Open research questions in Ocean Acidification Effects and Responses

What the literature leaves open

• Interpreting pH variability in shallow habitats remains a major challenge for Mediterranean research. Biological 'noise' can often mask the underlying anthropogenic signal. The synergistic effect of acidification and rising temperatures may soon exceed the physiological thresholds of key coralline species.

  Multiscale pH fluctuations on a stable algal reef community (SE Sardinia, Tyrrhenian Sea) · 2026 · DOI

• The paper identifies a gap in predicting how marine biota will be affected by ocean acidification. It notes that taxonomic diversity alone is not a robust metric of calcifier sensitivity to ocean acidification.

  Ocean acidification pushes Mediterranean marine calcifiers toward a tipping point · 2026 · DOI

• One challenge is the complexity of the interactions between microorganisms, hosts, and the environment. Another challenge is the need to simulate the effects of oil contamination and reduced seawater pH under controlled conditions. The analysis of high-throughput sequencing data and biochemical markers also poses technical challenges.

  Effects of Reduced Seawater pH and Oil Contamination on Bacterial Communities and Biochemical Markers of Estuarine Animal Hosts · 2024 · DOI

• The ecological and socio-economic consequences of OA were first identified around 10–15 years ago but remain poorly understood.

  Historic ocean acidification of Loch Sween revealed by correlative geochemical imaging and high-resolution boron isotope analysis of Boreolithothamniom cf. soriferum · 2024 · DOI

• However, little is known about the impact of pan-Arctic sea-ice decline on carbon export processes.

  Release of ballast material during sea-ice melt enhances carbon export in the Arctic Ocean · 2024 · DOI

• The study highlights the need for further research on the impacts of ocean acidification on marine ecosystems.

  Shell hash promotes growth in Pacific littleneck clams (Leukoma staminea) by altering pore water chemistry · 2026 · DOI

• The study had a limited number of replicates. The study only tested two species of penguins. The study did not account for other factors that may influence the behavior of the organisms.

  Effects of penguin guano on spatial behavior of Antarctic marine invertebrate species: an exploratory study · 2026 · DOI

• Further research is needed to evaluate the long-term effects of emission control policies on air quality and environmental justice. The framework developed in this study can be applied to other regions to evaluate the impacts of emission control policies. More research is needed to understand the non-linear responses of PM2.5 and O3 to specific interventions.

  Impacts of Emission Control Policies on Air Quality and Environmental Justice Over the Pearl River Delta for 2021–2025 · 2026 · DOI

• The current control strategies may be ineffective and inequitable. There is a need to develop a more comprehensive framework to evaluate the impacts of emission control policies on air quality and environmental justice.

  Impacts of Emission Control Policies on Air Quality and Environmental Justice Over the Pearl River Delta for 2021–2025 · 2026 · DOI

• There is a need for a fully autonomous, off-grid, floating deployment platform for natural bodies of water. Prior systems, such as the SPCA-1, are not fully autonomous or off-grid.

  Amendment CCCLXX — SPCA-2: SOL Pool Coherence Amplifier, Aquatic Edition: Portable, Off-Grid, Floating Phi-Harmonic Coherence System for Lakes, Ponds, and Open Water · 2026 · DOI

• Ocean acidification (OA) remains a major and underexplored threat to marine fishes, particularly regarding reproductive physiology and early life stages (ELS).

  Impacts of Ocean Acidification on Reproduction and Early Life Development in Marine Teleost Fish—A Synthesis · 2026 · DOI

• The gap is the scarcity of integrated assessments in China's coastal waters. The paper identifies the need to understand the combined effects of climate and anthropogenic change on threatened marine species. The gap is the lack of knowledge on the dominant natural and anthropogenic drivers of habitat suitability.

  Combined effects of climate and anthropogenic change on habitat suitability and distribution of threatened marine species in China’s coastal waters · 2026 · DOI

• The combined effects of ocean warming and acidification on tropical marine gastropods are not well understood. There is a need to investigate the interactive effects of these drivers on the survival, growth, and physiological performance of marine invertebrate larvae.

  Extreme warming increases metabolic demand and diminishes acidification effects on larval survival in the dog conch Strombus canarium · 2026 · DOI

• The need for a better understanding of the impact of ocean acidification on mussel attachment. The lack of studies analyzing the byssus as an intact functional unit. The need to investigate the effects of elevated pCO2 on byssus production, thread morphology, and whole-byssus mechanics.

  Elevated pCO2 impairs overall byssus attachment strength in the blue mussel (Mytilus edulis) without altering byssus thread quality · 2026 · DOI

• The lack of understanding of the role of small particles in the ocean carbon cycle. The need to investigate the spatial distribution and seasonality of small particles in the mesopelagic ocean.

  Global patterns in small organic particle loss in the mesopelagic ocean · 2026 · DOI

• The BCP is very active in highly productive eastern boundary upwelling systems (EBUSs); however, the extent to which climate change will affect this key ecosystem service remains uncertain.

  The ecology of carbon sequestration in coastal upwelling ecosystems · 2026 · DOI

• While resolving mesoscale activity is important for accurately simulating MHWs, the sensitivity of biogeochemical extremes to model resolution remains unclear.

  The Role of Ocean Model Resolution in Simulating Marine Biogeochemical Extremes · 2026 · DOI

• There is a lack of long-term evolution experiments with the marine diatom Chaetoceros muelleri, comparing abrupt and gradual CO2 increases. The impact of gradual acidification on diatom growth and carbon fixation responses is not well understood.

  Abrupt pH changes overestimate the responses of Chaetoceros muelleri to ocean acidification · 2026 · DOI

• At mid-century (2035–2050), scallop growth was projected to increase in most areas except the southern Mid-Atlantic, and OA effects were limited to the deep Gulf of Maine.

  Modeling the spatiotemporal effects of ocean acidification and warming on Atlantic sea scallop growth to guide adaptive fisheries management · 2025 · DOI

• The study's findings are based on climate model projections and may not reflect actual future events. The study's focus on enclosed marginal seas may not be representative of all marine ecosystems.

  The world’s enclosed seas highlight the need for urgent emission reductions and societal adaptation · 2026 · DOI

• The MHW metrics are calculated using a 30-year rolling window for frequency, duration, and MHW days, but the paper does not justify why this temporal window length is appropriate for capturing inter-annual and decadal variability in marine heatwave characteristics within enclosed seas with potentially different oceanographic timescales than global ocean basins.

  The world’s enclosed seas highlight the need for urgent emission reductions and societal adaptation · 2026 · DOI

• The principal recommendation (Recommendation 1) for this project involves greater consideration of community wellbeing in NSW Government reporting and socioeconomic impact assessment processes. Subsequent recommendations were assigned a level of priority (High, Medium or Low) by the project team (Table 32).

  Climate-change resilience and positive scope for growth in wild adult Sydney rock oysters, Saccostrea glomerata (Gould, 1850) · 2026 · DOI

• Negligible interannual variations in benthic dynamics are expected in this deep habitat, - The probe-based and benthic records were decoupled to avoid potential disturbance, - Interpreting pH variability in shallow habitats remains a major challenge for Mediterranean…

  Multiscale pH fluctuations on a stable algal reef community (SE Sardinia, Tyrrhenian Sea) · 2026 · DOI

• Investigate the potential for each of the processes to contribute to the observed patterns in POCsp, - Assess whether particles may be sinking, - Explore the potential for other factors to drive the observed…

  Global patterns in small organic particle loss in the mesopelagic ocean · 2026 · DOI

• Further studies should investigate the effects of gradual acidification on other diatom species, - Research should focus on long-term experimental evolution and gradual increase of CO2 in laboratory…

  Abrupt pH changes overestimate the responses of Chaetoceros muelleri to ocean acidification · 2026 · DOI

Most-cited papers in Ocean Acidification Effects and Responses

• Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms · Nature · 2005 · 3,750 citations
• Anthropogenic carbon and ocean pH · Nature · 2003 · 2,975 citations
• Declining oxygen in the global ocean and coastal waters · Science · 2018 · 2,694 citations
• The Impact of Climate Change on the World’s Marine Ecosystems · Science · 2010 · 2,532 citations
• Climate Warming and Disease Risks for Terrestrial and Marine Biota · Science · 2002 · 2,093 citations
• Viruses and Nutrient Cycles in the Sea · BioScience · 1999 · 1,065 citations
• Ocean Acidification and Its Potential Effects on Marine Ecosystems · Annals of the New York Academy of Sciences · 2008 · 494 citations
• Meta‐analysis reveals complex marine biological responses to the interactive effects of ocean acidification and warming · Ecology and Evolution · 2013 · 466 citations
• Impacts of hypoxic events surpass those of future ocean warming and acidification · Nature Ecology & Evolution · 2021 · 265 citations
• Biogeochemical extremes and compound events in the ocean · Nature · 2021 · 258 citations

Most recent work

• A standardised experimental setup for simulating ocean warming and acidification in benthic marine invertebrates · Biodiversity Data Journal · 2026
• Mineralogy and organic content are major predictors of shell loss in bivalves under reduced salinity, ocean freshening conditions · Royal Society Open Science · 2026
• Colony formation sustains the global competitiveness of nitrogen-fixing Trichodesmium under ocean acidification · Communications Earth & Environment · 2026
• A high-resolution nested model to study the effects of alkalinity additions in Halifax Harbour, a mid-latitude coastal fjord · Biogeosciences · 2026
• Thinking at the megaton scale: Community reflections across three different marine carbon-dioxide removal strategies · Energy Research & Social Science · 2026
• The Effects of Ocean Warming and Acidification on Fatty Acid Contents of Marine Organisms: A Global Meta‐Analysis · Global Change Biology · 2026
• A novel methodology to characterize the potential impacts of electrochemical ocean alkalinity enhancement on juvenile coho salmon (Oncorhynchus kisutch) · Frontiers in Climate · 2026
• Climate benefit and ecological cost trade-offs for ocean iron fertilization · Nature · 2026
• The Role of Ocean Model Resolution in Simulating Marine Biogeochemical Extremes · Journal of Geophysical Research Oceans · 2026
• Explaining the Equatorial Pacific Thermocline Response to Climate Change With a Model Hierarchy · Journal of Geophysical Research Oceans · 2026

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