Non‐seagrass carbon contributions to seagrass sediment blue carbon

Oreska, Matthew P. J.; Wilkinson, Grace M.; McGlathery, Karen J.; Bost, Molly C.; McKee, Brent A.

doi:10.1002/lno.10718

Cited by 50 publications

(39 citation statements)

References 60 publications

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“…). These findings align with other studies that have found largely allochthonous contributions to seagrass sediment OC stocks, with 50% or more of the carbon originating from non‐seagrass sources such as macroalgae, salt marsh vegetation, benthic microalgae, plankton, or terrestrial sources (Kennedy et al ; Miyajima et al ; Greiner et al ; Oreska et al ). While the isotope sources used here are distinct from one another, overlapping source signatures can make it challenging to decipher relative contributions to the sediments.…”

Section: Discussionsupporting

confidence: 91%

“…Seagrasses often exhibit high rates of primary productivity, and this biomass can become incorporated into the sediment carbon pool. Seagrass canopies also facilitate particle capture and settlement from the water column, which can further enhance carbon stocks and accretion rates (Hendriks et al ; Duarte et al ; Macreadie et al ) Thus, the OC found in seagrass meadow sediments can be autochthonous—produced within a given meadow—or allochthonous—produced outside the meadow (Kennedy et al ; Miyajima et al ; Oreska et al ). The OC buried in seagrass sediments is generally subject to low rates of remineralization, as the sediments tend to be low in oxygen below the first few millimeters, resulting in reduced microbial decomposition (Fourqurean et al ; Duarte et al ; Greiner 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: 91%

mentioning

confidence: 99%

Reduced water motion enhances organic carbon stocks in temperate eelgrass meadows

Prentice

Hessing‐Lewis

Sanders‐Smith

et al. 2019

Limnology & Oceanography

View full text Add to dashboard Cite

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“…Our isotopic data suggest that the organic carbon that ends up in eelgrass meadow sediments is largely derived from noneelgrass sources, which aligns with previous findings that upward of 50% of carbon in seagrass sediments may be allochthonous in origin (Kennedy et al, ; Miyajima et al, ; Oreska et al, ; Prentice et al, ). While we did not have enough replicates of sediment isotope values or enough localized signatures of potential carbon sources to determine the relative proportion of carbon sources using an isotope mixing model, the biplot shows a clear separation of signatures in the sediments from those of Z. marina across various regions (Figure ).…”

Section: Discussionsupporting

confidence: 91%

A Synthesis of Blue Carbon Stocks, Sources, and Accumulation Rates in Eelgrass (Zostera marina) Meadows in the Northeast Pacific

Prentice

Poppe

Lutz

et al. 2020

Global Biogeochemical Cycles

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There is increasing urgency to implement climate change mitigation strategies that enhance greenhouse gas removal from the atmosphere and reduce carbon dioxide (CO2) emissions. Recently, coastal “blue carbon” habitats⁠—mangroves, salt marshes, and seagrass meadows—have received attention for their ability to capture CO2 and store organic carbon (OC), primarily in their sediments. Across habitat types and regions, however, information about the sequestration rates and sources of carbon to local sediments remains sparse. Here we compiled recently obtained estimates of sediment OC stocks and sequestration rates from 139 cores collected from temperate seagrass (Zostera marina) meadows in Alaska, British Columbia, Washington, and Oregon. Across all cores sediment OC content averaged 0.75%. Organic carbon stocks in the top 25 cm and 1 m of the sediment averaged 1,846 and 7,168 g OC m−2, respectively. Carbon sequestration rates ranged from 4.6 to 93.0 g OC m−2 yr−1 and averaged 24.8 g OC m−2 yr−1. Isotopic data from this region suggest that OC in the sediments is largely from noneelgrass sources. In general, these values are comparable to those from other temperate Z. marina meadows, but significantly lower than previously reported values for seagrasses globally. These results further highlight the need for local and species‐level quantification of blue carbon parameters. While temperate eelgrass meadows may not sequester and store as much carbon as seagrass meadows elsewhere, climate policy incentives should still be implemented to protect existing sediment carbon stocks and the other critical ecosystem services associated with eelgrass habitats.

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“…The literature is equivocal regarding the effects of eutrophication on seagrass carbon storage and burial, reporting both higher storage and burial due to an increased input of sestonic particles (Gacia et al, 2002;Mazarrasa et al, 2017;Samper-Villarreal et al, 2017), and decreased storage and burial due to detrimental effects on seagrass productivity and survival (Macreadie et al, 2012;Jiang et al, 2018). Here, the level of eutrophication appeared to increase C stock (Figures 4C-F and Table 1), suggesting that Danish eelgrass meadows have a relatively high reliance on allochthonous carbon (Oreska et al, 2017b). In fact, for 10 of the sites used in this study, the eelgrass net primary production only explained 2.3% of the variation in C stock indicating a low contribution of autochthonous carbon (Röhr et al, 2016).…”

Section: Eutrophication Effects On Eelgrass Sediment Stocksmentioning

confidence: 93%

Sediment Stocks of Carbon, Nitrogen, and Phosphorus in Danish Eelgrass Meadows

et al. 2018

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Seagrass ecosystems provide an array of ecosystem services ranging from habitat provision to erosion control. From a climate change and eutrophication mitigation perspective, the ecosystem services include burial and storage of carbon and nutrients in the sediments. Eelgrass (Zostera marina) is the most abundant seagrass species along the Danish coasts, and while its function as a carbon and nutrient sink has been documented in some areas, the spatial variability of these functions, and the drivers behind them, are not well understood. Here we present the first nationwide study on eelgrass sediment stock of carbon (C stock ), nitrogen (N stock ), and phosphorus (P stock ). Stocks were measured in the top 10 cm of eelgrass meadows spanning semi-enclosed estuaries (inner and outer fjords) to open coasts. Further, we assessed environmental factors (level of exposure, sediment properties, level of eutrophication) from each area to evaluate their relative importance as drivers of the spatial pattern in the respective stocks. We found large spatial variability in sediment stocks, representing 155-4413 g C m −2 , 24-448 g N m −2 , and 7-34 g P m −2 . C stock and N stock were significantly higher in inner fjords compared to outer fjords and open coasts. C stock , N stock , and P stock showed a significantly positive relationship with the silt-clay content in the sediments. Moreover, C stock was also significantly higher in more eutrophied areas with high concentrations of nutrients and chlorophyll a (chl a) in the water column. Conversely, siltclay content was not related to nutrients or chl a, suggesting a spatial dependence of the importance of these factors in driving stock sizes and implying that local differences in sediment properties and eutrophication level should be included when evaluating the storage capacity of carbon, nitrogen, and phosphorus in Danish eelgrass meadows. These insights provide guidance to managers in selecting priority areas for carbon and nutrient storage for climate-and eutrophication mitigation initiatives.

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Non‐seagrass carbon contributions to seagrass sediment blue carbon

Cited by 50 publications

References 60 publications

Reduced water motion enhances organic carbon stocks in temperate eelgrass meadows

Reduced water motion enhances organic carbon stocks in temperate eelgrass meadows

A Synthesis of Blue Carbon Stocks, Sources, and Accumulation Rates in Eelgrass (Zostera marina) Meadows in the Northeast Pacific

Sediment Stocks of Carbon, Nitrogen, and Phosphorus in Danish Eelgrass Meadows

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