Accurately predicting future ocean acidification (OA) conditions is crucial for advancing OA research at regional and global scales, and guiding society's mitigation and adaptation efforts. This study presents a new model-data fusion product covering 10 global surface OA indicators based on 14 Earth System Models (ESMs) from the Coupled Model Intercomparison Project Phase 6 (CMIP6), along with three recent observational ocean carbon data products.

Negative emissions strategies will be essential for keeping global temperatures at or below target levels. Many of these techniques are promising in theory, but most are currently in their infancy and require additional research to evaluate their effectiveness and scalability and explore potential co-benefits and environmental risk. Here, we will profile NOAA's recent Research Strategy for Carbon Dioxide Removal in context with other ongoing efforts.

This webinar will present various biogeochemistry studies focusing on the Tropical and South Atlantic Ocean, including perspectives on air-sea CO2 exchanges and ocean acidification. First, we will discuss the results of the main studies developed at the upwelling system of Perú focused on the oceanographic dynamics, the carbonate system and the implementation of a low cost coastal marine observatory to monitor natural stressors and contribute to the ODS 14. Secondly, we will present some of the main studies developed by the Brazilian Ocean Acidification Network (BrOA) in the western Tropical Atlantic, in the South Atlantic and in the Antarctic Peninsula. Finally, we will provide an overview of our current knowledge of carbon chemistry, from air-sea CO2 exchanges to ocean acidification.

High-quality measurements of the seawater carbonate system allow us to quantify and understand the oceanic uptake of atmospheric carbon dioxide (CO2) and monitor ocean acidification. Those seawater carbonate system measurements rely on the availability of reference materials (RMs). The COVID-19 pandemic highlighted the fragility of the production system of the seawater RMs for the carbonate system, currently depending on one single laboratory. With that in mind, a new model for seawater RMs for the carbonate system, centered on regional hubs, is being discussed to create a more resilient system. The proposed new model for seawater RMs for the carbonate system requires unprecedented involvement of National Metrology Institutes (NMIs) on a global level. The integration of the new model into the global metrology landscape will help to produce the RMs that are comparable and metrologically traceable to the International System of Units.

Long-term environmental change, sudden pulses of extreme perturbation, or a combination of both can trigger regime shifts by changing the processes and feedbacks which determine community assembly, structure, and function, altering the state of ecosystems. Our understanding of the mechanisms that stabilise against regime shifts or lock communities into altered states is limited, yet also critical to anticipating future states, preventing regime shifts, and reversing unwanted state change. Ocean acidification contributes to the restructuring and simplification of algal systems, however the mechanisms through which this occurs and whether additional drivers are involved requires further study. Using monthly surveys over three years at a shallow-water volcanic seep we examined how the composition of algal communities change with exposure to increasing levels of ocean acidification, between seasons, and following periods of significant physical disturbance by typhoons.

The French national observation network for the carbonate system was initiated in 2021 in the framework of the CocoriCO2 project (EMFF, 2020-2022). Along the French littoral, 6 areas were chosen based on their importance in terms of shellfish production and the presence of low-frequency monitoring activities. In each one, pH autonomous loggers (SeaFET pH) were deployed both inside and outside shellfish production areas, next to CTD probes operated through two existing networks. The building of this network, the implementation of the sampling strategy and the quality process assurance will be explained. While this network is up and running for more than two years, the acquired data set will be exposed, as it already revealed important differences in terms of pH variations between monitored sites related to the influence of diverse processes (freshwater inputs, tides, temperature, biological processes).

The Mediterranean Sea is a hotspot of Global Change due to its semi-enclosed configuration. Mediterranean sea surface warming is expected to be 20% above the global mean projections. As for warming, Mediterranean acidification seems to be more intense than the global ocean. Throughout this webinar, we will present the impact of ocean acidification and warming on some emblematic Mediterranean calcifying species. First, we will present a project assessing the impact and tolerance to low pH of different life stages of two endemic coral species, Astroides calycularis, and Cladocora caespitosa, living in CO2 vent sites as naturally acidified environments. Secondly, we discuss a project analyzing the changes in mitochondrial abundance and size in crabs and mussels due to their exposure to future projections of pH and temperature.

The first response by animals to a changing environment is predominantly through modification of their behaviour. In this context, investigating behavioural responses of fish living under low-ph/high-CO2 conditions (e.g. off volcanic seep sites) may contribute to a better understanding of how marine species might adjust or adapt to environmental conditions under projected ocean change scenarios. We carried out field-based observations and translocation experiments in the Vulcano island natural CO2 seep (southern Italy) to assess whether there is evidence for local behavioural adaptation and/or acclimatization of fish after long and short-term exposure to ocean acidification conditions predicted to occur by the end of this century. The responses of two temperate fish species, characterized by a limited home range, have been investigated and compared between fish from low-pH/high pCO2 sites and fish from control sites. Furthermore, understanding the molecular underpinnings responsible for acclimatization to acidified waters, by means of an integrated study of the brain transcriptional program of wild fish species, can elucidate on the variation in responses. We collected 130 individuals of six different reef fish species from a natural volcanic CO2 seep and nearby control reefs in Papua New Guinea. Differences in brain gene expression in fish from CO2 seeps compared to fish from control sites as well as differences among species identified the molecular pathways controlling the cellular responses to elevated CO2. These studies provide a broader understanding as to the behavioural and molecular alterations crucial for coping with naturally elevated CO2 conditions.

The August 2022 GOA-ON webinar, "Ocean Acidification Monitoring and Scientific Research in the PI-TOA Region" was held on August 25, 11am Fiji. The webinar was moderated by Dr Kim Currie with presentations by Dr Antoine De Ramon N’Yeurt, Associate Professor Patila Amosa and Ms Luia Taise. The three speakers spanned topics such as establishing a pH time-series on the Suva reef, the effects of ocean acidification on organismal calcification such as corals and bryozoans, and the impacts on the photosynthetic physiology of a green seaweed. These research topics are important in understanding the impact of ocean acidification on coastal ecosystems of the Pacific.

Although laboratory experiments have shown various effects of climate change and ocean acidification on coral reef organisms, the underlying mechanisms and ecosystem effects remain uncertain. The International CO2 Natural Analogues (ICONA) network was created to foster the use of natural analogues such as volcanic CO2 vents and enclosed bays, harmonize the techniques, and enhance exchanges and collaboration. Here, we will present results obtained at multiple natural analogues, focusing on the effects on scleractinian corals, and on the diversity of understudied invertebrate groups such as zooxanthellate zoantharians and octocorals. By studying resistant or resilient species and individuals, we aim to understand the eco-physiological traits and adaptation mechanisms that will determine the shape and diversity of future coral communities.

South Asia has some of the largest and biologically rich marine ecosystems including mangroves, estuaries, coastal lagoons and coral reefs.More than 200 million people in South Asia are directly dependent on coastal and open ocean bioresources. As the second fastest economically growing region in the world, the regional seas and oceans of South Asia are facing multi-faceted pressures including from relative rise in sea-level, salinity intrusion, nitrogen and plastic pollution, in addition to emerging threats of ocean acidification. Ocean acidification (OA) in South Asia can have huge consequences for the coastal blue economy and linked GDP. South Asia Regional Hub on Ocean Acidification (SAROA), a GOA-ON endorsed Hub intends to bring together early career and experienced scientists with a common interest on documenting geographically distributed data on OA across seas and oceans of South Asia; monitor OA and effects on coastal bioresources and beyond such as involving citizen scientists. SAROA intends to play a key role by engaging with policy makers, social scientists and citizens of South Asia through existing programs such as the South Asia Co-operative Environment Programme (SACEP) so as to highlight and mainstream OA research outcomes towards long-term sustainability and achieving healthy regional seas and oceans across the region and beyond.

The latest IPCC Working Group 2 report, released in late February, assessed the current state of knowledge about ocean acidification and its impacts on ocean systems both globally and regionally. New model projections detail the development of ocean acidification through the water column, and how its future development depends on global emissions choices. The report also assesses how ocean acidification is acting individually and in combination with other stressors, driving a variety of outcomes for ocean ecosystems and the people that depend on them. Climate change will affect how we live, work and play in coastal regions including impacts on biodiversity, cultural connections, food and livelihoods. Each of the presenters was a lead author on a different WG2 chapter and will provide insights accordingly.

Due to ongoing anthropogenic CO2 emissions and the parallel active ocean physical CO2 pumping causing acidification of waters, studying past changes in seawater carbonate chemistry has become a major focus in paleoclimate research. Insight into past marine carbon cycling and perturbations therein critically depends on robust reconstructions of the seawater carbonate system (C-system) through well-controlled experimental setups and accurate C-system manipulations. In the ocean, small calcifying micro-organisms (i.e. foraminifera) incorporate various elements into biogenic calcium carbonate in equilibrium with specific environmental parameters. Here we explore the use of deep-sea foraminiferal Sr/Ca ratio as a new C-system proxy for paleoclimate research studies. We use decoupled carbonate chemistry controls, i.e. changing pH at constant Dissolved Inorganic Carbon (DIC) and changing DIC at constant pH. This experiment was performed for the first time with a new generation of environmental simulator designed for experimentation in ecology (Ecolab system – CEREEP-ECOTRON). Four controlled and regulated climatic chambers were used with four different concentrations of atmospheric pCO2 (180 ppm, 410 ppm, 1000 ppm, 1500 ppm) simulating the last glacial maximum, the current and future projection pCO2 values. Preliminary results describe a positive correlation between Sr/Ca and the carbonate system, namely bicarbonate ion concentration.

Estuaries are diverse and important aquatic ecosystems; and yet until now we have lacked information on the response of estuaries to climate change. In this seminar I will present data from a twelve-year monitoring program, involving 6200 observations of 166 estuaries along 1100 kilometers of the Australian coastline. Estuary temperatures increased by 2.16 °C on average over 12 years, at a rate of 0.2 °C/year, with waters acidifying at a rate of 0.09 pH units and freshening at 0.086 PSU/year. Lagoons and rivers are warming and acidifying at the fastest rate because of shallow average depths and limited oceanic exchange. The changes measured are an order of magnitude faster than predicted by global ocean and atmospheric models, indicating that existing global models may not be useful to predict change in estuaries. Estuaries are also home to diverse ecosystems and valuable economies supported by oysters. Oysters rely on bacterial communities forming a microbiome for their health and survival. Oysters are also vulnerable to disease and this is may be exacerbated by climate change in estuaries. We found that warming and acidification can shift the microbiome of Sydney rock oysters (Saccostrea glomerata), however, these effects can be ameliorated by selective breeding. We show that oyster genetic background may influence the microbiome under climate change and that future assisted evolution breeding programs could be used to enhance resilience in the oyster microbiome.

The Southern Ocean accounts for nearly half of the global ocean’s sink of anthropogenic carbon. Despite this important contribution, many climate models do not represent the mesoscale features that characterize the region due to limited spatial resolution. Here we apply a high-resolution ocean model that incorporates biogeochemistry with high-emission (RCP8.5) forcing in order to identify regions of pronounced change due to carbon uptake into the near future. We find that the annual uptake of carbon in the Southern Ocean south of 40° S is projected to double over the first half of the 21st century. The changes due to the increase in carbon will lead to acidification and lowering of aragonite saturation. We will present regions where changes to carbon system variables are respectively more and less pronounced to inform the siting of near-future observations.

The Canary Current and the Benguela Current upwelling systems support significant local and international fish resources along the west coast of Africa. These fisheries contribute to the region's economy and provide important food and employment opportunities to coastal communities. In 2017, the 30-year long Ecosystem Assessment for Fisheries (EAF) Nansen Program, which is supported by the FAO and the Norwegian Ministry of Foreign Affairs, initiated studies on ocean acidification in these upwelling systems. The Canary Current Large Marine Ecosystem survey was performed between May 2017 and December 2019 aboard the R/V Dr. Fridtjof Nansen. It consisted of 110 stations situated at twenty seven sections perpendicular from the coast. Total alkalinity (TA) and pH data were collected using potentiometric titration and spectrophotometric pH measurements, respectively. The other parameters describing the carbonate chemistry and ocean acidification state were derived from TA and pH using the CO2SYS calculation program. Large variability along the coast was observed, connected to salinity changes, primary production, temperature, and biological processes. Results from a similar study focused on the Benguela Current upwelling system will also be shared during this webinar.

The MEOPAR OA Community of Practice (CoP) was formed in 2018, with the overarching goal of sharing knowledge and improving linkages between OA knowledge creators and end-users across Canada. The OA CoP is led by two Co-Leads, Dr. Helen Gurney-Smith (DFO) and Dr. Brent Else (University of Calgary), and a Coordinator, Dr. Kristina Barclay (University of Calgary, MEOPAR), with guidance from an interdisciplinary Steering Committee from across the country. OA CoP objectives include the development of: knowledge transfer and community engagement via accessible content, resources, and databases, and best-practices for data collection and sharing involving research groups, stake-holders, and community-based research. We will present some of our key activities to date, our new online resources and blog series, as well as updates on the development of future projects. Current and future activities are focused on increasing online content and resources to increase OA CoP awareness and engagement, the development of a low-cost OA sensor package to aid aquaculture operations and larger monitoring efforts, conducting regional vulnerability assessments, and participation in partner OA organizations, including the GOA-ON North American Hub, the OA Information Exchange, DFO-NOAA OA Working Groups, the OA Alliance, and MEOPAR.