Oceanography | Vol. 38, No. 3
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FEATURE ARTICLE
PERSPECTIVES ON
MARINE CARBON DIOXIDE REMOVAL
FROM THE GLOBAL OCEAN ACIDIFICATION OBSERVING NETWORK
By Helen S. Findlay, Richard A. Feely, Kalina Grabb, Elizabeth B. Jewett, Elise F. Keister, Gabby Kitch,
Yuri Artioli, Punyasloke Bhadury, Jeremy Blackford, Odile Crabeck, Anwesha Ghosh, Yaru Li, Kaitlyn B. Lowder,
Shreya Mehta, Bryce Van Dam, Houda Beghoura, Noam Karo, Andrij Z. Horodysky, Sebastian Hennige,
Sally M. Salaah, Federica Ragazzola, and Liza Wright-Fairbanks
ABSTRACT. Along with other carbon monitoring groups, the ocean acidification (OA) community has been observing, modeling,
and projecting the impacts of changing carbonate chemistry for over two decades. The Global Ocean Acidification Observing Network
(GOA-ON) has three key goals related to these issues: (1) improve understanding of global OA conditions, (2) improve understanding
of ecosystem responses to OA, and (3) acquire and exchange data necessary to optimize modeling for OA and its impacts. GOA-ON and
associated networks have a wealth of knowledge, data, models, and best practice guides on how to monitor global carbonate chemistry,
and GOA-ON regional hubs collaborate at local scales to inform policy and action for coastal communities. Here, the GOA-ON com-
munity shares lessons learned relevant for marine carbon dioxide removal (mCDR) research and development. Understanding whether,
how, and where mCDR approaches should be deployed will require knowledge of the carbonate system, robust observations, sensor tech-
nology, and modeling capacities. Ongoing monitoring, reporting, and verification during field trials and any eventual implementation of
mCDR will again require these resources. The GOA-ON community’s knowledge about environmental impacts, running laboratory and
field experiments, and deriving biological indicators of change is of fundamental importance for assessing the environmental impacts
of mCDR and of the potential for mitigating or exacerbating OA. Finally, we present recommendations for utilizing this OA experience
toward mCDR research.
INTRODUCTION
Due to human activity, carbon dioxide (CO2) concentrations in
the atmosphere continue to rise. The ocean is absorbing about
30% of the extra CO2 and at present continues to store carbon
(Friedlingstein et al., 2024). Because the rate of CO2 uptake into
the ocean is too fast for natural geological buffering processes
to keep pace, the excess carbon alters the marine carbonate sys-
tem and results in a measurable decrease in ocean pH, commonly
referred to as ocean acidification (OA; see Box 1; Caldiera and
Wickett, 2003). The changing chemistry is impacting important
biological and biogeochemical processes that rely on stable pH or
specific saturation state levels of important minerals such as arago-
nite or calcite (Kroeker et al., 2013). These impacts have knock-on
consequences for the ecosystem and the services they provide
(Hall-Spencer and Harvey, 2019).
The continuing rise in CO2 emissions has also spurred inter-
est in carbon dioxide removal (CDR) mechanisms that are now
needed alongside continued emissions reductions to meet cli-
mate goals (Smith et al., 2024). Given the ocean’s ability to
take up and store CO2, there is increased interest in exploring
methods that could exploit these natural storage mechanisms, as
so-called marine CDR (mCDR) approaches. All mCDR methods
require additional research and development to determine car-
bon removal efficiency and potential environmental responses.
If mCDR approaches are implemented at scale, they must have
the potential to remove carbon durably (1,000+ years; Brunner
et al., 2024) and without causing detrimental side effects. Unlike
solar radiation management and other non-carbon removal geo-
engineering solutions, mCDR, alongside drastic emissions reduc-
tions, has the potential to mitigate climate change while also pre-
venting further OA by capturing carbon. However, the ability to
mitigate OA that has already occurred will depend on many fac-
tors, including the methods used and scales of application.
Some mCDR approaches are being pursued more seriously
than others, as they have greater potential to remove carbon dura-
bly and at scale (NASEM, 2022). Macroalgae cultivation, involves
rapidly growing marine seaweeds to fix carbon and store it as bio-
mass. Subsequently, this biomass can either be harvested to pro-
duce long-lasting bio-products, including biochar, which can
result in some passive carbon storage, or be deliberately sunk to the