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. 2020 Apr 30;10(1):7325.
doi: 10.1038/s41598-020-64094-1.

The greenhouse gas offset potential from seagrass restoration

Matthew P J Oreska  1 , Karen J McGlathery  2 , Lillian R Aoki  2   3 , Amélie C Berger  2 , Peter Berg  2 , Lindsay Mullins  2   4
Affiliations

The greenhouse gas offset potential from seagrass restoration

Matthew P J Oreska et al. Sci Rep. .

Abstract

Awarding CO2 offset credits may incentivize seagrass restoration projects and help reverse greenhouse gas (GHG) emissions from global seagrass loss. However, no study has quantified net GHG removal from the atmosphere from a seagrass restoration project, which would require coupled Corg stock and GHG flux enhancement measurements, or determined whether the creditable offset benefit can finance the restoration. We measured all of the necessary GHG accounting parameters in the 7-km2 Zostera marina (eelgrass) meadow in Virginia, U.S.A., part of the largest, most cost-effective meadow restoration to date, to provide the first seagrass offset finance test-of-concept. Restoring seagrass removed 9,600 tCO2 from the atmosphere over 15 years but also enhanced both CH4 and N2O production, releasing 950 tCO2e. Despite tripling the N2O flux to 0.06 g m-2 yr-1 and increasing CH4 8-fold to 0.8 g m-2 yr-1, the meadow now offsets 0.42 tCO2e ha-1 yr-1, which is roughly equivalent to the seagrass sequestration rate for GHG inventory accounting but lower than the rates for temperate and tropical forests. The financial benefit for this highly successful project, $87 K at $10 MtCO2e-1, defrays ~10% of the restoration cost. Managers should also consider seagrass co-benefits, which provide additional incentives for seagrass restoration.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Seagrass meadow sediment Corg concentrations are typically highest below the surface in a region corresponding with the rhizosphere and approach the background concentration observed at unvegetated sites with increasing depth (data adapted from Greiner et al. and used with permission). The seagrass-enhanced sediment Corg stock (light gray) can be quantified by integrating the area under the profile and subtracting the background Corg stock that one would expect to find absent the meadow (dark gray); note that this approach does not require establishing a reference plane or quantifying bed accretion (black gradient) attributable to the meadow by sediment dating.
Figure 2
Figure 2
The South Bay, Virginia, study area, showing the locations of biomass and sediment Corg sample sites (black circles), original restoration seed plots (established in 2000–2001: Orth et al., the central meadow extent prior to sampling in 2013, and the expanded meadow extent prior to sampling in 2016. Meadow expansion areas to the west and south (light green areas enclosed by dashed lines) were excluded from the net GHG benefit calculations in this study. The figure was created in ArcGIS 10.2 (www.esri.com) and Photoshop CS6 (www.adobe.com).
Figure 3
Figure 3
Sequestered GHG pools (aboveground biomass - AGB, belowground biomass - BGB, and net sediment Corg – SOC) in 2013 and in 2016 resulting from seagrass restoration; maps generated by kriging data measured at sample sites (n = 21: circles in inset map); note that the bed volume has changed over time due to both meadow expansion and accretion (see Supplement). The mid-meadow SOC decline in the 2016 accreted interval reflects a local seagrass die-off event in 2015. The figure was created in ArcGIS 10.2 (www.esri.com) and Photoshop CS6 (www.adobe.com).
Figure 4
Figure 4
CH4 (A) and N2O (B) ebullition flux (μmol m−2 hr−1) box plots (quartiles) at sites (n = 10) by observation month (Oct. 2015–Oct. 2016) and by treatment (bare and seagrass). See Table 4 for log-likelihood ratio test results for assessing the treatment effect.
Figure 5
Figure 5
Porewater profile CH4 concentrations measured at bare and seagrass sites in August (A: site n = 6) and in October 2016 (B: site n = 4).
Figure 6
Figure 6
Cumulative background (A) and gross meadow (B) GHG stocks in the meadow areas over time; sequestration (i.e., GHG uptake from the atmosphere) in this figure is shown as positive, GHG release (i.e., a GHG flux to the atmosphere) is negative; CH4 and N2O quantities were standardized to CO2e; ‘CaCO3’ relates CO2 evasion attributable to CaCO3; background stocks were calculated by scaling average bare site values by total meadow area at each time step; net stock enhancement attributable to the meadow (see Table 3) can be calculated by subtracting the bare values (A) from equivalent gross meadow values (B); Error bars represent SE for the sediment Corg (SOC) stock.
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References

    1. Duarte CM, Middelburg JJ, Caraco N. Major role of marine vegetation on the oceanic carbon cycle. Biogeosciences. 2005;2:1–8. doi: 10.5194/bg-2-1-2005. - DOI
    1. Champenois W, Borges AV. Seasonal and interannual variations of community metabolism rates of a Posidonia oceanica seagrass meadow. Limnol. Oceanogr. 2012;57(1):347–361. doi: 10.4319/lo.2012.57.1.0347. - DOI
    1. Tokoro T, et al. Net uptake of atmospheric CO2 by coastal submerged aquatic vegetation. Glob. Chang. Biol. 2014;20(6):1873–1884. doi: 10.1111/gcb.12543. - DOI - PMC - PubMed
    1. Gullström M, et al. Blue carbon storage in tropical seagrass meadows relates to carbonate stock dynamics, plant sediment processes, and landscape context: insights from the Western Indian Ocean. Ecosys. 2018;21:511–566. doi: 10.1007/s10021-017-0170-8. - DOI
    1. Fourqurean JW, et al. Seagrass ecosystems as a globally significant carbon stock. Nat. Geosci. 2012;5:505–509. doi: 10.1038/ngeo1477. - DOI

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