Seagrass losses since mid-20th century fuelled CO emissions from soil carbon stocks
Salinas, Cristian (Edith Cowan University. School of Science)
Duarte, Carlos M.. (Red Sea Research Center)
Lavery, Paul S. (Edith Cowan University. School of Science)
Masqué Barri, Pere (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)
Arias Ortiz, Ariane (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)
Leon, Javier X. (University of the Sunshine Coast. Global Change Ecology Research Group)
Callaghan, David (The University of Queensland. School of Civil Engineering)
Kendrick, G. A.. (The UWA Oceans Institute)
Serrano, Oscar (Edith Cowan University. School of Science)

Data:	2020
Resum:	Seagrass meadows store globally significant organic carbon (Corg) stocks which, if disturbed, can lead to CO2 emissions, contributing to climate change. Eutrophication and thermal stress continue to be a major cause of seagrass decline worldwide, but the associated CO2 emissions remain poorly understood. This study presents comprehensive estimates of seagrass soil Corg erosion following eutrophication-driven seagrass loss in Cockburn Sound (23 km2 between 1960s and 1990s) and identifies the main drivers. We estimate that shallow seagrass meadows (<5 m depth) had significantly higher Corg stocks in 50 cm thick soils (4. 5 ± 0. 7 kg Corg/m2) than previously vegetated counterparts (0. 5 ± 0. 1 kg Corg/m2). In deeper areas (>5 m), however, soil Corg stocks in seagrass and bare but previously vegetated areas were not significantly different (2. 6 ± 0. 3 and 3. 0 ± 0. 6 kg Corg/m2, respectively). The soil Corg sequestration capacity prevailed in shallow and deep vegetated areas (55 ± 11 and 21 ± 7 g Corg m−2 year−1, respectively), but was lost in bare areas. We identified that seagrass canopy loss alone does not necessarily drive changes in soil Corg but, when combined with high hydrodynamic energy, significant erosion occurred. Our estimates point at ~0. 20 m/s as the critical shear velocity threshold causing soil Corg erosion. We estimate, from field studies and satellite imagery, that soil Corg erosion (within the top 50 cm) following seagrass loss likely resulted in cumulative emissions of 0. 06–0. 14 Tg CO2-eq over the last 40 years in Cockburn Sound. We estimated that indirect impacts (i. e. eutrophication, thermal stress and light stress) causing the loss of ~161,150 ha of seagrasses in Australia, likely resulted in the release of 11–21 Tg CO2-eq since the 1950s, increasing cumulative CO2 emissions from land-use change in Australia by 1. 1%–2. 3% per annum. The patterns described serve as a baseline to estimate potential CO2 emissions following disturbance of seagrass meadows.
Ajuts:	Ministerio de Economía y Competitividad MDM2015-0552 Agència de Gestió d'Ajuts Universitaris i de Recerca 2017/SGR-1588
Nota:	Unidad de excelencia María de Maeztu CEX2019-000940-M
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, sempre que no sigui amb finalitats comercials, i sempre que es reconegui l'autoria de l'obra original.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	Blue Carbon ; Carbon sinks ; Climate change ; Conservation ; Erosion ; Eutrophication ; Seagrass meadows
Publicat a:	Global change biology, Vol. 26, issue 9 (Sep. 2020) , p. 4772-4784, ISSN 1365-2486

DOI: 10.1111/gcb.15204
PMID: 32633058

13 p, 2.1 MB

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