Superficial sedimentary stocks and sources of carbon and nitrogen in coastal vegetated assemblages along a flow gradient

Santos, Rui; Duque-Núñez, Natalia; Santos, Carmen B. de los; Martins, Márcio; Carrasco, A. Rita; Veiga-Pires, C.

doi:10.1038/s41598-018-37031-6

Cited by 30 publications

(36 citation statements)

References 66 publications

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“…In other words, meadows with lower water motion exhibited higher sediment OC stocks, likely due to enhanced particle deposition and reduced rates of erosion and resuspension in these calmer hydrodynamic environments. Our results agree with previous field studies examining the role of hydrodynamics on seagrass meadow carbon storage, where greater sediment carbon content was associated with lower wave heights (Samper‐Villarreal et al ), lower wave exposure (Mazarrasa et al ), and lower current velocities (Santos et al ). Carbon stocks have also been shown to be significantly higher in inner fjords compared to outer fjords and open coasts (Kindeberg et al ), which aligns with our finding that more sheltered inner‐coast sites such as Pruth Bay had much higher OC stocks than exposed outer coast sites such as Choked Pass (Table ; Fig.…”

Section: Discussionsupporting

confidence: 92%

“…The scarcity of data on the spatial heterogeneity in carbon stocks and accumulation rates creates challenges for scaling up carbon estimates and incorporating blue carbon into such climate policies (Lavery et al ; Oreska et al ; Mazarrasa et al ). Furthermore, the mechanisms that regulate spatial variability across different scales are only beginning to be understood (Samper‐Villarreal et al ; Kindeberg et al ; Mazarrasa et al ; Santos et al ).…”

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confidence: 99%

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Reduced water motion enhances organic carbon stocks in temperate eelgrass meadows

Prentice

Hessing‐Lewis

Sanders‐Smith

et al. 2019

Limnology & Oceanography

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Organic carbon (OC) storage in coastal vegetated ecosystems is increasingly being considered in carbon financing and climate change mitigation strategies. However, spatial heterogeneity in these “blue carbon” stocks among and within habitats has only recently been examined, despite its considerable implications. Seagrass meadows have potential to store significant amounts of carbon in their sediments, yet studies comparing sediment OC content at regional and meadow scales remain sparse. Here, we collected sediment cores from six temperate eelgrass (Zostera marina) meadows on the coast of British Columbia, Canada, to quantify sediment OC stocks, accumulation rates, and sources, and to examine local and regional drivers of variability. Sediment OC content was highly variable—across all sites, stocks in the top 0–5 cm ranged from 83 to 1089 g OC m−2, while the 15–20 cm stocks exhibited a 24‐fold difference, from 59 to 1407 g OC m−2. Carbon accumulation rates ranged from 4 to 33 g OC m−2 yr−1. Isotopic mixing models revealed that sediment OC was primarily terrestrial carbon (41.3%) and canopy‐forming kelps (33.3%), with a smaller contribution of eelgrass (25.3%). Here, we show that regional variability in OC content exceeds meadow‐scale variability. This result is likely driven by landscape factors, most notably relative water motion, representing a more dominant control on seagrass OC accumulation than meadow‐scale factors such as canopy complexity. These findings elicit caution when scaling up seagrass meadow OC content and demonstrate that measures of the hydrodynamic environment could improve estimates of carbon storage in temperate soft sediment habitats.

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Section: Discussionsupporting

confidence: 92%

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confidence: 99%

Reduced water motion enhances organic carbon stocks in temperate eelgrass meadows

Prentice

Hessing‐Lewis

Sanders‐Smith

et al. 2019

Limnology & Oceanography

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“…Some tropical seagrass species can, for instance, be a direct source of inorganic carbon to the sediment by formation of aragonite crystals in the leaves (Enríquez & Schubert, ); this has, however, not been seen in any temperate seagrass species. The C: N ratio was similar to previous studies on the Swedish west coast (Dahl, Deyanova, Gütschow, et al, ; Pihl et al, ) and elsewhere in the region (Kindeberg et al, ), with low nitrogen content in relation to organic carbon levels, which is also commonly found in other seagrass areas (Gullström et al, ; Santos et al, ). The highest nitrogen content was found in the carbon‐rich, sheltered site of Getevik, as the nitrogen content is known to positively correlate to both carbon‐ and silt‐clay content (Kindeberg et al, ).…”

Section: Discussionsupporting

confidence: 89%

High Seasonal Variability in Sediment Carbon Stocks of Cold‐Temperate Seagrass Meadows

et al. 2020

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Seagrass meadows have a high ability to capture and store atmospheric CO 2 in the plant biomass and underlying sediment and thereby function as efficient carbon sinks. The seagrass Zostera marina is a common species in the temperate Northern Hemisphere, a region with strong seasonal variations in climate. How seasonality affects carbon storage capacity in seagrass meadows is largely unknown, and therefore, in this study, we aimed to assess variations in sedimentary total organic carbon (TOC) content over a 1-year cycle in seagrass meadows on the Swedish west coast. The TOC was measured in two Z. marina sites, one wave exposed and one sheltered, and at two depths (1.5 and 4 m) within each site, every second month from August 2015 to June 2016. We found a strong seasonal variation in carbon density, with a peak in early summer (June), and that the TOC was negatively correlated to the net community production of the meadows, presumably related to organic matter degradation. There was seasonal variation in TOC content at all sediment sections, indicating that the carbon content down to 30 cm is unstable on a seasonal scale and therefore likely not a long-term carbon sink. The yearly mean carbon stocks were substantially higher in the sheltered meadow (3,965 and 3,465 g m −2 ) compared to the exposed one (2,712 and 1,054 g m −2 ) with similar seasonal variation. Due to the large intra-annual variability in TOC content, seasonal variation should be considered in carbon stock assessments and management for cold-temperate seagrass meadows.

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“…Variability in seagrass sedimentary C org stocks has been described at a range of spatial scales: from cm and meters, at the seagrass patch and meadow scale [18][19][20] to bioregions and latitudinal scales 7,9 . Studies at small scales (up to ~1′s km) have shown how sedimentary C org can be spatially distributed inside seagrass meadows 18,20,21 . However, in studies at higher spatial scales (~100′s to ~1000′s km), comparisons and estimates are usually made based on a relatively low number of sediment cores from each site [22][23][24] , therefore, not accounting for the potential spatial variability in seagrass sedimentary C org stocks among meadows in the same area.…”

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confidence: 99%

High variability of Blue Carbon storage in seagrass meadows at the estuary scale

Ricart

York

Bryant

et al. 2020

Sci Rep

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Seagrass meadows are considered important natural carbon sinks due to their capacity to store organic carbon (c org) in sediments. However, the spatial heterogeneity of carbon storage in seagrass sediments needs to be better understood to improve accuracy of Blue Carbon assessments, particularly when strong gradients are present. We performed an intensive coring study within a subtropical estuary to assess the spatial variability in sedimentary c org associated with seagrasses, and to identify the key factors promoting this variability. We found a strong spatial pattern within the estuary, from 52.16 mg c org cm −3 in seagrass meadows in the upper parts, declining to 1.06 mg C org cm −3 in seagrass meadows at the estuary mouth, despite a general gradient of increasing seagrass cover and seagrass habitat extent in the opposite direction. the sedimentary c org underneath seagrass meadows came principally from allochthonous (non-seagrass) sources (~70-90 %), while the contribution of seagrasses was low (~10-30 %) throughout the entire estuary. Our results showed that C org stored in sediments of seagrass meadows can be highly variable within an estuary, attributed largely to accumulation of fine sediments and inputs of allochthonous sources. Local features and the existence of spatial gradients must be considered in Blue carbon estimates in coastal ecosystems.

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Superficial sedimentary stocks and sources of carbon and nitrogen in coastal vegetated assemblages along a flow gradient

Cited by 30 publications

References 66 publications

Reduced water motion enhances organic carbon stocks in temperate eelgrass meadows

Reduced water motion enhances organic carbon stocks in temperate eelgrass meadows

High Seasonal Variability in Sediment Carbon Stocks of Cold‐Temperate Seagrass Meadows

High variability of Blue Carbon storage in seagrass meadows at the estuary scale

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