Applications of OA Science
Developing an Ocean Acidification Indicator for Federal Water Quality Reporting
The Clean Water Act (CWA) is the primary federal law in the United States governing water pollution. Implemented by the U.S. Environmental Protection Agency (EPA), its core objective is to restore and maintain the chemical, physical, and biological integrity of the nation's waters by regulating surface water quality and prohibiting the unpermitted discharge of pollutants. Section 303(d) of the CWA requires U.S. states, territories, and authorized tribes to identify and list "impaired waters" within their boundaries. The resulting 303(d) list is a state’s official inventory of impaired and threatened water, and must be submitted in an Integrated Report every two years for review and approval. For the 2024 Integrated Report, the State of Oregon’s Department of Environmental Quality (DEQ) incorporated new and revised assessment methodologies, including a new methodology to assess ocean acidification in Oregon's territorial sea. The EPA accepted this new methodology in May 2026.
Ocean acidification has been on Oregon DEQ's radar as an emerging water quality stressor since 2012. For more than a decade, local researchers have submitted information on ocean acidification through calls for data, public comment periods, and letters directly urging agencies to report the acidification status of Oregon's waters to the EPA. By 2018, Oregon's Coordinating Council on Ocean Acidification and Hypoxia (OAH Council) released a report that directly influenced the development of the State of Oregon Ocean Acidification and Hypoxia Action Plan in 2019. This action plan lists "Mobilize agencies to address Ocean Acidification and Hypoxia (OAH) priorities" as a key action to take by 2025. When Oregon DEQ began the long process of revising the state's CWA assessment and reporting, the OAH Council submitted ample evidence in a joint letter urging the agency to include ocean acidification into the 2024 Integrated Report.
Heeding the evidence and growing public demand, Oregon DEQ committed to developing a narrative biocriteria for assessing the impact of ocean acidification in Oregon's territorial sea. In 2022, DEQ partnered with local, regional, State and Federal agencies to form a Technical Workgroup to facilitate the sharing of scientific information, interpret standards for developing a methodology, and inform an assessment program that allows DEQ to determine water quality impairment.
The Marine Biocriteria Assessment Framework was the first major product developed in consultation with the Technical Workgroup and serves as DEQ’s assessment roadmap to interpret the narrative biocriteria. EPA guidance recommends using measurable components of an ecological system, including stress response signatures of organism condition, as indicators of aquatic life beneficial use support. In applying the marine biocriteria assessment framework, the Technical Workgroup identified Pteropods (L. helicina) as sensitive taxa that represent the most developed indicators with the clearest lines of evidence to assess biological impacts related to ocean acidification. Pteropods are pelagic sea snails that rely on the biomineral aragonite (CaCO3) to form and maintain their shells. As such, the degree of pteropod shell dissolution is closely linked with the saturation state of aragonite (Ωar) in the water column. Thanks to this well-documented acidification stress-specific sensitivity, Pteropods are among the most sensitive pelagic indicators of changing ocean acidification conditions known to date. Benchmark Ωar values for this assessment methodology were chosen to signify likely biological impact based on the aragonite/pteropod shell dissolution exposure-response relationship. Detailed procedures outlined in existing literature serve as the basis for quantification of pteropod shell dissolution and calculation of biological metrics used in this assessment.
After undergoing two public comment periods, the proposed ocean acidification assessment and methodology updates were added to the 2024 Integrated Report, along with two proposed 303(d) listings of marine waters for ocean acidification. Oregon DEQ submitted the Integrated Report and the proposed content was accepted in May of 2026. This is the first time an ocean area has been listed as impaired for ocean acidification in the United States. Following Oregon's example, other states in the U.S. are working to identify indicators to assess biological impacts and develop assessment frameworks related to ocean acidification. Oregon is now working with existing management efforts to help access the resources to better understand what is possible at the state level and within Oregon's sphere of influence to control or mitigate the effects of ocean acidification.
Logistics
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Oregon Department of Environmental Quality (DEQ) led a technical workgroup comprising the following academic, State, and Federal partners:
Oregon Department of Fish and Wildlife
Oregon Department of Land Conservation and Development
Southern California Coastal Water Research Project
California State Water Board
Washington Department of Ecology
Alaska Department of Environmental Conservation
California Ocean Protection Council
U.S. Environmental Protection Agency (EPA)
National Oceanic and Atmospheric Administration
EPA Office of Research and Development
Oregon State University
University of Washington - NANOOS
University of Connecticut
Monterey Bay Aquarium Research Institute
Oregon Sea Grant
Individual contributors are listed in this project overview.
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Oregon DEQ's Ocean Acidification and Hypoxia Technical Workgroup was established in 2021 and began work in earnest in 2022. DEQ held two public processes for the Draft Assessment Methodology for public comment, in January and May of 2023. In XX, the 2024 Integrated Report was submitted, including the methodologies to assess the impacts of hypoxia and ocean acidification in Oregon's territorial sea. Approval of the submitted methodologies was granted by the EPA in May 2026.
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In order to develop and apply the Marine Biocriteria Assessment Framework, synthesis of existing data identified criteria for impairment by utilizing chemical and biological data from intertidal areas, the open ocean, and laboratory manipulation experiments.
Oregon DEQ determined biological measurements of severe shell dissolution and chemical measurements of aragonite (Ωar) to be the basis for biological impact assessment, based on existing research that indicates a robust and well-defined relationship between pteropod shell dissolution and aragonite. Aragonite saturation state (Ωar) thresholds for severe shell dissolution were derived experimentally, through expert consensus, and through a field stress-response study. The workgroup selected widely approved procedures and core principles to quantify aragonite, as well as pteropod sample processing and categorization schemes, that are outlined in the existing literature.
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To characterize conditions in Oregon waters, Oregon DEQ assembles water quality data and information available from monitoring locations or sampling points on a water body. Samples may have been collected from one or more sampling locations and analyzed for a variety of pollutants or other chemical or physical characteristics. Monitoring may have occurred once or multiple times at a single location. Each Assessment Unit must have five unique (different date/time) vertical profiles.
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Aragonite saturation state (Ωar)
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To gather information on water quality for the report, Oregon DEQ assembles all available internal data, conducts a data query from publicly available state and federal databases, and issues a public call for data. All data and information are reviewed by DEQ to determine completeness (required metadata elements) and data quality requirements.
All data used in the report must have a Quality Assurance Project Plan or similar and use widely accepted sampling and analysis methods. Data quality levels for parameters measured in the field are assigned following DEQ’s Data Quality Matrix. Learn more in the Integrated Report.
Objectives
Through collaboration with expert and community input, the State of Oregon Department of Environmental Quality (DEQ) has established a narrative biological criteria for listing impairment of territorial marine waters for ocean acidification through mandatory bi-annual reporting to the United States Environmental Protection Agency. By developing a methodology for assessing dissolution of pteropod shells and aragonite saturation state, Oregon has become the first state in the nation to list an ocean area as impaired for ocean acidification. The state is now investigating ways to address this emerging climate change-related threat to Oregon’s marine waters.
Challenges
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Most State agencies do not have the resources to conduct large scale monitoring. Instead, they rely on partnerships with local long-term monitoring projects and the researchers who represent a wealth of specialized knowledge in these areas. At the time of this project, Oregon DEQ did not have a marine program and relied heavily on partner expertise. This project benefitted from long-term monitoring and continuous monitoring through the federally-funded Ocean Observatories Initiative, data collected by NOAA-PMEL cruises, and Oregon State University data collected through the ODFW Marine Reserves Program. Without these investments in long-term monitoring that allowed Oregon DEQ to use data in this way, this project would not have been possible.
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The scientific method of inquiry leads researchers from one question to the next in their exploration of how the world works, encouraging them to tease out questions that arise from uncertainty, in pursuit of cutting-edge knowledge. However, policymakers must make decisions with the most accurate information they have access to at the time, even if many related questions have yet to be answered. Policymakers rely on the support of subject matter experts to help them establish a solid foundation of current data from which to draw conclusions and confidently make decisions. In order to do so, scientists must identify levels of uncertainty in collecting and analyzing data and interpreting results, and then support policymakers in negotiating this uncertainty. When it comes to translating and balancing uncertainty in a way that fosters confidence to move forward, researchers and policymakers must work together to determine which questions need to be answered by whom. As any entity attempting something similar should expect, Oregon DEQ faced many challenges in the process of science-to-policy translation. By assembling a panel of experts on the Technical Workgroup, DEQ was able to deftly navigate the complexities of this project and avoid the pitfall of decision paralysis.
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This is the first of its kind ocean acidification narrative biocriteria for water quality standards in the nation. Without a blueprint to guide the process, Oregon DEQ knew that to risk trying something new would require them to be practical and effective. As DEQ representatives have since reflected, "Cultivating partnerships was the only way to make this happen". Tapping into State and Federal partnerships allowed DEQ to build off of existing frameworks, research, knowledge, wisdom, and insight. Partners developed a common language that avoided jargon and encouraged viewing shared goals as mutually-achievable by combining the different tools of each field. Stakeholder considerations are built into Oregon's rule-making policies and guided the Technical Workgroup's efforts. Together, project partners charted a path forward to take small steps that affect change now, while the bureaucratic machine catches up to the bigger picture.