Abstract
Increasing threats to natural ecosystems from local and global stressors are reinforcing the need for baseline data on the distribution and abundance of organisms. We quantified spatial and/or temporal patterns of seagrass distribution, shoot density, leaf area index, biomass, productivity, and sediment carbon content in shallow water (0–5 m) at Lizard Island, Great Barrier Reef, Australia, in field surveys conducted in December 2011 and October 2012. Seagrass meadows were mapped using satellite imagery and field validation. A total of 18.3 ha of seagrass, composed primarily of Thalassiahemprichii and Halodule uninervis, was mapped in shallow water. This was 46% less than the area of seagrass in the same region reported in 1995, although variations in mapping methods may have influenced the magnitude of change detected. There was inter-annual variability in shoot density and length, with values for both higher in 2011 than in 2012. Seagrass properties and sediment carbon content were representative of shallow-water seagrass meadows on a mid-shelf Great Barrier Reef island. The data can be used to evaluate change, to parameterize models of the impact of anthropogenic or environmental variability on seagrass distribution and abundance, and to assess the success of management actions.
About the authors

Megan I. Saunders is a research fellow in the Global Change Institute and Marine Spatial Ecology Lab at The University of Queensland, Australia. Her interests include the effects of human stressors on coastal marine ecosystems and conservation ecology of seagrass meadows, coral reefs, mangroves and kelp beds.

Elisa Bayraktarov is a research fellow in the Global Change Institute at the University of Queensland, Australia. Her research interests include ecology and restoration of coastal marine habitats.

Chris M. Roelfsema is a Research Fellow and Lecturer Remote Sensing in the Biophysical Remote Sensing Group, School of Geography, Planning and Environmental Management, The University of Queensland, Australia. His interests include pure and applied research in remote sensing of coastal habitats.

Javier X. Leon is a Lecturer in Physical Geography at the University of the Sunshine Coast, Australia. His interests include remote sensing of shallow coastal marine environments and effects of sea-level rise on shorelines.

Jimena Samper-Villarreal is a PhD Student in the Marine Spatial Ecology Lab in the School of Biological Sciences, at The University of Queensland, Australia. Her interests include carbon sequestration in coastal vegetated habitats such as seagrass and mangroves.

Stuart R. Phinn is a Professor of Geography and Director of the Centre for Spatial Environmental Research in the School of Geography, Planning and Environmental Management at the University of Queensland, Australia. He uses satellite and airborne imaging systems to develop approaches for mapping, measuring and monitoring changes in the earth’s environments.

Catherine E. Lovelock is a Professor in the School of Biological Sciences at the University of Queensland, Australia. Her research focuses on the influence of environmental change on the ecology of coastal and marine plant communities, and in providing knowledge to underpin conservation and restoration of these systems now and in the future.

Peter J. Mumby is a Professor in the School of Biological Sciences at the University of Queensland and head of the Marine Spatial Ecology Lab. His research focuses on delivering science to improve the management of coral reef environments.
Acknowledgments
We thank S. Atkinson, C. Brown, C. Woodroffe, E. van Sluis Menk, D. Callaghan, T. Baldock, V. Harwood, A. Harborne, and S. Hamylton for assistance and collaboration in the field; R. Canto for analysis of underwater photos; and L. McKenzie for providing the maps of seagrass distribution in 1995. We are grateful for support from L. Vail, A. Hoggett, and staff of the Australian Museum Lizard Island Research Station. This project is a contribution of the Australia Sea-Level Rise Partnership and was funded by the ARC Superscience Research Fellowship #FS100100024, UQ New Staff Research Funds to MIS and JL, and UQ Early Career Research Grant to MIS.
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