Scientists learn how to monitor ocean acidification during IAEA training course


Photo credit: IAEA

Fifteen participants from three different IAEA Technical Cooperation projects met this week at the IAEA Environment Laboratories in Monaco to receive training on ocean acidification monitoring. Participants learned how to measure pH and total alkalinity using a set of simplified methodologies developed by The Ocean Foundation, the IAEA OA-ICC and experts in the field in the framework of the Global Ocean Acidification Observing network (GOA-ON). The training aimed to empower participants to start ocean acidification monitoring in their countries, report toward the UN Sustainable Development Goal 14.3.1 on ocean acidification, and, ultimately, to inspire mitigation and adaptation actions. The course included both lectures and practical sessions on carbonate chemistry, sampling design and data quality and assurance, as well as biological impacts, experimental design, and opportunities for international networking and collaboration.

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Linking internal carbonate chemistry regulation and calcification in corals growing at a Mediterranean CO2 vent

Corals exert a strong biological control over their calcification processes, but there is a lack of knowledge on their capability of long-term acclimatization to ocean acidification (OA). We used a dual geochemical proxy approach to estimate the calcifying fluid pH (pHcf) and carbonate chemistry of a Mediterranean coral (Balanophyllia europaea) naturally growing along a pH gradient (range: pHTS 8.07–7.74). The pHcf derived from skeletal boron isotopic composition (δ11B) was 0.3–0.6 units above seawater values and homogeneous along the gradient (mean ± SEM: Site 1 = 8.39 ± 0.03, Site 2 = 8.34 ± 0.03, Site 3 = 8.34 ± 0.02). Also carbonate ion concentration derived from B/Ca was homogeneous [mean ± SEM (μmol kg–1): Site 1 = 579 ± 34, Site 2 = 541 ± 27, Site 3 = 568 ± 30] regardless of seawater pH. Furthermore, gross calcification rate (GCR, mass of CaCO3 deposited on the skeletal unit area per unit of time), estimated by a “bio-inorganic model” (IpHRAC), was homogeneous with decreasing pH. The homogeneous GCR, internal pH and carbonate chemistry confirm that the features of the “building blocks” – the fundamental structural components – produced by the biomineralization process were substantially unaffected by increased acidification. Furthermore, the pH up-regulation observed in this study could potentially explain the previous hypothesis that less “building blocks” are produced with increasing acidification ultimately leading to increased skeletal porosity and to reduced net calcification rate computed by including the total volume of the pore space. In fact, assuming that the available energy at the three sites is the same, this energy at the low pH sites could be partitioned among fewer calicoblastic cells that consume more energy given the larger difference between external and internal pH compared to the control, leading to the production of less building blocks (i.e., formation of pores inside the skeleton structure, determining increased porosity). However, we cannot exclude that also dissolution may play a role in increasing porosity. Thus, the ability of scleractinian corals to maintain elevated pHcf relative to ambient seawater might not always be sufficient to counteract declines in net calcification under OA scenarios.

Continue reading ‘Linking internal carbonate chemistry regulation and calcification in corals growing at a Mediterranean CO2 vent’

Defining CO2 and O2 syndromes of marine biomes in the anthropocene

Research efforts have intensified to foresee the prospects for marine biomes under climate change and anthropogenic drivers over varying temporal and spatial scales. Parallel with these efforts is the utilization of terminology, such as ‘ocean acidification’ (OA) and ‘ocean deoxygenation’ (OD), that can foster rapid comprehension of complex processes driving carbon dioxide (CO2) and oxygen (O2) concentrations in the global ocean and thus, are now widely used in discussions within and beyond academia. However, common usage of the terms ‘acidification’ and ‘deoxygenation’ alone are subjective and, without adequate contextualization, have the potential to mislead inferences over drivers that may ultimately shape the future state of marine ecosystems. Here we clarify the usage of the terms OA and OD as global, climate change‐driven processes and discuss the various attributes of elevated CO2 and reduced O2 syndromes common to coastal ecosystems. We support the use of the existing terms ‘coastal acidification’ and ‘coastal deoxygenation’ because they help differentiate the sometimes rapid and extreme nature of CO2 and O2 syndromes in coastal ecosystems from the global, climate change‐driven processes of OA and OD. Given the complexity and breadth of the processes involved in altering CO2 and O2 concentrations across marine ecosystems, we provide a workflow to enable contextualization and clarification of the usage of existing terms and highlight the close link between these two gases across spatial and temporal scales in the ocean. These distinctions are crucial to guide effective communication of research within the scientific community and guide policymakers responsible for intervening on the drivers to secure desirable future ocean states.

Continue reading ‘Defining CO2 and O2 syndromes of marine biomes in the anthropocene’

Ocean acidification-relevant side events at the UNFCCC COP25, 2-13 December 2019, Madrid, Spain

“From Knowledge to OA Action: Mobilizing Global Leadership to Protect Coastal Communities and Livelihoods from a Changing Ocean- Perspectives from the NE Atlantic.”

Description: The event will convene government and civil society leaders who are advancing tangible actions that protect coastal communities by addressing regional and local impacts of ocean acidification in the NE Atlantic.

Thursday, 5 December 2019, 10:00am-11:30am, French Pavilion, COP25 Madrid, Spain

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Interview with Mr. Tomohiko Tsunoda, Senior Research Fellow at the Ocean Policy Research Institute, Sasakawa Peace Foundation on ocean warming and acidification

Presentation at an international workshop on ocean acidification (GOA-ON workshop 2019)

Presentation at an international workshop on ocean acidification (GOA-ON workshop 2019)

Ocean warming, acidification, deoxygenation, and marine heatwaves are all pressing marine issues that are quietly intensifying around the world. These challenges are diverse and occur on a massive scale, making it difficult for people to understand the full extent of the problem. To shed some light on this topic, the Sasakawa Peace Foundation (SPF) spoke with Mr. Tsunoda, Senior Research Fellow at the Ocean Policy Research Institute (OPRI).

— What is ocean acidification and why is it occurring?

Mr. Tsunoda: In short, ocean acidification is the process whereby carbon dioxide dissolves in the ocean and makes the water more acidic. Seawater is normally slightly alkaline on the pH scale, but as more carbon dioxide is dissolved in the oceans, the pH moves toward neutrality, or in other words, becomes more acidic. The more carbon dioxide in the air, the more carbon dioxide dissolves into the sea. Ocean acidification, like global warming, is caused by the carbon dioxide that is produced by human activities.

Continue reading ‘Interview with Mr. Tomohiko Tsunoda, Senior Research Fellow at the Ocean Policy Research Institute, Sasakawa Peace Foundation on ocean warming and acidification’

Fish assemblages cope with ocean acidification in a shallow volcanic CO2 vent benefiting from an adjacent recovery area


• pH played a role in shaping nekto-benthic fish assemblages.

• Fish diversity did not show unique spatial patterns or significant pH-relations.

• Species richness and abundance correlated with seagrass canopy, regardless of pH.

• Unexpected among-site similarity was found in the abundance of juveniles.

• The area close to low pH site seems to work as a recovery area for fish.


Shallow CO2 vents are used to test ecological hypotheses about the effects of ocean acidification (OA). Here, we studied fish assemblages associated with Cymodocea nodosa meadows exposed to high pCO2/low pH conditions at a natural CO2 vent in the Mediterranean Sea. Using underwater visual census, we assessed fish community structure and biodiversity in a low pH site (close to the CO2 vent), a close control site and a far control site, hypothesising a decline in biodiversity and a homogenization of fish assemblages under OA conditions. Our findings revealed that fish diversity did not show a unique spatial pattern, or even significant relationships with pH, but correlated with seagrass leaf canopy. Among-site similarity was found in the abundance of juveniles, contrary to the expected impacts of OA on early life stages. However, pH seems an important driver in structuring fish assemblage in the low pH site, despite its high similarity with the close control site. This unexpected pattern may represent a combined response of fish mobility, enhanced food resources in the acidified site, and a ‘recovery area’ effect of the adjacent control site.

Continue reading ‘Fish assemblages cope with ocean acidification in a shallow volcanic CO2 vent benefiting from an adjacent recovery area’

Impacts of acidic seawater on early developmental stages of Fucus gardneri at Burrard Inlet, British Columbia

Increases in stressors associated with climate change such as ocean acidification and warming temperatures pose a serious threat to intertidal ecosystems. Of crucial importance are the effects on foundational species, such as fucoid algae, a critical component of rocky intertidal shorelines around the world. The impact of climate change on adult fronds of fucoid algae has been documented but effects on early developmental stages are not as well understood. In particular, ocean acidification stands to impact these stages because zygotes and embryos are known to maintain internal pH and develop a cytosolic pH gradient during development. To assess the effects of seawater acidification on early development, zygotes of Fucus gardneri were exposed to artificial seawater (ASW) buffered to conditions that approximate current global averages and extend largely beyond future projections. Exposure to acidic seawater had significant effects on embryonic growth. Specifically, rhizoid elongation, which occurs by a process known as tip growth, was significantly reduced with each 0.5 unit drop in pH. When pH was decreased from 8.0 to 7.5, which is similar to levels that have been observed in Burrard Inlet, there was reduction in rhizoid growth rate of almost 20%. Under more extreme conditions, at pH 6, rhizoid growth rates were reduced by 64% in comparison to embryos exposed to seawater at pH 8.0. On the other hand, acidic seawater had no effect on earlier processes; zygotes became multicellular embryos with well-formed rhizoids on a similar time course within the first 24 h of development, even when exposed to pH 6, an extreme pH well below what is expected in the future. This suggests that zygotes can maintain an internal pH that allows germination and cell division to occur. Tip growth, however, depends on the extended maintenance of an internal pH gradient. It is therefore possible that disruptions to this gradient could account for the observed reductions in rhizoid elongation. Under acidic conditions proton influx into the cell becomes energetically more favorable than at pH 8, and expulsion would be more difficult. This could disrupt the cytosolic pH gradient and in turn affect rhizoid growth.

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Ocean acidification in the IPCC AR5 WG II

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