Sustained productivity and respiration of degrading kelp detritus in the shallow benthos: Detached or broken, but not dead

Frontier, Nadia; Bettignies, Florian de; Foggo, Andy; Davoult, Dominique

doi:10.1016/j.marenvres.2021.105277

Cited by 29 publications

(28 citation statements)

References 73 publications

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“…Detached macroalgal biomass, which has been exported and deposited subtidally, cannot necessarily be treated as detritus because it has been found to be actively respiring and growing without degrading or contributing carbon to the underlying sediments (Frontier et al. 2021). In these experiments, the amount of mass lost from the detritus deposited over time, or the change in concentration or amount of carbon mass in the underlying sediment or pore water (Barreiro et al.…”

Section: Resultsmentioning

confidence: 99%

“…These types of experiments are conducted mostly on sandy shore ecosystems, but similar degradation experiments have been conducted in benthic subtidal habitats (de Bettignies et al 2020, estuarine sandflats (Gladstone-Gallagher et al 2016), and in specific seabed hollows where algal blades are known to accumulate (Norkko et al 2004). Detached macroalgal biomass, which has been exported and deposited subtidally, cannot necessarily be treated as detritus because it has been found to be actively respiring and growing without degrading or contributing carbon to the underlying sediments (Frontier et al 2021). In these experiments, the amount of mass lost from the detritus deposited over time, or the change in concentration or amount of carbon mass in the underlying sediment or pore water (Barreiro et al 2013) serves as a measure of carbon transferred through abiotic decay or detritivore activity.…”

Section: Must Be In Englishmentioning

confidence: 99%

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Whole System Analysis Is Required To Determine The Fate Of Macroalgal Carbon: A Systematic Review

Dolliver

O’Connor

2022

Journal of Phycology

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The role of marine primary producers in capturing atmospheric CO2 has received increased attention in the global mission to mitigate climate change. Yet, our understanding of carbon sequestration performed by macroalgae has been limited to a relatively small number of studies that have estimated the ultimate fate of macroalgal‐derived carbon. This systematic review was conducted to provide a timely synthesis of the methods used to determine the fate of macroalgal carbon in this rapidly expanding research area. It also aimed to provide suggestions for more effective future research. We found that the most common methods to estimate the fate of macroalgal carbon can be categorized into groups based on those that quantify: (i) export of macroalgal carbon to other environments—known as horizontal transport; (ii) sequestration of macroalgal carbon into deep‐sea sediments—known as vertical transport; (iii) burial of macroalgal carbon directly beneath a benthic community; (iv) the loss of macroalgal carbon as particulate carbon or dissolved carbon to the water column; (v) the loss of macroalgal carbon to primary consumers; and finally (vi) those studies that combined multiple methods in one location. Based on this review, several recommendations for future research were formulated, which require the combination of multiple methods in a whole system analysis approach.

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Section: Resultsmentioning

confidence: 99%

Section: Must Be In Englishmentioning

confidence: 99%

Whole System Analysis Is Required To Determine The Fate Of Macroalgal Carbon: A Systematic Review

Dolliver

O’Connor

2022

Journal of Phycology

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“…Warm temperate kelp has a 42%–45% lower total photosynthetic pigment concentration than cold temperate kelps (Wright & Foggo, 2021), suggesting it has lower photosynthetic capacity which is in line with the 48%–50% lower photosynthetic activity reported here. Although Frontier, de Bettignies, et al (2021) found no difference in net and gross primary production and photosynthetic efficiency (chlorophyll fluorescence) between in vitro L. hyperborea and L. ochroleuca , a subsequent field experiment by the same authors suggests declining photosynthetic efficiency with detrital age in L. ochroleuca and no change in L. hyperborea (Frontier, Mulas, et al, 2021). This case supports our findings and highlights that in situ experimental validation is essential.…”

Section: Discussionmentioning

confidence: 98%

Climate‐driven shifts in kelp forest composition reduce carbon sequestration potential

Wright

Pessarrodona

Foggo

2022

Global Change Biology

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The potential contribution of kelp forests to blue carbon sinks is currently of great interest but interspecific variance has received no attention. In the Northeast Atlantic, kelp forest composition is changing due to climate-driven poleward range shifts of cold temperate Laminaria digitata and L. hyperborea and warm temperate L. ochroleuca. To understand how this might affect the carbon sequestration potential of these ecosystems, we quantified interspecific differences in carbon export and decomposition alongside changes in detrital photophysiology and biochemistry. We found that while warm temperate kelp exports up to 71% more carbon per plant, it decomposes up to 155% faster than its boreal congeners. Elemental stoichiometry and polyphenolic content cannot fully explain faster carbon turnover, which may be attributable to contrasting tissue toughness or unknown biochemical and structural defences. Faster decomposition causes the detrital photosynthetic apparatus of L. ochroleuca to be overwhelmed after 20 d and lose integrity after 36 d, while detritus of cold temperate species maintains carbon assimilation. Depending on the photoenvironment, detrital photosynthesis could further exacerbate interspecific differences in decomposition via a potential positive feedback loop. Via compositional change such as the predicted prevalence of L. ochroleuca, ocean warming will therefore likely reduce the carbon sequestration potential of these temperate marine forests. Keywords biogeography; carbon budget uncertainty; carbon flux; climate change; C:N; decay; degradation; ecophysiology; erosion; photosynthesis Introduction Over the last decade humans have emitted around 11 billion tons of carbon per year (Canadell et al., 2021). In the Paris Agreement, 193 countries pledged to reduce this emission and enhance carbon sink capacity. Ocean-based biological carbon dioxide removal (CDR) is now acknowledged as an integral part of fulfilling this goal (Canadell et al., 2021). Such CDR may be facilitated by marine macrophytes, whose role in carbon sequestration was first recognised four decades ago (Smith, 1981) but has only recently come to mainstream attention as blue carbon (Canadell et al., 2021). Despite the potential involvement of marine vegetated habitats in CDR and their location within national jurisdiction, few ocean-based nationally determined contributions (NDCs) have been put forward by affluent Annex I parties such as the UK, US and Australia (Gallo et al., 2017) which hold some of the highest blue carbon wealth (Bertram et al., 2021). In part, this may be due to the ongoing debate on the blue carbon status of temperate kelp forests that dominate the coasts of these countries (Krause-Jensen et al., 2018). Therefore, identifying the magnitude and fate of carbon assimilated by these marine plants is key to our understanding of their carbon sequestration potential (CSP) and their consequent inclusion in blue carbon frameworks (Krause-Jensen et al., 2018). CSP is a function of carbon export and fate (Duarte and Cebriá...

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“…Degradation of kelp POM may take several weeks or even months (de Bettignies et al, 2020b;Smale et al, 2022), with the photosynthetic capacity still partially intact (Frontier et al, 2021). This impacts on the potential for large-scale and longterm transport, and for how long the POM is left on the sea floor has bearing on the degradation rates and the associated bacterial community (Brunet et al, 2021).…”

Section: Sinking Speeds and Transportmentioning

confidence: 99%

“…Macroalgal tissue may be transported distances at the order of 1000 km and to depths of several thousands of meters (Harrold et al, 1998;Ortega et al, 2019). Simulation studies and in situ observations have also shown that POM from natural kelp populations can be transported beyond the natural habitats, both horizontally and vertically (Filbee-Dexter et al, 2018, 2020, and that it may degrade over time periods of months (Frontier et al, 2021;Smale et al, 2022). Despite this, it is yet unclear how exported biomass of kelp detritus is dispersed (Pedersen et al, 2021), how far it is transported, and how the matter is distributed between the near and far field.…”

Section: Introductionmentioning

confidence: 99%

Dispersal and Deposition of Detritus From Kelp Cultivation

2022

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A high resolution coastal and ocean hydrodynamic model system was used to investigate the transport and deposition patterns of Particulate Organic Matter (POM) from kelp farmed at three locations of different properties: a sheltered location, an exposed location, and an offshore location. Published values on the sinking speeds of organic particles from kelp were used, spanning several orders of magnitude. Recent work on quantifying the release of particulate organic matter from farmed kelp was used to link the release of carbon to possible cultivation volumes and scenarios, and finally to link this to the potential for carbon loading on the ocean floor. The results are presented in terms of loading and distribution per unit harvested kelp, and the loading estimates are compared with estimates of natural (background) primary production. According to the simulation results, organic matter may be transported anything from a few (hundred) meters up to a hundred km away from the release site, depending on the sinking rates, time of release, and the location. The depth at which the matter settles on the sea floor likewise depends on the properties of the matter and the sites. The time until settlement varied from minutes to several hundred hours. The results underscore the importance of constraining the dispersal and deposition of detritus from kelp cultivation in order to better understand and quantify associated environmental risks posed by organic loading, and the potential for seafloor carbon sequestration by kelp farming as a nature based climate solution.

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Sustained productivity and respiration of degrading kelp detritus in the shallow benthos: Detached or broken, but not dead

Cited by 29 publications

References 73 publications

Whole System Analysis Is Required To Determine The Fate Of Macroalgal Carbon: A Systematic Review

Whole System Analysis Is Required To Determine The Fate Of Macroalgal Carbon: A Systematic Review

Climate‐driven shifts in kelp forest composition reduce carbon sequestration potential

Dispersal and Deposition of Detritus From Kelp Cultivation

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