Ocean acidification in the Working Group II contribution to the IPCC Fifth Assessment Report

Posted on OA: 31 Mar 2014

Ocean acidification is well covered in the Working Group II contribution to the IPCC Fifth Assessment Report (Climate Change 2014: impacts, adaptation and vulnerability) released today, 31 March 2014. Several experts of ocean acidification were involved as authors or review editors: P. Boyd, P. Brewer, V. J. Fabry, J.-P. Gattuso, O. Hoegh-Guldberg, Y. Nojiri, H.-O. Pörtner, D. Schmidt and C. Turley.

Ocean acidification is covered in depth in the following chapters:
5: Coastal and low lying areas
6: Ocean systems
30: The oceans

There is also a cross-chapter box on ocean acidification (Box CC-OA) in the main report as well as in the technical summary (Box TS.7):

Gattuso J.-P., Brewer P., Hoegh-Guldberg O., Kleypas J. A., Pörtner H.-O. & Schmidt D., 2014. Ocean Acidification. In: Field C. et al. (Eds.), Climate Change 2014: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge: Cambridge University Press.

Field C., Barros V., Mach K., Mastrandrea M., van Aalst M., Adger N., Aldunce P., Arent D., Barnett J., Betts R., Bilir E., Birkmann J., Carmin J., Chadee D., Challinor A., Chatterjee M., Cramer W., Estrada Y., Gattuso J.-P., Hijioka Y., Hoegh-Guldberg O., Huang H.-Q., Insarov G., Jones R., Kovats S., Romero Lankao P., Nymand L. J., Losada I., Marengo J., McLean R., Mearns L., Mechler R., Morton J., Niang I., Oki T., Olwoch J. M., Opondo M., Poloczanska E., Poörtner H.-O., Redsteer M. H., Reisinger A., Revi A., Schmidt D., Shaw R., Solecki W., Stone J., Strzepek K., Suarez A., Tschakert P., Valentini R., Vicuna S., Villamizar A., Vincent K., Warren R., Wilbanks T., Wong P. P. & Yohe G., 2014. Technical summary. In: Field C. et al. (Eds.), Climate Change 2014: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate ChangeCambridge: Cambridge University Press.

Finally, additional coverage of ocean acidification in the context of coral reefs can be found in the cross-chapter box on coral reefs (Box CC-CR):

Gattuso J.-P., Hoegh-Guldberg O. & Pörtner H.-O., 2014. Coral Reefs. In: Field C. et al. (Eds.), Climate Change 2014: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge: Cambridge University Press.

Below are excerpts of the executive summaries of chapters 5, 6 and 30.

Coastal ecosystems are particularly sensitive to three key drivers related to climate change: sea level, ocean temperature and ocean acidification (very high confidence)[5.3.2,,]. Despite the lack of attribution of observed coastal changes, there is a long-term commitment to experience the impacts of sea level rise because of a delay in its response to temperature [5.5.8] (high agreement). In contrast, coral bleaching and species ranges can be attributed to ocean temperature change and ocean acidity [,]. For many other coastal changes, the impacts of climate change are difficult to tease apart from human-related drivers (e.g. land-use change, coastal development, pollution) (high agreement, robust evidence).

Acidification and warming will continue with significant consequences for coastal ecosystems (high confidence). The increase in acidity will be higher in areas where eutrophication or coastal upwellings are an issue. It will have negative impacts for many calcifying organisms (high confidence) []. Warming and acidification will lead to coral bleaching, mortality and decreased constructional ability (high confidence) making coral reefs the most vulnerable marine ecosystem with little scope for adaptation [, Box CC-OA]…

Rising atmospheric CO2 over the last century and into the future not only causes ocean warming but also changes carbonate chemistry in a process termed ocean acidification (WGI, Chs. 3.8.2, 6.4.4). Impacts of ocean acidification range from changes in organism physiology and behavior to population dynamics (medium to high confidence) and will affect marine ecosystems for centuries if emissions continue (high confidence). Laboratory and field experiments as well as field observations show a wide range of sensitivities and responses within and across organism phyla (high confidence). Most plants and microalgae respond positively to elevated CO2 levels by increasing photosynthesis and growth (high confidence). Within other organism groups, vulnerability decreases with increasing capacity to compensate for elevated internal CO2 concentration and falling pH (low to medium confidence). Among vulnerable groups sustaining fisheries, highly calcified corals, mollusks and echinoderms, are more sensitive than crustaceans (high confidence) and fishes (low confidence). Trans-generational or evolutionary adaptation has been shown in some species, reducing impacts of projected scenarios (low to medium confidence). Limits to adaptive capacity exist but remain largely unexplored. [6.3.2, CC-OA].

Few field observations conducted in the last decade demonstrate biotic responses attributable to anthropogenic ocean acidification, as in many places these responses are not yet outside their natural variability and may be influenced by confounding local or regional factors. Shell thinning in planktonic foraminifera and in Southern Ocean pteropoda has been attributed fully or in part to acidification trends (medium to high confidence). Coastward shifts in upwelling CO2-rich waters of the Northeast-Pacific cause larval oyster fatalities in aquaculture (high confidence) or shifts from mussels to fleshy algae and barnacles (medium confidence), providing an early perspective on future effects of ocean acidification. This supports insight from volcanic CO2 seeps as natural analogues that macrophytes (seaweeds and seagrasses) will outcompete calcifying organisms. During the next decades ecosystems, including cold- and warm-water coral communities, are at increasing risk of being negatively affected by ocean acidification (OA), especially as OA will be combined with rising temperature extremes (medium to high confidence, respectively). [6.1.2, 6.3.2, 6.3.5]

Uptake of CO2 has decreased ocean pH (approximately 0.1 unit over 100 years), fundamentally changing ocean carbonate chemistry in all ocean sub-regions, particularly at high latitudes (high confidence). The current rate of ocean acidification is unprecedented within the last 65 Ma (high confidence) if not the last 300 Ma (medium confidence). Warming temperatures, declining pH and carbonate ion concentrations represent risks to the productivity of fisheries and aquaculture, and the security of regional livelihoods given the direct and indirect effects of these variables on physiological processes (e.g., skeleton formation, gas exchange, reproduction, growth, and neural function) and ecosystem processes (e.g., primary productivity, reef building, and erosion) (high confidence) [6.2, 6.3, 30.3.1, 30.3.2; 6.1.2; WGI 3.8.2, Box 3.2, 5.3.1].

Regional risks and vulnerabilities to ocean warming and acidification can be compounded by non-climate related stressors such as pollution, nutrient runoff from land, and over-exploitation of marine resources, as well as natural climate variability (high confidence). These influences confound the detection and attribution of the impacts of climate change and ocean acidification on ecosystems yet may also represent opportunities for reducing risks through management strategies aimed at reducing their influence, especially in CBS, SES, and HLSBS [30.1.2, 30.5, 5.3.4, 18.3.3–4].

The productive EBUE and EUS involve upwelling waters that are naturally high in CO2 concentrations and low in pH, and hence are potentially vulnerable to ocean warming and acidification (medium confidence). There is limited evidence and low agreement, as to how upwelling systems are likely to change (low confidence). Declining O2 and shoaling of the aragonite saturation horizon through ocean acidification increases the risk of upwelling water being low in pH and O2 with impacts on coastal ecosystems and fisheries, as has been seen already (e.g., California Current EBUE). These risks and uncertainties are likely to involve significant challenges for fisheries and livelihoods along the west coasts of South America, Africa, and North America (low to medium confidence) [, 30.5.2, 30.5.5, Box CC-UP, Box CC-PP].

Working Group II contribution to the IPCC Fifth Assessment Report, 31 March 2014.Report.

Present-day nearshore pH differentially depresses fertilization in congeneric sea urchins

Posted on OA: 26 Mar 2014

 Ocean acidification impacts fertilization in some species of sea urchin, but whether sensitivity is great enough to be influenced by present-day pH variability has not been documented. In this study, fertilization in two congeneric sea urchins,Strongylocentrotus purpuratus and S. franciscanus, was found to be sensitive to reduced pH, <7.50, but only within a range of sperm-egg ratios that was species-specific. By further testing fertilization across a broad range of pH, pH-fertilization curves were generated and revealed that S. purpuratus was largely robust to pH, while fertilization in S. franciscanus was sensitive to even modest reductions in pH. Combining the pH-fertilization response curves with pH data collected from these species’ habitat demonstrated that relative fertilization success remained high for S. purpuratus but could be as low as 79% for S. franciscanus during periods of naturally low pH. In order for S. franciscanus to maintain high fertilization success in the present and future, adequate adult densities, and thus sufficient sperm-egg ratios, will be required to negate the effects of low pH. In contrast, fertilization of S. purpuratus was robust to a broad range of pH, encompassing both present-day and future ocean acidification scenarios, even though the two congeners have similar habitats.



Frieder C. A., 2014. Present-day nearshore pH differentially depresses fertilization in congeneric sea urchins. The Biological Bulletin 226(1):1-7. Article (subscription required).

Strategic Plan for Federal Research and Monitoring of Ocean Acidification

Prepared by the Interagency Working Group on Ocean Acidification

 This document, prepared by the IWGOA, is now available on the C-CAN website under Resources.

“Things you should know about ocean acidification” – a slide set for scientists introducing ocean acidification to a wider audience

Posted on OA: 7 March 2014

 The SOLAS IMBER Working Group on Ocean Acidification (SIOA) and the Ocean Acidification International Coordination Centre (OA-ICC) have developed a set of 10 slides on ocean acidification, intended as a resource for scientists when communicating on ocean acidification to non-scientific audiences, including the general public, media, and policy makers.
The slide set is proposed as a starting point only, and should be modified and adapted by scientists for their intended audience.

This is a living resource. Please send any comments and suggestions to Lina Hansson (l.hansson(at)iaea.org).

Download the slides from the OA-ICC website

Ocean acidification research at the School of Aquatic & Fisheries Sciences (SAFS), University of Washington

Posted on OA: 5 Mar 2014

 The world’s oceans are rapidly changing in response to human activities. Carbon emissions are causing the warming of oceans, loss of sea ice, and what is now a new hot topic—ocean acidification. About one-third of carbon emitted into the atmosphere is absorbed by ocean water. This ultimately results in increasing acidity and decreasing availability of calcium carbonate, the chemical that many organisms use to build their shells.

These changes pose a potential risk to numerous marine species. Eggs and larvae of most organisms are sensitive to environmental change, and oyster farms in Washington state have already felt the effect of ocean acidification, which has killed larvae in hatcheries.

Ocean acidification can potentially affect species further up the food chain. As a result, consequences may multiply. While some clear threats are evident, a number of unknowns remain.

At SAFS, ocean acidification has come under increasing scrutiny in recent years. For example, in 2011, it was the focus of the Bevan Series on Sustainable Fisheries. To better understand this problem, SAFS researchers, including Carolyn Friedman (CF),André Punt (AP), and graduate student Emma Hodgson (EH, Tim Essington, advising professor), are focusing on ocean acidification from different perspectives.

MD: How might ocean acidification impact different species and their ecosystems?

CF: We are examining the influence of ocean acidification on the life history and transgenerational effects of key local species such as the Pacific oyster and two native Species of Concern: the pinto abalone and Olympia oyster.

EH: We are addressing how the California Current ecosystem may change in response to ocean acidification. I am using a risk framework to better understand which key ecological or fishery species might be most susceptible to ocean acidification.

AP: Dusanka Poljak (MS, 2013) developed population models for red king crab in Bristol Bay, and I am extending these models to other crab stocks in the Bering Sea.

MD: What have you learned so far?

CF: The bacterial pathogen Vibrio tubiashii has caused losses in local bivalve hatcheries for the last eight years. It first re-emerged in association with upwelling off the Oregon coast and low pH waters. Elene Dorfmeier (MS student) found that this bacterium’s ability to cause disease in larval oysters did not change with pH, but its growth was enhanced by declining pH due to increased CO2.

We observed increased mortality and reduced growth in all species we examined. Pinto abalone and Pacific oyster larvae survival was most affected when the parents matured under current conditions but the larvae experienced an ocean acidification event. On the other hand, Olympia oyster larvae held under constant, very high CO2conditions showed no visible ill effects, suggesting greater resilience than other tested species. Even so, under ocean acidification conditions, fewer larvae were released, and those releases were delayed.

EH: When risk analyses are conducted for a species, they often consider only one life history stage, such as adults. In our work, we are looking at each life history stage (eggs, larvae, juveniles, and adults) separately. This can help us to get a better idea of how risk might change for a species over the course of its life. For example, adult Dungeness crab are at lower risk than their eggs.

AP: Ocean acidification may profoundly impact the North Pacific crab fishery. The high mortality rates for juvenile red king crab associated with ocean acidification mean that harvests may decrease, with potentially enormous economic consequences. However, those impacts won’t be evident for at least 20 years, so we have time to plan.

MD: Your projects are interdisciplinary. Can you explain?

CF: We are investigating host susceptibility to disease and parasite responses to changing ocean pH and carbonate chemistry in collaboration with Assistant Professor Steven Roberts and partnering with Joth Davis (SAFS affiliate Associate Professor) and Emily Carrington (Biology Professor, Friday Harbor Marine Labs).

EH: Much of the research on ocean acidification focuses on the direct response of potentially sensitive species, but does not make the link to how this might affect the whole ecosystem. Tim and I are working with partners at the NOAA Northwest Fishery Science Center to use an ecosystem model to investigate what changes might occur throughout the food web as different organisms respond to ocean acidification. Ultimately, we plan to bring this to the port level and hence to fishing communities.

AP: We are exploring the impact of ocean acidification all the way from the larval stage to fishery impacts. This involves collaboration with ecologists and economists at NOAA.

MD: What will you focus on next?

CF: Our data suggest that some shellfish species appear to be in peril as a result of ocean acidification. Tested shellfish were negatively impacted, but some species appear more resilient to than others. We need more cross-generational studies to understand the effects of acidification at the population level.

EH: We will use the risk analysis to develop different scenarios for an ecosystem model. For example, if we find one species to be at high risk, we would use the ecosystem model to simulate low survival for that species, which would enable us to look at how declines in one species might impact other parts of the food chain.

AP: I am working with my NOAA partners to develop models for Bering Sea snow crab and Tanner crab because much of the catch of Tanner crab is due to the fishery for snow crab. I am interested in determining the cumulative effects of ocean acidification and bycatch on the profitability of the fishery.

SAFS website. Full article.