Seagrass sediments as a global carbon sink: Isotopic constraints

Authors

Hilary Kennedy, School of Ocean Sciences, Bangor UniversityFollow
Jeff Beggins, Seagrass Recovery, Incorporated, Indian Rocks Beach
Carlos M. Duarte, Department of Global Change Research, IMEDEA, CSIC-UIBFollow
James W. Fourqurean, Department of Biological Sciences and Southeast Environmental Research Center, Florida International UniversityFollow
Marianne Holmer, Institute of Biology, University of Southern DenmarkFollow
Núria Marbà, Department of Global Change Research, IMEDEA, CSIC-UIBFollow
Jack J. Middleburg, Faculty of Geosciences, Utrecht University and Centre for Estuarine and Marine Ecology, Netherlands Institute of EcologyFollow

Abstract

Seagrass meadows are highly productive habitats found along many of the world's coastline, providing important services that support the overall functioning of the coastal zone. The organic carbon that accumulates in seagrass meadows is derived not only from seagrass production but from the trapping of other particles, as the seagrass canopies facilitate sedimentation and reduce resuspension. Here we provide a comprehensive synthesis of the available data to obtain a better understanding of the relative contribution of seagrass and other possible sources of organic matter that accumulate in the sediments of seagrass meadows. The data set includes 219 paired analyses of the carbon isotopic composition of seagrass leaves and sediments from 207 seagrass sites at 88 locations worldwide. Using a three source mixing model and literature values for putative sources, we calculate that the average proportional contribution of seagrass to the surface sediment organic carbon pool is ∼50%. When using the best available estimates of carbon burial rates in seagrass meadows, our data indicate that between 41 and 66 gC m⁻² yr⁻¹ originates from seagrass production. Using our global average for allochthonous carbon trapped in seagrass sediments together with a recent estimate of global average net community production, we estimate that carbon burial in seagrass meadows is between 48 and 112 Tg yr⁻¹, showing that seagrass meadows are natural hot spots for carbon sequestration.

Comments

This material is based upon work supported by the National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research program under Cooperative Agreements #DBI-0620409 and #DEB-9910514. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Recommended Citation

Kennedy, H., J. Beggins, C.M. Duarte, J.W. Fourqurean, M. Holmer, N. Marba, J.J. Middelburg. 2010. Seagrass sediments as a global carbon sink: Isotopic constraints. Global Biogeochemical Cycles 24: GB4026.