Large global variations in the carbon dioxide removal potential of seaweed farming due to biophysical constraints

Arzeno-Soltero, Isabella; Saenz, Benjamin; Frieder, Christina A.; Long, Matthew C.; DeAngelo, Julianne; Davis, Steven J.; Davis, Kristen A.

doi:10.1038/s43247-023-00833-2

Cited by 12 publications

(12 citation statements)

References 99 publications

(141 reference statements)

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“…Additionally, other unaccounted environmental variables could represent confounding factors. Nevertheless, adverse climatic changes and anthropogenic activities are predicted to elevate the duration and intensity of seawater light penetration through mechanisms like increased stratification, thermocline shoaling and by influencing primary productivity. , The former two are especially concerning for the development of seaweed aquaculture in offshore waters, where nutrient availability is typically lower. While excessive light may induce stress and impair photosynthesis in kelp, kelp typically adapts to fluctuating light levels, rendering such negative impacts transient, after which kelp may resume normal functioning .…”

Section: Discussionmentioning

confidence: 99%

Adverse Environmental Perturbations May Threaten Kelp Farming Sustainability by Exacerbating Enterobacterales Diseases

Zhang,

Nair,

Zhang

et al. 2024

Environ. Sci. Technol.

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Globally kelp farming is gaining attention to mitigate land-use pressures and achieve carbon neutrality. However, the influence of environmental perturbations on kelp farming remains largely unknown. Recently, a severe disease outbreak caused extensive kelp mortality in Sanggou Bay, China, one of the world's largest high-density kelp farming areas. Here, through in situ investigations and simulation experiments, we find indications that an anomalously dramatic increase in elevated coastal seawater light penetration may have contributed to dysbiosis in the kelp Saccharina japonica's microbiome. This dysbiosis promoted the proliferation of opportunistic pathogenic Enterobacterales, mainly including the genera Colwellia and Pseudoalteromonas. Using transcriptomic analyses, we revealed that high-light conditions likely induced oxidative stress in kelp, potentially facilitating opportunistic bacterial Enterobacterales attack that activates a terrestrial plant-like pattern recognition receptor system in kelp. Furthermore, we uncover crucial genotypic determinants of Enterobacterales dominance and pathogenicity within kelp tissue, including pathogen-associated molecular patterns, potential membrane-damaging toxins, and alginate and mannitol lysis capability. Finally, through analysis of kelp-associated microbiome data sets under the influence of ocean warming and acidification, we conclude that such Enterobacterales favoring microbiome shifts are likely to become more prevalent in future environmental conditions. Our study highlights the need for understanding complex environmental influences on kelp health and associated microbiomes for the sustainable development of seaweed farming.

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Section: Discussionmentioning

confidence: 99%

Adverse Environmental Perturbations May Threaten Kelp Farming Sustainability by Exacerbating Enterobacterales Diseases

Zhang,

Nair,

Zhang

et al. 2024

Environ. Sci. Technol.

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“…alkalinity enhancement and ocean fertilization; thousands to tens of thousands of Tg C year −1 ; NASEM, 2021), but compares favourably to other blue carbon ecosystems (Krause-Jensen & Duarte, 2016). Unlike other coastal vegetated habitats, the area occupied by macroalgae forests can be extensively increased by the expansion of coastal and open ocean farms (Arzeno-Soltero et al, 2023). Some of the carbon assimilated into biomass during the farming process can be lost before harvesting and buried under the farm soils under the right sedimentary conditions, potentially remaining stored long-term (Pan et al, 2021).…”

Section: Main Macroalgal Carbon Sequestration Pathwaysmentioning

confidence: 99%

“…We focus on wild macroalgal ecosystems and intentionally refrain from contextualising these topics in relation to macroalgae farming. This focus arises because interventions around wild ecosystems presently have substantially higher potential abatement (NASEM, 2021), present more co-benefits (Forbes et al, 2022), and the CO 2removal capacity of macroalgae farming has been explored elsewhere (Arzeno-Soltero et al, 2023;Ross et al, 2022;Wu, Keller & Oschlies, 2023). Specifically, our review is largely centered on macroalgal forests formed by large brown algae (sensu Wernberg & Filbee-Dexter, 2019), which draw the greatest atmospheric CO 2 flux of any macroalgae habitat (Duarte et al, 2022;Pessarrodona et al, 2022) and whose contribution to sequestration is presumably the largest (Krause-Jensen & .…”

Section: Introductionmentioning

confidence: 99%

Carbon sequestration and climate change mitigation using macroalgae: a state of knowledge review

et al. 2023

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The conservation, restoration, and improved management of terrestrial forests significantly contributes to mitigate climate change and its impacts, as well as providing numerous co‐benefits. The pressing need to reduce emissions and increase carbon removal from the atmosphere is now also leading to the development of natural climate solutions in the ocean. Interest in the carbon sequestration potential of underwater macroalgal forests is growing rapidly among policy, conservation, and corporate sectors. Yet, our understanding of whether carbon sequestration from macroalgal forests can lead to tangible climate change mitigation remains severely limited, hampering their inclusion in international policy or carbon finance frameworks. Here, we examine the results of over 180 publications to synthesise evidence regarding macroalgal forest carbon sequestration potential. We show that research efforts on macroalgae carbon sequestration are heavily skewed towards particulate organic carbon (POC) pathways (77% of data publications), and that carbon fixation is the most studied flux (55%). Fluxes leading directly to carbon sequestration (e.g. carbon export or burial in marine sediments) remain poorly resolved, likely hindering regional or country‐level assessments of carbon sequestration potential, which are only available from 17 of the 150 countries where macroalgal forests occur. To solve this issue, we present a framework to categorize coastlines according to their carbon sequestration potential. Finally, we review the multiple avenues through which this sequestration can translate into climate change mitigation capacity, which largely depends on whether management interventions can increase carbon removal above a natural baseline or avoid further carbon emissions. We find that conservation, restoration and afforestation interventions on macroalgal forests can potentially lead to carbon removal in the order of 10's of Tg C globally. Although this is lower than current estimates of natural sequestration value of all macroalgal habitats (61–268 Tg C year−1), it suggests that macroalgal forests could add to the total mitigation potential of coastal blue carbon ecosystems, and offer valuable mitigation opportunities in polar and temperate areas where blue carbon mitigation is currently low. Operationalizing that potential will necessitate the development of models that reliably estimate the proportion of production sequestered, improvements in macroalgae carbon fingerprinting techniques, and a rethinking of carbon accounting methodologies. The ocean provides major opportunities to mitigate and adapt to climate change, and the largest coastal vegetated habitat on Earth should not be ignored simply because it does not fit into existing frameworks.

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“…In addition to the natural fluxes of seaweed carbon beyond the continental shelf, there is considerable interest in enhancing these processes by growing seaweeds on artificial structures in the open ocean, termed “ocean (macroalgal) afforestation,” and sinking resulting biomass to the deep ocean (Figure 1b; Arzeno‐Soltero et al., 2023; Ocean Visions and Monterey Bay Aquarium Research Institute, 2022; Ross et al., 2023; Figures S1, S4, S5, S7). As seaweeds sink, a range of processes (as above) will affect their degradation and the amount of biomass that reaches the deep ocean floor (Figure 1b).…”

Section: Seaweed Carbon Storage Poolsmentioning

confidence: 99%

“…;Arzeno- Soltero et al, 2023; Ocean Visions and Monterey Bay Aquarium Research Institute, 2022;Ross et al, 2023; Figures …”

mentioning

confidence: 99%

Air‐sea carbon dioxide equilibrium: Will it be possible to use seaweeds for carbon removal offsets?

Hurd,

Gattuso,

Boyd

2023

Journal of Phycology

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To limit global warming below 2°C by 2100, we must drastically reduce greenhouse gas emissions and additionally remove ~100–900 Gt CO2 from the atmosphere (carbon dioxide removal, CDR) to compensate for unavoidable emissions. Seaweeds (marine macroalgae) naturally grow in coastal regions worldwide where they are crucial for primary production and carbon cycling. They are being considered as a biological method for CDR and for use in carbon trading schemes as offsets. To use seaweeds in carbon trading schemes requires verification that seaweed photosynthesis that fixes CO2 into organic carbon results in CDR, along with the safe and secure storage of the carbon removed from the atmosphere for more than 100 years (sequestration). There is much ongoing research into the magnitude of seaweed carbon storage pools (e.g., as living biomass and as particulate and dissolved organic carbon in sediments and the deep ocean), but these pools do not equate to CDR unless the amount of CO2 removed from the atmosphere as a result of seaweed primary production can be quantified and verified. The draw‐down of atmospheric CO2 into seawater is via air‐sea CO2 equilibrium, which operates on time scales of weeks to years depending upon the ecosystem considered. Here, we explain why quantifying air‐sea CO2 equilibrium and linking this process to seaweed carbon storage pools is the critical step needed to verify CDR by discrete seaweed beds and nearshore and open ocean aquaculture systems prior to their use in carbon trading.

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Large global variations in the carbon dioxide removal potential of seaweed farming due to biophysical constraints

Cited by 12 publications

References 99 publications

Adverse Environmental Perturbations May Threaten Kelp Farming Sustainability by Exacerbating Enterobacterales Diseases

Adverse Environmental Perturbations May Threaten Kelp Farming Sustainability by Exacerbating Enterobacterales Diseases

Carbon sequestration and climate change mitigation using macroalgae: a state of knowledge review

Air‐sea carbon dioxide equilibrium: Will it be possible to use seaweeds for carbon removal offsets?

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