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

Abstract. Salt marshes and seagrass meadows can sequester and store high quantities of organic carbon (OC) in their sediments relative to other marine and terrestrial habitats. Assessing carbon stocks, carbon sources, and the transfer of carbon between habitats within coastal seascapes are each integral in identifying the role of blue carbon habitats in coastal carbon cycling. Here, we quantified carbon stocks, sources, and exchanges in seagrass meadows, salt marshes, and unvegetated sediments in six bays along the California coast. In the top 20 cm of sediment, the salt marshes contained approximately twice as much OC as seagrass meadows did, 4.92 ± 0.36 kg OC m−2 compared to 2.20 ± 0.24 kg OC m−2, respectively. Both salt marsh and seagrass sediment carbon stocks were higher than previous estimates from this region but lower than global and US-wide averages, respectively. Seagrass-derived carbon was deposited annually into adjacent marshes during fall seagrass senescence. However, isotope mixing models estimate that negligible amounts of this seagrass material were ultimately buried in underlying sediment. Rather, the vast majority of OC in sediment across sites was likely derived from planktonic/benthic diatoms and/or C3 salt marsh plants.

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Blue Carbon Stocks and Exchanges Along the Pacific West Coast

10.5194/bg-2021-27 ◽

2021 ◽

Author(s):

Melissa A. Ward ◽

Tessa M. Hill ◽

Chelsey Souza ◽

Tessa Filipczyk ◽

Aurora M. Ricart ◽

...

Keyword(s):

Salt Marsh ◽

Salt Marshes ◽

Carbon Sources ◽

Carbon Stocks ◽

Blue Carbon ◽

Seagrass Meadows ◽

The Pacific ◽

Terrestrial Habitats ◽

Isotope Mixing Models ◽

Sediment Carbon

Abstract. Salt marshes and seagrass meadows can sequester and store high quantities of organic carbon (OC) in their sediments relative to other marine and terrestrial habitats. Assessing carbon stocks, carbon sources, and the transfer of carbon between habitats within coastal seascapes are each integral in identifying the role of blue carbon habitats in coastal carbon cycling. Here, we quantified carbon stocks, sources, and exchanges in seagrass meadows, salt marshes, and unvegetated sediments in six bays along the Pacific coast of California. The salt marshes studied here contained approximately twice as much OC as did seagrass meadows, 23.51 ± 1.77 kg OC m−3 compared to 11.01 ± 1.18 kg OC m−3, respectively. Both seagrass and salt marsh sediment carbon stocks were higher than previous estimates from this region but lower than global and U.S.-wide averages, respectively. Seagrass-derived carbon was deposited annually into adjacent marshes during fall seagrass senescence. However, isotope mixing models estimate that negligible amounts of this seagrass material were ultimately buried in underlying sediment. Rather, the vast majority of OC in sediment across sites was likely derived from planktonic/benthic diatoms and C3 salt marsh plants.

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Factors Influencing Carbon Stocks and Accumulation Rates in Eelgrass Meadows Across New England, USA

Estuaries and Coasts ◽

10.1007/s12237-020-00754-9 ◽

2020 ◽

Vol 43 (8) ◽

pp. 2076-2091 ◽

Cited By ~ 1

Author(s):

A. B. Novak ◽

M. C. Pelletier ◽

P. Colarusso ◽

J. Simpson ◽

M. N. Gutierrez ◽

...

Keyword(s):

Grain Size ◽

New England ◽

Structural Characteristics ◽

Sediment Cores ◽

Carbon Stocks ◽

Carbon Accumulation ◽

Accumulation Rates ◽

Seagrass Meadows ◽

Terrestrial Habitats ◽

C And N

Abstract Increasing the protection of coastal vegetated ecosystems has been suggested as one strategy to compensate for increasing carbon dioxide (CO2) in the atmosphere as the capacity of these habitats to sequester and store carbon exceeds that of terrestrial habitats. Seagrasses are a group of foundation species that grow in shallow coastal and estuarine systems and have an exceptional ability to sequester and store large quantities of carbon in biomass and, particularly, in sediments. However, carbon stocks (Corg stocks) and carbon accumulation rates (Corg accumulation) in seagrass meadows are highly variable both spatially and temporally, making it difficult to extrapolate this strategy to areas where information is lacking. In this study, Corg stocks and Corg accumulation were determined at 11 eelgrass meadows across New England, representing a range of eutrophication and exposure conditions. In addition, the environmental factors and structural characteristics of meadows related to variation in Corg stocks were identified. The objectives were accomplished by assessing stable isotopes of δ13C and δ15N as well as %C and %N in plant tissues and sediments, measuring grain size and 210Pb of sediment cores, and through assessing site exposure. Variability in Corg stocks in seagrass meadows is well predicted using commonly measured environmental variables such as grain size distribution. This study allows incorporation of data and insights for the northwest Atlantic, where few studies on carbon sequestration by seagrasses have been conducted.

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Lagoon Biogeochemical Processing is Reflected in Spatial Patterns of Sediment Stable Isotopic Ratios

Journal of Marine Science and Engineering ◽

10.3390/jmse8110874 ◽

2020 ◽

Vol 8 (11) ◽

pp. 874

Author(s):

Elizabeth Burke Watson ◽

Alejandro Hinojosa-Corona ◽

Johannes R. Krause ◽

Juan Carlos Herguera ◽

Julianna McDonnell ◽

...

Keyword(s):

Stable Isotope ◽

Spatial Patterns ◽

Nitrogen Isotopes ◽

Carbon Accumulation ◽

Isotopic Ratios ◽

Spatial Gradients ◽

Seagrass Meadows ◽

The Pacific ◽

Stable Isotopic ◽

Sediment Carbon

The spatial analysis of biota, particulate organic matter, and sediments for stable isotopes of carbon (δ13C), nitrogen (δ15N), and sulfur (δ34S) have proved useful for identifying patterns in productivity, nutrient pollution, and relationships between biological and physiochemical variables at the local and global scales. Yet such approaches are rarely applied to studies of lagoon or estuarine metabolism. Focusing on Bahía San Quintín, a heterotrophic seagrass-dominated lagoon on the Pacific coast of Baja California, México, we report on spatial patterns in surficial sediment CNS stable isotopic ratios as tracers of lagoon biogeochemical function. Stable nitrogen isotopes highlighted potential spatial variability in the balance between denitrification and nitrogen-fixation within the lagoon and identified an association between elevated δ15N levels and oyster culture, suggesting that oyster presence may be enhancing N2 production. Spatial patterns in δ34S covaried with sediment particle size, underlining the importance of sediment texture in determining the depth of sub-oxic-anoxic redox zones. Sediment carbon stable isotope ratios highlighted the lack of incorporation of seagrass carbon into seagrass meadow sediments, thus emphasizing the importance of phytoplankton or microphytobenthos for carbon accumulation in seagrass meadows. This report highlights the value of sediment isotopic values in corroborating spatial patterns in estuarine metabolism or macronutrient processing identified from chamber or flux-based studies. Stable isotope mapping can provide a useful addition to assessment of estuarine metabolism, or act as a stand-alone tool for generating hypotheses, identifying the influence of spatial gradients, and/or suggesting prime locations for investigation of microbial abundance or function.

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Environmental drivers of sediment carbon storage in temperate seagrass meadows

Hydrobiologia ◽

10.1007/s10750-019-04153-5 ◽

2019 ◽

Vol 847 (7) ◽

pp. 1773-1792 ◽

Cited By ~ 6

Author(s):

Mariana do Amaral Camara Lima ◽

Raymond D. Ward ◽

Chris B. Joyce

Keyword(s):

Carbon Storage ◽

Environmental Drivers ◽

Seagrass Meadows ◽

Sediment Carbon

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Biomass and productivity of seagrasses in Africa

Botanica Marina ◽

10.1515/bot-2015-0075 ◽

2016 ◽

Vol 59 (2-3) ◽

Cited By ~ 5

Author(s):

Michael N. Githaiga ◽

Linda Gilpin ◽

James G. Kairo ◽

Mark Huxham

Keyword(s):

West Africa ◽

East Africa ◽

Carbon Stocks ◽

Seagrass Ecosystems ◽

Stocks And Flows ◽

Below Ground ◽

The Mean ◽

Sediment Carbon

AbstractThere is growing interest in carbon stocks and flows in seagrass ecosystems, but recent global reviews suggest a paucity of studies from Africa. This paper reviews work on seagrass productivity, biomass and sediment carbon in Africa. Most work was conducted in East Africa with a major geographical gap in West Africa. The mean above-ground, below-ground and total biomasses from all studies were 174.4, 474.6 and 514 g DW m

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Seagrass Recovery Following Marine Heat Wave Influences Sediment Carbon Stocks

Frontiers in Marine Science ◽

10.3389/fmars.2020.576784 ◽

2021 ◽

Vol 7 ◽

Author(s):

Lillian R. Aoki ◽

Karen J. McGlathery ◽

Patricia L. Wiberg ◽

Matthew P. J. Oreska ◽

Amelie C. Berger ◽

...

Keyword(s):

Heat Wave ◽

Heat Waves ◽

Central Area ◽

Shoot Density ◽

Seagrass Meadows ◽

C Stocks ◽

Sediment Carbon ◽

The Impact ◽

Marine Heat Wave

Worldwide, seagrass meadows accumulate significant stocks of organic carbon (C), known as “blue” carbon, which can remain buried for decades to centuries. However, when seagrass meadows are disturbed, these C stocks may be remineralized, leading to significant CO2 emissions. Increasing ocean temperatures, and increasing frequency and severity of heat waves, threaten seagrass meadows and their sediment blue C. To date, no study has directly measured the impact of seagrass declines from high temperatures on sediment C stocks. Here, we use a long-term record of sediment C stocks from a 7-km2, restored eelgrass (Zostera marina) meadow to show that seagrass dieback following a single marine heat wave (MHW) led to significant losses of sediment C. Patterns of sediment C loss and re-accumulation lagged patterns of seagrass recovery. Sediment C losses were concentrated within the central area of the meadow, where sites experienced extreme shoot density declines of 90% during the MHW and net losses of 20% of sediment C over the following 3 years. However, this effect was not uniform; outer meadow sites showed little evidence of shoot declines during the MHW and had net increases of 60% of sediment C over the following 3 years. Overall, sites with higher seagrass recovery maintained 1.7x as much C compared to sites with lower recovery. Our study demonstrates that while seagrass blue C is vulnerable to MHWs, localization of seagrass loss can prevent meadow-wide C losses. Long-term (decadal and beyond) stability of seagrass blue C depends on seagrass resilience to short-term disturbance events.

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