCS coral reefs.
Continue reading ‘Carbon budgets of coral reef ecosystems in the South China Sea’Historic ocean acidification of Loch Sween revealed by correlative geochemical imaging and high-resolution boron isotope analysis of Boreolithothamniom cf. soriferum
Published 18 September 2024 Science ClosedTags: algae, biogeochemistry, biological response, calcification, laboratory, North Atlantic
Highlights
- The δ11B of coralline algae skeleton offer a means to reconstruct coastal pH.
- 2D maps of trace element content and δ11B were collected on Boreolithothamniom cf. soriferum.
- These images were aligned using correlated multimodal imaging techniques.
- We reconstruct an ocean acidification trend of −0.018 pH units yr-1 in Loch Sween.
- Loch Sween switched from being a substantial sink of CO2 to a source in ∼2008.
Abstract
Ocean Acidification (OA) arises from the increase in atmospheric carbon dioxide concentration following the industrial revolution. The ecological and socio-economic consequences of OA were first identified around 10–15 years ago but remain poorly understood. This is particularly true in coastal regions where local processes can have dramatic consequences on pH trends through time, obscuring and compounding the long-term effects from rising atmospheric CO2. Here we explore the possibility of generating long records of coastal ocean pH using the skeletons of widely distributed coralline algae (CA). The skeletons of these slow growing (<1 mm/year) taxa often contain micron-scale heterogeneities, making sampling for high-resolution climate reconstructions using bulk sampling techniques difficult. Here we use laser ablation coupled to inductively coupled plasma mass spectrometers to generate high-resolution 2D images of the element/calcium ratios and boron isotope composition (δ11B) of a sample of Boreolithothamniom cf. soriferum from Loch Sween in Scotland, UK where we have been monitoring temperature since 2004 and pH during 2014. By carefully correlating the geochemical images with a scanning electron microscopy image we can segment them to remove the marginal portions of the skeleton, isolating the central growth axis to generate an age model and growth rate. The δ11B-pH is significantly elevated above the seawater pH in Loch Sween (8.4 to 8.9 vs. 7.9 to 8.1) consistent with other CA that show internal pH elevation. On a seasonal scale, internal pH is negatively correlated with temperature and also exhibits a long-term decline. By removing this temperature effect, internal pH can be correlated to seawater pH during the 2014 monitoring period allowing us to reconstruct a seawater acidification trend from 2004 to 2018 of -0.018 pH units per year, 10x higher than open ocean trends but consistent with contemporaneous monitoring efforts of UK coastal waters. Reconstructed aqueous CO2 suggests that prior to ∼2008 Loch Sween was a sink of CO2 but after this date, particularly during the early summer, it was a substantial CO2 source. Comparison of reconstructed aqueous CO2 with a record of calcification rate of our sample of Boreolithothamniom cf. soriferum suggests this acidification and associated rise in local seawater pCO2 may have freed this sample from carbon limitation leading to a recent increase in calcification.
Continue reading ‘Historic ocean acidification of Loch Sween revealed by correlative geochemical imaging and high-resolution boron isotope analysis of Boreolithothamniom cf. soriferum’Physiological resilience of intertidal chitons in a persistent upwelling coastal region
Published 13 September 2024 Science ClosedTags: biological response, calcification, field, mollusks, physiology, South Pacific
Current climate projections for mid-latitude regions globally indicate an intensification of wind-driven coastal upwelling due to warming conditions. The dynamics of mid-latitude coastal upwelling are marked by environmental variability across temporal scales, which affect key physiological processes in marine calcifying organisms and can impact their large-scale distribution patterns. In this context, marine invertebrates often exhibit phenotypic plasticity, enabling them to adapt to environmental change. In this study, we examined the physiological performance (i.e., metabolism, Thermal Performance Curves, and biomass and calcification rates) of individuals of the intertidal mollusk Chiton granosus, a chiton found from northern Peru to Cape Horn (5° to 55°S). Our spatial study design indicated a pattern of contrasting conditions among locations. The Talcaruca site, characterized by persistent upwelling and serving as a biogeographic break, exhibited lower pH and carbonate saturation states, along with higher pCO2, compared to the sites located to the north and south of this location (Huasco and Los Molles, respectively). In agreement with the spatial pattern in carbonate system parameters, long-term temperature records showed lower temperatures that changed faster over synoptic scales (1–15 days) at Talcaruca, in contrast to the more stable conditions at the sites outside the break. Physiological performance traits from individuals from the Talcaruca population exhibited higher values and more significant variability, along with significantly broader and greater warming tolerance than chitons from the Huasco and Los Molles populations. Moreover, marked changes in local abundance patterns over three years suggested population-level responses to the challenging environmental conditions at the biogeographic break. Thus, C. granosus from the Talcaruca upwelling zone represents a local population with wide tolerance ranges that may be capable of withstanding future upwelling intensification on the Southern Eastern Pacific coast and likely serving as a source of propagules for less adapted populations.
Continue reading ‘Physiological resilience of intertidal chitons in a persistent upwelling coastal region’Including ocean acidification effects on biocalcification through dynamic energy budget modelling
Published 12 August 2024 Science ClosedTags: biological response, calcification, mollusks, review
Highlights
- We developed a mechanistic model of biocalcification based on bioenergetics.
- Biocalcification processes are linked to the physiological state of the individual.
- The approach is integrated into the dynamic energy budget framework.
- We propose ways to include the effects of calcium carbonate saturation state on biocalcification.
- The model is validated for five commercially important bivalve species.
Abstract
Climate change impacts on ocean biogeochemistry are expected to alter calcium carbonate formation by organisms, necessitating accurate predictive models based on physiological mechanisms. The dynamic energy budget (DEB) theory offer a mechanistic and integrative framework to model organism metabolism under environmental stressors. In this work, we 1) review the physiological and energetic mechanisms of biogenic calcification, 2) propose a generalized approach for inclusion in DEB modelling based on stylized facts, and 3) formulate the effects of saturation state changes on the bioenergetics of calcification. While applicable to any species performing biogenic calcification (microalgae, shellfish, fish, corals), we tested the model on bivalve species for which extensive tissue and shell data are available. The model was successfully applied to larval, juvenile, and adult life stages compared to published data. The model reproduced typical tissue and shell growth patterns under favourable saturation states and we explored the effects of more detrimental values for biocalcification on shell and tissue dynamics. We also identified missing data and experiments that should help calibrate model parameters. This work represents a necessary step to predict the physiological response of biocalcifiers to ocean acidification and provides a mechanistic tool for shell dynamics in nutrient cycling models.
Continue reading ‘Including ocean acidification effects on biocalcification through dynamic energy budget modelling’Intraspecific variation in response to elevated pCO2 and temperature in the branching reef coral Acropora digitifera from different habitats
Published 27 June 2024 Science ClosedTags: biological response, BRcommunity, calcification, chemistry, corals, laboratory, morphology, mortality, multiple factors, North Pacific, photosynthesis, protists, temperature
Ocean acidification (OA) and ocean warming (OW) affect the calcification of corals, and intraspecific variations in response to these stressors in the population level need to be clarified for better future predictions. Using Acropora digitifera as our subject, we examined the intraspecific variability in calcification and maximum quantum yield (Fv/Fm) of photosystem II of symbiotic zooxanthella in responses to OA, OW, and OA + OW. Samples were taken from two different sites: Sesoko Station (warmer) and Sesoko South (cooler) in Okinawa, Japan. Calcification rates varied between the two sites, and noticeable differences were observed only among coral colonies from the Sesoko South site, specifically under control and OA treatments. Furthermore, Fv/Fm showed no variation between the sites due to those stresses. Hence, the calcification rates among A. digitifera colonies varied by habitat, and we found within-site variation only in the lower temperature location, Sesoko South. We observed diminished variation in response among colonies in the warmer site. The adapting to diverse environmental conditions and responding to changes such as seawater pCO2 and temperature, may lead to differences in sensitivity between the two populations to OA, OW, and OA + OW. These intraspecific variation could arise from factors like acclimatizations, the influence of specific genotypes, or phenotypic plasticity of the colonies.
Continue reading ‘Intraspecific variation in response to elevated pCO2 and temperature in the branching reef coral Acropora digitifera from different habitats’Rubble persistence under ocean acidification threatened by accelerated bioerosion and lower-density coral skeletons
Published 20 June 2024 Science ClosedTags: abundance, biological response, BRcommunity, calcification, chemistry, community composition, corals, dissolution, laboratory, morphology, North Atlantic, otherprocess, primary production, protists, respiration
As the balance between erosional and constructive processes on coral reefs tilts in favor of framework loss under human-induced local and global change, many reef habitats worldwide degrade and flatten. The resultant generation of coral rubble and the beds they form can have lasting effects on reef communities and structural complexity, threatening the continuity of reef ecological functions and the services they provide. To comprehensively capture changing framework processes and predict their evolution in the context of climate change, heavily colonized rubble fragments were exposed to ocean acidification (OA) conditions for 55 days. Controlled diurnal pH oscillations were incorporated in the treatments to account for the known impact of diel carbonate chemistry fluctuations on calcification and dissolution response to OA. Scenarios included contemporary pH (8.05 ± 0.025 diel fluctuation), elevated OA (7.90 ± 0.025), and high OA (7.70 ± 0.025). We used a multifaceted approach, combining chemical flux analyses, mass alteration measurements, and computed tomography scanning images to measure total and chemical bioerosion, as well as chemically driven secondary calcification. Rates of net carbonate loss measured in the contemporary conditions (1.36 kg m−2 year−1) were high compared to literature and increased in OA scenarios (elevated: 1.84 kg m−2 year−1 and high: 1.59 kg m−2 year−1). The acceleration of these rates was driven by enhanced chemical dissolution and reduced secondary calcification. Further analysis revealed that the extent of these changes was contingent on the density of the coral skeleton, in which the micro- and macroborer communities reside. Findings indicated that increased mechanical bioerosion rates occurred in rubble with lower skeletal density, which is of note considering that corals form lower-density skeletons under OA. These direct and indirect effects of OA on chemical and mechanical framework-altering processes will influence the permanence of this crucial habitat, carrying implications for biodiversity and reef ecosystem function.
Continue reading ‘Rubble persistence under ocean acidification threatened by accelerated bioerosion and lower-density coral skeletons’Macroalgal presence decreases coral calcification rates more than ocean acidification
Published 12 June 2024 Science ClosedTags: algae, biological response, BRcommunity, calcification, chemistry, corals, growth, laboratory, mesocosms, morphology, Red Sea
Global coral reef degradation has precipitated phase shifts toward macroalgal-dominated communities. Despite the negative repercussions for reefscapes, higher abundances of primary producers have the potential to positively impact the physicochemical environment and mitigate negative impacts of ocean acidification (OA). In this study, we investigated the influence of macroalgal (cf. Sargassum vulgare) density on coral (Acropora millepora and A. hemprichii) calcification rates under current and future OA conditions. Corals were resistant to OA up to ~ 1100 µatm, with no changes in calcification rates. However, the presence of (low and high density) algae reduced calcification rates by ~ 41.8%, suggesting either a chemical defense response due to algal metabolites or potential physical impacts from shading or abrasion. Documented beneficial buffering effects of macroalgae in OA may also elicit negative impacts on coral calcification, suggesting further work is needed to elucidate how species interactions influence responses to projected climate change.
Continue reading ‘Macroalgal presence decreases coral calcification rates more than ocean acidification’Multiple carbonate system parameters independently govern shell formation in a marine mussel
Published 23 May 2024 Science ClosedTags: biological response, calcification, chemistry, laboratory, mollusks, morphology, North Atlantic, physiology
Calcification is vital to marine organisms that produce calcium carbonate shells and skeletons. However, how calcification is impacted by ongoing environmental changes, including ocean acidification, remains incompletely understood due to complex relationships among the carbonate system variables hypothesized to drive calcification. Here, we experimentally decouple these drivers in an exploration of shell formation in adult marine mussels, Mytilus californianus. In contrast to models that focus on single parameters like calcium carbonate saturation state, our results implicate two independent factors, bicarbonate concentration and seawater pH, in governing calcification. While qualitatively similar to ideas embodied in the related substrate-inhibitor ratio (bicarbonate divided by hydrogen ion concentration), our data highlight that merging bicarbonate ion and hydrogen ion concentrations into a simple quotient obscures important features of calcification. Considering a dual-parameter framework improves mechanistic understanding of how calcifiers interact with complex and changing chemical conditions.
Continue reading ‘Multiple carbonate system parameters independently govern shell formation in a marine mussel’Disparate response of decapods to low pH: a meta-analysis of life history, physiology and behavior traits across life stages and environments
Published 5 April 2024 Science ClosedTags: biological response, calcification, crustaceans, growth, mortality, performance, physiology, reproduction, review
Highlights
- Predicted level of ocean acidification is a threat for calcifier marine invertebrates.
- Decapods, thought debatable, are presumably resilient.
- Our meta-analysis revealed few impacts that mainly vary across biological traits.
- Effect sizes little vary depending on the life stages and environments.
Abstract
We employed a meta-analysis to determine if the presumed resilience of decapods to ocean acidification extends to all biological aspects, environments, and life stages. Most response categories appeared unaffected by acidification. However, certain fitness-related traits (growth, survival, and, to some extent, calcification) were impacted. Acid-base balance and stress response scaled positively with reductions in pH, which maintains homeostasis, possibly at the cost of other processes. Juveniles were the only stage impacted by acidification, which is believed to reduce recruitment. We observed few differences in responses to acidification among decapods inhabiting contrasting environments. Our meta-analysis shows decapods as a group slightly to moderately sensitive to low pH, with impacts on some biological aspects rather than on all specific life stages or habitats. Although extreme pH scenarios may not occur in the open ocean, coastal and estuarine areas might experience lower pH levels in the near to medium future, posing potential challenges for decapods.
Continue reading ‘Disparate response of decapods to low pH: a meta-analysis of life history, physiology and behavior traits across life stages and environments’Trade-off between growth and reproduction in Argopecten purpuratus (L.) scallops exposed to medium-term hypoxia and acidification
Published 25 March 2024 Science ClosedTags: biological response, calcification, growth, laboratory, mollusks, mortality, multiple factors, physiology, reproduction, South Pacific
Highlights
- •Scallops showed physiological adaptations to survive and reproduce under medium-term exposure.
- •The most pronounced impact of hypoxia and low pH were on clearance and calcification rates.
- •The combined effect of hypoxia and low pH produced relatively high survival (>70%).
- •Hypoxia and low pH generated early gonad development and high reproductive potential.
Abstract
Peruvian bays that are home to aquatic organisms of commercial interest are increasingly affected by hypoxia and low pH events. These stressors produce unfavorable conditions for the aquatic fauna, leading to mass mortality events. In this study, we evaluated the ecophysiological responses of the scallop Argopecten purpuratus exposed to moderate hypoxia (20% DO saturation) and low pH (OA, pH 7.4) using a 2 × 2 factorial design. We found that a 51-day exposure to low pH (OA treatment) had greater negative effects on A. purpuratus performances than hypoxia (lower survival and decreased clearance and calcification rates), but stimulated early gonad maturation. The survival rate was 1.3-fold higher under hypoxia than under acidic treatment. The interaction between hypoxia and low pH had an antagonistic effect on survival, since the combined treatment (HOA) resulted in lower scallop mortality than the single stress treatments. Calcification was negatively affected by all stress treatments, whereas hypoxia and OA both stimulated gametogenesis. OA treatment resulted in higher frequencies of previtellogenic and vitellogenic oocytes, greater gonad coverage area, and lower frequency of atretic oocytes, suggesting higher reproductive potential. HOA was positively related to oocyte development and high frequency of post-vitellogenic and atretic oocytes. These results suggest that, due to hypoxia and low pH, feeding is reduced and energy allocation prioritizes scallop gonad maturation. This trend would have negative effects on scallop growth and calcification, while increased reproduction under environmental stress could mitigate the effect on recruitment.
Continue reading ‘Trade-off between growth and reproduction in Argopecten purpuratus (L.) scallops exposed to medium-term hypoxia and acidification’Physiological impacts of climate change on juvenile American lobster Homarus americanus (Decapoda: Astacidea: Nephropidae), a commercially important species
Published 6 March 2024 Science ClosedTags: abundance, biological response, BRcommunity, calcification, crustaceans, laboratory, morphology, multiple factors, North Atlantic, otherprocess, temperature
The American lobster, Homarus americanus, H. Milne Edwards, 1837 is an ecologically, economically, and culturally valuable marine resource for the coastal communities in the Gulf of Maine. Lobsters in the Gulf of Maine are experiencing the effects of rapid warming and acidification due to climate change. Lobster shells are comprised of chitin with precisely precipitated minerals (calcite, amorphous calcium carbonate, and carbonate apatite) that provide structural integrity to the shell and protection against predators and microbial intrusion. We examined the combined effects of ocean warming and acidification on shell mineralogy, epibiont abundance, and growth in early benthic juveniles. Lobsters were grown under six different temperature/pCO2 treatment conditions over 52 days (three replicates per treatment) aligned with environmentally relevant as well as predicted future extremes. Elevated pCO2 and temperature led to a decrease in shell calcium and magnesium content, suggesting that these environmental stressors inhibit shell biomineralization. There was an interactive effect of the stressors on epibiont abundance with the probability of epibiont coverage increasing with increasing pCO2 and temperature. Elevated pCO2 alone was significantly correlated (P = 0.002) to decreased growth, but only for female lobsters. Ocean acidification and warming significantly affect shell integrity in juvenile lobster, increasing risk to injury and disease with potential downstream consequences for the lobster fishery.
Continue reading ‘Physiological impacts of climate change on juvenile American lobster Homarus americanus (Decapoda: Astacidea: Nephropidae), a commercially important species ‘Probing the role of carbonic anhydrase in shell repair mechanisms in the eastern oyster Crassostrea virginica under experimental acidification stress
Published 29 February 2024 Science ClosedTags: biological response, calcification, laboratory, molecular biology, mollusks, North Atlantic, physiology
Highlights
- Shell repair dramatically decreased in oysters after chronic high pCO2 exposure.
- Carbonic anhydrase (CA) inhibition further reduces shell repair.
- Oysters increased hemocyte intracellular pH under low pH seawater.
- Ability to increase intracellular pH of hemocytes was lost when CA was inhibited.
- CA plays a role in maintaining calcification under low pH.
Abstract
The reduction in pH from atmospheric inputs of CO2 (ocean acidification, OA) threatens marine calcifiers, including the eastern oyster (Crassostrea virginica), that precipitate biogenic CaCO3 for shell formation. Recent investigations have demonstrated that alterations in gene expression enable bivalves to respond to episodic low pH. Evidence generated from several studies highlighted the importance of upregulating genes related to biomineralization, ion transport, and acid-base balance such as carbonic anhydrase (CA) genes. Two experiments were designed to evaluate the effect of acidification on calcification processes and to probe the specific role of CA in oyster resilience to low pH. First, adult oysters were exposed to eight months of chronic acidification stress (pH ∼7.3, pCO2 ∼3300 ppm) or control conditions (pH ∼7.9, pCO2 ∼500 ppm) before shells were artificially damaged and shell repair monitored. Results showed a dramatic decrease in shell regeneration after chronic high pCO2 exposure (only 30% of oysters regrew any shell) suggesting that mechanisms that promote calcification under high pCO2 conditions may not be sustainable for extended periods of time. To further explore these mechanisms, a second experiment was designed by focusing on the role of CA in mitigating acidification stress. Here, adult oysters received an injection of acetazolamide in dimethyl sulfoxide (DMSO) to inhibit CA or DMSO (control) before rearing in control (pH ∼8.1, pCO2 ∼340 ppm) or acidified (pH ∼7.3, pCO2 ∼3300 ppm) conditions. After three weeks, oyster shells were damaged and shell repair monitored. Oysters incubated at low pH seawater with CA inhibition had the least amount of shell regeneration at the end of 21-day regrowth period. Interestingly, oysters were able to increase intracellular pH (pHi) of hemocytes under low pH conditions; however, this ability was significantly diminished with CA inhibition. Results highlight the role of CA in maintaining calcification under low pH conditions by establishing an intracellular environment favorable to calcium carbonate precipitation.
Continue reading ‘Probing the role of carbonic anhydrase in shell repair mechanisms in the eastern oyster Crassostrea virginica under experimental acidification stress’Turf algae drives coral bioerosion under high CO2
Published 20 February 2024 Science ClosedTags: abundance, algae, biogeochemistry, biological response, BRcommunity, calcification, chemistry, communityMF, corals, dissolution, field, laboratory, morphology, multiple factors, North Pacific, otherprocess, photosynthesis, respiration, temperature, vents
Turf algal prevalence will increase in coral ecosystems under ocean acidification yet their contribution towards the ongoing and projected degradation of reefs is often overlooked. Turf algal settlement was induced on exposed coral skeleton adjacent to live coral tissue to investigate coral-turf algal interactions through a combination of laboratory and field transplantation (shallow volcanic CO2 seep) experiments across two temperature regimes. Here, we show that turf algae are competitively favored over corals under high pCO2 conditions. Turf algae-associated biological activity locally acidified the microenvironment overlying the exposed coral skeleton, leading to its bioerosion. Increases in coral-turf algal interactions could shift coral ecosystems towards net dissolution and should be integrated into global accretion models when considering future carbonate budgets under climate change.
Continue reading ‘Turf algae drives coral bioerosion under high CO2’Effects of year-long exposure to elevated pCO2 on the metabolism of back reef and fore reef communities
Published 16 February 2024 Science ClosedTags: abundance, biological response, BRcommunity, calcification, corals, dissolution, field, otherprocess, primary production, South Pacific
The implications of ocean acidification are acute for calcifying organisms, notably tropical reef corals, for which accretion generally is depressed and dissolution enhanced at reduced seawater pH. We describe year-long experiments in which back reef and fore reef (17-m depth) communities from Moorea, French Polynesia, were incubated outdoors under pCO2 regimes reflecting endpoints of representative concentration pathways (RCPs) expected by the end the century. Incubations were completed in three to four flumes (5.0 × 0.3 m, 500 L) in which seawater was refreshed and circulated at 0.1 m s−1, and the response of the communities was evaluated monthly by measurements of net community calcification (NCC) and net community productivity (NCP). For both communities, NCC (but not NCP) was affected by treatments and time, with NCC declining with increasing pCO2, and for the fore reef, becoming negative (i.e., dissolution was occurring) at the highest pCO2 (1067–1433 μatm, RCP8.5). There was scant evidence of community adjustment to reduce the negative effects of ocean acidification, and inhibition of NCC intensified in the back reef as the abundance of massive Porites spp. declined. These results highlight the risks of dissolution under ocean acidification for coral reefs and suggest these effects will be most acute in fore reef habitats. Without signs of amelioration of the negative effects of ocean acidification during year-long experiments, it is reasonable to expect that the future of coral reefs in acidic seas can be predicted from their current known susceptibility to ocean acidification.
Continue reading ‘Effects of year-long exposure to elevated pCO2 on the metabolism of back reef and fore reef communities’Hidden cost of pH variability in seagrass beds on marine calcifiers under ocean acidification
Published 9 February 2024 Science ClosedTags: biological response, calcification, chemistry, communityMF, echinoderms, growth, laboratory, light, mortality, multiple factors, North Atlantic
Highlights
- The presence of seagrass creates variability in pH/pCO2.
- High pCO2/low pH negatively impacts growth and calcification of sea urchin larvae.
- The variability associated with the presence of seagrass negatively impacts growth under ocean acidification.
- Two different calcification strategies are observed in presence and absence of seagrass.
Abstract
Coastal ecosystems experience large environmental variability leading to local adaptation. The key role of variability and adaptation in modulating the biological sensitivity to ocean acidification is increasingly acknowledged. Monitoring and understanding the ecological niche at the right spatio-temporal scale is key to understand the sensitivity of any organism and ecosystems. However, the role of the variability in relevant carbonate chemistry parameters as a driver is often overlooked. For example, the balance between photosynthesis and respiration over the day/night cycle is leading to high pH/pCO2 variability in seagrass beds. We hypothesized that (i) the calcifying larvae of the sea urchin Echinus esculentus exposed to seagrass-driven variability would have some physiological mechanisms to respond to such variability; and (ii) these mechanisms would reach their limit under ocean acidification. We compared the presence and absence of the seagrass Zostera marina in flow through mesocosms fed with seawater with 4 pHs. The carbonate chemistry was monitored and biological response of a sea urchin larvae was documented over 3 weeks. Growth and net calcification rates were measured twice a day to encompass diurnal variability. Our results show that larvae growth rate significantly decreased with decreasing average pHT in both absence and presence of seagrass. Moreover, sea urchin larvae showed a slower growth rate in presence of seagrass, only visible in the lowest pH conditions. In addition, larvae raised in presence of seagrass, maximized calcification during the day, and lower their calcification during the night. In contrast, no significant difference was observed between day and night for the net calcification rate in larvae raised in absence of seagrass. Our results demonstrate the limit of local adaptation to the present range of variability under ocean acidification conditions. It also demonstrates that photosynthetic ecosystems such as seagrass may not play a role of refuge against future ocean acidification.
Continue reading ‘Hidden cost of pH variability in seagrass beds on marine calcifiers under ocean acidification’Modeled foraminiferal calcification and strontium partitioning in benthic foraminifera helps reconstruct calcifying fluid composition
Published 5 February 2024 Science ClosedTags: biological response, calcification, individualmodeling, modeling, physiology, protists
Foraminifera are unicellular organisms that inhabit the oceans. They play an important role in the global carbon cycle and record valuable paleoclimate information through the uptake of trace elements such as strontium into their calcitic shells. Understanding how foraminifera control their internal fluid composition to make calcite is important for predicting their response to ocean acidification and for reliably interpreting the chemical and isotopic compositions of their shells. Here, we model foraminiferal calcification and strontium partitioning in the benthic foraminifera Cibicides wuellerstorfi and Cibicidoides mundulus based on insights from inorganic calcite experiments. The numerical model reconciles inter-ocean and taxonomic differences in benthic foraminifer strontium partitioning relationships and enables us to reconstruct the composition of the calcifying fluid. We find that strontium partitioning and mineral growth rates of foraminiferal calcite are not strongly affected by changes in external seawater pH (within 7.8–8.1) and dissolved inorganic carbon (DIC, within 2100–2300 μmol/kg) due to a regulated calcite saturation state at the site of shell formation.
Continue reading ‘Modeled foraminiferal calcification and strontium partitioning in benthic foraminifera helps reconstruct calcifying fluid composition’Examining the impacts of elevated, variable pCO2 on larval Pacific razor clams (Siliqua patula) in Alaska
Published 29 January 2024 Science ClosedTags: biological response, calcification, laboratory, molecular biology, mollusks, morphology, North Pacific, physiology
An increase in anthropogenic carbon dioxide is driving oceanic chemical shifts resulting in a long-term global decrease in ocean pH, colloquially termed ocean acidification (OA). Previous studies have demonstrated that OA can have negative physiological consequences for calcifying organisms, especially during early life-history stages. However, much of the previous research has focused on static exposure to future OA conditions, rather than variable exposure to elevated pCO2, which is more ecologically relevant for nearshore species. This study examines the effects of OA on embryonic and larval Pacific razor clams (Siliqua patula), a bivalve that produces a concretion during early shell development. Larvae were spawned and cultured over 28 days under three pCO2 treatments: a static high pCO2 of 867 μatm, a variable, diel pCO2 of 357 to 867 μatm, and an ambient pCO2 of 357 μatm. Our results indicate that the calcium carbonate polymorphism of the concretion phase of S. patula was amorphous calcium carbonate which transitioned to vaterite during the advanced D-veliger stage, with a final polymorphic shift to aragonite in adults, suggesting an increased vulnerability to dissolution under OA. However, exposure to elevated pCO2 appeared to accelerate the transition of larval S. patula from the concretion stage of shell development to complete calcification. There was no significant impact of OA exposure to elevated or variable pCO2 conditions on S. patula growth or HSP70 and calmodulin gene expression. This is the first experimental study examining the response of a concretion producing bivalve to future predicted OA conditions and has important implications for experimentation on larval mollusks and bivalve management.
Continue reading ‘Examining the impacts of elevated, variable pCO2 on larval Pacific razor clams (Siliqua patula) in Alaska’
