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Review

Phototrophic Carbon Capture in Marine Algae: Comparative Efficiencies, Sequestration Dynamics, and Climate Implications

by
Leonel Pereira
1,2,3
1
Department of Life Sciences, University of Coimbra, 3000-456 Coimbra, Portugal
2
Centre for Functional Ecology—Science for People & the Planet (CFE), Associate Laboratory TERRA, University of Coimbra, Campus at Figueira da Foz, Quinta das Olaias, 3080-183 Figueira da Foz, Portugal
3
IATV—Instituto do Ambiente, Tecnologia e Vida, 3030-790 Coimbra, Portugal
J. Mar. Sci. Eng. 2026, 14(5), 518; https://doi.org/10.3390/jmse14050518
Submission received: 3 February 2026 / Revised: 1 March 2026 / Accepted: 4 March 2026 / Published: 9 March 2026
(This article belongs to the Special Issue Combining Field Observations and Satellite Remote Sensing to Monitor Marine Ecosystem Dynamics)
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Abstract

Algae-based carbon dioxide removal (CDR) systems are increasingly recognized as versatile climate solutions that combine rapid biological uptake with multiple pathways for durable sequestration. Macroalgae and microalgae offer comparative efficiencies that exceed many terrestrial options, while simultaneously contributing to food security, bioeconomic innovation, and ocean stewardship. Yet significant challenges remain in ensuring permanence, developing robust remote monitoring, reporting, and verification (RMRV) frameworks, and integrating algae into carbon markets and policy regimes. Societal acceptance and ethical considerations, including equity, cultural heritage, and governance transparency, will be critical to legitimacy and scale. Future research must advance biological and technological innovation, refine sequestration pathways, and embed social sciences into deployment strategies. Taken together, algae-based systems represent a promising but complex component of the global portfolio of climate mitigation, requiring interdisciplinary collaboration to unlock their full potential and ensure that climate benefits are coupled with broader societal gains.

1. Introduction

Anthropogenic climate change continues to accelerate as global greenhouse gas emissions rise, with carbon dioxide (CO2) remaining the dominant long-lived forcing agent driving planetary warming. Although water vapor amplifies radiative forcing through feedback, its concentration is temperature-dependent and not directly controllable, underscoring the centrality of CO2 mitigation in climate policy. Current strategies emphasize emission reductions, terrestrial afforestation, and engineered carbon capture, yet these approaches alone are insufficient to meet mid-century climate targets. Ocean-based carbon dioxide removal (CDR), despite the ocean’s role as Earth’s largest active carbon sink, remains comparatively underdeveloped in both research and deployment frameworks.
Within this oceanic context, marine algae (microalgae and macroalgae) are critical primary producers that underpin global biogeochemical cycles. Through photosynthesis and subsequent carbon export, they contribute substantially to the biological carbon pump, which has sequestered an estimated ~34 Pg C between 1994 and 2007 and ~77 Pg C by 2018. Emerging analyses from multidecadal hydrographic and biogeochemical datasets suggest that oceanic carbon uptake may be stronger and more dynamic than previously recognized, with algal productivity playing a central role even as circulation patterns, nutrient regimes, and acidification evolve.
Emerging analyses from multidecadal global hydrographic and biogeochemical datasets, including the recent global synthesis by Wang et al. (2023) [1], indicate that oceanic carbon uptake may be stronger and more dynamic than previously recognized. These studies show increases in global carbon-pump efficiency, including higher export production and deeper remineralization horizons, which together contribute to revised estimates of cumulative oceanic carbon uptake that exceed earlier model projections.
Despite this evidence, algae-mediated carbon capture remains marginal in climate mitigation portfolios, overshadowed by terrestrial biomass strategies and engineered CDR technologies. Several factors contribute to this gap: uncertainties in sequestration permanence, limited comparative assessments of algal productivity across taxa and environments, and insufficient integration of biological mechanisms into climate-modeling frameworks. As a result, the potential of marine algae to contribute scalable, durable carbon sequestration is not yet fully understood or systematically evaluated.
This study addresses these gaps by comparing phototrophic carbon-capture efficiencies across major algal groups, examining the dynamics of carbon fixation and export, and evaluating the climate relevance of algae-based CDR relative to other mitigation pathways. By situating algal productivity within the broader landscape of natural and engineered carbon sinks, we aim to clarify the conditions under which marine algae can meaningfully contribute to global CO2 drawdown and to identify the biological and environmental constraints that shape their sequestration potential (Table 1) [1,2,3].

2. Comparative Efficiencies of Algal Systems

Marine algae exhibit remarkable efficiencies in phototrophic carbon capture compared to terrestrial vegetation. Microalgae demonstrate rapid growth rates and high photosynthetic yields, enabling them to fix carbon at scales far exceeding those of forests under optimized cultivation conditions. Studies indicate that microalgal systems can achieve 10–50 times higher areal biomass productivity than temperate forests, with an average sequestration of ~1.8 kg CO2 per kg of dry algal biomass [14,15,16,17,18,19]. This efficiency arises from their unicellular structure, which allows direct absorption of dissolved inorganic carbon across the entire cell surface, bypassing the vascular and structural limitations of terrestrial plants [20].
Photobioreactors (PBRs) further enhance algal productivity by optimizing light exposure, nutrient delivery, and CO2 supplementation. Closed PBR systems can achieve controlled growth cycles, minimize contamination, and enable continuous harvesting, making them suitable for industrial-scale carbon capture near emission sources [21,22]. Contamination refers to the introduction of predators, competing algal species, or microorganisms such as bacteria and fungi. Closed photobioreactors mitigate these risks through sterilized media, filtered air supply, strict hygiene protocols, and regular microbiological monitoring.
In contrast, open pond systems, while less costly, are more vulnerable to environmental fluctuations and invasive species, leading to lower overall yields. Comparative analyses suggest that closed PBRs are up to 400 times more efficient than trees in CO2 removal per unit area, though energy inputs and infrastructure costs remain significant barriers to deployment. Cost estimates for closed PBRs include CAPEX (reactor construction, pumps, sensors) and OPEX (energy, nutrients, labor). Typical values range from USD 80–250 m−2 for CAPEX and USD 5–15 kg−1 dry biomass for OPEX, equivalent to roughly USD 300–900 per tCO2 depending on climate and irradiance conditions [23,24].
Macroalgae, cultivated in coastal aquaculture or integrated multitrophic aquaculture (IMTA) systems, provide complementary sequestration pathways. Their large thalli and rapid growth rates allow substantial carbon assimilation, while cultivation can simultaneously improve water quality and support biodiversity. Unlike microalgae, macroalgae are less amenable to closed-system cultivation but offer scalability in nearshore environments, particularly when integrated with shellfish or finfish farming. Recent Earth system modeling suggests that nearshore macroalgae cultivation could contribute meaningfully to CDR (Figure 1), though permanence and monitoring remain challenges [25,26,27]. Comparative life-cycle assessments highlight that macroalgae cultivation can achieve net-negative emissions when biomass is directed toward durable products or long-term storage. Permanence risks include harvest-related emissions, remineralization of biomass, and leakage of carbon during transport or after sinking. Critical monitoring gaps involve biomass quantification, the fraction of carbon exported to long-term storage, and the poorly constrained fate of material in the deep ocean [28]. Macroalgae cultivation can generate biodiversity benefits by providing structural habitat for invertebrates and juvenile fish, enhancing local trophic interactions, and increasing refuge and feeding opportunities in otherwise simplified coastal environments. However, potential negative impacts must also be considered, including shading of benthic communities, alteration of nutrient dynamics, and the risk of non-native species proliferation if cultivated taxa escape or spread beyond farm boundaries. These ecological outcomes depend strongly on local hydrodynamics, species selection, and farm design [29].

3. Durable Sequestration and RMRV Challenges

The effectiveness of algae-based carbon capture depends not only on rapid fixation but also on the permanence of storage. Without durable sequestration, much of the assimilated carbon risks rapid remineralization and re-release to the atmosphere, undermining mitigation goals [30]. Several pathways have been proposed to ensure permanence, including burial of biomass in deep ocean sediments [31], conversion into long-lived bioproducts such as bioplastics or construction composites [32], and chemical transformation into stable carbonates [32]. Sediment burial offers millennial-scale storage but is logistically complex and raises ecological concerns [31], while durable products extend carbon residence times for decades, though eventual degradation must be accounted for [32]. Deep-ocean burial provides the highest durability but has the weakest MRV feasibility and the greatest ecological uncertainty. Durable bioproducts offer medium-term storage with strong MRV but limited scale. Carbonate formation provides high durability and good MRV potential but is energy-intensive and constrained by mineral availability.
Leakage and displacement represent additional challenges. Cultivation systems must avoid indirect emissions that offset gains. Energy-intensive photobioreactors, if powered by fossil fuels, can erode net benefits [32]. Similarly, large-scale macroalgae cultivation may alter nutrient dynamics or displace other coastal uses, requiring integrated life cycle assessments [33]. These considerations highlight the importance of coupling biological efficiency with systemic sustainability.
RMRV frameworks are essential for integrating algae into carbon markets. Current approaches include isotopic tracers [34], satellite remote sensing [35], and in situ biogeochemical monitoring [35]. However, variability in growth rates, environmental conditions, and biomass fate complicates standardized accounting [34]. Emerging frameworks propose coupling Earth system models with empirical monitoring to quantify sequestration efficiency and permanence [33]. Without robust RMRV, claims of carbon removal risk are contested or excluded from certification schemes [33] (Table 2).
Policy and certification frameworks remain underdeveloped. For algae-based carbon removal to be recognized, it must align with international standards such as the IPCC (Intergovernmental Panel on Climate Change) Guidelines for National Greenhouse Gas Inventories [36]. Certification schemes are beginning to explore “blue carbon credits,” but consensus on permanence thresholds and RMRV methodologies remains limited. Without clear governance, investment in algal carbon removal risks being sidelined despite its technical potential. Addressing these challenges will be critical to positioning algae as credible contributors to climate mitigation portfolios. Missing elements include standardized MRV methodologies, clear permanence rules, leakage accounting protocols, and minimum monitoring requirements. Near-term actions such as developing unified MRV standards, defining acceptable permanence horizons, establishing leakage accounting consistent with IPCC guidance, and supporting pilot-scale monitoring programs would significantly reduce current policy gaps.

4. Satellite Remote Sensing of Seaweeds

Remote sensing has become an essential component of large-scale monitoring, reporting, and verification (RMRV) frameworks for marine algae, providing synoptic, repeatable observations that complement in situ measurements and modeling approaches. Advances in multispectral satellite sensors now enable the detection and mapping of intertidal and shallow-subtidal macroalgal assemblages, supporting assessments of biomass distribution, seasonal dynamics, and long-term ecological change. Although water column attenuation and tidal variability impose constraints, modern satellite platforms offer increasingly robust tools for tracking seaweed habitats at regional to global scales, thereby strengthening the evidence base for algae-based carbon sequestration and coastal ecosystem management [37].

Multispectral Satellites

Multispectral sensors remain the backbone of operational seaweed monitoring due to their global coverage, consistent revisit times, and well-calibrated spectral bands. Sentinel-2 MSI, with its 10–20 m spatial resolution and high radiometric quality, is widely used for mapping intertidal and shallow subtidal macroalgae, particularly in clear-water environments. Its red-edge and near-infrared bands enhance discrimination between seaweeds, seagrasses, and benthic substrates, enabling detailed habitat classification and seasonal phenology analyses. Landsat 8 and 9 OLI, while coarser in resolution, provide an unparalleled multi-decadal time series that supports trend detection, historical baselines, and assessments of long-term change in coastal vegetation [37]. Together, these multispectral platforms form a critical foundation for monitoring macroalgal extent and condition, informing both ecological assessments and the development of RMRV protocols for algae-based carbon removal.
Satellite monitoring is feasible mainly in clear-water intertidal and shallow-subtidal zones and becomes unreliable in turbid or deeper waters. Macroalgae cultivation is most plausible in temperate regions with moderate wave exposure and existing aquaculture infrastructure, but constrained by storms, competing coastal uses, and regulatory limits.

5. Algae in Bioeconomy and Food Security

Beyond their role in carbon sequestration, algae are increasingly recognized as pivotal resources in the emerging bioeconomy. Macroalgae and microalgae provide diverse applications ranging from food and feed to pharmaceuticals, bioplastics, and biofuels (Figure 2). Their rapid growth rates, high protein content, and abundance of bioactive compounds position them as sustainable alternatives to terrestrial crops, particularly in regions facing land and freshwater constraints [38].
In the food sector, edible macroalgae such as Saccharina (Phaeophyceae), Porphyra/Pyropia (Rhodophyta), and Ulva (Chlorophyta) are integral to traditional diets in Asia and are gaining popularity in Europe and North America [38]. They offer essential micronutrients, including iodine, iron, and vitamins, while also supplying polysaccharides with prebiotic and immunomodulatory properties [39]. Microalgae such as Athrospira/Limnospira (formerly Spirulina) (Cyanophyceae) and Chlorella (Chlorophyta) are cultivated globally as protein-rich supplements, with potential to alleviate nutritional deficiencies in vulnerable populations [40].
Algae also contribute to animal feed innovations. Incorporating algal biomass into aquaculture and livestock diets can reduce reliance on fishmeal and soy, lowering environmental footprints while improving feed efficiency [41]. Moreover, certain algal species produce compounds that mitigate methane emissions in ruminants, offering co-benefits for climate mitigation [42].
In the bioeconomy, algae-derived biopolymers and biofuels are advancing as substitutes for fossil-based products. Algal polysaccharides such as alginate, carrageenan, and agar are already widely used in food processing and pharmaceuticals [43]. Emerging technologies aim to upscale algal lipids for biodiesel and jet fuel, though economic viability remains a challenge [44]. Integrating algal cultivation into circular economy frameworks, such as wastewater treatment and nutrient recycling, enhances sustainability and reduces production costs [45] (Table 3).
From a food security perspective, algae offer resilience against climate change impacts on terrestrial agriculture. Their cultivation requires no arable land, minimal freshwater, and can be integrated into coastal and offshore systems. As global demand for protein and sustainable materials rises, algae are poised to become central to diversified food systems and bioeconomic innovation [46].

6. Integration into Climate Policy and Carbon Markets

For algae-based carbon removal to achieve global relevance, it must be embedded within climate policy frameworks and recognized in carbon markets. While technical efficiencies and durable sequestration pathways are critical, policy integration determines whether algal systems can scale beyond pilot projects. Current climate governance emphasizes transparency, permanence, and additionality, all of which present unique challenges for biological systems such as algae [47].
At the international level, the Paris Agreement provides mechanisms for countries to account for CDR in their nationally determined contributions (NDCs). However, algae-based CDR remains underrepresented compared to terrestrial afforestation or engineered carbon capture [48]. This gap reflects uncertainties in RMRV, as well as limited consensus on permanence thresholds. Without standardized methodologies, algal sequestration risks exclusion from compliance markets, despite its technical potential [49] (Figure 3).
Voluntary carbon markets are beginning to explore “blue carbon” credits, particularly for mangroves, seagrasses, and salt marshes [50]. Extending these frameworks to macroalgae and microalgae requires robust RMRV protocols and clear definitions of sequestration permanence. Certification bodies such as Verra and Gold Standard are evaluating methodologies for ocean-based CDR, but algae-specific pathways remain in early stages [51]. The development of credible standards will be essential to attract investment and ensure environmental integrity.
National policies also play a role in enabling algal CDR. Coastal nations with strong aquaculture sectors, such as China, Japan, and Norway, are well positioned to integrate macroalgae cultivation into climate strategies [52]. Incentives for renewable energy integration, nutrient recycling, and circular bioeconomy frameworks can further enhance the viability of algae-based systems [53]. Aligning these efforts with international carbon accounting standards will ensure that algal CDR contributes meaningfully to global mitigation targets.
Ultimately, the integration of algae into climate policy and carbon markets hinges on bridging scientific innovation with governance. Establishing transparent RMRV, ensuring permanence, and embedding algae within recognized certification frameworks will determine whether these systems evolve from experimental projects into scalable climate solutions [54].

7. Societal Acceptance and Ethical Considerations

The deployment of algae-based carbon removal strategies extends beyond technical feasibility into the realm of societal acceptance and ethics. Public perception of ocean-based interventions is shaped by concerns over ecological impacts, governance, and equity. Large-scale macroalgae cultivation, for example, may be viewed with skepticism if communities perceive risks to fisheries, tourism, or coastal ecosystems [55]. Transparent communication and participatory governance are therefore essential to build trust and legitimacy.
Ethical considerations also arise in relation to equity and justice. Many coastal regions most suitable for macroalgae cultivation are located in the Global South, where communities may lack the resources to influence decision-making or benefit equitably from carbon markets [56]. Ensuring that local stakeholders are included in planning and that benefits, whether financial, nutritional, or ecological, are shared fairly is critical to avoiding exploitation and reinforcing climate justice [57].
Cultural dimensions further shape acceptance. In regions where seaweed has long been integrated into diets, traditions, and livelihoods, expansion of cultivation may be welcomed as an extension of heritage [58]. Conversely, in areas unfamiliar with algae as food or resource, societal acceptance may depend on education, outreach, and demonstration of co-benefits such as improved water quality or biodiversity enhancement [59]. Ethical deployment must therefore respect cultural contexts and avoid imposing external models of resource use.
Finally, societal acceptance is linked to governance transparency. Clear RMRV protocols, certification standards, and accountability mechanisms reduce the risk of “greenwashing” and enhance credibility in both compliance and voluntary carbon markets [60]. Ethical frameworks should also address unintended consequences, such as ecological displacement or inequitable distribution of benefits, ensuring that algae-based carbon removal contributes positively to both climate mitigation and social resilience [61].

8. Future Research Directions and Innovation Pathways

The advancement of algae-based carbon removal requires sustained research into both fundamental biology and applied engineering. Future work must address the scalability of cultivation systems, the durability of sequestration pathways, and the integration of algae into broader climate and bioeconomic frameworks.
Biological innovation is central to this effort. Genomic and metabolic engineering of microalgae can enhance carbon fixation rates, stress tolerance, and production of high-value co-products [62]. Advances in synthetic biology may enable tailored strains optimized for specific environments or sequestration pathways, though ethical and ecological safeguards must accompany deployment [63]. Macroalgae research should also focus on selective breeding and cultivation techniques that maximize growth while minimizing ecological disruption [64].
Technological pathways offer another frontier. Photobioreactor design remains critical, with innovations in materials, light management, and energy integration poised to reduce costs and improve efficiency [65]. Coupling algal cultivation with renewable energy and wastewater treatment provides opportunities for circular economy integration [66]. Emerging approaches such as offshore floating platforms and modular bio-shields may expand cultivation into new marine spaces, enhancing resilience and scalability [67].
Ensuring sequestration permanence remains a priority. Research must refine pathways for durable carbon storage, including deep-ocean deposition, biochar conversion, and incorporation into long-lived products [68]. Life-cycle assessments and Earth system modeling are essential to quantify permanence and avoid unintended consequences [69]. Developing RMRV protocols will be critical to ensure credibility in carbon markets and policy frameworks [70].
Finally, societal and governance innovation must accompany technical advances. Future research should integrate social sciences to understand public acceptance, equity, and governance challenges. Participatory approaches that involve coastal communities in design and benefit-sharing will enhance legitimacy [71]. International collaboration is needed to harmonize standards and ensure that algae-based carbon removal contributes equitably to global mitigation efforts [72].

9. Conclusions and Outlook

Algae-based systems are emerging as one of the most versatile approaches to carbon dioxide removal, combining rapid biological uptake with diverse pathways for durable sequestration. The preceding sections have highlighted both the promise and the challenges of scaling these systems. Comparative efficiencies demonstrate that algae can outperform many terrestrial options in terms of productivity per unit area, while durable sequestration pathways and robust RMRV frameworks remain essential to ensure permanence and credibility. Integration into climate policy and carbon markets will determine whether algae-based carbon removal transitions from experimental projects to recognized mitigation strategies.
Societal acceptance and ethical considerations underscore the importance of transparency, equity, and cultural sensitivity. Without inclusive governance and fair benefit-sharing, large-scale deployment risks exacerbating inequalities or provoking public resistance. Conversely, when aligned with local traditions and livelihoods, algae cultivation can strengthen food security, diversify economies, and reinforce climate resilience.
Looking forward, innovation pathways in biology, engineering, and governance will shape the trajectory of algae-based carbon removal. Advances in synthetic biology, photobioreactor design, and offshore cultivation platforms promise to enhance efficiency and scalability. At the same time, interdisciplinary research must integrate ecological safeguards, life-cycle assessments, and social sciences to ensure that deployment is both environmentally sound and socially legitimate.
Ultimately, algae-based carbon removal should be viewed not as a standalone solution but as part of a portfolio of climate strategies. Its success will depend on bridging scientific innovation with policy frameworks, embedding RMRV standards into carbon markets, and fostering international collaboration. If these conditions are met, algae could play a pivotal role in achieving net-zero targets, while simultaneously contributing to food security, bioeconomic innovation, and ocean stewardship. The outlook is therefore cautiously optimistic—algae offer a unique opportunity to couple climate mitigation with broader societal benefits, provided that research, governance, and public engagement advance in tandem [72].

Funding

This research was funded by the Center for Functional Ecology Strategic Project (UIDB/04004/2025, UIDP/04004/2025) and TERRA Associate Laboratory (LA/P/0092/2020).

Data Availability Statement

No new data were created or analyzed in this study.

Conflicts of Interest

The author declares no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
BECCSBioenergy with Carbon Capture and Storage
CDRCarbon Dioxide Removal
CO2Carbon Dioxide
IMTAIntegrated Multitrophic Aquaculture
MSIMultispectral Imager
NDCsNationally Determined Contributions
OLIOperational Land Imager
PBRPhotobioreactor
RMRVRemote Monitoring Reporting Verification

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Figure 1. Comparative carbon uptake rates of macroalgae, microalgae, and terrestrial CDR systems (e.g., afforestation, BECCS)—estimated carbon dioxide uptake rates (g CO2 m−2 day−1) for representative macroalgae (e.g., Saccharina, Laminaria), microalgae (e.g., Chlorella, Nannochloropsis), and terrestrial carbon dioxide removal systems including afforestation and bioenergy with carbon capture and storage (BECCS). Algae-based systems demonstrate significantly higher productivity per unit area under optimal conditions, highlighting their potential for scalable carbon removal. Values represent upper-range estimates from peer-reviewed sources and are normalized for comparative visualization. Together, microalgae and macroalgae represent distinct but synergistic strategies: microalgae excel in controlled, high-efficiency carbon capture near emission sources, while macroalgae provide ecosystem-based sequestration with co-benefits for food security and coastal resilience. This figure compares upper-bound productivity values under optimized/experimental conditions. All data were normalized to g CO2 m−2 day−1 using a scaling-to-reference approach to allow cross-system comparison. These values represent potential rather than site-specific real-world performance.
Figure 1. Comparative carbon uptake rates of macroalgae, microalgae, and terrestrial CDR systems (e.g., afforestation, BECCS)—estimated carbon dioxide uptake rates (g CO2 m−2 day−1) for representative macroalgae (e.g., Saccharina, Laminaria), microalgae (e.g., Chlorella, Nannochloropsis), and terrestrial carbon dioxide removal systems including afforestation and bioenergy with carbon capture and storage (BECCS). Algae-based systems demonstrate significantly higher productivity per unit area under optimal conditions, highlighting their potential for scalable carbon removal. Values represent upper-range estimates from peer-reviewed sources and are normalized for comparative visualization. Together, microalgae and macroalgae represent distinct but synergistic strategies: microalgae excel in controlled, high-efficiency carbon capture near emission sources, while macroalgae provide ecosystem-based sequestration with co-benefits for food security and coastal resilience. This figure compares upper-bound productivity values under optimized/experimental conditions. All data were normalized to g CO2 m−2 day−1 using a scaling-to-reference approach to allow cross-system comparison. These values represent potential rather than site-specific real-world performance.
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Figure 2. Integration of algae into the emerging bioeconomy. Algal resources support diverse applications across food, animal feed, bioproducts, and circular economy sectors. Edible algae such as Spirulina and Chlorella contribute to nutrition; algal biomass enhances aquaculture and livestock feed while reducing reliance on fishmeal and soy; and biofuels and pigments exemplify bioproduct innovation; and algae-based systems enable wastewater treatment and nutrient recycling, reinforcing sustainability.
Figure 2. Integration of algae into the emerging bioeconomy. Algal resources support diverse applications across food, animal feed, bioproducts, and circular economy sectors. Edible algae such as Spirulina and Chlorella contribute to nutrition; algal biomass enhances aquaculture and livestock feed while reducing reliance on fishmeal and soy; and biofuels and pigments exemplify bioproduct innovation; and algae-based systems enable wastewater treatment and nutrient recycling, reinforcing sustainability.
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Figure 3. Integration of algae-based carbon removal into climate policy and carbon markets. Conceptual pathways for embedding algal CDR within international governance frameworks, including the Paris Agreement, RMRV protocols, and market mechanisms. Key challenges, transparency, permanence, and additionality, are illustrated alongside the potential for recognition in compliance and voluntary carbon markets.
Figure 3. Integration of algae-based carbon removal into climate policy and carbon markets. Conceptual pathways for embedding algal CDR within international governance frameworks, including the Paris Agreement, RMRV protocols, and market mechanisms. Key challenges, transparency, permanence, and additionality, are illustrated alongside the potential for recognition in compliance and voluntary carbon markets.
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Table 1. Comparative overview of marine algal groups and their deployment status in carbon-capture initiatives.
Table 1. Comparative overview of marine algal groups and their deployment status in carbon-capture initiatives.
Algal Group/Representative TaxaKey Biological Features Relevant to Carbon CaptureSequestration PathwaysCurrent Deployment StatusExample Projects/ApplicationsReferences
Microalgae (General)High photosynthetic efficiency; rapid biomass turnover; adaptable to engineered systemsBiomass harvest for BECCS, biochar, bioproducts; potential sinking; dissolved inorganic carbon uptakePilot to early commercial, especially in land-based photobioreactorsIndustrial CO2-capture photobioreactors; wastewater-coupled cultivation[4]
Diatoms (Bacillariophyta)Silica frustules enhance sinking; major contributors to oceanic primary productionBallasted particulate organic carbon (POC) export; natural carbon-pump enhancementResearch only; no engineered deploymentOcean-fertilization experiments; natural pump monitoring[5]
Coccolithophores (e.g., Emiliania huxleyi)Calcification affects alkalinity; mixed CO2 uptake effectsCarbonate export; alkalinity modificationResearch onlyMesocosm studies on alkalinity enhancement[6]
Cyanophyceae (e.g., Prochlorococcus, Synechococcus)Extremely abundant; efficient light harvesting; nitrogen fixation in some taxaDOC production; microbial-loop carbon retentionFundamental research; no deploymentOpen-ocean productivity studies; genetic engineering research[7,8]
Green Microalgae (Chlorophyta)High lipid content; robust in engineered systemsBiomass harvest for BECCS, biofuelsPilot to commercial (land-based)Raceway ponds; integrated biorefineries[8]
Brown Macroalgae (e.g., Macrocystis, Laminaria)High biomass yield; fast growth; strong carbon-storage potentialSinking of detritus; deep-sea export; long-lived biomassPilot to early field trials; growing interest in open-ocean CDROffshore kelp farms; kelp-sinking trials; kelp forest carbon-accounting studies[9]
Red Macroalgae (e.g., Gracilaria, Kappaphycus)High carbohydrate content; widely cultivatedBiomass harvest; limited natural sinkingCommercial aquaculture, but not CDR-orientedBiopolymer production; food and hydrocolloid industries[10,11]
Green Macroalgae (e.g., Ulva)Extremely fast growth; thrives in eutrophic watersBiomass harvest; coastal carbon removalCommercial biomass production; emerging CDR interestCoastal bioremediation; valorization of Ulva blooms[12]
Sargassum spp.Free-floating mats; episodic large-scale biomass accumulationNatural export to deep sea (variable); biomass harvestExploratory research; early-stage valorizationSargassum-to-biochar initiatives; coastal mitigation projects[13]
Table 2. Monitoring techniques for algae-based carbon accounting, the components they address, and remaining uncertainties [33,34,35].
Table 2. Monitoring techniques for algae-based carbon accounting, the components they address, and remaining uncertainties [33,34,35].
Monitoring TechniqueCarbon Accounting Component AddressedStrengthsKey Uncertainties/Limitations
Isotopic tracers (e.g., δ13C, radiocarbon)Quantifying carbon uptake, distinguishing anthropogenic vs. natural carbonHigh specificity; useful for source attributionLimited spatial coverage; difficult to apply at large scales; tracer dilution during export
Satellite remote sensing (multispectral, hyperspectral)Biomass distribution, surface extent, seasonal dynamicsLarge-scale, repeatable, cost-effectivePoor penetration in turbid waters; cannot quantify subsurface biomass; uncertain conversion from optical signal to carbon
In situ biogeochemical sensors (O2, pH, DIC/TA)Net community production, carbon fluxes, remineralizationHigh temporal resolution; direct measurement of water-column changesAttribution to algal biomass vs. other processes; limited spatial coverage
Acoustic and optical profiling (LIDAR, sonar, fluorometry)Vertical export flux, sinking rates, particle concentrationUseful for tracking export pathwaysCannot directly determine carbon content; deep-ocean fate remains poorly constrained
Harvest-based biomass measurementsCarbon removed through biomass extractionHigh accuracy at farm scaleDoes not capture unharvested export; post-harvest remineralization uncertain
Earth system models coupled with empirical dataLong-term sequestration potential, deep-ocean fateIntegrates multiple data streams; scenario testingLarge uncertainties in remineralization rates, burial efficiency, and ocean circulation impacts
Table 3. Bioeconomy applications of algae and associated co-benefits, highlighting circular-economy linkages [38,39,40,41,42,43,44,45].
Table 3. Bioeconomy applications of algae and associated co-benefits, highlighting circular-economy linkages [38,39,40,41,42,43,44,45].
Application AreaExample ProductsPrimary Co-BenefitsCircular-Economy Linkages
Human foodEdible macroalgae (Saccharina, Porphyra), microalgae (Spirulina, Chlorella)Nutrient-dense proteins, vitamins, minerals; diversification of food systemsLow land and freshwater use; integration with wastewater nutrient recovery
Animal feedAquafeed additives, livestock supplementsReduced reliance on fishmeal and soy; improved feed efficiency; methane-reducing compounds in ruminantsValorization of algal by-products; reduced pressure on terrestrial crops
Bioplastics & biopolymersAlginate, carrageenan, agar, biodegradable packagingSubstitution of fossil-based plastics; reduced wasteUse of residual biomass; closed-loop material cycles
BiofuelsBiodiesel, bioethanol, biogas, jet fuel precursorsRenewable energy; reduced lifecycle emissionsCoupling with CO2 capture and wastewater treatment to lower inputs
Pharmaceuticals & nutraceuticalsPigments, antioxidants, bioactive compoundsHigh-value products; health benefitsExtraction cascades enabling full biomass utilization
Environmental servicesWastewater treatment, nutrient removal, bioremediationImproved water quality; reduced eutrophicationRecovery of nitrogen and phosphorus for reuse in cultivation
Agriculture & soil amendmentsBiofertilizers, biostimulantsEnhanced soil health; reduced synthetic fertilizer useRecycling of nutrients from algal residues back into agriculture
Note: Many pathways enable multi-product “biorefinery” approaches, where sequential extraction maximizes value and minimizes waste, reinforcing circular-economy principles.
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Pereira, L. Phototrophic Carbon Capture in Marine Algae: Comparative Efficiencies, Sequestration Dynamics, and Climate Implications. J. Mar. Sci. Eng. 2026, 14, 518. https://doi.org/10.3390/jmse14050518

AMA Style

Pereira L. Phototrophic Carbon Capture in Marine Algae: Comparative Efficiencies, Sequestration Dynamics, and Climate Implications. Journal of Marine Science and Engineering. 2026; 14(5):518. https://doi.org/10.3390/jmse14050518

Chicago/Turabian Style

Pereira, Leonel. 2026. "Phototrophic Carbon Capture in Marine Algae: Comparative Efficiencies, Sequestration Dynamics, and Climate Implications" Journal of Marine Science and Engineering 14, no. 5: 518. https://doi.org/10.3390/jmse14050518

APA Style

Pereira, L. (2026). Phototrophic Carbon Capture in Marine Algae: Comparative Efficiencies, Sequestration Dynamics, and Climate Implications. Journal of Marine Science and Engineering, 14(5), 518. https://doi.org/10.3390/jmse14050518

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