Macroalgal habitats support a sustained flux of floating biomass but limited carbon export beyond a Greenland fjord

Ager, Thomas  Gjerluff; Krause‐Jensen, Dorte; Olesen, Birgit; Carlson, Daniel F.; Winding, Mie S.; Sejr, Mikael K.

doi:10.1016/j.scitotenv.2023.162224

Cited by 11 publications

(4 citation statements)

References 60 publications

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“…Kokubu et al 42 confirmed the presence of positively buoyant Sargassum horneri originating from the northeastern coast of Japan up to 800 km offshore and in water depths up to 1800 m and related this to the presence of ocean fronts. In contrast, Ager et al 43 found that 80% of positively buoyant kelp detritus was retained within a Greenland fjord and was not transported into the open ocean. These studies highlight the need to consider different transport mechanisms for kelp species with different buoyancy, as well as the relevant dynamics in different regions.…”

Section: Discussionmentioning

confidence: 89%

Substantial kelp detritus exported beyond the continental shelf by dense shelf water transport

van der Mheen,

Wernberg,

Pattiaratchi

et al. 2024

Sci Rep

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Kelp forests may contribute substantially to ocean carbon sequestration, mainly through transporting kelp carbon away from the coast and into the deep sea. However, it is not clear if and how kelp detritus is transported across the continental shelf. Dense shelf water transport (DSWT) is associated with offshore flows along the seabed and provides an effective mechanism for cross-shelf transport. In this study, we determine how effective DSWT is in exporting kelp detritus beyond the continental shelf edge, by considering the transport of simulated sinking kelp detritus from a region of Australia’s Great Southern Reef. We show that DSWT is the main mechanism that transports simulated kelp detritus past the continental shelf edge, and that export is negligible when DSWT does not occur. We find that 51% per year of simulated kelp detritus is transported past the continental shelf edge, or 17–29% when accounting for decomposition while in transit across the shelf. This is substantially more than initial global estimates. Because DSWT occurs in many mid-latitude locations around the world, where kelp forests are also most productive, export of kelp carbon from the coast could be considerably larger than initially expected.

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Section: Discussionmentioning

confidence: 89%

Substantial kelp detritus exported beyond the continental shelf by dense shelf water transport

van der Mheen,

Wernberg,

Pattiaratchi

et al. 2024

Sci Rep

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“…Coastal geomorphological features facilitating long water residence times (e.g. fjords, estuaries) can however limit long‐range transport, with most algae sinking before being exported (Ager et al ., 2023). Interestingly, non‐buoyant algae can become intertwined with buoyant macroalgae, potentially facilitating export (Ager et al ., 2023).…”

Section: Main Macroalgal Carbon Sequestration Pathwaysmentioning

confidence: 99%

“…fjords, estuaries) can however limit long‐range transport, with most algae sinking before being exported (Ager et al ., 2023). Interestingly, non‐buoyant algae can become intertwined with buoyant macroalgae, potentially facilitating export (Ager et al ., 2023). Buoyant macroalgae sink to the bottom as a result of progressive degradation (e.g.…”

Section: Main Macroalgal Carbon Sequestration Pathwaysmentioning

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 Greenland, wild floating macroalgal biomass was mostly retained within the Nuup Kangerlua Fjord, with unknown carbon sequestration potential. Only 6.92 t C yr -1 of the biomass was exported beyond the fjord (Ager et al 2023). In sediment cores collected on the northwest coast of Norway at depths between 200-500 m, a qPCR approach was applied to detect and quantify the kelp species present in the sediments.…”

Section: Potential For Carbon Capturementioning

confidence: 99%

The sugar kelp Saccharina latissima II: Recent Advances in farming and applications

Sather,

Diehl,

Monteiro

et al. 2023

Preprint

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The sugar kelp Saccharina latissima has received intense scientific attention over the last decades. In recent years, interest in cultivation of the species has strongly increased in the North Atlantic Ocean and the Eastern Pacific Ocean, driven by the great potential of S. latissima to be utilised for various industrial applications, including food, feed, and biomaterials. Accordingly, current research has focused on improving farming methods and technology, environmental impacts, and site selection. In addition, many studies have investigated the varying chemical composition of S. latissima, extraction of commercially interesting components, and the use of the biomass and its derived components in various applications. This review provides acomprehensive overview of farming and applications of S. latissima from the last 15 years. Additional insights on other research topics, such as ecology, physiology, biochemical and molecular biology of S. latissima, are given in the first review, “The sugar kelp Saccharina latissima I: recent advances in a changing climate” (Diehl et al. 2023).

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Macroalgal habitats support a sustained flux of floating biomass but limited carbon export beyond a Greenland fjord

Cited by 11 publications

References 60 publications

Substantial kelp detritus exported beyond the continental shelf by dense shelf water transport

Substantial kelp detritus exported beyond the continental shelf by dense shelf water transport

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

The sugar kelp Saccharina latissima II: Recent Advances in farming and applications

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