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Non‐seagrass carbon contributions to seagrass sediment blue carbon
Author(s) -
Oreska Matthew P. J.,
Wilkinson Grace M.,
McGlathery Karen J.,
Bost Molly,
McKee Brent A.
Publication year - 2018
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.1002/lno.10718
Subject(s) - seagrass , spartina alterniflora , blue carbon , zostera marina , environmental science , salt marsh , sediment , benthic zone , total organic carbon , oceanography , carbon fibers , ecology , marsh , ecosystem , wetland , geology , biology , geomorphology , materials science , composite number , composite material
Non‐seagrass sources account for ∼ 50% of the sediment organic carbon (SOC) in many seagrass beds, a fraction that may derive from external organic matter (OM) advected into the meadow and trapped by the seagrass canopy or produced in situ. If allochthonous carbon fluxes are responsible for the non‐seagrass SOC in a given seagrass bed, this fraction should decrease with distance from the meadow perimeter. Identifying the spatial origin of SOC is important for closing seagrass carbon budgets and “blue carbon” offset‐credit accounting, but studies have yet to quantify and map seagrass SOC stocks by carbon source. We measured sediment δ 13 C, δ 15 N, and δ 34 S throughout a large (6 km 2 ), restored Zostera marina (eelgrass) meadow and applied Bayesian mixing models to quantify total SOC contributions from possible autotroph sources, Z. marina , Spartina alterniflora , and benthic microalgae (BMA). Z. marina accounted for < 40% of total meadow SOC, but we did not find evidence for outwelling from the fringing S. alterniflora salt‐marsh or OM advection from bare subtidal areas. S. alterniflora SOC contributions averaged 10% at sites both inside and outside of the meadow. The BMA fraction accounted for 51% of total meadow SOC and was highest at sites furthest from the bare subtidal‐meadow edge, indicative of in situ production. 210 Pb profiles confirmed that meadow‐enhanced sedimentation facilitates the burial of in situ BMA. Deducting this contribution from total SOC would underestimate total organic carbon fixation within the meadow. Seagrass meadows can enhance BMA burial, which likely accounts for most of the non‐seagrass SOC stored in many seagrass beds.