Presentation Abstract

Carbon storage in marine vegetated habitats (blue carbon) is increasingly being considered in carbon financing and coastal ecosystem management. Amongst other ecosystem functions, seagrass meadows are reported to be highly efficient at sequestering and storing significant amounts of carbon. However, seagrass blue carbon data remain sparse and regionally biased to tropical regions. In the Pacific Northwest, we lack information on the magnitude and variability of carbon stocks, as well as local drivers of variability. We collected sediment cores from six eelgrass meadows on the central coast of British Columbia, Canada, to quantify sedimentary organic carbon (Corg) stocks and accumulation rates. Carbon stocks exhibited 10-fold variability (335.35 – 3664. 48 g Corg m-2) in the top 20cm of sediment; these values align with other temperate eelgrass meadows, but are lower than reported global seagrass values. On average, Corg stocks within seagrass beds and adjacent unvegetated habitat overlapped, although stocks in the meadow interior (1392.05 g Corg m-2) were greater than those along meadow edges (1129.82 g Corg m-2) and in adjacent unvegetated sediments (977.10 g Corg m-2). Corg accumulation rates ranged from 12.57 to 50.45 g Corg m-2 year-1, lower than the global average reported for seagrasses (138 g Corg m-2 year-1), but again similar to other eelgrass meadows. Further, Corg in sediments beneath eelgrass meadows appears to be largely from non-eelgrass sources (terrestrial, benthic microalgae and macroalgae). Generalized linear mixed effects models suggest that hydrodynamic regime is the strongest driver of carbon stocks in the top 5cm of sediment, more important than the structural complexity of seagrass beds, or the proportion of fine sediments. Lower water velocities may allow greater deposition of particles within meadows, together with reduced erosion and resuspension. These results support physical characteristics over seagrass features as primary determinants of blue carbon storage in nearshore soft sediment habitats.

Session Title

Seagrass Cross-Border Connections: Management

Keywords

Eelgrass, Blue carbon

Conference Track

SSE4: Ecosystem Management, Policy, and Protection

Conference Name

Salish Sea Ecosystem Conference (Seattle, WA : 2018)

Document Type

Event

SSEC Identifier

SSE4-38

Start Date

5-4-2018 4:15 PM

End Date

5-4-2018 4:30 PM

Type of Presentation

Oral

Contributing Repository

Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.

Geographic Coverage

Salish Sea (B.C. and Wash.)

Rights

This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.

Type

text

Language

English

Format

application/pdf

Share

COinS
 
Apr 5th, 4:15 PM Apr 5th, 4:30 PM

Hydrodynamic regime determines the magnitude of surface sediment 'blue carbon' stocks in British Columbia eelgrass meadows

Carbon storage in marine vegetated habitats (blue carbon) is increasingly being considered in carbon financing and coastal ecosystem management. Amongst other ecosystem functions, seagrass meadows are reported to be highly efficient at sequestering and storing significant amounts of carbon. However, seagrass blue carbon data remain sparse and regionally biased to tropical regions. In the Pacific Northwest, we lack information on the magnitude and variability of carbon stocks, as well as local drivers of variability. We collected sediment cores from six eelgrass meadows on the central coast of British Columbia, Canada, to quantify sedimentary organic carbon (Corg) stocks and accumulation rates. Carbon stocks exhibited 10-fold variability (335.35 – 3664. 48 g Corg m-2) in the top 20cm of sediment; these values align with other temperate eelgrass meadows, but are lower than reported global seagrass values. On average, Corg stocks within seagrass beds and adjacent unvegetated habitat overlapped, although stocks in the meadow interior (1392.05 g Corg m-2) were greater than those along meadow edges (1129.82 g Corg m-2) and in adjacent unvegetated sediments (977.10 g Corg m-2). Corg accumulation rates ranged from 12.57 to 50.45 g Corg m-2 year-1, lower than the global average reported for seagrasses (138 g Corg m-2 year-1), but again similar to other eelgrass meadows. Further, Corg in sediments beneath eelgrass meadows appears to be largely from non-eelgrass sources (terrestrial, benthic microalgae and macroalgae). Generalized linear mixed effects models suggest that hydrodynamic regime is the strongest driver of carbon stocks in the top 5cm of sediment, more important than the structural complexity of seagrass beds, or the proportion of fine sediments. Lower water velocities may allow greater deposition of particles within meadows, together with reduced erosion and resuspension. These results support physical characteristics over seagrass features as primary determinants of blue carbon storage in nearshore soft sediment habitats.