Ocean alkalinity enhancement (OAE) is an emerging strategy that aims to mitigate climate change by increasing the alkalinity of seawater. This approach involves increasing the alkalinity of the ocean to enhance its capacity to absorb and store carbon dioxide (CO2) from the atmosphere. This chapter presents an overview of the technical aspects associated with the full range of OAE methods being pursued and discusses implications for undertaking research on these approaches. Various methods have been developed to implement OAE, including the direct injection of alkaline liquid into the surface ocean; dispersal of alkaline particles from ships, platforms, or pipes; the addition of minerals to coastal environments; and the electrochemical removal of acid from seawater. Each method has its advantages and challenges, such as scalability, cost effectiveness, and potential environmental impacts. The choice of technique may depend on factors such as regional oceanographic conditions, alkalinity source availability, and engineering feasibility. This chapter considers electrochemical methods, the accelerated weathering of limestone, ocean liming, the creation of hydrated carbonates, and the addition of minerals to coastal environments. In each case, the technical aspects of the technologies are considered, and implications for best-practice research are drawn. The environmental and social impacts of OAE will likely depend on the specific technology and the local context in which it is deployed. Therefore, it is essential that the technical feasibility of OAE is undertaken in parallel with, and informed by, wider impact assessments. While OAE shows promise as a potential climate change mitigation strategy, it is essential to acknowledge its limitations and uncertainties. Further research and development are needed to understand the long-term effects, optimize techniques, and address potential unintended consequences. OAE should be viewed as complementary to extensive emission reductions, and its feasibility may be improved if it is operated using energy and supply chains with minimal CO2 emissions.
Continue reading ‘Assessing the technical aspects of ocean-alkalinity-enhancement approaches’Archive Page 93
Assessing the technical aspects of ocean-alkalinity-enhancement approaches
Published 5 December 2023 Science ClosedTags: methods, mitigation, review
Recording available: IAEA/OA-ICC side event at COP28, “Ocean Acidification in the Persian Gulf, the Red Sea and the Mediterranean: Scaling Down Risks and Scaling Up Solutions, 3 December 2023, Dubai, UAE
Published 4 December 2023 Events ClosedThe IAEA Ocean Acidification International Coordination Centre (OA-ICC) held an engaging event addressing ocean acidification impacts and solutions on the sidelines of this year’s UNFCCC climate conference (COP28) at Expo City Dubai, UAE. The side event highlighted the success stories and lessons learned, emphasized current and projected challenges to marine food chains, human sustenance, economic activities and seafood security, and discussed sustainable pathways for effective adaptation and mitigation solutions.
Continue reading ‘Recording available: IAEA/OA-ICC side event at COP28, “Ocean Acidification in the Persian Gulf, the Red Sea and the Mediterranean: Scaling Down Risks and Scaling Up Solutions, 3 December 2023, Dubai, UAE’General considerations for experimental research on ocean alkalinity enhancement
Published 4 December 2023 Science ClosedTags: methods, mitigation
Ocean alkalinity enhancement (OAE) is proposed as an approach to capture carbon by adding alkaline substances to seawater to enhance the ocean’s natural carbon sink. These substances include minerals, such as olivine, or artificial substances, such as lime or some industrial byproducts. Deployment of OAE will lead to complex and dynamic changes in the seawater carbonate chemistry, and in some cases the addition of other compounds and impurities from the minerals. While OAE alters the carbonate chemistry in a very different way, much can be learned from the abundant literature on ocean acidification documenting the impact of changes in the carbonate chemistry on marine life from genes to ecosystems. A vast majority of the experimental work was performed by manipulating the concentration of carbon dioxide in seawater under constant alkalinity (TA) to simulate near-future ocean acidification. Understanding the impact of changes in alkalinity on marine species and the ecosystem is less understood. In the context of OAE, it is critical to resolve such impacts, alone or in combination with other compounds and impurities from the minerals to be co-released during implementation, to ensure that any field manipulation does not translate into damaging biological effects. As for other environmental drivers, this will require an understanding across all the levels of biological organizations from species to ecosystems over relevant time exposure considering the method of deployment (e.g., dilution, repeated exposure) and factors such as local adaptation. Such complex questions cannot be resolved using a single approach, and a combination of monitoring, modeling, laboratory, natural (i.e., proxies or analogs), and field experiments will be required. This chapter summarizes some key general considerations for experimental design. It also compares strengths and weaknesses of the different approaches. We will also consider best practices relevant to OAE such as the need to properly monitor and consider the addition of trace elements and byproducts, as well as potential interactions with other naturally occurring drivers.
Continue reading ‘General considerations for experimental research on ocean alkalinity enhancement’The interactions between olivine dissolution and phytoplankton in seawater: potential implications for ocean alkalinization
Published 4 December 2023 Science ClosedTags: chemistry, field, Mediterranean
Highlights
- Olivine dissolution promotes the growth of phytoplankton.
- The highly silicified diatom benefits most from olivine dissolution.
- Diatoms promote olivine dissolution by enhancing stoichiometric dissolution.
Abstract
Ocean alkalinity enhancement, one of the ocean-based CO2 removal techniques, has the potential to assist us in achieving the goal of carbon neutrality. Olivine is considered the most promising mineral for ocean alkalinization enhancement due to its theoretically high CO2 sequestration efficiency. Olivine dissolution has been predicted to alter marine phytoplankton communities, however, there is still a lack of experimental evidence. The olivine dissolution process in seawater can be influenced by a range of factors, including biotic factors, which have yet to be explored. In this study, we cultivated two diatoms and one coccolithophore with and without olivine particles to investigate their interactions with olivine dissolution. Our findings demonstrate that olivine dissolution promoted the growth of all phytoplankton species, with the highly silicified diatom Thalassiosira pseudonana benefiting the most. This was probably due to the highly silicified diatom having a higher silicate requirement and, therefore, growing more quickly when silicate was released during olivine dissolution. Based on the structural characteristics and chemical compositions on the exterior surface of olivine particles, T. pseudonana was found to promote olivine dissolution by inhibiting the formation of the amorphous SiO2 layer on the surface of olivine and therefore enhancing the stoichiometric dissolution of olivine. However, the positive effects of T. pseudonana on olivine dissolution were not observed in the coccolithophore Gephyrocapsa oceanica or the non-silicate obligate diatom Phaeodactylum tricornutum. This study provides the first experimental evidence of the interaction between phytoplankton and olivine dissolution, which has important implications for ocean alkalinization research.
Continue reading ‘The interactions between olivine dissolution and phytoplankton in seawater: potential implications for ocean alkalinization’Within- and transgenerational stress legacy effects of ocean acidification on red abalone (Haliotis rufescens) growth and survival
Published 4 December 2023 Science ClosedTags: adaptation, biological response, growth, laboratory, mollusks, mortality, otherprocess, reproduction
Understanding the mechanisms by which individual organisms respond and populations adapt to global climate change is a critical challenge. The role of plasticity and acclimation, within and across generations, may be essential given the pace of change. We investigated plasticity across generations and life stages in response to ocean acidification (OA), which poses a growing threat to both wild populations and the sustainable aquaculture of shellfish. Most studies of OA on shellfish focus on acute effects, and less is known regarding the longer term carryover effects that may manifest within or across generations. We assessed these longer term effects in red abalone (Haliotis rufescens) using a multi-generational split-brood experiment. We spawned adults raised in ambient conditions to create offspring that we then exposed to high pCO2 (1180 μatm; simulating OA) or low pCO2 (450 μatm; control or ambient conditions) during the first 3 months of life. We then allowed these animals to reach maturity in ambient common garden conditions for 4 years before returning the adults into high or low pCO2 treatments for 11 months and measuring growth and reproductive potential. Early-life exposure to OA in the F1 generation decreased adult growth rate even after 5 years especially when abalone were re-exposed to OA as adults. Adult but not early-life exposure to OA negatively impacted fecundity. We then exposed the F2 offspring to high or low pCO2 treatments for the first 3 months of life in a fully factorial, split-brood design. We found negative transgenerational effects of parental OA exposure on survival and growth of F2 offspring, in addition to significant direct effects of OA on F2 survival. These results show that the negative impacts of OA can last within and across generations, but that buffering against OA conditions at critical life-history windows can mitigate these effects.
Continue reading ‘Within- and transgenerational stress legacy effects of ocean acidification on red abalone (Haliotis rufescens) growth and survival’IAEA/OA-ICC side event at COP28: Ocean Acidification in the Persian Gulf, the Red Sea and the Mediterranean: Scaling Down Risks and Scaling Up Solutions, 3 December 2023, Expo City Dubai, UAE
Published 1 December 2023 Events ClosedDate and time: 3 December 2023, 14:00-15:45 (GMT +4)
Location: Blue Zone, IAEA “Atoms4Climate” Pavilion, Zone B7, Building 88 (watch online streamed via YouTube here)
Event description:
The abundant coral reefs found in the Persian Gulf, the Red Sea and the Mediterranean Sea, which provide countless ecosystem services for millions of inhabitants of coastal areas, are some of the most climate change-vulnerable ecosystems in the global ocean. Since 2012, the IAEA Ocean Acidification International Coordination Centre (OA-ICC) has successfully collaborated with scientific communities and governance structures in the region to address ocean acidification. The side event will highlight the success stories and lessons learned, emphasize current and projected challenges to marine food chains, human sustenance, economic activities and seafood security, and discuss sustainable pathways for effective adaptation and mitigation solutions.
Continue reading ‘IAEA/OA-ICC side event at COP28: Ocean Acidification in the Persian Gulf, the Red Sea and the Mediterranean: Scaling Down Risks and Scaling Up Solutions, 3 December 2023, Expo City Dubai, UAE’OA-ICC virtual exhibition booth at COP28 Virtual Ocean Pavilion
Published 1 December 2023 Events , Resources Closed
The IAEA Ocean Acidification International Coordination Centre (OA-ICC) joined this year’s Virtual Ocean Pavilion running on the sidelines of the UNFCCC COP28 in Dubai, UAE, from 22 November to 12 December 2023.
Our exhibition booth, located under the Exhibit Hall area of the pavilion, offers all visitors relevant information on the main project activities in the areas of science, capacity building and communication, also emphasizing the role that the IAEA plays in ocean acidification research through the use of nuclear sciences and technology, its leadership in coordinated global action and potential solution design. The booth gives access to useful resources developed under the project (news stream, bibliographic database, data compilation on the biological response to ocean acidification), publications, videos and links to other relevant information platforms curated by OA-ICC’s partners.
Continue reading ‘OA-ICC virtual exhibition booth at COP28 Virtual Ocean Pavilion’An updated version of the OA-ICC bibliographic database is available online.
The database currently contains 10,621 references and includes citations, abstracts and assigned keywords. Updates are made every month.
The database is available as a group on Zotero. Subscribe online or, for a better user experience, download the Zotero desktop application and sync with the group OA-ICC in Zotero. Please see the “User instructions” for further details.
OA-ICC, 1 December 2023.
Porcelaneous larger foraminiferal responses to Oligocene–Miocene global changes
Published 1 December 2023 Science ClosedTags: biological response, BRcommunity, community composition, Indian, Mediterranean, North Pacific, otherprocess, paleo, protists, review, sediment, South Pacific
Highlights
- Porcelaneous large foraminifera diversified during the Oligocene–Miocene.
- The Aquitanian and Langhian–Serravallian peaks in richness occurred when SST ∼ 29 °C.
- Detrimental effects of high pCO2 (> 600 ppm) in the Rupelian–early Chattian.
- Detrimental effects of high tropical SST (> 31 °C) during the beginning of MCO
- Detrimental effects of low tropical SST (< 26 °C) in the Tortonian
- Sea-level highstands affected diversification of Oligocene–Miocene pLBF
Abstract
Sea surface temperatures (SST) have been identified as a main controlling factor on larger benthic foraminifera (LBF) living in tropical to sub-tropical shallow-water carbonate and mixed siliciclastic‑carbonate platforms. Changes in SST, along with those in ocean acidification and nutrient content recorded in the global oceans throughout their history will not only continue but also be amplified in the future at an unprecedented rate of change possibly reaching levels recorded in the geological record. This study focuses on the Oligocene (mean SST 8 °C higher than present) and the Miocene (SST 5–8 °C higher than present) epochs which were characterized by a higher richness in porcelaneous LBF (pLBF) than today. A systematic re-assessment and comprehensive literature survey of stratigraphic ranges and palaeogeographic distribution in the Western Tethyan (Mediterranean) and Indo-Pacific regions are used to evaluate the impact of changes in SST, seawater pCO2 and pH on the biodiversity of the Oligocene–Miocene pLBF Alveolinella, Austrotrillina, Borelis, Bullalveolina, Flosculinella and Praebullalveolina. Two peaks in species richness were identified during the Aquitanian and Langhian–Serravallian. These peaks occurred when SST was ∼29 °C, with pCO2 of ∼400 ppm and pH > 7.8. These values are comparable to those of today. The minima in species richness recorded in the Rupelian–early Chattian, in the Burdigalian and from the Tortonian onward can be correlated to the detrimental effects of both minima (< 26 °C) and maxima (> 31 °C) SST thresholds. High pCO2 (> 600 ppm) values, which are limited to the Rupelian–early Chattian, are also detrimental to species richness. Seawater pH higher than 7.7 did not negatively affect species richness. These historical trends have serious implications for the future diversity of pLBFs with the increasing likely scenario of rising SST and pCO2 and lowering of pH values in the near future. These developments can potentially lead to diversity decrease and even extinction of pLBFs. However, the resilience of present-day pLBF species to rising SST and pCO2 levels is underpinned by the evolutionary histories of their fossil counterparts during climate variations, albeit at much different rates of change.
Continue reading ‘Porcelaneous larger foraminiferal responses to Oligocene–Miocene global changes’Observed amplification of the seasonal CO2 cycle at the Southern Ocean Time Series
Published 30 November 2023 Science ClosedTags: Antarctic, chemistry, field
The Subantarctic Zone, the circumpolar region of the Southern Ocean between the Subtropical and Subantarctic fronts, plays an important role in air-sea CO2 exchange, the storage of anthropogenic CO2, and the ventilation of the lower thermocline. Here we use a time series from moored platforms deployed between 2011 and 2021 as part of the Southern Ocean Time Series (SOTS) observatory to investigate the seasonality and interannual variability of upper ocean hydrography and seawater CO2 partial pressure (pCO2). The region is a net sink for atmospheric CO2 over the nearly 10-year record, with trends revealing that the ocean pCO2 may be increasing slightly faster than the atmosphere, suggesting that oceanic as well as anthropogenic atmospheric forcing contributes to the decadal change, which includes a decline in pH on the order of 0.003 yr−1. The observations also show an amplification of the seasonal cycle in pCO2, potentially linked to changes in mixed layer depth and biological productivity.
Continue reading ‘Observed amplification of the seasonal CO2 cycle at the Southern Ocean Time Series’Media representations and farmer perceptions: a case study of reporting on ocean acidification and the shellfish farming sector in British Columbia, Canada
Published 30 November 2023 Science ClosedTags: fisheries, North Pacific, socio-economy
Ocean Acidification (OA) creates corrosive conditions that impact organisms that produce calcium carbonate shells, such as clams and oysters. The Salish Sea, a body of water where much of British Columbia’s shellfish farming sector operates, has been growing more corrosive. We present a case study of reporting on OA and the shellfish farming sector in British Columbia, Canada. We convey results from a survey with shellfish farmers and a thematic analysis that sought to understand how the science and local implications of OA were presented in a sample of media articles. All articles employed narratives of crisis, and slightly over 75% conveyed scientific uncertainty. Just over 55% incorporated interviews with one or more of scientists, shellfish sector representatives, and shellfish farmers. Survey findings reveal that respondents saw OA as a threat but often deprioritized it relative to a wider range of operational challenges. We introduce “situatedness” and draw in ideas from “solutions journalism” to expand. While telling stories about people and places is important, we conclude that new opportunities for locally salient climate change reporting stand to be unlocked by looking beyond boundaries typically drawn around “the local” and the sorts of credentials typically ascribed to “environmental experts”.
Continue reading ‘Media representations and farmer perceptions: a case study of reporting on ocean acidification and the shellfish farming sector in British Columbia, Canada’High light intensity and CO2 enrichment synergistically mitigated the stress caused by low salinity in Pyropia yezoensis
Published 30 November 2023 Science ClosedTags: algae, biological response, growth, laboratory, light, multiple factors, North Pacific, photosynthesis, physiology, salinity
Macroalgae, playing a crucial role in coastal marine ecosystems, are subject to multiple environmental challenges due to tidal and seasonal alterations. In this work, we investigated the physiological responses of Pyropia yezoensis to ocean acidification (ambient CO2 (AC: 400 μatm) and elevated CO2 (HC: 1000 μatm)) under changing salinity (20, 30 psu) and light intensities (50, 100 μmol photons m−2 s−1) by measuring the growth, pigment content, chlorophyll fluorescence, and soluble sugar content. The key results are the following: (1) P. yezoensis exhibited better growth under normal salinity (30 psu) compared to hyposaline conditions (20 psu). (2) Intermediate light intensity increased phycoerythrin content, ultimately enhancing thalli growth without significant changes to the contents of chlorophyll a and carotenoids. (3) Ocean acidification alleviated hyposaline stress by enhancing pigment production in P. yezoensis only at a salinity of 20 psu, highlighting the complex interplay of these environmental factors. These findings indicate that higher light intensities and elevated pCO2 levels could mitigate the stress caused by low salinity.
Continue reading ‘High light intensity and CO2 enrichment synergistically mitigated the stress caused by low salinity in Pyropia yezoensis’Planktonic foraminifers and shelled pteropods in the Barents Sea: seasonal distribution and contribution to the carbon pump of the living fauna, and foraminiferal development during the last three millennia
Published 30 November 2023 Science ClosedTags: abundance, Arctic, biological response, BRcommunity, community composition, field, morphology, otherprocess, paleo, protists, sediment
The Arctic Ocean in general and the Barents Sea specifically, are highly affected by the human induced carbon dioxide (CO2) emissions and increasing temperatures. Atlantification, caused by an increase in warm Atlantic Water inflow, and polar amplification, caused by a higher impact of the increasing temperatures at high latitudes, have already been observed. Moreover, the Barents Sea has been described as a hotspot for ocean acidification. Ocean acidification is the decrease of pH, calcium carbonate saturation state, and carbonate ion concentration due to an increase in CO2 uptake from the atmosphere by the ocean. This alteration of the carbonate chemistry of the water affects the marine biota, especially planktonic marine calcifiers. They are organisms living in the water column with a shell made of calcium carbonate (CaCO3). They contribute significantly to the carbon cycle by exporting mainly CaCO3 from the surface water to the seabed when they die. The main goal of this thesis is to study the distribution of marine calcifiers (planktonic foraminifers and shelled pteropods) in the Barents Sea and the adjacent Arctic Basin. We have (1) investigated their distribution patterns and contribution to carbon dynamics in the north Svalbard margin and in a seasonal basin in the northern Barents Sea; and (2) reconstructed the foraminiferal production and preservation patterns from the late Holocene in sediment cores from the northern and southern Barents Sea. The results from this thesis show that pteropods are important contributors to the carbon dynamics in all seasons in the northern Barents Sea and northern Svalbard margin. Due to the higher sensitivity of their shells compared to foraminifers, they are more likely to be affected by ocean acidification. Moreover, the abundance of foraminifers in the sediment suggests higher productivity in the southern than in the northern Barents Sea. The almost zero abundances observed in the northern Barents Sea core, combined with the seasonality of marine calcifiers, the water carbonate chemistry, and the presence of agglutinated foraminifers suggest dissolution of CaCO3 in the sediment. Due to the use of their shells in paleoceanography, further investigations of CaCO3 dissolution are needed to use them as proxies for the reconstruction of the paleoenvironmental and paleoclimatic conditions in the Barents Sea.
Continue reading ‘Planktonic foraminifers and shelled pteropods in the Barents Sea: seasonal distribution and contribution to the carbon pump of the living fauna, and foraminiferal development during the last three millennia’Challenging Greek primary students’ knowledge of ocean acidification using the carbon cycle context
Published 29 November 2023 Science ClosedTags: education
The purpose of the present study was to investigate the impact of an intervention on primary school students’ construction of knowledge on ocean acidification and the development of their systems thinking. Eighty-five 11 to 12-year-old students from five different classes of two public primary schools in Greece participated in the 8-h intervention. The intervention included inquiry-based and knowledge-integration activities, and students worked in groups during all activities. Rich pictures, made by the groups at the beginning and the end of the intervention, were used to evaluate their progress in their knowledge concerning the carbon cycle, as well as in their systems thinking. Our findings showed that the intervention contributed to primary students’ conceptual knowledge of the carbon cycle and the inclusion of ocean acidification in the carbon cycle. It also helped them improve their systems thinking, indicating that students’ systems thinking at this age could be developed through formal instruction with interventions which emphasize content knowledge and use an earth systems approach. Moreover, our findings indicate that the systems thinking perspective can serve as an effective approach to help children better understand and critically engage with complex environmental issues, such as ocean acidification.
Continue reading ‘Challenging Greek primary students’ knowledge of ocean acidification using the carbon cycle context’Scientists publish 37-year record of ocean acidification off southern California
Published 29 November 2023 Press releases ClosedThe longest ocean time series of dissolved carbon dioxide in the Pacific — part of the “Keeling Curve of the ocean” — is revealed.
For the first time, scientists at UC San Diego’s Scripps Institution of Oceanography have published nearly four decades’ worth of dissolved carbon dioxide measurements from waters off Southern California. The measurements reveal a slight but consistent trend of ocean acidification, a process characterized by a decrease in the ocean’s pH over time due to its absorption of carbon dioxide (CO2) from the atmosphere.
Since the early 1980s, samples of ocean carbonate chemistry have been collected by the California Cooperative Oceanic Fisheries Investigations (CalCOFI) program, which was established in 1949 to investigate the collapse of the sardine population off California. In a new study, Scripps Oceanography researchers present 37 years of measurements from CalCOFI Line 90 Station 90 (station 90.90), a measuring site located 450 kilometers (280 miles) off the coast of San Diego. The team’s findings were published on Nov. 3 in Communications Earth & Environment, a journal affiliated with Nature.
The measurements from station 90.90 establish the oldest time series of direct inorganic carbon observations in the Pacific Ocean. While measurements at the station carry on to the present day, the study details quarterly measurements collected from 1984 to 2021, with a gap from 2002 to 2008 due to a lack of funding. Notably, the data show that the seawater at the study site is getting more acidic, with a measured decrease in pH of 0.0015 per year.
Continue reading ‘Scientists publish 37-year record of ocean acidification off southern California’NOAA ocean acidification lecture, 1 December 2023, University of Delaware
Published 29 November 2023 Events ClosedDate and time: 1 December 2023, 11:30 a.m.
Location: Trabant Theater, University of Delaware
Dr Richard A. Feely, NOAA Senior Fellow at the NOAA Pacific Marine Environmental Laboratory, will give lecture on the chemical and ecological impacts of ocean acidification.
Please join us on Friday, Dec. 1, at 11:30 a.m. in Trabant Theater for a special School of Marine Science and Policy seminar on the chemical and ecological impacts of ocean acidification: “The Combined Effects of Ocean Acidification and Respiration on Habitat Suitability for Marine Calcifiers Along the West Coast of North America”.
The lecture will be followed by a reception in Trabant Multipurpose Rooms A/B.
Registration is required for this event. Register online.
Continue reading ‘NOAA ocean acidification lecture, 1 December 2023, University of Delaware’MOPGA 2024: Visiting fellowship program for early career researchers
Published 28 November 2023 Jobs ClosedApplication deadline: 9 January 2024
Launched in 2018, the Make Our Planet Great Again (MOPGA) initiative has met with worldwide enthusiasm, generating expressions of interest from a large number of highly qualified students and researchers.
France, as a major player in the fight against climate change and guarantor of the spirit of the Paris Agreement, is launching a new MOPGA visiting fellowship program geared towards strengthening scientific contributions to climate change issues raised by the COPs.
This seventh Make Our Planet Great Again (MOPGA) call for applications is intended to welcome at least 40 early career researchers wishing to carry out their research in France. The program is funded by the French Ministry for Europe and Foreign Affairs, in collaboration with the French Ministry for Higher Education and Research, and implemented by Campus France.
The MOPGA 2024 Visiting Fellowship Program for Early Career Researchers will support researchers working on topics listed in the “Research Themes” section.
Continue reading ‘MOPGA 2024: Visiting fellowship program for early career researchers’Porites’ coral calcifying fluid chemistry regulation under normal- and low-pH seawater conditions in Palau Archipelago: impacts on growth properties
Published 28 November 2023 Science ClosedTags: biological response, calcification, corals, field, morphology, physiology, South Pacific
Highlights
- •Palau’s reef has a long-term naturally acidified inshore seawater (pH ~ 7.85).
- •Porites corals up-regulate calcifying fluid pH (~8.41) at normal- and low-pH sites.
- •Porites corals adapt calcifying fluid chemistry to long-term low-pH conditions.
- •Porites shows 15 % lower skeletal density under low-pH (~7.85) vs. open-ocean (~8.03).
Abstract
Ongoing ocean acidification is known to be a major threat to tropical coral reefs. To date, only few studies have evaluated the impacts of natural long-term exposure to low-pH seawater on the chemical regulation and growth of reef-building corals. This work investigated the different responses of the massive Porites coral living at normal (pHsw ~ 8.03) and naturally low-pH (pHsw ~ 7.85) seawater conditions at Palau over the last decades. Our results show that both Porites colonies maintained similar carbonate properties (pHcf, [CO32−]cf, DICcf, and Ωcf) within their calcifying fluid since 1972. However, the Porites skeleton of the more acidified conditions revealed a significantly lower density (~ 1.21 ± 0.09 g·cm−3) than the skeleton from the open-ocean site (~ 1.41 ± 0.07 g·cm−3). Overall, both Porites colonies exerted a strong biological control to maintain stable calcifying fluid carbonate chemistry that favored the calcification process, especially under low-pH conditions. However, the decline in skeletal density observed at low pH provides critical insights into Porites vulnerability to future global change.
Continue reading ‘Porites’ coral calcifying fluid chemistry regulation under normal- and low-pH seawater conditions in Palau Archipelago: impacts on growth properties’Effects of ocean acidification on growth and photophysiology of two tropical reef macroalgae
Published 28 November 2023 Science ClosedTags: algae, biological response, calcification, chemistry, field, morphology, North Atlantic, photosynthesis, primary production, respiration
Macroalgae can modify coral reef community structure and ecosystem function through a variety of mechanisms, including mediation of biogeochemistry through photosynthesis and the associated production of dissolved organic carbon (DOC). Ocean acidification has the potential to fuel macroalgal growth and photosynthesis and alter DOC production, but responses across taxa and regions are widely varied and difficult to predict. Focusing on algal taxa from two different functional groups on Caribbean coral reefs, we exposed fleshy (Dictyota spp.) and calcifying (Halimeda tuna) macroalgae to ambient and low seawater pH for 25 days in an outdoor experimental system in the Florida Keys. We quantified algal growth, calcification, photophysiology, and DOC production across pH treatments. We observed no significant differences in the growth or photophysiology of either species between treatments, except for lower chlorophyll b concentrations in Dictyota spp. in response to low pH. We were unable to quantify changes in DOC production. The tolerance of Dictyota and Halimeda to near-future seawater carbonate chemistry and stability of photophysiology, suggests that acidification alone is unlikely to change biogeochemical processes associated with algal photosynthesis in these species. Additional research is needed to fully understand how taxa from these functional groups sourced from a wide range of environmental conditions regulate photosynthesis (via carbon uptake strategies) and how this impacts their DOC production. Understanding these species-specific responses to future acidification will allow us to more accurately model and predict the indirect impacts of macroalgae on coral health and reef ecosystem processes.
Continue reading ‘Effects of ocean acidification on growth and photophysiology of two tropical reef macroalgae’California Ocean Acidification and Hypoxia Portal
Published 28 November 2023 Web sites and blogs ClosedThe California OAH Portal is a centralized information center serving relevant, timely, and reliable OAH information to managers, researchers, industry, and other marine stakeholders. This new information hub is designed to support the automated generation of data-driven products to solve user needs within the region. The Portal integrates standardized, quality controlled data from diverse sources and platforms, incorporate existing data layers from models and satellites, and collaborate with state and West Coast partners to serve additional data streams and curated synthesis products. We serve automated and interoperable data and synthesis products that incorporate the most current data to generate indicators of status and trends. Data and information products will be downloadable and shareable for a variety of uses.
