Ocean Acidification: Frequently Asked Questions

Changes from November 3, 2022 to April 25, 2023

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Ocean Acidification:
~~November 3, 2022~~April 25, 2023
Frequently Asked Questions
Caitlin Keating-Bitonti
The ocean absorbs carbon dioxide (CO2) from the atmosphere. Chemical reactions between CO2 The ocean absorbs carbon dioxide (CO2) from the atmosphere. Chemical reactions between CO2
Analyst in Natural Analyst in Natural
and water can change the pH of seawater (pH is a measure of water’s acidity or basicity). The and water can change the pH of seawater (pH is a measure of water’s acidity or basicity). The
Resources Policy Resources Policy
current shift in the chemistry of seawater is toward a lower pH, commonly referred to as current shift in the chemistry of seawater is toward a lower pH, commonly referred to as ocean

acidification (OA). Scientific consensus is that rising CO2 concentrations in the atmosphere will (OA). Scientific consensus is that rising CO2 concentrations in the atmosphere will
Eva Lipiec
continue to contribute to OA globally, primarily affecting the ocean’s surface waters continue to contribute to OA globally, primarily affecting the ocean’s surface waters., over the
Analyst in Natural Analyst in Natural
~~Resources Policy~~
~~Some~~ 21st century. Other factors, such as seawater temperature and freshwater input, also can influence Resources Policy ocean acidification. Certain U.S. regions are experiencing impacts from OA (e.g., coastal waters of Oregon), and U.S. regions are experiencing impacts from OA (e.g., coastal waters of Oregon), and

some scientists expect that nearly all U.S. coastlines and open ocean waters will experience impacts of scientists expect that nearly all U.S. coastlines and open ocean waters will experience impacts of
~~OA by 2100. OA also has negatively affected some marine organisms, such as reef-building~~

~~corals and shellfish, and may affect others in the future. These impacts~~OA by 2100. In addition, some scientists project large freshwater bodies, such as the Great Lakes, may exhibit acidification trends and impacts similar to those in the ocean by 2100. Impacts of OA include inhibiting the ability of some marine organisms to grow their shells and corroding existing carbonate reef structures—a similar pattern is shown in the fossil record from a period of widespread OA approximately 56 million years ago. These impacts to shell-building marine organisms have had consequences have had consequences
for U.S. fisheries and aquaculture. for U.S. fisheries and aquaculture. ~~Future OA’s economic impacts~~Economic impacts of increased OA going forward may include higher risks of storm damage to coastal may include higher risks of storm damage to coastal
communities and loss of tourism revenue from OA-caused degradation of coral reefs. communities and loss of tourism revenue from OA-caused degradation of coral reefs.
Congress has authorized federal agencies, such as the National Oceanic and Atmospheric Administration (NOAA) and the Congress has authorized federal agencies, such as the National Oceanic and Atmospheric Administration (NOAA) and the
Environmental Protection Agency, to support activities that aim to adapt to and mitigate OA impacts. Environmental Protection Agency, to support activities that aim to adapt to and mitigate OA impacts. ~~In 2009, Congress~~
~~passed the~~The Federal Ocean Acidification Research and Monitoring Act (FOARAM; 33 U.S.C. §§3701 et seq.) Federal Ocean Acidification Research and Monitoring Act (FOARAM; 33 U.S.C. §§3701 et seq.)~~, which, among~~
~~other things,~~ was enacted in 2009. Among other things, the law established the federal Interagency Working Group on Ocean Acidification (IWGOA) to coordinate OA established the federal Interagency Working Group on Ocean Acidification (IWGOA) to coordinate OA
activities across the federal government. IWGOA’s work includes studying OA’s potential impact on marine species and activities across the federal government. IWGOA’s work includes studying OA’s potential impact on marine species and
ecosystems as well as identifying adaptation and mitigation strategies. ecosystems as well as identifying adaptation and mitigation strategies.
Congress Congress ~~continues~~has continued to show interest in OA. to show interest in OA. InFor example, in 2022, Congress 2022, Congress ~~enacted~~passed the Coastal and Ocean Acidification Research and the Coastal and Ocean Acidification Research and
Innovation Act of 2021 (P.L. 117-167, Innovation Act of 2021 (P.L. 117-167, Division B, Title VI, Subtitle E), which amended FOARAM. The amendments added acidification Title VI, Subtitle E), which amended FOARAM. The amendments added acidification
of coastal waters as a concern to be addressed; established an advisory board to the IWGOA; emphasized research on OA of coastal waters as a concern to be addressed; established an advisory board to the IWGOA; emphasized research on OA
adaptation and mitigation strategies, the compounding effects of OA with other environmental stressors, and the adaptation and mitigation strategies, the compounding effects of OA with other environmental stressors, and the
socioeconomic impacts of OA; and authorized appropriations for NOAA and the National Science Foundation to conduct OA socioeconomic impacts of OA; and authorized appropriations for NOAA and the National Science Foundation to conduct OA
activities.activities.
~~Also in 2022, Congress provided~~ Congress also has provided funding for certain OA activities. For example, Congress specified funding to NOAA for OA activities in the funding to NOAA for OA activities in the explanatory statement accompanying the Consolidated Appropriations Act, Consolidated Appropriations Act, ~~2022~~2023 (P.L. (P.L.
117-117-~~103). During the 117th Congress, Members~~328). Some Members of Congress have introduced have introduced, and congressional committees have considered, additional OA-related legislation. For example, bills introduced during the 117th Congress ~~and considered other bills related to OA, some of which~~
focused on examining and addressing the impacts of OA, focused on examining and addressing the impacts of OA, among other activities. As another example, some Members have proposed legislation to increase federal engagement and collaboration with tribes on OA issues in the 118th Congress. ~~among other activities. Proposed FY2023 appropriations bills~~
~~would provide NOAA with increased funding compared with FY2022 levels and additional OA-related directives.~~
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5 Ocean Acidification: Frequently Asked Questions Introduction Rising atmospheric carbon dioxide (CO2) levels impact the ocean in several ways, including by altering its seawater chemistry. The increased uptake of atmospheric CO2 by the surface of the ocean contributes to ocean acidification (OA).1 Parts of the ocean currently are experiencing OA, and scientists project that OA will continue over the 21st century.2 The effects of OA vary geographically, and with ocean depth, due to other factors that influence seawater chemistry. Similarly, not all marine organisms will be impacted by OA in the same way; however, many shell-building organisms are harmed by OA. U.S. ocean and coastal waters, as well as the Great Lakes, are threatened by OA, and Congress has shown and continues to show interest in addressing OA and its impacts. This report answers nine frequently asked questions about OA. What Is Ocean Acidification? Atmospheric gases, such as CO2, continuously diffuse into the surface of the ocean.3 Dissolved gases in the surface of the ocean are in near equilibrium with gases in the atmosphere. Thus, as more CO2 is emitted into the atmosphere, the surface of the ocean absorbs more CO2. Figure 1 shows the direct relationship between seawater CO2 concentrations (green data and line) and atmospheric CO2 concentrations (red points and line). The increased uptake of atmospheric CO2 by the ocean alters the chemistry of seawater by decreasing its pH in a process referred to as ocean acidification, or OA (blue data and line).4 1 Woods Hole Oceanographic Institution, “Ocean Acidification,” at https://www.whoi.edu/know-your-ocean/ocean-topics/how-the-ocean-works/ocean-chemistry/ocean-acidification/. 2 Josep G. Canadell et al., “Chapter 5: Global Carbon and Other Biogeochemical Cycles and Feedbacks,” in Changing Climate 2021: The Physical Science Basis, Intergovernmental Panel on Climate Change (IPCC), eds. Valerie Masson-Delmotte et al., 2021, p. 720 (hereinafter referred to as IPCC, AR6 Physical Science Basis). 3~~Ocean Acidification: Frequently Asked Questions~~

~~What Is Ocean Acidification?~~
~~Atmospheric gases, such as carbon dioxide (CO2), continuously diffuse into the surface of the~~
~~ocean.1 Dissolved gases in the surface of the ocean are in near equilibrium with gases in the~~
~~atmosphere. Thus, as more CO2 is emitted into the atmosphere, the surface of the ocean takes up~~
~~more CO2. The increased uptake of atmospheric CO2 by the ocean alters the chemistry of~~
~~seawater by decreasing its pH in a process referred to as ocean acidification, or OA (Figure 1).2~~
~~Figure 1. Pacific Atmospheric and Seawater Carbon Dioxide Concentrations and~~
~~Seawater pH~~

Source: National Oceanic and Atmospheric Administration (NOAA), “Hawaii Carbon Dioxide Time-Series,” at
~~https://www.pmel.noaa.gov/co2/file/Hawaii+Carbon+Dioxide+Time-Series.~~
Notes: Figure shows the relationship between atmospheric carbon dioxide (CO2) concentrations (red points
~~and line) and dissolved CO2 concentrations of seawater in surface ocean (green points and line), as well as the~~
~~relationship between increasing dissolved CO2 concentrations in surface ocean (green points and line) and~~
~~decreasing seawater pH (blue points and line). Atmospheric CO2 measurements were made at Mauna Loa~~
~~Baseline Observatory (refer to Station Mauna Loa on the insert map), which has been continuously monitoring~~
~~and col ecting data related to atmospheric change since the 1950s (NOAA, “Mauna Loa Baseline Observatory,”~~
~~at https://gml.noaa.gov/obop/mlo/). Dissolved CO2 and pH measurements were made at Station ALOHA, a circle~~

1 The surface mixed layer depth of the ocean varies seasonally and geographically but generally is between 0 and 200 The surface mixed layer depth of the ocean varies seasonally and geographically but generally is between 0 and 200
meters beneath the surface of the ocean. meters beneath the surface of the ocean.
24 Rising carbon dioxide (CO2) emissions are the root cause for current surface ocean acidification (OA). In the ocean Rising carbon dioxide (CO2) emissions are the root cause for current surface ocean acidification (OA). In the ocean
interior, bacteria break down organic matter during interior, bacteria break down organic matter during cellular respiration, which adds CO2 to seawater (see “What , which adds CO2 to seawater (see “What
Factors Influence Ocean Acidification?”). Factors Influence Ocean Acidification?”). ~~Woods Hole Oceanographic Institution~~National Oceanic and Atmospheric Administration (NOAA), “Ocean Acidification,” at , “Ocean Acidification,” at
~~https://www.whoi.edu/know-your-ocean/ocean-topics/how-the-ocean-works/ocean-chemistry~~https://www.noaa.gov/education/resource-collections/ocean-coasts/ocean-acidification/ocean-acidification~~/; and~~. Congressional Research Service 1 Ocean Acidification: Frequently Asked Questions Figure 1. Pacific Atmospheric and Seawater Carbon Dioxide Concentrations and Seawater pH Source:
National Oceanic and Atmospheric Administration (NOAA), “National Oceanic and Atmospheric Administration (NOAA), “~~Ocean Acidification~~Hawaii Carbon Dioxide Time-Series,” at https://www.,” at https://www.pmel.noaa.gov/co2/file/Hawaii+Carbon+Dioxide+Time-Series. Notes: ppm = parts-per-mil ion, µatm = microatmosphere. Figure shows the relationship between atmospheric carbon dioxide (CO2) concentrations (red points and line) and dissolved CO2 concentrations of seawater in surface ocean (green points and line), as well as the relationship between increasing dissolved CO2 concentrations in surface ocean (green points and line) and decreasing seawater pH (blue points and line). Atmospheric CO2 measurements were made at Mauna Loa Baseline Observatory (refer to Station Mauna Loa on the insert map), which has been continuously monitoring and col ecting data related to atmospheric change since the 1950s (NOAA, “Mauna Loa Baseline Observatory,” at https://gml.noaa.gov/obop/mlo/). Dissolved CO2 and pH measurements were made at Station ALOHA, a circle ~~noaa.gov/~~
~~education/resource-collections/ocean-coasts/ocean-acidification.~~
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of a 6-mile radius in the Pacific Ocean north of Hawaii (refer to Station ALOHA on the insert map), which has of a 6-mile radius in the Pacific Ocean north of Hawaii (refer to Station ALOHA on the insert map), which has
been col ecting oceanographic data since 1988 (Station ALOHA, at https://aco-ssds.soest.hawaii.edu/ALOHA/). been col ecting oceanographic data since 1988 (Station ALOHA, at https://aco-ssds.soest.hawaii.edu/ALOHA/).
OA alters seawater chemistry following a series of chemical reactions. When atmospheric CO2 OA alters seawater chemistry following a series of chemical reactions. When atmospheric CO2
dissolves into water (H2O), it forms carbonic acid (H2CO3). Some of the carbonic acid breaks up dissolves into water (H2O), it forms carbonic acid (H2CO3). Some of the carbonic acid breaks up
in ocean water, producing free hydrogen ionsin ocean water, producing free hydrogen ions ~~(H+)~~. As the number of free hydrogen ions . As the number of free hydrogen ions
increases, the pH of the ocean decreases and the water becomes more acidic. The prevailing increases, the pH of the ocean decreases and the water becomes more acidic. The prevailing
global average pH (a measure of hydrogen ion concentration) of water near the ocean surface is global average pH (a measure of hydrogen ion concentration) of water near the ocean surface is
around 8.1, with regional variations.around 8.1, with regional variations.35 5 The pH scale is an inverse logarithmic representation of hydrogen ion concentration, indicating the activity of hydrogen ions (or their equivalent) in the solution. A pH of less than 7.0 is considered acidic, a pH greater than 7.0 is considered basic, and a pH level of 7.0 is defined as neutral. Congressional Research Service 2 link to page 6 link to page 6 link to page 6 Ocean Acidification: Frequently Asked Questions
How Might Ocean Acidification Change over the
21st Century?
Over the past two centuries, the average pH of water near the ocean surface has decreased by Over the past two centuries, the average pH of water near the ocean surface has decreased by
almost 0.1 unit.almost 0.1 unit.46 That change represents a 26% increase in the concentration of free hydrogen That change represents a 26% increase in the concentration of free hydrogen
ions dissolved in seawater, because the pH scale is logarithmic (i.e., water with a pH of 8.0 is 10 ions dissolved in seawater, because the pH scale is logarithmic (i.e., water with a pH of 8.0 is 10
times less acidic than water with a pH of 7.0 and 100 times less acidic than water with a pH of times less acidic than water with a pH of 7.0 and 100 times less acidic than water with a pH of
6.0). 6.0).
Modeling studies project that OA will continue over the 21st century, but the rate of OA likely will Modeling studies project that OA will continue over the 21st century, but the rate of OA likely will
depend on the rate of atmospheric CO2 emissions.depend on the rate of atmospheric CO2 emissions.57 Under the Intergovernmental Panel on Under the Intergovernmental Panel on
Climate Change’s scenario involving a doubling of the concentration of atmospheric CO2 by Climate Change’s scenario involving a doubling of the concentration of atmospheric CO2 by
2050 2050 ~~with~~based on no additional climate change policies, models project that average surface ocean pH no additional climate change policies, models project that average surface ocean pH
may decrease by 0.4 units by the year 2100 may decrease by 0.4 units by the year 2100 ((see the maroon line in Figure 2).68 However, using a scenario in which CO2 However, using a scenario in which CO2
emissions reach net zero by 2050 or shortly thereafter, models project that average surface ocean emissions reach net zero by 2050 or shortly thereafter, models project that average surface ocean
pH may decrease by less than 0.1 unit by 2050 and may rise slightly in the second half of the 21st pH may decrease by less than 0.1 unit by 2050 and may rise slightly in the second half of the 21st
~~century (Figure 2).7~~century (see the light and dark blue lines i n Figure 2).9 Figure 2 also shows the projected pathway of ocean surface pH for other also shows the projected pathway of ocean surface pH for other
CO2 emissions scenarios in modeling studies.CO2 emissions scenarios in modeling studies.8

~~3 The pH scale is an inverse logarithmic representation of hydrogen ion (H+) concentration, indicating the activity of~~
~~hydrogen ions (or their equivalent) in the solution. A pH of less than 7.0 is considered acidic, a pH greater than 7.0 is~~
~~considered basic, and a pH level of 7.0 is defined as neutral.~~
410 Figure 2. Scenario Projections of Global Ocean Surface pH Source: CRS with information from Intergovernmental Panel on Climate Change, “Summary for Policymakers,” in Changing Climate 2021: The Physical Science Basis, eds. Valerie Masson-Delmotte et al., 2021, p. SMP-22. Notes: CO2 = carbon dioxide; GHG = greenhouse gas. Model scenarios with intermediate to very high GHG emissions (yellow, red, and maroon lines) project decreasing ocean surface pH through the 21st century. Other model scenarios with very low to low GHG emissions (light and dark blue lines) project decreasing pH until around 2070 that rises slightly after 2070. The light blue line holds global warming to about 1.5 degrees Celsius (°C), in line with the goals of the Paris Agreement; the dark blue line holds global warming to beneath 2°C. 6 James Orr et al., “Anthropogenic Ocean Acidification over the Twenty-First Century and Its Impact on Calcifying James Orr et al., “Anthropogenic Ocean Acidification over the Twenty-First Century and Its Impact on Calcifying
Organisms,” Organisms,” Nature, vol. 437 (2005); and NOAA, “Ocean Acidification,” at https://www.noaa.gov/education/resource-, vol. 437 (2005); and NOAA, “Ocean Acidification,” at https://www.noaa.gov/education/resource-
collections/ocean-coasts/ocean-acidification. collections/ocean-coasts/ocean-acidification.
57 IPCC, IPCC, AR6 Physical Science Basis, Chapter 5, p. 720. , Chapter 5, p. 720.
68 Ibid., p. 714. Ibid., p. 714.
79 Net-zero emissions means that some greenhouse gases (GHGs) are emitted, but these emissions are offset by means that some greenhouse gases (GHGs) are emitted, but these emissions are offset by
removing an equivalent amount of GHGs from the atmosphere and storing it permanently in soil, plants, or materials. removing an equivalent amount of GHGs from the atmosphere and storing it permanently in soil, plants, or materials.
Achieving Achieving net-zero emissions may be considered more feasible than releasing no GHGs to the atmosphere (i.e., may be considered more feasible than releasing no GHGs to the atmosphere (i.e., zero
emissions). ).
810 IPCC, IPCC, AR6 Physical Science Basis, Chapter 5, p. 720. , Chapter 5, p. 720.
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7 Ocean Acidification: Frequently Asked Questions ~~Ocean Acidification: Frequently Asked Questions~~

~~Figure 2. Scenario Projections of Global Ocean Surface pH~~

Source: CRS with information from Intergovernmental Panel on Climate Change, “Summary for Policymakers,”
~~in Changing Climate 2021: The Physical Science Basis, eds. Valerie Masson-Delmotte et al., 2021, p. SMP-22.~~
Notes: CO2 = carbon dioxide; GHG = greenhouse gas. Models project decreasing ocean surface pH through
~~the 21st century for scenarios with intermediate to very high GHG emissions (yellow, red, and maroon lines) and~~
~~decreasing pH until around 2070, but that rises slightly after 2070 for scenarios with very low to low GHG~~
~~emissions (light and dark blue lines). The light blue line holds global warming to about 1.5 degrees Celsius (°C),~~
~~in line with the goals of the Paris Agreement; the dark blue line holds global warming to beneath 2°C.~~
Model projections of average global OA changes, such as the projections shown inModel projections of average global OA changes, such as the projections shown in Figure 2, are are
driven primarily by atmospheric CO2 simulations.driven primarily by atmospheric CO2 simulations.911 In general, the global trend would reflect In general, the global trend would reflect
surface pH decline with increasing atmospheric CO2 concentrations. Regional seawater properties surface pH decline with increasing atmospheric CO2 concentrations. Regional seawater properties
may influence the surface pH value, resulting in geographic variations in OA.may influence the surface pH value, resulting in geographic variations in OA.1012 See See “What
Factors Influence Ocean Acidification?” for a further discussion on the factors that may amplify for a further discussion on the factors that may amplify
regional variations in seawater pH. regional variations in seawater pH.
What Factors Influence Ocean Acidification?
Not all ocean and coastal regions experience OA in the same way. Increased CO2 concentrations Not all ocean and coastal regions experience OA in the same way. Increased CO2 concentrations
in the atmosphere contribute to OA, but other factors also influence coastal and ocean in the atmosphere contribute to OA, but other factors also influence coastal and ocean
acidification. Rates of acidification can vary geographically for numerous reasons, including acidification. Rates of acidification can vary geographically for numerous reasons, including
temperature, ocean circulation, biological activity, coastal upwelling, freshwater input, temperature, ocean circulation, biological activity, coastal upwelling, freshwater input, ~~and~~
~~nutrient runoff~~nutrient runoff, and atmospheric deposition, among other influences., among other influences.1113
  Temperature. Gases, such as CO2, are more soluble in colder water than in . Gases, such as CO2, are more soluble in colder water than in
warmer water. Thus, marine waters near the poles have a much greater capacity warmer water. Thus, marine waters near the poles have a much greater capacity
to absorb atmospheric CO2 than do ocean waters in the tropics. As a to absorb atmospheric CO2 than do ocean waters in the tropics. As a
consequence, polar regions tend to experience greater regional changes due to consequence, polar regions tend to experience greater regional changes due to
OA.OA.1214
  Ocean Circulation. Dissolved CO2 is transported from the ocean surface into . Dissolved CO2 is transported from the ocean surface into
deeper ocean water at high latitudes, because cold polar surface waters have a deeper ocean water at high latitudes, because cold polar surface waters have a
higher density than warm tropical waters. The cold polar surface waters sink to higher density than warm tropical waters. The cold polar surface waters sink to
depth (i.e., vertical ocean mixing), and both observations and modeling studies depth (i.e., vertical ocean mixing), and both observations and modeling studies

~~9 IPCC, AR6 Physical Science Basis, Chapter 5, p. 719.~~
~~10 Ibid.~~
~~11 Josep G. Canadell et al., “Chapter 5: Global Carbon and Other Biogeochemical Cycles and Feedbacks,” in~~ ~~Changing~~
~~Climate 2021: The Physical Science Basis, Intergovernmental Panel on Climate Change (IPCC), eds. Valerie Masson-~~
~~Delmotte et al., 2021, p. 720 (hereinafter referred to as IPCC, AR6 Physical Science Basis).~~
~~12 IPCC, AR6 Physical Science Basis, Chapter 5, p. 677.~~
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~~Ocean Acidification: Frequently Asked Questions~~

show that the vertical ocean mixing contributes to acidification of the deeper show that the vertical ocean mixing contributes to acidification of the deeper
ocean.ocean.1315 For example, OA below 2,000 meters has been detected in polar regions For example, OA below 2,000 meters has been detected in polar regions
in both the North Atlantic and the Southern Ocean.in both the North Atlantic and the Southern Ocean.1416
  Biological Activity. The breakdown of organic carbon in the ocean interior by . The breakdown of organic carbon in the ocean interior by
bacteria, via a biological process known as bacteria, via a biological process known as cellular respiration, adds CO2 to , adds CO2 to
seawater. Deep ocean water is enriched in CO2 due to cellular respiration, in seawater. Deep ocean water is enriched in CO2 due to cellular respiration, in
addition to the capacity of colder water in the deep ocean to absorb CO2. addition to the capacity of colder water in the deep ocean to absorb CO2.
Phytoplankton near the ocean surface and marine plants (i.e., kelp, seaweed, Phytoplankton near the ocean surface and marine plants (i.e., kelp, seaweed,
seagrass) take up CO2 during seagrass) take up CO2 during photosynthesis, which may offset some effects of , which may offset some effects of
OA. OA.
  Coastal Upwelling. . Coastal upwelling is a process by which coastal winds push is a process by which coastal winds push
warm surface waters offshore, causing cold deep water to rise to the surface. warm surface waters offshore, causing cold deep water to rise to the surface.
Upwelled ocean waters have high CO2 concentrations, because deep ocean Upwelled ocean waters have high CO2 concentrations, because deep ocean
waters carry dissolved CO2 from two sources: (1) atmospheric CO2 from waters carry dissolved CO2 from two sources: (1) atmospheric CO2 from ~~when~~
cold polar waters cold polar waters ~~were last~~that absorbed CO2 at the surface at the surface ~~of the ocean~~and sank to depth and (2) CO2 11 IPCC, AR6 Physical Science Basis, Chapter 5, p. 719. 12 Ibid. 13 IPCC, AR6 Physical Science Basis, Chapter 5, p. 720. 14 IPCC, AR6 Physical Science Basis, Chapter 5, p. 677. 15 IPCC, AR6 Physical Science Basis, Chapter 5, p. 717. 16 Ibid. Congressional Research Service 4 Ocean Acidification: Frequently Asked Questions ~~and (2) CO2~~ respired by respired by
bacteria during the decomposition of organic carbon in the ocean interior.bacteria during the decomposition of organic carbon in the ocean interior.1517
  Freshwater Input. Riverine influx associated with high-intensity precipitation . Riverine influx associated with high-intensity precipitation
events or glacial melt can yield large freshwater inputs that contribute dissolved events or glacial melt can yield large freshwater inputs that contribute dissolved
inorganic carbon, organic carbon, and nutrients to coastal waters. These inorganic carbon, organic carbon, and nutrients to coastal waters. These
contributions can alter the chemistry of waters located at the mouths of large contributions can alter the chemistry of waters located at the mouths of large
rivers or the toes of glaciers. rivers or the toes of glaciers. ~~In addition, rainwater is naturally acidic, due to CO2~~
~~and other atmospheric gases, such as nitrogen dioxide.16~~Rivers and streams also can deliver gases and particles deposited within the watershed via atmospheric deposition (see below) to freshwater bodies or coastal waters.
  Nutrient Runoff. Riverine inputs with high nutrient loads (often nitrogen and . Riverine inputs with high nutrient loads (often nitrogen and
phosphorous associated with farming practices) can lead to excessive plant and phosphorous associated with farming practices) can lead to excessive plant and
algae growth in coastal settings, a process known as algae growth in coastal settings, a process known as eutrophication..1718 The The
resulting decomposition of algae and plants in coastal waters produces increased resulting decomposition of algae and plants in coastal waters produces increased
amounts of CO2 in the water column, which can lead to a lowering of seawater amounts of CO2 in the water column, which can lead to a lowering of seawater
pH.pH.1819  Atmospheric Deposition. Fossil fuel combustion and biomass burning release sulfur dioxide and nitrogen oxide gases to the atmosphere, where these gases are chemically transformed into sulfuric acid and nitric acid.20 Wet atmospheric deposition is commonly known as acid rain, and it includes any form of precipitation (e.g., sleet, snow) that contains acidic compounds, such as sulfuric and nitric acids.21 Uncontaminated precipitation (normal rain) is naturally acidic with a pH of 5.6; acid rain generally has a pH between 4.2 and 4.4.22 Acid rain plays a minor role in making the ocean more acidic on a global scale, but it can have a greater impact on ocean coastal waters and freshwater systems.23
How Does Ocean Acidification Impact Marine Life?
The influence of OA on marine life is complicated. A pH of less than the global average of 8.1 The influence of OA on marine life is complicated. A pH of less than the global average of 8.1
may cause some organisms to expend more energy, but organisms may be able to adapt in may cause some organisms to expend more energy, but organisms may be able to adapt in
complex and species-specific ways to OA. OA may affect more marine species when complex and species-specific ways to OA. OA may affect more marine species when
its effects are compounded by the effects of climate change, including warming seawater temperatures and compounded by the effects of climate change, including warming seawater temperatures and
deoxygenation (loss of oxygen).deoxygenation (loss of oxygen).1924 In particular, OA poses physiological stress to invertebrate In particular, OA poses physiological stress to invertebrate

~~13 IPCC, AR6 Physical Science Basis, Chapter 5, p. 717.~~
~~14 Ibid.~~
15 17 U.S. Global Change Research Program (USGCRP), “Chapter 13: Ocean Acidification and Other Ocean Changes,” U.S. Global Change Research Program (USGCRP), “Chapter 13: Ocean Acidification and Other Ocean Changes,”
in in Climate Science Special Report: Fourth National Climate Assessment, vol. I, eds. Donald J. Wuebbles et al., 2017, p. vol. I, eds. Donald J. Wuebbles et al., 2017, p.
373 (hereinafter referred to as USGCRP, NCA4 vol. I). For a discussion on coastal upwelling, see CRS Report R47021, 373 (hereinafter referred to as USGCRP, NCA4 vol. I). For a discussion on coastal upwelling, see CRS Report R47021,
Federal Involvement in Ocean-Based Research and Development, by Caitlin Keating-Bitonti. , by Caitlin Keating-Bitonti.
~~16 Rainwater is naturally acidic at a pH of around 5.6.~~
1718 U.S. Environmental Protection Agency (EPA), “The Sources and Solutions: Agriculture,” at https://www.epa.gov/ U.S. Environmental Protection Agency (EPA), “The Sources and Solutions: Agriculture,” at https://www.epa.gov/
nutrientpollution/sources-and-solutions-agriculture. nutrientpollution/sources-and-solutions-agriculture.
1819 NOAA, “What Is Eutrophication?,” at https://oceanservice.noaa.gov/facts/eutrophication.html. NOAA, “What Is Eutrophication?,” at https://oceanservice.noaa.gov/facts/eutrophication.html.
~~19 IPCC, AR6 Physical Science Basis, p. 721.~~
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420 Scott C. Doney et al., “Impact of Anthropogenic Atmospheric Nitrogen and Sulfur Deposition on Ocean Acidification and the Inorganic Carbon System,” Proceedings of the National Academy of Sciences, vol. 104 (2007), p. 14580 (hereinafter referred to as Scott Doney et al., 2007). 21 EPA, “What is Acid Rain,” at https://www.epa.gov/acidrain/what-acid-rain. 22 Ibid. 23 Scott Doney et al., 2007, p. 14580, and EPA, “Effects of Acid Rain,” at https://www.epa.gov/acidrain/effects-acid-rain. 24 IPCC, AR6 Physical Science Basis, Chapter 5, p. 721. Congressional Research Service 5

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organisms that build their hard parts (i.e., shells, skeletons, reef structures) with carbonate organisms that build their hard parts (i.e., shells, skeletons, reef structures) with carbonate
minerals.minerals.2025
Marine Invertebrates
For many marine invertebrate organisms, the abundance and availability of carbonate ions (CO 2-For many marine invertebrate organisms, the abundance and availability of carbonate ions (CO 2-
3 ) 3 )
in seawater are critical for survival. Most marine invertebrates have biochemical mechanisms to in seawater are critical for survival. Most marine invertebrates have biochemical mechanisms to
regulate internal pH and are able, within limits, to grow regulate internal pH and are able, within limits, to grow ~~their hard parts~~ and secrete their shells or exoskeletons even when water even when water ~~external~~
toin their their ~~internal~~surrounding environment is acidic. At current average ocean pH levels (about 8.1), ocean environment is acidic. At current average ocean pH levels (about 8.1), ocean
waters near the surface have ample carbonate ions to support shell formation and coral reef waters near the surface have ample carbonate ions to support shell formation and coral reef
growth. However, as more CO2 dissolves into the ocean, the growth. However, as more CO2 dissolves into the ocean, the resulting chemical reactions decrease the abundance and availability of abundance and availability of
carbonate ionscarbonate ions ~~decline due to chemical reactions.21~~.26 A reduction in the availability of carbonate A reduction in the availability of carbonate
ions in the ocean makes it physiologically challenging for shell-forming marine organisms to ions in the ocean makes it physiologically challenging for shell-forming marine organisms to
grow shells, especially those in early stages of their life cycle (i.e., larval and juvenile stages). If grow shells, especially those in early stages of their life cycle (i.e., larval and juvenile stages). If
the availability of carbonate ions becomes too low (i.e., undersaturated) in seawater, then shells the availability of carbonate ions becomes too low (i.e., undersaturated) in seawater, then shells
made with carbonate minerals tend to dissolve. made with carbonate minerals tend to dissolve.
The following sections expound on current or potential impacts of OA on The following sections expound on current or potential impacts of OA on specific types of invertebrate species, invertebrate species,
including corals, oysters, lobsters, and crabs. including corals, oysters, lobsters, and crabs.
Corals
OA reduces corals’ ability to build and maintain reefs, the majority of which are located in OA reduces corals’ ability to build and maintain reefs, the majority of which are located in
tropical and subtropical shallow waters. Most corals are colonial organisms, comprising hundreds tropical and subtropical shallow waters. Most corals are colonial organisms, comprising hundreds
to hundreds of thousands of individual animals, called to hundreds of thousands of individual animals, called polyps..2227 Some polyps secrete carbonate Some polyps secrete carbonate
skeletons that can grow into very large reef structures, called skeletons that can grow into very large reef structures, called coral reefs. Modeling studies . Modeling studies
employing an emissions scenario in which very little climate change mitigation is undertaken this employing an emissions scenario in which very little climate change mitigation is undertaken this
century projectcentury project ~~2100~~ seawater pH conditions seawater pH conditions by 2100 that are less favorable to the growth of coral reefs that are less favorable to the growth of coral reefs
(refer to the maroon line i(refer to the maroon line in Figure 2)..2328
Coral reefs are biodiverse, productive ecosystems that can provide socioeconomic benefits to Coral reefs are biodiverse, productive ecosystems that can provide socioeconomic benefits to
coastal communities. For example, studies show that reefs provide protection against coastal communities. For example, studies show that reefs provide protection against erosion by, and flooding from, waves waves
comparable to that provided by artificial structures such as comparable to that provided by artificial structures such as breakwaters..2429 Coral reef recreation Coral reef recreation
~~and tourism generate an estimated $192 million per year for Puerto Rico and $96 million per year~~
~~for the U.S. Virgin Islands.25 Coral reefs contribute an estimated $477 million to Hawaii’s~~
~~economy every year.26~~and tourism also provide economic benefits for coastal communities. For example, in 2015, reef-related tourism generated an estimated $217 million for Puerto Rico and $108 million for the U.S. Virgin Islands.30 In addition to potential impacts on tourism, declines in coral reef cover In addition to potential impacts on tourism, declines in coral reef cover
may reduce fisheries’ maximum catch potential in the
2025 Carbonate minerals include aragonite, calcite, and high-magnesium calcite. Carbonate minerals include aragonite, calcite, and high-magnesium calcite.
2126 As more CO As more CO
1- 1-
2- 2-
2 dissolves into the ocean, bicarbonate ions (HCO3 ) form at the expense of carbonate ions (CO3 ), 2 dissolves into the ocean, bicarbonate ions (HCO3 ) form at the expense of carbonate ions (CO3 ),
which is described by the following reaction: CO which is described by the following reaction: CO
2- 2-
1- 1-
2 + CO3 + H2O = 2HCO3 . 2 + CO3 + H2O = 2HCO3 .
2227 NOAA, “What Are Corals?,” at https://oceanservice.noaa.gov/education/tutorial_corals/coral01_intro.html. NOAA, “What Are Corals?,” at https://oceanservice.noaa.gov/education/tutorial_corals/coral01_intro.html.
2328 USGCRP, “Chapter 27: Hawai’i and U.S.-Affiliated Pacific Islands,” in USGCRP, “Chapter 27: Hawai’i and U.S.-Affiliated Pacific Islands,” in Impacts, Risks, and Adaptation in the United
States: Fourth National Climate Assessment, vol. II, eds. David R. Reidmiller et al., 2018, p. 1264 (hereinafter referred , vol. II, eds. David R. Reidmiller et al., 2018, p. 1264 (hereinafter referred
to as USGCRP, NCA4 vol. II); and K.L. Ricke et al., “Risks to Coral Reefs from Ocean Carbonate Chemistry Changes to as USGCRP, NCA4 vol. II); and K.L. Ricke et al., “Risks to Coral Reefs from Ocean Carbonate Chemistry Changes
in Recent Earth System Model Projections,” Environmental Research Letters, vol. 8 (2013), p. 5. in Recent Earth System Model Projections,” Environmental Research Letters, vol. 8 (2013), p. 5.
2429 Filippo Ferrario et al., “The Effectiveness of Coral Reefs for Coastal Hazard Risk Reduction and Adaptation,” Filippo Ferrario et al., “The Effectiveness of Coral Reefs for Coastal Hazard Risk Reduction and Adaptation,”
Nature Communications, vol. 5 (2014); and U.S. National Park Service, “Breakwaters, Headlands, Sills, and Reefs,” at , vol. 5 (2014); and U.S. National Park Service, “Breakwaters, Headlands, Sills, and Reefs,” at
https://www.nps.gov/articles/breakwaters-headlands-sills-and-reefs.htm. https://www.nps.gov/articles/breakwaters-headlands-sills-and-reefs.htm.
2530 USGCRP, NCA4 vol. II, Chapter 20, p. 829. USGCRP, NCA4 vol. II, Chapter 20, p. 829.
~~26 USGCRP, NCA4 vol. II, Chapter 27, p. 1245.~~
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~~may reduce fisheries’ maximum catch potential in the~~ exclusive economic zones of most central exclusive economic zones of most central
and western Pacific islands and in the Caribbean region.and western Pacific islands and in the Caribbean region.2731
Shellfish
OA’s effects on certain shellfish has impacted shellfish fishery revenues and may continue to do OA’s effects on certain shellfish has impacted shellfish fishery revenues and may continue to do
so should OA expand to new regions and greater water depths.so should OA expand to new regions and greater water depths.2832 Of particular relevance to Of particular relevance to
shellfish hatcheries, relatively acidic ocean conditions caused by OA may impair the ability of shellfish hatcheries, relatively acidic ocean conditions caused by OA may impair the ability of
larval shellfish to build shells. For example, in the mid-2000s, oyster growers from Washington to larval shellfish to build shells. For example, in the mid-2000s, oyster growers from Washington to
California experienced financial hardships from widespread death of larval shellfish (seed) at California experienced financial hardships from widespread death of larval shellfish (seed) at
hatcheries.hatcheries.2933 In 2008, scientists from the National Oceanic and Atmospheric Administration In 2008, scientists from the National Oceanic and Atmospheric Administration
(NOAA) and various universities linked the oyster seed losses to OA; in turn, oyster hatcheries (NOAA) and various universities linked the oyster seed losses to OA; in turn, oyster hatcheries
shifted their operations to adapt to the OA conditions (see shifted their operations to adapt to the OA conditions (see “What ~~Is the Federal Government~~
Are Federal Agencies Doing About Ocean Acidification?”)..3034 An additional consideration regarding OA’s impact on An additional consideration regarding OA’s impact on
oysters is oysters is ~~the~~ potential potential ~~reduction~~reductions in shell thickness and hardness, which could devalue oysters in shell thickness and hardness, which could devalue oysters
commercially commercially because shells that are easily shucked and do not break or chip (i.e., thick and hard shells) are a sought-after characteristic of oysters on the half shell.35~~because a sought-after characteristic of oysters on the half shell is a shell that is~~
~~easily shucked and does not break or chip.31~~
OA also may affect other economically valuable shellfish, including the American lobster and OA also may affect other economically valuable shellfish, including the American lobster and
Dungeness crab. In Dungeness crab. In ~~2019~~2021, the most recent year reported by NOAA Fisheries, the American lobster , the most recent year reported by NOAA Fisheries, the American lobster
found along the coast of New England was the highest-valued shellfish species in North found along the coast of New England was the highest-valued shellfish species in North
America.America.3236 The Gulf of Maine, an area with record high stock abundance of American lobster, The Gulf of Maine, an area with record high stock abundance of American lobster,3337
has experienced changing oceanographic conditions.has experienced changing oceanographic conditions.3438 Ocean warming has influenced lobster Ocean warming has influenced lobster
fisheries in the region,fisheries in the region,3539 and some research studies project the Gulf of Maine will experience OA and some research studies project the Gulf of Maine will experience OA
conditions by 2050.conditions by 2050.3640 In the laboratory, researchers have shown that OA impacts both juvenile In the laboratory, researchers have shown that OA impacts both juvenile
and adult lobsters by causing erratic heart rates and fewer infection-fighting blood cells; should and adult lobsters by causing erratic heart rates and fewer infection-fighting blood cells; should
these laboratory conditions occur in nature, they may impact lobsters’ survival.these laboratory conditions occur in nature, they may impact lobsters’ survival.~~37 On the U.S.~~41

2731 USGCRP, NCA4 vol. II, Chapter 27, p. 1264; and USGCRP, NCA4 vol. II, Chapter 20, p. 853. USGCRP, NCA4 vol. II, Chapter 27, p. 1264; and USGCRP, NCA4 vol. II, Chapter 20, p. 853.
2832 Sarah Cooley and Scott Doney, “Anticipating Ocean Acidification’s Economic Consequences for Commercial Sarah Cooley and Scott Doney, “Anticipating Ocean Acidification’s Economic Consequences for Commercial
Fisheries,” Fisheries,” Environmental Research Letters, vol. 4 (2009). , vol. 4 (2009).
2933 Ryan Kelly, “Narratives Can Motivate Environmental Action: The Whiskey Creek Ocean Acidification Story,” Ryan Kelly, “Narratives Can Motivate Environmental Action: The Whiskey Creek Ocean Acidification Story,”
Ambio, vol. 43 (2014), pp. 592-599. , vol. 43 (2014), pp. 592-599.
3034 Ibid. and NOAA, “Improving an Ocean Acidification Observation System in Support of Pacific Coast Shellfish Ibid. and NOAA, “Improving an Ocean Acidification Observation System in Support of Pacific Coast Shellfish
Growers,” at https://ioos.noaa.gov/project/turning-headlights-high/. Growers,” at https://ioos.noaa.gov/project/turning-headlights-high/.
3135 Catherine Liberti et al., “The Impact of Oyster Aquaculture on the Estuarine Carbonate System,” Catherine Liberti et al., “The Impact of Oyster Aquaculture on the Estuarine Carbonate System,” Elementa: Science
of the Anthropocene, vol. 10 (2022). , vol. 10 (2022).
3236 NOAA Fisheries reported a total commercial catch of NOAA Fisheries reported a total commercial catch of ~~132.6~~nearly 134.7 million pounds of American lobster, yielding million pounds of American lobster, yielding ~~nearly~~
~~$910~~over $924.7 million dollars, in 2021 (NOAA Fisheries, “Landings,” at https://www.fisheries.noaa.gov/foss/f?p= million dollars, in 2021 (NOAA Fisheries, “Landings,” at https://www.fisheries.noaa.gov/foss/f?p=
215:200:14333709901427:Mail:NO, hereinafter referred to as NOAA Fisheries, Landings Database). 215:200:14333709901427:Mail:NO, hereinafter referred to as NOAA Fisheries, Landings Database). ~~NOAA Fisheries,~~
~~“U.S. Fisheries by the Numbers,” at https://www.fishwatch.gov/sustainable-seafood/by-the-numbers.~~
33 37 NOAA, “American Lobster,” at https://www.fisheries.noaa.gov/species/american-lobster. NOAA, “American Lobster,” at https://www.fisheries.noaa.gov/species/american-lobster.
3438 Samantha Siedlecki et al., “Projecting Ocean Acidification Impacts for the Gulf of Maine into 2050: New Tools and Samantha Siedlecki et al., “Projecting Ocean Acidification Impacts for the Gulf of Maine into 2050: New Tools and
Expectations,” Expectations,” Elementa: Science of the Anthropocene, vol. 9 (2021). , vol. 9 (2021).
3539 Katherine Mills et al., “Fisheries Management in a Changing Climate: Lessons from the 2012 Ocean Heat Wave in Katherine Mills et al., “Fisheries Management in a Changing Climate: Lessons from the 2012 Ocean Heat Wave in
the Northwest Atlantic,” the Northwest Atlantic,” Oceanography, vol. 26 (2013), pp. 191-195. , vol. 26 (2013), pp. 191-195.
3640 Samantha Siedlecki et al., “Projecting Ocean Acidification Impacts for the Gulf of Maine into 2050: New Tools and Samantha Siedlecki et al., “Projecting Ocean Acidification Impacts for the Gulf of Maine into 2050: New Tools and
Expectations,” Expectations,” Elementa: Science of the Anthropocene, vol. 9 (2021). , vol. 9 (2021).
3741 Amalia Harrington and Heather Hamlin, “Ocean Acidification Alters Thermal Cardiac Performance, Hemocyte Amalia Harrington and Heather Hamlin, “Ocean Acidification Alters Thermal Cardiac Performance, Hemocyte
Abundance, and Hemolymph Chemistry in Subadult American Lobsters Abundance, and Hemolymph Chemistry in Subadult American Lobsters Homarus americanus H. Milne Edwards, 1837 H. Milne Edwards, 1837
(Decapoda: Malcostraca: Nephropidae),” (Decapoda: Malcostraca: Nephropidae),” Journal of Crustacean Biology, vol. 39, no. 4 (2019), pp. 468-476. , vol. 39, no. 4 (2019), pp. 468-476.
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On the U.S. West Coast, Dungeness crabs are a valuable shellfish.West Coast, Dungeness crabs are a valuable shellfish.3842 Thus far, Dungeness crabs have shown no change Dungeness crabs have shown no change
in natural population dynamics due to changing oceanographic conditions. in natural population dynamics due to changing oceanographic conditions. ~~Laboratory~~
However, laboratory experiments have found decreased survival rates in Dungeness crabs hatched in waters with a pH experiments have found decreased survival rates in Dungeness crabs hatched in waters with a pH
of 7.5 (a level that has been observed in upwelled waters along the Washington coast) compared of 7.5 (a level that has been observed in upwelled waters along the Washington coast) compared
with those hatched in laboratory waters with a global average pH of 8.1.with those hatched in laboratory waters with a global average pH of 8.1.3943
Marine Vertebrates
Whereas invertebrate organisms primarily build their hard parts Whereas invertebrate organisms primarily build their hard parts (e.g., shells, carapace) with carbonate minerals, with carbonate minerals,
vertebrate bones, including those of fish, are composed of a phosphate mineral. OA does not vertebrate bones, including those of fish, are composed of a phosphate mineral. OA does not
affect the chemical structure of phosphate. Some studies, however, show that the durability and affect the chemical structure of phosphate. Some studies, however, show that the durability and
robustness of some fish bones and shark teeth increase under OA conditions.robustness of some fish bones and shark teeth increase under OA conditions.4044 Other studies have Other studies have
claimed that OA can alter the behaviors of certain fish species, but the research methodology claimed that OA can alter the behaviors of certain fish species, but the research methodology
behind these studies is debated.behind these studies is debated.4145
How Might U.S. Regions Be Affected by Ocean
Acidification?
Some U.S. regions have experienced measurable impacts from OA. Scientists expect that nearly Some U.S. regions have experienced measurable impacts from OA. Scientists expect that nearly
all U.S. coastlines will experience the impacts of OA by 2100.all U.S. coastlines will experience the impacts of OA by 2100.4246 As shown i As shown in Figure 2, models odels
project a decrease in global ocean surface pH ranging from about 0.05 to 0.10 units by 2050. As project a decrease in global ocean surface pH ranging from about 0.05 to 0.10 units by 2050. As
discussed abovediscussed above, in “What Factors Influence Ocean Acidification?,” regional seawater properties may affect the surface pH value, resulting in regional seawater properties may affect the surface pH value, resulting in
geographic variations of OA. geographic variations of OA.
For example, Pacific waters along the Pacific waters along the ~~West Coast of the United States~~U.S. West Coast are influenced by coastal upwelling. are influenced by coastal upwelling.47
Observations and models project the California Current System may experience an expansion and Observations and models project the California Current System may experience an expansion and
intensification of low-pH water due to upwelling.intensification of low-pH water due to upwelling.4348 OA has impacted some oyster hatcheries OA has impacted some oyster hatcheries
along the West Coast. In particular, in 2007, the Oregon-based Whiskey Creek Shellfish Hatchery along the West Coast. In particular, in 2007, the Oregon-based Whiskey Creek Shellfish Hatchery
was unable to provide shellfish growers with late-stage oyster larvae because the low-pH was unable to provide shellfish growers with late-stage oyster larvae because the low-pH
~~seawater corroded the shells of early stage larvae.44 Waters circulating around Alaska’s Pacific~~

3842 NOAA Fisheries reported a total commercial catch of NOAA Fisheries reported a total commercial catch of ~~64.2~~nearly 69.3 million pounds of Dungeness crab in 2021, yielding a million pounds of Dungeness crab in 2021, yielding a
total revenue of total revenue of ~~$311.9~~over $332.2 million for the Pacific Coast million for the Pacific Coast~~. Of this total, the total catch for Alaska was 9.0 million pounds,~~
~~with a revenue of $37.8 million.~~ (NOAA Fisheries, Landings DatabaseNOAA Fisheries, Landings Database). .
3943 Nina Bednarŝek et al., “Exoskeleton Dissolution with Mechanoreceptor Damage in Larval Dungeness Crab Related Nina Bednarŝek et al., “Exoskeleton Dissolution with Mechanoreceptor Damage in Larval Dungeness Crab Related
to Severity of Present-Day Ocean Acidification Vertical Gradients,” to Severity of Present-Day Ocean Acidification Vertical Gradients,” Science of the Total Environment, vol. 716 (2020); , vol. 716 (2020);
and NOAA, “Dungeness Crab Larvae Already Showing Effects of Coastal Acidification,” January 23, 2020, at and NOAA, “Dungeness Crab Larvae Already Showing Effects of Coastal Acidification,” January 23, 2020, at
https://research.noaa.gov/article/ArtMID/587/ArticleID/2581. https://research.noaa.gov/article/ArtMID/587/ArticleID/2581.
4044 Jonathan Leung et al., “Shark Teeth Can Resist Ocean Acidification,” Jonathan Leung et al., “Shark Teeth Can Resist Ocean Acidification,” Global Change Biology, vol. 28, no. 7 (2022); , vol. 28, no. 7 (2022);
Valentina Di Santo, “Ocean Acidification and Warming Affect Skeletal Mineralization in a Marine Fish,” Valentina Di Santo, “Ocean Acidification and Warming Affect Skeletal Mineralization in a Marine Fish,” Proceedings
of the Royal Society B: Biological Sciences, vol. 268 (2019); and Alice Mirasole et al., “Evidences On Alterations in , vol. 268 (2019); and Alice Mirasole et al., “Evidences On Alterations in
Skeleton Composition and Mineralization in a Site-Attached Fish Under Naturally Acidified Conditions in a Shallow Skeleton Composition and Mineralization in a Site-Attached Fish Under Naturally Acidified Conditions in a Shallow
CO2 Vent,” CO2 Vent,” Science of the Total Environment, vol. 761 (2021). , vol. 761 (2021).
4145 See Martin Enserink, “Sea of Doubts,” See Martin Enserink, “Sea of Doubts,” Science (2021), at https://www.science.org/content/article/does-ocean- (2021), at https://www.science.org/content/article/does-ocean-
acidification-alter-fish-behavior-fraud-allegations-create-sea-doubt. acidification-alter-fish-behavior-fraud-allegations-create-sea-doubt.
4246 USGCRP, NCA4 vol. I; and USGCRP, NCA4 vol. II. USGCRP, NCA4 vol. I; and USGCRP, NCA4 vol. II.
~~43 See the previous question for~~47 For more information about more information about ~~coastal~~ocean upwelling, see CRS Report R47021, Federal Involvement in Ocean-Based Research and Development, by Caitlin Keating-Bitonti. 48 See “What Factors Influence Ocean Acidification” for more information about coastal upwelling. IPCC, AR6 Physical Science Basis, Chapter 5, p. 721. Congressional Research Service 8 link to page 5 Ocean Acidification: Frequently Asked Questions seawater corroded the shells of early stage larvae.49 Waters circulating around Alaska’s Pacific ~~upwelling. IPCC, AR6 Physical Science Basis, Chapter~~
~~5, p. 721.~~
~~44 NOAA, “Improving an Ocean Acidification Observation System in Support of Pacific Coast Shellfish Growers,” at~~
~~https://ioos.noaa.gov/project/turning-headlights-high/; and R. Kelly, “Narratives Can Motivate Environmental Action:~~
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coastline also are derived from upwelled cold waters and may be impacted by OA.coastline also are derived from upwelled cold waters and may be impacted by OA.4550 Moreover, Moreover,
glacial runoff may further amplify OA along the Alaskan coast (e.g., Gulf of Alaska).glacial runoff may further amplify OA along the Alaskan coast (e.g., Gulf of Alaska).4651
U.S. coastal regions near agricultural watersheds and urbanized estuaries may be susceptible to U.S. coastal regions near agricultural watersheds and urbanized estuaries may be susceptible to
OA due to eutrophication.OA due to eutrophication.4752 For example, the Mississippi River delivers riverine inputs of For example, the Mississippi River delivers riverine inputs of
nutrients (nitrogen and phosphorus) to the Gulf of Mexico, contributing to eutrophication of nutrients (nitrogen and phosphorus) to the Gulf of Mexico, contributing to eutrophication of
coastal waters and a decrease in pHcoastal waters and a decrease in pH~~.48~~ along the Gulf coast.53 Similarly, runoff into the Chesapeake Bay is contributing to Similarly, runoff into the Chesapeake Bay is contributing to
eutrophication and a decrease in pH in the Bay’s waters.eutrophication and a decrease in pH in the Bay’s waters.4954 In addition, coastal waters of the East In addition, coastal waters of the East
~~Coast and the mid-Atlantic~~ Coast are influenced by freshwater inputs from riverine and estuarine are influenced by freshwater inputs from riverine and estuarine
sources, which may contribute to OA.sources, which may contribute to OA.5055
Tropical oceans are expected to experience the greatest change in seawater chemistry associated Tropical oceans are expected to experience the greatest change in seawater chemistry associated
with rising atmospheric CO2 concentrations.with rising atmospheric CO2 concentrations.5156 The seawater pH off the Hawaiian Island of Oahu The seawater pH off the Hawaiian Island of Oahu
has declined from an annual average of about 8.11 has declined from an annual average of about 8.11 in 1988 to 8.07 (roughly an 8.7% increase in acidity), to 8.07 (roughly an 8.7% increase in acidity),
according to according to 3435 years of ocean data collection at Station ALOHA years of ocean data collection at Station ALOHA (Figure 1).5257 Although oceanic Although oceanic
pH varies geographically, scientists consider the conditions at Station ALOHA to be broadly pH varies geographically, scientists consider the conditions at Station ALOHA to be broadly
representative of those across the western and central Pacific Ocean.representative of those across the western and central Pacific Ocean.5358 The tropical and The tropical and
subtropical Pacific Ocean also is projected to experience the highest levels of thermal stresssubtropical Pacific Ocean also is projected to experience the highest levels of thermal stress from climate change, ,
which could exacerbate the effects of increasing OA.which could exacerbate the effects of increasing OA.5459 Big freshwater systems, such as the Great Lakes, may be susceptible to acidification.60 The Great Lakes are projected to experience acidification at a similar rate to the oceans by 2100 as a result of atmospheric CO2 emissions.61 Currently, there are no long-term monitoring programs in the Great Lakes that are designed to detect acidification.62 49 NOAA, “Improving an Ocean Acidification Observation System in Support of Pacific Coast Shellfish Growers,” at https://ioos.noaa.gov/project/turning-headlights-high/; and R. Kelly, “Narratives Can Motivate Environmental Action: The Whiskey Creek Ocean Acidification Story,” Ambio, vol. 43 (2014). 50
~~Has Ocean Acidification Happened in the Past?~~
~~OA has occurred in the past when geologic events (e.g., volcanic eruptions) emitted large~~
~~quantities of CO2 and other gases to the atmosphere. The fossil record suggests that some mass~~
~~extinction events of marine organisms that have occurred in geologic history may have been~~
~~related to changes in ocean pH. For example, approximately 56 million years ago, a large pulse of~~
~~methane locked in ocean sediments was released into the ocean-atmosphere system over a 3,000-~~
~~20,000 year period.55 Methane released into the ocean-atmosphere undergoes a chemical reaction~~
~~to become CO2 within about 10 years. Chemical analyses of marine sediments suggest this~~

~~The Whiskey Creek Ocean Acidification Story,” Ambio, vol. 43 (2014).~~
45 Jeremy Mathis, “Ocean Acidification Risk Assessment for Alaska’s Fishery Sector,” Jeremy Mathis, “Ocean Acidification Risk Assessment for Alaska’s Fishery Sector,” Progress in Oceanography, vol. , vol.
136 (2015). 136 (2015).
4651 Ibid; IPCC, Ibid; IPCC, AR6 Physical Science Basis, Chapter 5, p. 720. , Chapter 5, p. 720.
4752 NOAA, “What Is Eutrophication?,” at https://oceanservice.noaa.gov/facts/eutrophication.html. NOAA, “What Is Eutrophication?,” at https://oceanservice.noaa.gov/facts/eutrophication.html.
4853 IPCC, IPCC, AR6 Physical Science Basis, Chapter 5, p. 721. , Chapter 5, p. 721.
4954 NOAA, “OPA Projects in the Southeast U.S.,” at https://oceanacidification.noaa.gov/CurrentProjects/ NOAA, “OPA Projects in the Southeast U.S.,” at https://oceanacidification.noaa.gov/CurrentProjects/
Southeast.aspx#. Southeast.aspx#.
5055 USGCRP, NCA4 vol. I, Chapter 13, p. 373. USGCRP, NCA4 vol. I, Chapter 13, p. 373.
5156 OA generally occurs in shallow ocean waters in tropical regions because there is little to no vertical ocean mixing to OA generally occurs in shallow ocean waters in tropical regions because there is little to no vertical ocean mixing to
transport the atmospheric CO2 absorbed by the surface ocean into the deep ocean. transport the atmospheric CO2 absorbed by the surface ocean into the deep ocean.
5257 Data collection and observations began at the Station ALOHA in October 1988. Data collection and observations began at the Station ALOHA in October 1988.
5358 John Marra and Michael Kruk, “State of Environmental Conditions in Hawaii and the U.S. Affiliated Pacific Islands John Marra and Michael Kruk, “State of Environmental Conditions in Hawaii and the U.S. Affiliated Pacific Islands
und a Changing Climate: 2017,” NOAA National Centers for Environmental Information, 2017, p. 74, at und a Changing Climate: 2017,” NOAA National Centers for Environmental Information, 2017, p. 74, at
https://coralreefwatch.noaa.gov/satellite/publications/state_of_the_environment_2017_hawaii-usapi_noaa-nesdis-https://coralreefwatch.noaa.gov/satellite/publications/state_of_the_environment_2017_hawaii-usapi_noaa-nesdis-
ncei_oct2017.pdfncei_oct2017.pdf. 59 Ibid. 60 See, for example, Linda Weiss et al., “Rising pCO2 in Freshwater Ecosystems Has the Potential to Negatively Affect Predator-Induced Defenses in Daphnia,” Current Biology, vol. 28 (2018). 61 Mark Rowe et al., “Great Lakes Region Acidification Research,” NOAA Ocean, Coastal, and Great Lakes Acidification Research Plan: 2020-2029, 2020, p. 102 (hereinafter referred to as NOAA, Acidification Research Plan, 2020). 62 Ibid, p. 104. In 2022, NOAA’s Great Lakes Environmental Research Laboratory placed an instrumentation buoy in the Thunder Bay National Marine Sanctuary to monitor Lake Huron’s water column carbon dioxide pressure and pH Congressional Research Service 9 Ocean Acidification: Frequently Asked Questions Has Ocean Acidification Happened in the Past? OA has occurred in the past when geologic events (e.g., volcanic eruptions) emitted large quantities of CO2 and other gases to the atmosphere. The fossil record suggests that some mass extinction events of marine organisms that have occurred in geologic history may have been related to changes in ocean pH. For example, approximately 56 million years ago, a large pulse of methane locked in ocean sediments was released into the ocean-atmosphere system over a 3,000-20,000 year period.63 Methane released into the ocean-atmosphere undergoes a chemical reaction to become CO2 within about 10 years. Chemical analyses of marine sediments suggest this
~~54 Ibid.~~
~~55 Miriam Katz et al., “Uncorking the Bottle: What Triggered the Paleocene/Eocene Thermal Maximum Methane~~
~~Release?,” Paleoceanography, vol. 16 (2001); James Zachos et al., “Rapid Acidification of the Ocean During the~~
~~Paleocene-Eocene Thermal Maximum,” Science, vol. 308 (2005); and IPCC, AR6 Physical Science Basis, Chapter 5, p.~~
~~714.~~
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methane release was associated with a global surface ocean pH decline ranging from 0.15 to 0.30 methane release was associated with a global surface ocean pH decline ranging from 0.15 to 0.30
units. However, this change in pH occurred more slowly than the current rate of OA and units. However, this change in pH occurred more slowly than the current rate of OA and
continued over a long time interval.continued over a long time interval.5664
What Actions or Interventions Might Limit or
Reduce Ocean Acidification?
Some stakeholders may be interested in limiting or reducing OA and its impacts. Mitigating OA Some stakeholders may be interested in limiting or reducing OA and its impacts. Mitigating OA
involves decreasing the availability of CO2 in the ocean by removing it from either the involves decreasing the availability of CO2 in the ocean by removing it from either the
atmosphere or the ocean. The ocean’s rate of uptake of atmospheric CO2 would start to decrease atmosphere or the ocean. The ocean’s rate of uptake of atmospheric CO2 would start to decrease
if the concentration of atmospheric CO2 decreased. if the concentration of atmospheric CO2 decreased.
Some shellfish industries have implemented approaches to mitigate CO2 concentrations in the Some shellfish industries have implemented approaches to mitigate CO2 concentrations in the
water. Some shellfish farmers on the Pacific and Atlantic coasts of the United States grow marine water. Some shellfish farmers on the Pacific and Atlantic coasts of the United States grow marine
plants (e.g., kelp, seaweed, seagrass) as a nature-based approach to offset the effects of OA.plants (e.g., kelp, seaweed, seagrass) as a nature-based approach to offset the effects of OA.5765
Researchers also are exploring an approach that involves placing bags of oyster shells near oyster Researchers also are exploring an approach that involves placing bags of oyster shells near oyster
farms to improve the health of the living oysters.farms to improve the health of the living oysters.5866 These researchers are testing the hypothesis These researchers are testing the hypothesis
that, over time, the shells in the bags will dissolve and provide a natural buffer to OA. The that, over time, the shells in the bags will dissolve and provide a natural buffer to OA. The
placement of oyster shells, or pulverized silicate or carbonate rocks, in seawater can alter the placement of oyster shells, or pulverized silicate or carbonate rocks, in seawater can alter the
water chemistry by fixing the CO2 dissolved in the seawater to the added material (i.e., shell, water chemistry by fixing the CO2 dissolved in the seawater to the added material (i.e., shell,
~~pulverized rock or mineral). This approach for removing dissolved CO2 from the water is known~~
~~as ocean alkalinity enhancement or enhanced weathering.59~~
~~What Is the Federal Government Doing About~~
~~Ocean Acidification?~~
~~Congress has shown interest in OA and its impacts over the past few decades and has directed~~
~~federal agencies to take certain actions to address OA. Congress passed the Federal Ocean~~
~~Acidification Research and Monitoring Act of 2009 (FOARAM; P.L. 111-11) and amended the~~
~~act in 2022 (amendments described under~~ ~~“What Are Recent Congressional Actions Addressing~~
~~Ocean Acidification?”).60 As amended, FOARAM~~

~~56 IPCC, AR6 Physical Science Basis, Chapter 5, p. 714.~~
57 level—both measurements are needed to study acidification. NOAA aims to expand the monitoring network in Lake Huron and establish monitoring stations in Lakes Erie, Michigan, Ontario, and Superior. (John Flesher, “Scientists: Atmospheric Carbon Might Turn Great Lakes More Acidic,” Associated Press, December 19, 2022, at https://apnews.com/article/science-us-news-fish-plants-oceans-4db7ea795573e9d9260f6432b3e9b9f6, and NOAA, Acidification Research Plan, 2020, p. 104). 63 Miriam Katz et al., “Uncorking the Bottle: What Triggered the Paleocene/Eocene Thermal Maximum Methane Release?,” Paleoceanography, vol. 16 (2001); James Zachos et al., “Rapid Acidification of the Ocean During the Paleocene-Eocene Thermal Maximum,” Science, vol. 308 (2005); and IPCC, AR6 Physical Science Basis, Chapter 5, p. 714. 64 IPCC, AR6 Physical Science Basis, Chapter 5, p. 714. 65 Marine plants remove CO Marine plants remove CO
2 from the surface waters of the ocean via photosynthesis. See, for example, World 2 from the surface waters of the ocean via photosynthesis. See, for example, World
Wildlife Foundation, “Exploring the Benefits of Kelp Farming in Maine,” 2021, at https://www.worldwildlife.org/ Wildlife Foundation, “Exploring the Benefits of Kelp Farming in Maine,” 2021, at https://www.worldwildlife.org/
magazine/issues/winter-2021/articles/exploring-the-benefits-of-kelp-farming-in-maine; and Marketplace, “Could Kelp magazine/issues/winter-2021/articles/exploring-the-benefits-of-kelp-farming-in-maine; and Marketplace, “Could Kelp
Help Mitigate Ocean Acidification?,” February 22, 2018, at https://www.marketplace.org/2018/02/22/could-kelp-help-Help Mitigate Ocean Acidification?,” February 22, 2018, at https://www.marketplace.org/2018/02/22/could-kelp-help-
oyster-industry-mitigate-effects-ocean-acidification/. oyster-industry-mitigate-effects-ocean-acidification/.
5866 NOAA, “Researchers Explore Using Empty Oyster Shells to Decrease Acidic Seawater,” October 13, 2017, at NOAA, “Researchers Explore Using Empty Oyster Shells to Decrease Acidic Seawater,” October 13, 2017, at
https://seagrant.noaa.gov/News/Article/ArtMID/1660/ArticleID/1661/Researchers-Explore-Using-Empty-Oyster-https://seagrant.noaa.gov/News/Article/ArtMID/1660/ArticleID/1661/Researchers-Explore-Using-Empty-Oyster-
Shells-to-Decrease-Acidic-Seawater. Shells-to-Decrease-Acidic-Seawater.
~~59 National Academies of Sciences, Engineering, and Medicine,~~ ~~A Research Strategy for Ocean-Based Carbon Dioxide~~
~~Removal and Sequestration~~ ~~(Washington, DC: National Academies Press, 2022), p. 181. For more information on~~
~~ocean-based CO2 removal technologies, see CRS Report R47172, Geoengineering: Ocean Iron Fertilization, by Caitlin~~
~~Keating-Bitonti.~~
~~60 33 U.S.C. §§3701 et seq. See “What Are Recent Congressional Actions Addressing Ocean Acidification” for~~
~~information on the amendments.~~
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~~Ocean Acidification: Frequently Asked Questions~~
Congressional Research Service 10 Ocean Acidification: Frequently Asked Questions pulverized rock or mineral). This approach for removing dissolved CO2 from the water is known as ocean alkalinity enhancement or enhanced weathering.67 What Are Federal Agencies Doing About Ocean Acidification? Congress has shown interest in OA and its impacts over the past few decades and has directed federal agencies to take certain actions to address OA. Federal Agency Research and Monitoring Activities In 2022, Congress amended the Federal Ocean Acidification Research and Monitoring Act of 2009 (FOARAM; P.L. 111-11).68 As amended, FOARAM
 Established and assigned responsibilities to the federal Interagency Working  Established and assigned responsibilities to the federal Interagency Working
Group on Ocean Acidification (IWGOA) and a nonfederal advisory board Group on Ocean Acidification (IWGOA) and a nonfederal advisory board;
 Directed the Secretary of Commerce to establish an OA program within NOAA  Directed the Secretary of Commerce to establish an OA program within NOAA
and defined the program’s and defined the program’s ~~activities61~~activities;69
 Instructed the National Science Foundation (NSF) to continue its OA research  Instructed the National Science Foundation (NSF) to continue its OA research
activities, supporting competitive proposals for OA research, observation, and activities, supporting competitive proposals for OA research, observation, and
monitoringmonitoring;
 Charged the National Aeronautics and Space Administration with ensuring space-  Charged the National Aeronautics and Space Administration with ensuring space-
based monitoring of OA and its impacts based monitoring of OA and its impacts
; and  Authorized appropriations for NOAA and NSF to carry out these activities from  Authorized appropriations for NOAA and NSF to carry out these activities from
FY2023 through FY2023 through ~~FY202762~~FY2027.70
The IWGOA released a strategic federal research and monitoring plan in 2014. The IWGOA released a strategic federal research and monitoring plan in 2014.6371 In that plan, the In that plan, the
working group listed seven thematic areas of federal research and monitoring activities.working group listed seven thematic areas of federal research and monitoring activities.64
~~1. Research to understand responses to OA~~
~~2. Monitoring of ocean chemistry and biological impacts~~
~~3. Modeling to predict changes in the ocean carbon cycle and impacts on marine~~
~~ecosystems and organisms~~
~~4. Technology development and standardization of measurements~~
~~5. Assessment of socioeconomic impacts and development of strategies to conserve~~
~~marine organisms and ecosystems~~
~~6. Education, outreach, and engagement strategy on OA~~
~~7. Data management and integration~~
~~Federal agencies, such as NOAA and the Environmental Protection Agency, also support~~
~~activities to adapt to and mitigate OA impacts.65 For example, following the significant drop in~~
~~oyster production levels at the Whiskey Creek Shellfish Hatchery in 2007, NOAA deployed a~~
~~network of sensors off the Northwest Pacific Coast to act as an early warning system for shellfish~~

6172 67 National Academies of Sciences, Engineering, and Medicine, A Research Strategy for Ocean-Based Carbon Dioxide Removal and Sequestration (Washington, DC: National Academies Press, 2022), p. 181. For more information on ocean-based CO2 removal technologies, see CRS Report R47172, Geoengineering: Ocean Iron Fertilization, by Caitlin Keating-Bitonti. 68 33 U.S.C. §§3701 et seq. See “What Are Recent Congressional Actions Addressing Ocean Acidification” for information on the 2022 amendments. 69 Under statute, the federal Interagency Working Group on Ocean Acidification (IWGOA) is chaired by a Under statute, the federal Interagency Working Group on Ocean Acidification (IWGOA) is chaired by a
representative from NOAA and includes representatives from the National Science Foundation; National representative from NOAA and includes representatives from the National Science Foundation; National ~~Atmospheric~~Aeronautic
and Space Administration; Smithsonian Institution; National Institute of Standards and Technology and Space Administration; Smithsonian Institution; National Institute of Standards and Technology ~~(NIST)~~ of the of the
Department of Commerce; EPA; Bureau of Indian AffairsDepartment of Commerce; EPA; Bureau of Indian Affairs ~~(BIA)~~, Bureau of Ocean Energy Management, National Park , Bureau of Ocean Energy Management, National Park
Service, U.S. Fish and Wildlife Service, and U.S. Geological Survey of the Department of the Interior; U.S. Service, U.S. Fish and Wildlife Service, and U.S. Geological Survey of the Department of the Interior; U.S.
Department of Agriculture; Department of State; Department of Energy; Department of the Navy; and other agencies as Department of Agriculture; Department of State; Department of Energy; Department of the Navy; and other agencies as
appropriate. appropriate.
6270 The Federal Ocean Acidification Research and Monitoring Act of 2009 (FOARAM; P.L. 111-11), as amended, The Federal Ocean Acidification Research and Monitoring Act of 2009 (FOARAM; P.L. 111-11), as amended, ~~does~~did
not not ~~provide~~specify an authorization of appropriations for the National Aeronautics and Space Administration. an authorization of appropriations for the National Aeronautics and Space Administration.
6371 IWGOA was charged with developing a strategic research and monitoring plan to guide federal research on OA and IWGOA was charged with developing a strategic research and monitoring plan to guide federal research on OA and
overseeing the plan’s implementation (33 U.S.C. §§3703(a)(2)). IWGOA is to submit an updated plan to Congress at overseeing the plan’s implementation (33 U.S.C. §§3703(a)(2)). IWGOA is to submit an updated plan to Congress at
least once every five years (33 U.S.C. §§3703(c)(3)). According to NOAA, a revised plan is forthcoming (email least once every five years (33 U.S.C. §§3703(c)(3)). According to NOAA, a revised plan is forthcoming (email
correspondence with NOAA Office of Legislative and Intergovernmental Affairs, correspondence with NOAA Office of Legislative and Intergovernmental Affairs, ~~August 17, 2022).~~
64April 12, 2023). 72 IWGOA, IWGOA, Strategic Plan for Federal Research and Monitoring of Ocean Acidification, March 2014, at March 2014, at
https://oceanacidification.noaa.gov/Portals/42/Images/IWGOA Strategic Plan.pdf. https://oceanacidification.noaa.gov/Portals/42/Images/IWGOA Strategic Plan.pdf.
~~65 For example, see NOAA Ocean Acidification Program, “Adaptation Strategies,” at~~
~~https://oceanacidification.noaa.gov/WhatWeDo/EducationOutreach/SOARCEWebinars/TabId/3463/PID/16157/evl/0/~~
~~CategoryID/207/CategoryName/adaptation-strategies/Default.aspx; and EPA, “What EPA Is Doing to Address Ocean~~
~~and Coastal Acidification,” at https://www.epa.gov/ocean-acidification/what-epa-doing-address-ocean-and-coastal-~~
~~acidification.~~
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10Congressional Research Service 11

link to page link to page 1516 Ocean Acidification: Frequently Asked Questions 1. Research to understand responses to OA 2. Monitoring of ocean chemistry and biological impacts 3. Modeling to predict changes in the ocean carbon cycle and impacts on marine ecosystems and organisms 4. Technology development and standardization of measurements 5. Assessment of socioeconomic impacts and development of strategies to conserve marine organisms and ecosystems 6. Education, outreach, and engagement strategy on OA 7. Data management and integration ~~Ocean Acidification: Frequently Asked Questions~~

~~hatcheries.66 The early warning system would alert hatchery managers when upwelling produced~~
~~relatively colder and lower pH seawater; managers could then time when coastal waters were~~
~~pumped into the hatchery’s oyster larvae tanks to avoid harming the hatcheries. Such early~~
~~warning systems can help buffer the shellfish industry against OA; larvae grown at the hatchery~~
~~are sold to commercial shellfish growers. The 2022 FOARAM amendments further emphasized~~
~~mitigating OA’s impacts on marine ecosystems.67~~
The IWGOA’s 2016 report on implementation of the strategic plan identified multiple OA-related The IWGOA’s 2016 report on implementation of the strategic plan identified multiple OA-related
activities across most of the IWGOA agencies.activities across most of the IWGOA agencies.6873 Of the seven thematic areas outlined in the 2014 Of the seven thematic areas outlined in the 2014
strategic plan, most OA activities reported in 2016 were related to (1) research to understand strategic plan, most OA activities reported in 2016 were related to (1) research to understand
responses to OA and (2) monitoring of ocean chemistry and biological impacts.responses to OA and (2) monitoring of ocean chemistry and biological impacts.6974 As of 2016 (the As of 2016 (the
latest update on implementation of the strategic plan), strategic plan actions remaining to be latest update on implementation of the strategic plan), strategic plan actions remaining to be
addressed were (7) data management and integration.addressed were (7) data management and integration.7075
The IWGOA’s summary report for The IWGOA’s summary report for ~~FY2016 and FY2017~~FY2018 and FY2019 (the most recent available) (the most recent available), identified identified
funding levels by agency and research and monitoring activities by geographic area, with a focus funding levels by agency and research and monitoring activities by geographic area, with a focus
on locations of interest to the United States on locations of interest to the United States (Figure 3)..~~71 In FY2017, total federal funding for OA~~
~~activities, including activities with a primary or secondary focus on OA, was approximately $45.7~~
~~million.~~76 Over the FY2012- Over the FY2012-~~FY2017~~FY2019 period, NSF and NOAA reported the highest amount of OA period, NSF and NOAA reported the highest amount of OA
activity funding in activity funding in ~~FY2017~~FY2019, with totals of $, with totals of $~~24.3~~ 67.9 million and $million and $1929.3 million, respectively..3 million, respectively.7277

~~66 NOAA, “Improving an Ocean Acidification Observation System in Support of Pacific Coast Shellfish Growers,” at~~
~~https://ioos.noaa.gov/project/turning-headlights-high/; and R. Kelly, “Narratives Can Motivate Environmental Action:~~
~~The Whiskey Creek Ocean Acidification Story,” Ambio, vol. 43 (2014).~~
~~67 P.L. 117-167, §10642(a)(4).~~
6873 According to the report, the Smithsonian Institution and the Department of Energy According to the report, the Smithsonian Institution and the Department of Energy~~’s Pacific Northwest National~~
~~Laboratory~~ were not members of IWGOA in 2014, so their activities were not included in the 2016 implementation were not members of IWGOA in 2014, so their activities were not included in the 2016 implementation
plan. In addition, the U.S. Navy did not contribute to the document because its work on OA is “limited.” plan. In addition, the U.S. Navy did not contribute to the document because its work on OA is “limited.” ~~BIA’s~~
~~activities~~Activities of the Bureau of Indian Affairs also were not included in the 2016 implementation plan also were not included in the 2016 implementation plan~~; NIST’s activities were included~~. (National Science (National Science
and Technology Council [NSTC] Subcommittee on Ocean Science and Technology, and Technology Council [NSTC] Subcommittee on Ocean Science and Technology, Implementation of the Strategic
Plan for Federal Research and Monitoring of Ocean Acidification, December 2016, p. 33, at , December 2016, p. 33, at
https://oceanacidification.noaa.gov/sites/oap-redesign/Documents/IWGOA/https://oceanacidification.noaa.gov/sites/oap-redesign/Documents/IWGOA/
OA%20Implementation%20Plan%20FINAL.pdf [hereinafter referred to as NSTC, OA%20Implementation%20Plan%20FINAL.pdf [hereinafter referred to as NSTC, Implementation Report, December , December
2016]). 2016]).
6974 NSTC, NSTC, Implementation Report, December 2016, p. 3. , December 2016, p. 3.
7075 Ibid. Ibid.
7176 IWGOA IWGOA, Sixth, ~~Fifth~~ Report on Federally Funded Ocean Acidification Research and Monitoring Activities~~: Fiscal Years~~
~~2016 and 2017, January 28, 2020, p. 29, at https://oceanacidification.noaa.gov/Portals/42/~~
~~Federal%20OA%20report%20FY%2016%2017%20%20January%202020.pdf~~, October 28, 2022, pp. 27-28, 36, and 38 (hereinafter referred to as IWGOA, (hereinafter referred to as IWGOA,
~~Fifth~~Sixth Report, , ~~January 2020~~October 2022). IWGOA is to submit updated reports on implementation and funding to Congress every ). IWGOA is to submit updated reports on implementation and funding to Congress every
two years (33 U.S.C. §two years (33 U.S.C. §§3703(c)(2)). According to NOAA, revised reports are forthcoming (email correspondence with 3703(c)(2)). According to NOAA, revised reports are forthcoming (email correspondence with
NOAA Office of Legislative and Intergovernmental Affairs, NOAA Office of Legislative and Intergovernmental Affairs, ~~August 17, 2022).~~
72 IWGOA, Fifth Report~~, January 2020, p. 29~~April 12, 2023). 77 IWGOA, Sixth Report, October 2023, pp. 36, 38. .
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Figure 3. Trends in Federal Funding of Ocean Acidification Research and Monitoring
Activities, FY2012~~–FY2017~~-FY2019

Source: CRS, usingCRS, using Interagency Working Group on Ocean Acidification (IWGOA), Interagency Working Group on Ocean Acidification (IWGOA), Third Report on Federally
Funded Ocean Acidification Research and Monitoring Activities, April 23, 2015, pp. 20 and 25-26, April 23, 2015, pp. 20 and 25-26~~, at~~
~~https://oceanacidification.noaa.gov/Portals/42/Images/~~
~~IWGOA%203rd%20Report%20on%20Federal%20Funding%202015%20FINAL%20REVISED.pdf~~; IWGOA,; IWGOA, Fourth
Report on Federally Funded Ocean Acidification Research and Monitoring Activities, December 20, 2016, pp. 43, 48, and , December 20, 2016, pp. 43, 48, and
5050~~, at https://oceanacidification.noaa.gov/sites/oap-redesign/Documents/IWGOA/~~
~~Fourth%20Report%20on%20OA%20Research%20Monitoring%20FY%2014-15.pdf; and~~; IWGOA IWGOA, Fifth Report on
Federally Funded Ocean Acidification Research and Monitoring Activities: Fiscal Years 2016 and 2017, January 28, 2020, , January 28, 2020,
~~p. 29, at https://oceanacidification.noaa.gov/Portals/42/~~
~~Federal%20OA%20report%20FY%2016%2017%20%20January%202020.pdf~~p. 29; and IWGOA, Sixth Report on Federally Funded Ocean Acidification Research and Monitoring Activities, October 28, 2022, pp. 27-28, 36, and 38. .
Notes: Fiscal year total funding for ocean acidification research and monitoring for all IWGOA member Fiscal year total funding for ocean acidification research and monitoring for all IWGOA member
agencies agencies (that submitted information in that year, including the Bureau of Indian Affairs, Bureau of Ocean Energy Management, Environmental Protection Agency, Department of State, Bureau of Ocean Energy Management, Environmental Protection Agency, Department of State,
National Aeronautics and Space Administration, National Oceanic and Atmospheric Administration National Aeronautics and Space Administration, National Oceanic and Atmospheric Administration ~~[NOAA],~~
~~National Science Foundation [NSF]~~(NOAA), National Park Service, National Science Foundation (NSF), Smithsonian Institution, U.S. Fish and Wildlife Service, and U.S. Geological Survey, and U.S. Geological Survey; , (solid black line)solid black line); and for the two agencies with and for the two agencies with
the most funding, NSF (dashed red line) and NOAA (dashed blue line).the most funding, NSF (dashed red line) and NOAA (dashed blue line). The IWGOA’s (The IWGOA’s (~~fifth~~sixth) summary report for ) summary report for
~~FY2016 and FY2017~~FY2018 and FY2019 provides the most recent publicly available funding levels provides the most recent publicly available funding levels ~~and~~. The IWGOA’s (fifth) summary report for FY2016 and FY2017 notes that the NSF notes that the NSF
contributions are underreported. For example, ship support for NSF research activities is provided by NSF-contributions are underreported. For example, ship support for NSF research activities is provided by NSF-
funded University National Oceanographic Laboratory System and is a major expense for OA activities; this funded University National Oceanographic Laboratory System and is a major expense for OA activities; this
expense was not expense was not included in data used by CRS to create this figure. NOAA is working on the summary report for FY2020 and FY2021 (email correspondence with NOAA Office of Legislative Affairs, April 12, 2023). Federal Agency Adaptation and Mitigation Activities Federal agencies also support activities to adapt to and mitigate OA impacts.78 For example, following the drop in oyster production levels at the Whiskey Creek Shellfish Hatchery in 2007, NOAA deployed a network of sensors off the Northwest Pacific Coast to act as an early warning system for shellfish hatcheries.79 The early warning system alerts hatchery managers when 78 For example, see NOAA Ocean Acidification Program, “Adaptation Strategies,” at https://oceanacidification.noaa.gov/WhatWeDo/EducationOutreach/SOARCEWebinars/TabId/3463/PID/16157/evl/0/CategoryID/207/CategoryName/adaptation-strategies/Default.aspx; and EPA, “What EPA Is Doing to Address Ocean and Coastal Acidification,” at https://www.epa.gov/ocean-acidification/what-epa-doing-address-ocean-and-coastal-acidification. 79 NOAA, “Improving an Ocean Acidification Observation System in Support of Pacific Coast Shellfish Growers,” at https://ioos.noaa.gov/project/turning-headlights-high/; and R. Kelly, “Narratives Can Motivate Environmental Action: The Whiskey Creek Ocean Acidification Story,” Ambio, vol. 43 (2014). Congressional Research Service 13 Ocean Acidification: Frequently Asked Questions upwelling produces relatively colder and lower pH seawater; these alerts allow hatchery managers to time when coastal waters are pumped into the hatchery’s oyster larvae tanks or treat the waters to avoid harming the oysters. Such early warning systems can help buffer the shellfish industry against OA, as larvae grown at the hatchery are sold to commercial shellfish growers. In another example, at the 2023 Our Ocean Conference in Panama, the United States (via the Department of State) joined the International Alliance to Combat Ocean Acidification (OA Alliance) and committed to drafting its national OA action plan. Members of the OA Alliance committed to take individual actions that address the environmental, cultural, and economic threat posed by OA by creating an action plan.80 In addition to the areas identified by the IWGOA in its 2014 strategic plan, the Ocean Policy Committee (OPC) has noted other actions to address OA, such as engaging with vulnerable communities, especially tribal communities, and ensuring that OA and its impacts are included in discussions of potential solar geoengineering and carbon dioxide removal approaches.81 OPC also identified other federal entities that may have a role in addressing OA, in addition to agencies in the IWGOA, including the National Science and Technology Council Subcommittee on Ocean Science and Technology and the National Security Council.82 ~~included in data used by CRS to create this figure.~~
What Are Recent Congressional Actions Addressing
Ocean Acidification?
In 2022, Congress In 2022, Congress ~~enacted~~passed the Coastal and Ocean Acidification Research and Innovation Act of the Coastal and Ocean Acidification Research and Innovation Act of
2021 (P.L. 117-167, 2021 (P.L. 117-167, Division B, Title VI, Subtitle E), which amended FOARAM. The amendments included Title VI, Subtitle E), which amended FOARAM. The amendments included
  ~~The addition of a coastal acidification definition and broadening of agency~~
~~activities to consider coastal acidification73~~
~~ The~~the addition of a definition for coastal acidification;83  the addition of several federal agencies and departments to IWGOA;  the establishment of an advisory board to IWGOA establishment of an advisory board to IWGOA;  a greater research focus on OA adaptation and mitigation strategies, on how OA may interact with other environmental stressors, and on the socioeconomic impacts of OA; and  authorization of appropriations for FY2023 through FY2027. 80 U.S. Department of State, “United States Announces $800 Million in International Commitments for Protecting Our Ocean,” press release, March 8, 2023, at https://www.state.gov/united-states-announces-800-million-in-international-commitments-for-protecting-our-ocean/. In addition to the United States as a whole, nine U.S. states are members of the OA Alliance and, of these nine states, California, Oregon, Maine, Washington, Maryland, and Hawaii have completed their respective action plans. New Jersey, New York, and Virginia are the remaining alliance members. OA Alliance, “Current Members,” at https://www.oaalliance.org/current-members, and OA Alliance, “Action Plans,” at https://www.oaalliance.org/action-plans. 81 The Ocean Policy Committee coordinates federal actions on ocean-related matters and was codified by the National Defense Authorization Act for Fiscal Year 2021 (P.L. 116-283, Title X, Subtitle E, §1055). 82 Ocean Policy Committee, Ocean Climate Action Plan, March 2023, p. 44, at https://www.whitehouse.gov/wp-content/uploads/2023/03/Ocean-Climate-Action-Plan_Final.pdf. 83

73 FOARAM only defined ocean acidification. The Coastal and Ocean Acidification Research and Innovation Act of The Coastal and Ocean Acidification Research and Innovation Act of
2021 (P.L. 117-167) amended the ocean acidification definition in FOARAM and defined 2021 (P.L. 117-167) amended the ocean acidification definition in FOARAM and defined coastal acidification as “the as “the
decrease in pH and changes in the water chemistry of coastal oceans, estuaries, and Great Lakes from atmospheric decrease in pH and changes in the water chemistry of coastal oceans, estuaries, and Great Lakes from atmospheric
pollutions, freshwater inputs, and excess nutrient run-off from land.” pollutions, freshwater inputs, and excess nutrient run-off from land.”
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~~ A greater research focus on OA adaptation and mitigation strategies, on how OA~~
~~may interact with other environmental stressors, and on the socioeconomic~~
~~impacts of OA~~
~~ Authorization of appropriations for FY2023 through FY2027~~
~~In FY2022, Congress appropriated $16~~Congress also has provided direction to federal agencies regarding OA via the appropriations process. For example, in FY2023, Congress appropriated $17 million to NOAA for the Integrated Ocean Acidification million to NOAA for the Integrated Ocean Acidification
Program.Program.7484 Language accompanying the Language accompanying the ~~FY2022~~FY2023 appropriations act directed appropriations act directed the agency~~the program to~~
~~prioritize efforts on “understanding, monitoring, and mitigating coastal ocean acidification,~~
~~especially where it impacts fisheries and aquaculture”; to provide grants to nonfederal partners to~~
~~operate “regional-scale research and education centers to address the impacts” of OA; and to~~
~~establish a prize competition to “stimulate innovation” to advance understanding~~ to continue to work with state, local, territorial, and tribal governments on ocean and coastal acidification research to complete vulnerability assessments required by FOARAM,85 and to work with the White House Office of Science and Technology Policy to competitively award prizes for innovation to understand, research, or monitor OA or its impacts,~~, research, or~~
~~monitoring of OA and its impacts~~ or to develop management or adaptation options or to develop management or adaptation options ~~for responding~~
~~to OA.75~~
~~Other bills regarding OA have been introduced in the 117th Congress. Some would direct the~~
to respond to OA.86 Some Members of Congress have introduced additional legislation regarding OA in recent years. For example, some bills in the 117th Congress would have directed the Secretary of Commerce or NOAA to work with the National Academies of Sciences, Secretary of Commerce or NOAA to work with the National Academies of Sciences,
Engineering, and Medicine to examine the impact of OA and other environmental stressors on Engineering, and Medicine to examine the impact of OA and other environmental stressors on
estuarine environments.estuarine environments.~~76 Another bill would direct~~87 One of these bills also would have directed NOAA to support state and local OA NOAA to support state and local OA
vulnerability assessments and strategic research planning related to OA and its impacts on coastal vulnerability assessments and strategic research planning related to OA and its impacts on coastal
communities, among other OA activities.communities, among other OA activities.~~77 Some~~88 Other bills would bills would ~~include~~have included OA and its impacts as part OA and its impacts as part
of broader climate change impacts or physical risks to be addressed in certain ways.of broader climate change impacts or physical risks to be addressed in certain ways.~~78 In addition,~~
~~proposed language to accompany House and Senate appropriations acts for FY2023 would~~
~~increase funding for NOAA’s Integrated Ocean Acidification Program.79 The House committee~~
~~report would support a prize competition to stimulate OA-related innovation,80 and the Senate~~

~~74 “Explanatory Statement Submitted by Ms. DeLauro, Chair of the House~~89 As another example, in the 118th Congress, the proposed Coastal Communities Ocean Acidification Act of 2023 (H.R. 676) would amend FOARAM to require federal engagement and collaboration with tribes.90 Author Information Caitlin Keating-Bitonti Eva Lipiec Analyst in Natural Resources Policy Analyst in Natural Resources Policy 84 “Explanatory Statement Submitted by Mr. Leahy, Chair of the Senate Committee on Appropriations, Regarding H.R. 2617, Division B—Commerce, Justice, Science, and Relate Agencies Appropriations Act, 2023 ~~Committee on Appropriations, Regarding~~
~~the House Amendment to the Senate Amendment to H.R. 2471~~, Consolidated Appropriations Act, , Consolidated Appropriations Act, ~~2022~~2023,” ,”
Congressional Record, , ~~vol. 168, No. 42 - Book III (March 9, 2022), p. H1778 (hereinafter referred to as explanatory~~
~~statement accompanying P.L. 117-103).~~
75daily edition, vol. 168 (December 20, 2022), p. S7911. Hereinafter, 2023 Explanatory Statement Accompanying P.L. 117-328, Division B. 85 Ibid. 86 U.S. Congress, House Committee on Appropriations, U.S. Congress, House Committee on Appropriations, Commerce, Justice, Science, and Related Agencies
Appropriations Bill, ~~2022,~~2023, Report Together with Minority Views to Accompany H.R. Report Together with Minority Views to Accompany H.R. ~~4505~~8256, 117th Cong., , 117th Cong., ~~1st~~2nd sess., sess., ~~July~~
~~19, 2021~~June 30, 2022, H.Rept. 117-, H.Rept. 117-97395, p. 43. The explanatory statement accompanying the , p. 43. The explanatory statement accompanying the ~~2022~~2023 Consolidated Appropriations Act states that “Unless otherwise noted, the language set forth in House Report 117-395 (‘the House report’) carries the same weight as language included in this joint explanatory statement and should be complied with unless specifically addressed to the contrary in this joint explanatory statement or the act. The explanatory statement, while repeating some language for emphasis, is not intended to negate the language referred to above unless expressly provided herein” (2023 Explanatory Statement Accompanying P.L. 117-328, Division B, p. S7898). 87 For example, in the 117th Congress see H.R. 2533 (passed by the House on May 18, 2021) and H.R. 3764, Section 1011 (placed on the Union Calendar on December 30, 2022). 88 In the 117th Congress, H.R. 3764, Section 1011 (placed on the Union Calendar on December 30, 2022). 89 For example, in the 117th Congress, see H.R. 1187, Title IV (passed by the House on June 16, 2021), H.R. 2570 (placed on the Union Calendar on May 20, 2021), H.R. 2780, Section 301 (placed on the Union Calendar on December 30, 2022), H.R. 2872 (placed on the Union Calendar on November 16, 2022), and S. 1217 (hearings held by the Senate ~~Consolidated Appropriations Act~~
~~states that the “agreement adopts House language regarding the Integrated Ocean Acidification Program” (explanatory~~
~~statement accompanying P.L. 117-103, p. H1779).~~
~~A prize competition to stimulate innovation in understanding and addressing OA was proposed in other legislation,~~
~~such as H.R. 3764, Section 1011, and H.R. 6061.~~
~~76 For example, H.R. 2533 (passed the House May 18, 2021) and H.R. 3764, Section 1406 (ordered to be reported by~~
~~the House Committee on Natural Resources).~~
~~77 For example, H.R. 3764, Section 1001 (ordered to be reported by the House Committee on Natural Resources).~~
~~78 For example, H.R. 1187 (passed the House June 16, 2021), H.R. 2570 (reported by the House Committee on~~
~~Financial Services), H.R. 2780 (ordered to be reported by the House Committee on Natural Resources), H.R. 2872~~
~~(ordered to be reported by the House Committee on Natural Resources), and S. 1217 (Senate~~ Committee on Banking, Committee on Banking,
~~Housing, and Urban Affairs hearings held).~~
~~79 U.S. Congress, House Committee on Appropriations,~~ ~~Commerce, Justice, Science, and Related Agencies~~
~~Appropriations Bill, 2023, Report Together with Minority Views to Accompany H.R. 8256, 117th Cong., 2nd sess., June~~
~~30, 2022, H.Rept. 117-395, p. 43 (hereinafter referred to as H.Rept. 117-395); and draft~~ ~~Explanatory Statement for~~
~~Commerce, Justice, Science, and Related Agencies Appropriations Bill, 2023, as posted on the Senate~~Housing, and Urban Affairs on September 14, 2021). 90 In the 118th Congress, H.R. 676 was ordered to be reported by the House Committee on Science, Space, and Technology on March 29, 2023. Congressional Research Service 15 ~~Committee on~~
~~Appropriations website, July 28, 2022, at https://www.appropriations.senate.gov/news/majority/breaking-chairman-~~
~~leahy-releases-fiscal-year-2023-senate-appropriations-bills (hereinafter referred to as draft~~ ~~Senate Explanatory~~
~~Statement, 2023).~~
~~80 H.Rept. 117-395.~~
~~Congressional Research Service~~

13

~~Ocean Acidification: Frequently Asked Questions~~

~~draft explanatory statement would direct NOAA to work with nonfederal entities on research to~~
~~complete FOARAM-mandated federal vulnerability assessments.81~~

~~Author Information~~

~~Caitlin Keating-Bitonti~~
~~Eva Lipiec~~
~~Analyst in Natural Resources Policy~~
~~Analyst in Natural Resources Policy~~

Ocean Acidification: Frequently Asked Questions

Disclaimer
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~~81 Draft Senate Explanatory Statement, 2023.~~
Congressional Research Service Congressional Research Service
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