AUTHOR=Bedulli Camila , Lavery Paul S. , Harvey Matt , Duarte Carlos M. , Serrano Oscar 

TITLE=Contribution of Seagrass Blue Carbon Toward Carbon Neutral Policies in a Touristic and Environmentally-Friendly Island

JOURNAL=Frontiers in Marine Science

VOLUME=7

YEAR=2020

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2020.00001

DOI=10.3389/fmars.2020.00001

ISSN=2296-7745

ABSTRACT=<p>Estimates of organic carbon (C<sub>org</sub>) storage by seagrass meadows which consider inter-habitat variability are essential to understand their potential to sequester carbon dioxide (CO<sub>2</sub>) and derive robust global and regional estimates of blue carbon storage. In this study, we provide baseline estimates of seagrass extent, and soil C<sub>org</sub> stocks and accumulation rates from different seagrass habitats at Rottnest Island (in <italic>Amphibolis</italic> spp., <italic>Posidonia</italic> spp., <italic>Halophila ovalis</italic>, and mixed <italic>Posidonia/Amphibolis</italic> spp. meadows). The C<sub>org</sub> stocks in 0.5 m thick seagrass soil deposits, derived from 24 cores, were 5.1 ± 0.7 kg C<sub>org</sub> m<sup>–2</sup> (mean ± SE, ranging from 0.05 to 12.9 kg C<sub>org</sub> m<sup>–2</sup>), accumulating at 23.2 ± 3.2 g C<sub>org</sub> m<sup>–2</sup> year<sup>–1</sup> (ranging from 0.22 to 58.9 g C<sub>org</sub> m<sup>–2</sup> year<sup>–1</sup>) over the last decades. There were significant differences in C<sub>org</sub> content (%) and stocks (mg C<sub>org</sub> cm<sup>–3</sup>), stable carbon isotope composition of the soil organic matter (δ<sup>13</sup>C), and soil grain size among the seagrass meadows studied, highlighting that biotic and abiotic factors influence seagrass soil C<sub>org</sub> storage. Mixed meadows of <italic>Posidonia/Amphibolis</italic> spp. and monospecific meadows of <italic>Posidonia</italic> spp. and <italic>Amphibolis</italic> spp. had the highest C<sub>org</sub> stocks (ranging from 6.2 to 6.4 kg C<sub>org</sub> m<sup>–2</sup>), while <italic>Halophila</italic> spp. meadows had the lowest C<sub>org</sub> stocks (1.2 ± 0.6 kg C<sub>org</sub> m<sup>–2</sup>). We estimated a total soil C<sub>org</sub> stock of 48.1 ± 8.5 Gg C<sub>org</sub> beneath the 755 ha of Rottnest Island’s seagrasses, and a C<sub>org</sub> sequestration capacity of 0.81 ± 0.06 Gg C<sub>org</sub> year<sup>–1</sup>, which is equivalent to the sequestration of ∼22% of the island’s current annual CO<sub>2</sub> emissions. Our results contribute to the existing global dataset on seagrass soil C<sub>org</sub> storage and show a significant potential of seagrass to sequester CO<sub>2</sub>, which are particularly relevant in the context of achieving carbon neutrality through conservation actions in environmentally-marketed, tourist destinations such as Rottnest Island.</p>