September 2025 | Oceanography
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archiving centers need to be connected and interoperable, so as
to essentially create one location for all the data, thus making data
discovery, sharing, and use easier. For example, a large portion of
the quality-controlled ocean carbon data from across the globe is,
by community agreement, archived in the United States at NOAA’s
Ocean Carbon and Acidification Data System, although many
countries have their own national data centers. This data shar-
ing facilitates use of the data beyond their immediate applications,
resulting in products such as SOCAT and GLODAP. Requirements
for reporting on OA are now being implemented at an interna-
tional policy level through the UN Sustainable Development Goal
(SDG) 14.3 target designed to “minimize and address the impacts
of ocean acidification,” which is also driving the development of
standardized metadata formats, common language, and a fed-
erated data system. However, there are still many challenges in
data sharing and reporting. In 2024, only 42 of 193 UN member
states reported OA observations to the IOC-UNESCO in support
of SDG 14.3. The SOCAT community also highlighted a decline
in surface pCO2 observations over recent years that is resulting in
enhanced uncertainties when these data are used for calculating
the global carbon budget (Dong et al., 2024).
HOW GOAL 1 SUPPORTS mCDR RESEARCH
Strategies for mCDR rely on a thorough understanding of the cur-
rent state of the ocean’s carbonate chemistry. The data generated by
the GOA-ON community, alongside other important, connected
observing networks and efforts, provide background information
on the state and dynamics of the carbon system that is essential
for identifying whether and where mCDR technologies would be
most effective, whether there is a meaningful perturbation from
the baseline condition, and what risks might arise from anthro-
pogenic alteration of local chemistry. Mapping of OA monitoring
activities against mCDR efforts already provides some insight into
what observational capacity may be available to support mCDR
(Figure 4a cf. 4b). Understanding where OA is proceeding most
rapidly, or what areas are at higher risk from OA, can also inform
where mCDR could be deployed, especially if co-benefits or the
ability to mitigate against the impacts of OA have been identified.
Monitoring carbonate chemistry before, during, and after
mCDR interventions is critical to assessing their efficacy and
to minimizing unintentional harm to marine ecosystems.
Availability of observation technology and resulting data will
be fundamental for assessing how much carbon can be feasibly
extracted without disturbing the natural balance of ocean chem-
istry and for ensuring that these interventions remain safe and
effective. In the mCDR community, this is referred to as moni-
toring, reporting, and verification (MRV). There is also a clear
requirement to standardize and report MRV measurements
using agreed upon methodologies and best practices (Boyd et al.,
2023; Oschlies et al., 2023). Further work is required to integrate
observational data with the OA and carbon communities’ data
for full data equity.
Only limited numbers of carbon system sensors are commer-
cially available with both the precision and accuracy needed to
detect an mCDR perturbation against the large background
ocean variability. The carbon community maintains a directory
of these systems (IOCCP hardware directory); however, there is
an ongoing need to continue to develop, maintain, and distrib-
ute low-cost, high-accuracy sensors and autonomous platforms
to increase observational capacity for monitoring mCDR (Pardis
et al., 2022; Li et al., 2023). The GOA-ON community’s experience
in building cost-effective, fit-for-purpose observing platforms is
ideally matched toward understanding how global climate change
measurements and monitoring for MRV can dovetail effectively.
The combination of both large- and small-scale monitoring
that is essential for understanding the overall impact of mCDR
will require enhancement of the existing ocean carbon observ-
ing infrastructure at both global and regional scales (Figure 4).
While it may be opportune to use well-established climate time
series as measurement baselines for small-scale mCDR projects in
some regions, limiting the amount of direct perturbation against
these baseline network stations will also be necessary to main-
tain the integrity of the globally important climate time-series
observing assets.
GOA-ON GOAL 2: IMPROVE UNDERSTANDING OF
ECOSYSTEM RESPONSES TO OCEAN ACIDIFICATION
The second goal of GOA-ON is to understand how marine eco-
systems, ranging from microscopic plankton to large coral reefs,
respond to OA. Members of GOA-ON have been studying the bio-
logical impacts of acidified conditions on various key species and
ecosystems in the laboratory, within mesocosms, and in the field,
using a wide range of techniques and skills. There are also efforts
to standardize protocols for laboratory experiments (Riebesell
et al., 2011) and for observing and monitoring impacts in the field
(Widdicombe et al., 2023; Currie et al., 2024).
GOAL 2 LESSONS LEARNED RELEVANT TO mCDR AND
CURRENT STATUS OF BIOLOGICAL UNDERSTANDING
Initial concern about the impact of OA was primarily related to
the reduction in calcium carbonate saturation state and the impact
this would have on calcium carbonate-forming (or calcifying)
organisms. Early laboratory and field studies demonstrated that
increased CO2 could lead to a 10%–50% reduction in calcification
rates of pteropods, oyster larvae, reef-building corals, and coralline
algae (e.g., Kleypas et al., 2005; Doney et al., 2009). However, fur-
ther laboratory work showed that many organisms could still calcify
but often with some energetic trade-offs (Wood et al., 2008). Since
this realization, many non-calcifying organisms have also been
shown to respond to OA, including phytoplankton (e.g., Hutchins
et al., 2009; Dutkiewicz et al., 2015), zooplankton (e.g., Keil et al.,
2021; Thor et al., 2022), benthos (e.g., Birchenough et al., 2015;
Bednaršek et al., 2021), and fish (e.g., Heuer and Grosell, 2014;
Sundin, 2023). OA has been shown to impact physiology, growth,