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Blue carbon stocks of great barrier reef deep-water seagrasses

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journal contribution
posted on 2018-12-12, 00:00 authored by P H York, Peter MacreadiePeter Macreadie, M A Rasheed
© 2018 The Author(s) Published by the Royal Society. All rights reserved. Shallow-water seagrasses capture and store globally significant quantities of organic carbon (OC), often referred to as 'Blue Carbon'; however, data are lacking on the importance of deep-water (greater than 15 m) seagrasses as Blue Carbon sinks. We compared OC stocks from deep-, mid- A nd shallow-water seagrasses at Lizard Island within the Great Barrier Reef (GBR) lagoon. We found deep-water seagrass (Halophila species) contained similar levels of OC to shallow-water species (e.g. Halodule uninervis) (0.64 ± 0.08% and 0.9 ± 0.1 mg C cm-3, 0.87 ± 0.19% and 1.3 ± 0.3 mg C cm-3, respectively), despite being much sparser and smaller in stature. Deep-water seagrass sediments contained significantly higher levels (approx. ninefold) of OC than surrounding bare areas. Inorganic carbon (CaCO3) levels were relatively high in deep-water seagrass sediments (8.2 ± 0.4%) and, if precipitated from epiphytes within the meadow, could offset the potential CO2-sink capacity of these meadows. The δ13C signatures of sediment samples varied among depths and habitats (-10.9 and-17.0), reflecting contributions from autochthonous and allochthonous sources. If the OC stocks reported in this study are similar to deep-water Halophila meadows elsewhere within the GBR lagoon (total area 31 000 km2), then OC bound within this system is roughly estimated at 27.4 million tonnes.

History

Journal

Biology letters

Volume

14

Issue

12

Publisher

Royal Society Publishing

Location

London, Eng.

ISSN

1744-9561

eISSN

1744-957X

Language

eng

Publication classification

C Journal article; C1 Refereed article in a scholarly journal

Copyright notice

2018, The Authors