The oceans have absorbed a significant portion of all anthropogenic (CO2) emissions (approximately a third of the CO2 emitted from fossil fuel emissions, cement production and deforestation; Sabine et al., 2004), and in doing so have tempered the rise in atmospheric CO2 levels and avoided some CO2-related climate warming. In addition to playing a pivotal role in moderating climate, oceanic uptake of CO2 is causing important changes in ocean chemistry and biology. Carbon dioxide dissolved in water acts as an acid, decreasing its pH,1 and fostering a series of chemical changes. The entire process is known as ocean acidification.2 Because it is another consequence of anthropogenic CO2 emissions, ocean acidification has been dubbed “the other CO2 problem” (Turley, 2005), and the “sleeper issue” (Freedman, 2008) of climate change. Ocean acidifica-
1 The pH scale describes how acidic or basic a substance is, which is determined by the concentration of hydrogen ions (H+). The scale ranges from 0 to 14, with 0 being highly acidic, 14 being highly basic, and 7 being neutral. Like the Richter scale, which measures earthquakes, the pH scale is logarithmic. Therefore, every unit on the pH scale represents a tenfold change in H+ concentration. For example, the H+ concentration at pH 4 is ten times more than at pH 5. Since preindustrial times, the pH of oceanic surface water has dropped from approximately 8.2 to 8.1; on a logarithmic scale, this approximately 0.1 unit change represents a 26% increase in the concentration of H+ ions. There are different pH scales used by oceanographers; but the differences among them are small and not important in the context of this report.
2 “Acidification” does not mean that the ocean has a pH below neutrality. The average pH of the ocean is still basic (8.1), but because the pH is decreasing, it is described as undergoing acidification.
tion, like climate change, is a growing problem that is linked to the rate and amount of CO2 emissions and is expected to affect ecosystems and society on a global scale. Unlike the uncertainties regarding the extent of CO2-induced climate change, the principal changes in seawater chemistry that result from an increase in CO2 concentration can be measured or calculated precisely. Importantly, these chemical changes are also practically irreversible on a time scale of centuries due to the inherently slow turnover of biogeochemical cycles in the oceans.
The mean pH of the ocean’s surface has decreased by about 0.1 unit (from approximately 8.2 to 8.1) since the beginning of the industrial revolution, representing a rate of change exceeding any known to have occurred for at least hundreds of thousands of years (Figure 1.1) (Raven et al., 2005). Model projections indicate that if emissions continue on their current trajectory (i.e., business-as-usual scenarios), pH may drop by another 0.3 units by the end of the century (e.g., Wolf-Gladrow et al., 1999; Caldeira and Wickett, 2003; Feely et al., 2004). Even under optimistic scenarios (i.e., SRES scenario B13), mean ocean surface pH is expected to drop below 7.9 (e.g., Cooley and Doney, 2009).
Scientific research on the biological effects of acidification is still in its infancy and there is much uncertainty regarding its ultimate effects on marine ecosystems. But marine organisms will be affected by the chemical changes in their environment brought about by ocean acidification; the question is how and how much. A number of biological processes are already known to be sensitive to the foreseeable changes in seawater chemistry. A prime example is the impairment in the ability of some organisms to construct skeletons or protective structures made of calcium carbonate resulting from even a modest degree of acidification, although the underlying mechanisms responsible for this effect are not well understood. Effects on the physiology of individual organisms can be amplified through food web and other interactions, ultimately affecting entire ecosystems. Organisms forming oceanic ecosystems have evolved over millennia to an aqueous environment of remarkably constant composition. There is reason to be concerned about how they will acclimate or adapt to the changes resulting from ocean acidification—changes that are occurring very rapidly on geochemical and evolutionary time scales.
3 The Intergovernmental Panel on Climate Change developed emissions projection scenarios by examining alternative development pathways that considered a wide range of demographic, economic, and technological drivers (IPCC, 2000).
FIGURE 1.1 Estimated past, present, and future ocean pH (seawater scale). In panel A, past ocean pH was calculated from boron isotopes (see Box 2.2) in planktonic foraminifera shells (Hönisch et al., 2009, blue circles) and from ice core records of pCO2, where alkalinity, salinity, and nutrients were assumed to remain constant (Petit et al., 1999, red circles). In panel B, the scale of the x-axis has been expanded to illustrate the pH trend projected over the next century. Future pH values (average for ocean surface waters) were calculated by assuming equilibrium with atmospheric pCO2 levels and constant alkalinity. Future pCO2 (atm) levels were assumed to follow the IS92 business-as-usual CO2 emissions scenario.
1.1 CONTEXT FOR DECISION MAKING
It may seem that ocean acidification is a concern for the future. But ocean acidification is occurring now, and the urgent need for decision support is already quite evident. Recently, failures in oyster hatcheries in Oregon and Washington have been blamed on ocean acidification, and costly treatment systems have been installed, despite the fact that the evidence linking the failures to acidification is largely anecdotal (Welch, 2009). On the other hand, there is quite convincing evidence that coral reefs will be affected by acidification (see Chapter 4), but coral reef managers, who are just now beginning to develop adaptation plans to deal with climate change, have limited information on how to address acidification as well. These two examples highlight the urgent need for information on not only the consequences of acidification, but also how affected groups can adapt to these changes.
Like climate change, ocean acidification potentially affects governments, private organizations, and individuals—many of whom have
insufficient information to consider fully the options for adaptation, mitigation, or policy development concerning the potentially far-reaching consequences of ocean acidification. While human activities have caused changes in the chemistry of the ocean in the past, none of those changes have been as fundamental, as widespread, and as long-lasting as those caused by ocean acidification. The resulting biological and ecological effects may not be as rapid and dramatic as those caused by other human activities (such as fishing and coastal pollution) but they will steadily increase over many years to come. Such long and gradual changes in ocean chemistry and biology—possibly punctuated by sudden ecological disruptions—undermines the foundation of existing empirical knowledge based on long-term studies of marine systems. Like climate change, ocean acidification renders past experience an undependable guide to decision making in the future.
To deal effectively with ocean acidification, decision makers will require new and different kinds of information and will need to develop new ways of thinking. For some, ocean acidification will be one more reason to reduce greenhouse gas emissions; for others, the priority will be coping with the ecological effects. But in all circumstances, more information to clarify, inform, and support choices will be needed. As is the case for climate change, decision support for ocean acidification will include “organized efforts to produce, disseminate, and facilitate the use of data and information in order to improve the quality and efficacy of (climate-related) decisions” (National Research Council, 2009a). The fundamental issue for ocean acidification decision support is the quality and timing of relevant information. Although the ongoing changes in ocean chemistry are well understood, the biological consequences are just now being elucidated. The problem is complicated because acidification is only one of a collection of stressful changes occurring in the world’s oceans. It is also fundamentally difficult to understand how biological effects will cascade through food webs, and modify the structure and function of marine ecosystems. It may never be possible to predict with precision how and when acidification will affect a particular ecosystem. Ultimately, the information needed is related to social and economic impacts and pertain to “human dimensions” as has been noted in previous reports (e.g., National Research Council, 2008, 2009a). It is not only important to identify what user groups will be affected and when, but also to understand how resilient these groups are to the consequences of acidification and how capable they are of adapting to the changing circumstances.
To begin to address these societal concerns, the report tries to answer the questions of what to measure and why by identifying high-priority research and monitoring needs. It also addresses the process by identifying elements of an effective national strategy to help federal agencies
provide the information needed by resource managers facing the impacts of ocean acidification in the marine environment.
1.2 STUDY ORIGIN AND POLICY CONTEXT
In the Magnuson-Stevens Fishery Conservation and Management Reauthorization Act of 2006 (P.L. 109-479, sec. 701), Congress called on “the Secretary of Commerce [to] request the National Research Council to conduct a study of the acidification of the oceans and how this process affects the United States.” This request was reiterated in the Consolidated Appropriations Act of 2008 (P.L. 110-161). Based on these requests, the National Oceanic and Atmospheric Administration (NOAA) approached the Ocean Studies Board (OSB) to develop a study. While NOAA is a key federal agency in the effort to understand and address the consequences of ocean acidification, there are many other agencies involved in this topic. Therefore, NOAA and the OSB also sought input and sponsorship from the other members of the National Science and Technology Council Joint Subcommittee on Ocean Science and Technology (JSOST), composed of representatives from the 25 agencies that address ocean science and technology issues. JSOST assisted in developing the study terms and, in addition to NOAA, the National Science Foundation (NSF), the National Aeronautics and Space Administration (NASA), and the U.S. Geological Survey (USGS) agreed to support the study.
As the study was being developed, Congress enacted an additional law that would influence the committee’s work. The Federal Ocean Acidification Research And Monitoring (FOARAM) Act of 2009 was passed as part of the Omnibus Public Land Management Act of 2009 (P.L. 111-11) and signed into law on March 30, 2009, shortly before the committee’s first meeting. The purposes of the FOARAM Act are to:
• develop and coordinate an interagency plan for monitoring and research,
• establish an ocean acidification program within NOAA,
• assess and consider ecosystem and socioeconomic impacts, and
• research adaptation strategies and techniques for addressing ocean acidification.
The FOARAM Act outlines specific activities for both NOAA and NSF and also authorizes funds for these two agencies to carry out the Act, beginning at $14 million in fiscal year 2009 and ramping up to $35 million in 2012.
In light of this new law, the committee’s work takes on added relevance. In parallel with the National Research Council (NRC) study, an
interagency working group was assembled by the JSOST to develop the strategic plan. The committee considers this working group a primary audience for the report and hopes that the findings and recommendations feed into ongoing and future planning efforts by Congress and the federal agencies on ocean acidification research, monitoring, and impacts assessment.
1.3 STUDY APPROACH
The Committee on the Development of an Integrated Science Strategy for Ocean Acidification Monitoring, Research, and Impacts Assessment was assembled by the NRC to provide recommendations to the federal agencies on an interagency strategic plan for ocean acidification. The committee is charged with reviewing the current state of knowledge and identifying key gaps in information to ultimately help guide federal agencies with efforts to better understand and address the consequences of ocean acidification (see Box S.1 for full statement of task).
The committee recognizes that many thorough scientific reviews have already been published on the topic of ocean acidification (e.g., Raven et al., 2005; Fabry et al., 2008b; Doney et al., 2009). Rather than duplicate the previous work, the committee chose to focus on the issues most relevant to the interagency working group: the high priority information needs of decision makers and the key elements of an effective interagency program. The committee relied heavily on peer-reviewed literature, but also considered workshop reports, presentations at scientific meetings, and other community statements (e.g., Kleypas et al., 2006; Fabry et al., 2008a; Orr et al., 2009), as well as presentations at committee meetings and their own expert judgment as key inputs for establishing the community consensus on the current state of the science, research and monitoring priorities, and elements of an effective national program.
1.4 REPORT ORGANIZATION
The report begins with three chapters that provide a brief summary of the current knowledge on ocean acidification. Chapter 2 reviews the effects of increasing CO2 concentration on seawater chemistry and discusses briefly what can be learned from the geological record, as well as possible mitigation options. Chapter 3 reviews what is known of the effects of acidification on the physiology of marine organisms. Chapter 4 addresses how these physiological affects may scale up and affect key marine ecosystems: tropical coral reefs, open ocean pelagic ecosystems, coastal margins, the deep sea (including cold-water corals), and high latitude ecosystems; it also includes a discussion of what may have occurred
in the distant past and some general principles related to biodiversity and ecosystem thresholds. Chapter 5 addresses the evaluation and response to socioeconomic concerns of ocean acidification, with examples from three systems: fisheries, aquaculture, and tropical coral reefs. In Chapter 6, the committee lays out the groundwork for a national ocean acidification program.