Ecological performance differs between range centre and trailing edge populations of a cold-water kelp: implications for estimating net primary productivity

King, Nathan G.; Moore, Pippa J.; Pessarrodona, Albert; Burrows, Michael T.; Porter, Joanne S.; Bué, Mathilde; Smale, Dan

doi:10.1007/s00227-020-03743-5

Cited by 14 publications

(14 citation statements)

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“…The greatest production of detritus via dislodgement was recorded in N Scotland, which supports large‐sized kelp plants and exhibited relatively high rates of plant loss. Previous work has shown that canopy‐forming plants at our colder northern sites attain a much greater size and biomass, and that kelp populations are considerably more productive, compared with our warmer southern sites (Smale et al 2016; Pessarrodona et al 2018; King et al 2020). This is likely a combination of lower temperatures and increased light availability at some northern sites (Smale et al 2020).…”

Section: Discussionmentioning

confidence: 59%

Examining the production, export, and immediate fate of kelp detritus on open‐coast subtidal reefs in the Northeast Atlantic

Smale

Pessarrodona

King

et al. 2021

Limnology & Oceanography

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Kelp forests are highly productive coastal habitats and are emerging as important sources of organic matter for other ecosystems. Although their high rates of productivity and detritus release are expected to lead to substantial export of carbon, few studies have actually quantified rates of export or the persistence of detritus. We addressed this in eight subtidal kelp forests (Laminaria hyperborea) spanning the length (9 of latitude) of the United Kingdom. Specifically, we quantified detritus production, retention/export from source and adjacent habitats, and in situ decomposition rates. Detritus released via both dislodgment of whole plants and "May cast" shedding of old growth was highly variable between sites with greatest values recorded in our colder, northern sites. This was attributable to greater plant size biomass in northern regions, rather than plant density or dislodgement rates. On average, the annual production of kelp detritus was 4706 AE 700 g FW m À2 yr À1 or 301 g C m À2 yr À1 . Low retention of detritus within the kelp forest and adjacent sedimentary habitats indicated very high rates of export (> 98% across the study). A litterbag experiment showed detritus may take > 4 months to decompose, suggesting great potential for long distance transport. Overall, our findings suggest that L. hyperborea forests export large amounts of detritus subsidies across their range, which can potentially shape the structure of distant benthic communities and constitute a relevant and largely overlooked flux in the coastal carbon cycle, which may represent an important component of natural carbon sequestration.

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Section: Discussionmentioning

confidence: 59%

Examining the production, export, and immediate fate of kelp detritus on open‐coast subtidal reefs in the Northeast Atlantic

Smale

Pessarrodona

King

et al. 2021

Limnology & Oceanography

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“…These data suggest that kelp forest CSP may already have declined and will continue to do so with further poleward movement of Laminaria species under continued ocean warming. These potential repercussions for ecosystem functioing represent just one of many vicious circles, since climate change is already reducing the extent of many temperate kelp forests (Smale, 2020) and their CSP is additionally expected to be diminished by climate-driven phase shifts (Krumhansl et al, 2014;Pessarrodona et al, 2021), heatwaves (Smale et al, 2019), forest miniaturisation (King et al, 2020;Pessarrodona et al, 2018) and coastal darkening (Blain et al, 2021). Our empirical findings on carbon remineralisation are supported by the feeding preference of the key kelp detritivores (de Bettignies et al, 2020a) Steromphala umbilicalis (Gilson et al, 2021), S. cineraria and Patella pellucida (Hargrave et al, 2017;Pessarrodona et al, 2019;Smale et al, 2015) for L. ochroleuca compared to boreal species.…”

Section: Discussionmentioning

confidence: 99%

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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“…This region is subject to episodes of higher sea surface temperatures and lower availability of nutrients, limiting kelp biomass and area 30 . Kelp forests found near their warm-distribution limit are more impacted by extreme climatic events 24,[30][31][32] , suggesting that future climate-driven impacts could significantly diminish the coverage of kelp in Baja California. Protection of persistent kelp in the region can minimize other local stressors, such as indirect negative effects of fishing (through the removal of predators and release of herbivores that can over-graze kelp 33 ), maintain sources for recovery of impacted habitat patches, and build the resilience required for these ecosystems to adapt and persist in the face of future changes.…”

Section: Discussionmentioning

confidence: 99%

Southward decrease in the protection of persistent giant kelp forests in the northeast Pacific

Arafeh‐Dalmau

Cavanaugh

Possingham

et al. 2021

Commun Earth Environ

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Kelp forests are globally important and highly productive ecosystems, yet their persistence and protection in the face of climate change and human activity are poorly known. Here, we present a 35-year time series of high-resolution satellite imagery that maps the distribution and persistence of giant kelp (Macrocystis pyrifera) forests along ten degrees of latitude in the Northeast Pacific Ocean. We find that although 7.7% of giant kelp is protected by marine reserves, when accounting for persistence only 4% of kelp is present and protected. Protection of giant kelp decreases southerly from 20.9% in Central California, USA, to less than 1% in Baja California, Mexico, which likely exacerbates kelp vulnerability to marine heatwaves in Baja California. We suggest that a two-fold increase in the area of kelp protected by marine reserves is needed to fully protect persistent kelp forests and that conservation of climate-refugia in Baja California should be a priority.

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Ecological performance differs between range centre and trailing edge populations of a cold-water kelp: implications for estimating net primary productivity

Cited by 14 publications

References 86 publications

Examining the production, export, and immediate fate of kelp detritus on open‐coast subtidal reefs in the Northeast Atlantic

Examining the production, export, and immediate fate of kelp detritus on open‐coast subtidal reefs in the Northeast Atlantic

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

Southward decrease in the protection of persistent giant kelp forests in the northeast Pacific

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