Harnessing the climate mitigation, conservation and poverty alleviation potential of seagrasses: prospects for developing blue carbon initiatives and payment for ecosystem service programmes

Hejnowicz, Adam P.; Kennedy, Hilary; Rudd, Murray A.; Huxham, Mark

doi:10.3389/fmars.2015.00032

Cited by 73 publications

(59 citation statements)

References 205 publications

(303 reference statements)

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“…As more studies emerge on the impacts of seagrass disturbance on SOC stocks and associated biogeochemical processes, we will better understand if the findings here are typical of other types of disturbances. Overall, the findings of this study, as well as other recent work on the carbonsink capacity of restored seagrass meadows [30,32,37], provide promising evidence that restoration of seagrass meadows represents an important strategy for offsetting carbon emissions and thereby mitigating climate change.…”

Section: Discussionsupporting

confidence: 60%

Losses and recovery of organic carbon from a seagrass ecosystem following disturbance

et al. 2015

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Seagrasses are among the Earth's most efficient and long-term carbon sinks, but coastal development threatens this capacity. We report new evidence that disturbance to seagrass ecosystems causes release of ancient carbon. In a seagrass ecosystem that had been disturbed 50 years ago, we found that soil carbon stocks declined by 72%, which, according to radiocarbon dating, had taken hundreds to thousands of years to accumulate. Disturbed soils harboured different benthic bacterial communities (according to 16S rRNA sequence analysis), with higher proportions of aerobic heterotrophs compared with undisturbed. Fingerprinting of the carbon (via stable isotopes) suggested that the contribution of autochthonous carbon (carbon produced through plant primary production) to the soil carbon pool was less in disturbed areas compared with seagrass and recovered areas. Seagrass areas that had recovered from disturbance had slightly lower (35%) carbon levels than undisturbed, but more than twice as much as the disturbed areas, which is encouraging for restoration efforts. Slow rates of seagrass recovery imply the need to transplant seagrass, rather than waiting for recovery via natural processes. This study empirically demonstrates that disturbance to seagrass ecosystems can cause release of ancient carbon, with potentially major global warming consequences. 1. Background Seagrass ecosystems are among the most effective carbon sinks on the Earth; they bury organic carbon (often referred to as 'blue carbon') into the seabed at a rate 35 times faster than tropical rainforests [1], and where rainforests bury carbon for decades, seagrasses are capable of storing carbon for millennia [2-4]. However, there is concern that if seagrass ecosystems are disturbed they could leak vast amounts of stored carbon back into the atmosphere, thereby shifting them from carbon sinks into carbon sources [5,6], as has been shown for high-profile terrestrial carbon sinks such as forests, peatlands and perma-frost [7-9]. Importantly, the latter studies show that the rate of carbon loss is much greater than the rate of accumulation. While loss of stored carbon has been demonstrated for other coastal vegetated habitats, such as saltmarshes and mangroves [10-12], there is still major uncertainty regarding whether seagrass ecosystems release soil carbon following disturbance [1]. Fourqurean et al. [13], who provided the first comprehensive survey of seagrass carbon stocks, estimated that present rates of decline in the aerial extent of seagrass ecosystems could result in the release of up to 299Tg carbon per year, assuming all of the organic carbon in seagrass biomass and the top metre of seagrass soils is remineralized (broken down and released

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Section: Discussionsupporting

confidence: 60%

Losses and recovery of organic carbon from a seagrass ecosystem following disturbance

et al. 2015

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“…Seagrasses are highly valued for nutrient processing and providing habitat for commercially important species; carbon sequestration and storage could provide an additional ecosystem service to promote conservation of this threatened, globally declining ecosystem (Waycott et al ; Hejnowicz et al ). Our analyses show that net CO 2 sequestration by seagrasses cannot simply be calculated by measuring existing C org stocks because of the relationships between net primary production and inorganic carbon reactions that also influence atmosphere‐ecosystem CO 2 flux.…”

Section: Resultsmentioning

confidence: 99%

“…First order approximations of integrated, long term net CO 2 invasion related to changes in water column pCO 2 can be made by taking inventory of the products of calcification and biological metabolism remaining in the sediment (i.e., particulate C org and C inorg ). The C org stored beneath seagrasses is assessed in terms of CO 2 (Fourqurean et al a ) and the CO 2 mitigation potential is referenced as grounds for seagrass conservation (Howard et al ; Hejnowicz et al ). Mazarrasa et al () have compared molar C org : C inorg content of seagrass sediments, indicating a slight trend toward C inorg dominance, and C inorg outweighs C org in all recorded regions (Table ); perhaps more emphasis needs to be placed on its importance to pCO 2 in water and exchange with the atmosphere.…”

Section: Discussionmentioning

confidence: 99%

CO₂ released by carbonate sediment production in some coastal areas may offset the benefits of seagrass “Blue Carbon” storage

Howard

Creed

Aguiar

et al. 2017

Limnology & Oceanography

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Seagrass ecosystems have been identified as long-term carbon sinks whose conservation could serve as a tool to mitigate carbon emissions. Seagrasses alter landscapes in a way that stimulates carbon biosequestration, but discussions of their role in atmospheric CO 2 mitigation disregard the co-occurring inorganic carbon cycle, whose antagonist effect on CO 2 sequestration can buffer and potentially outweigh the effects of C org production on net carbon exchange with the atmosphere. This study examines the extent of both organic carbon (C org ) and inorganic carbon (C inorg ) stocks as proxies for long-term production and calcification in the poorly studied seagrass meadows of southeastern (SE) Brazil and compares values to Florida Bay (U.S.A.), a well-studied system known for both high autotrophy and calcification, representing extremes of CaCO 3 soil content. Seagrass soils in SE Brazil contain an average of 67.6 6 14.7 Mg C org ha 21 in the top 1 m, compared to an average of 175.0 6 20.4 Mg C org ha 21 for their counterparts in Florida Bay. C inorg as CaCO 3 in SE Brazil averaged 141.5 6 60.0 Mg C inorg ha 21 in the top meter of soil while the warmer, calcification-promoting waters of Florida Bay had higher soil C inorg areal stock, averaging 754.6 6 26.7 Mg C inorg ha 21 . When the CO 2 evasion related to CaCO 3 production is considered, seagrass ecosystems with high CaCO 3 content may have CO 2 sequestered via C org accumulation negated by CO 2 produced by calcification. These findings prompt the reconsideration of carbon inventory methods and encourage regionally-and community-specific assessments of CO 2 sequestration abilities of seagrass ecosystems.

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“…There is increasing interest in the use of Payments for Ecosystem Services (PES) to support seagrass conservation (Hejnowicz et al . ), particularly with respect to their value for trapping and storing carbon dioxide. This type of financing offers considerable wider benefits for the economic well‐being of stakeholders, but it is important to realize that our understanding of the long‐term societal implications of such initiatives (particularly within the marine environment) remains in its infancy.…”

Section: Strategies For Actionmentioning

confidence: 99%

Strategies to enhance the resilience of the world's seagrass meadows

Cullen-Unsworth

Unsworth

2016

Journal of Applied Ecology

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Harnessing the climate mitigation, conservation and poverty alleviation potential of seagrasses: prospects for developing blue carbon initiatives and payment for ecosystem service programmes

Abstract: Harnessing the climate mitigation, conservation and poverty alleviation potential of seagrasses: prospects for developing blue carbon initiatives and payment for ecosystem service programmes.

Cited by 73 publications

References 205 publications

Losses and recovery of organic carbon from a seagrass ecosystem following disturbance

Losses and recovery of organic carbon from a seagrass ecosystem following disturbance

CO₂ released by carbonate sediment production in some coastal areas may offset the benefits of seagrass “Blue Carbon” storage

Strategies to enhance the resilience of the world's seagrass meadows

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Harnessing the climate mitigation, conservation and poverty alleviation potential of seagrasses: prospects for developing blue carbon initiatives and payment for ecosystem service programmes

Abstract: Harnessing the climate mitigation, conservation and poverty alleviation potential of seagrasses: prospects for developing blue carbon initiatives and payment for ecosystem service programmes.

Cited by 73 publications

References 205 publications

Losses and recovery of organic carbon from a seagrass ecosystem following disturbance

Losses and recovery of organic carbon from a seagrass ecosystem following disturbance

CO2 released by carbonate sediment production in some coastal areas may offset the benefits of seagrass “Blue Carbon” storage

Strategies to enhance the resilience of the world's seagrass meadows

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CO₂ released by carbonate sediment production in some coastal areas may offset the benefits of seagrass “Blue Carbon” storage