Seagrass on the Great Barrier Reef [Map]

Seagrass meadow boundaries 1984 - 2014 (NESP 3.1, JCU)

Seagrass site surveys 1984 - 2014 (NESP 3.1, JCU)

This map also includes additional historic seagrass datasets that might be of relevance. Expand the map to access these layers

This map shows the extent of the seagrass meadows on the Great Barrier Reef based on two datasets. The coastal seagrasses in waters shallower than -15 metres were mapped by dive surveys, under water cameras and inter-tidal aerial surveys from 38 surveys from 1984 to 2007. The offshore seagrasses were measured using a towed video system as part of the Seabed Biodiversity Project from 2003 - 2006. This video system recorded the habitat on the bottom of the seabed. Deep water seagrasses are dominated by Halophila decipiens or Halophila sinulosa which are adapted to low light environments.

Seagrass meadows change over time with the seasons and in response to environmental conditions such as light levels and physical damage from cyclones. This map does not capture this variation over time and thus only represents the approximate extent of where seagrass might be found.

If you expand the interactive map (by clicking the Expand Map Icon button) there are two extra layers that you can turn on showing the results of modelling the distribution of seagrasses in the wet and dry seasons.

Halodule uninervis

Seagrasses are unique in the marine environment in that like many land plants they reproduce by flowering and producing seeds. They are however also capable of asexual reproduction through horizontal rhizome growth. Seagrass meadows consist of a nested structure of clones, that sometimes fragement into individual plants. Meadows may appear static however the extent and density of the seagrass is highly dynamic.[2]

The name seagrass probably originated because some species look like grasses and form lawn-like meadows that resemble grasslands. There are around 17 species in Queensland that vary from the size of your fingernail to those with long strap like leaves and 11 species known from Torres Strait [1]. Different seagrass species have different tolerances to light and temperature and vary in their sensitivity to changes in environmental conditions

The seagrass ecosystems are of national significance due their role in sustaining fisheries and as a food source for the endangered marine mammal, the dugong.

Shallow water seagrasses are most common in sheltered areas where sediments accumulate.

See the Seagrass in Torres Strait article for more information about seagrasses.


1. Mellors, JE & McKenzie, LJ (2009) Seagrass-Watch: Guidelines for Monitoring Seagrass Habitats. Proceedings of a workshop held on Thursday Island, Torres Strait. March 4-8, 2009 (Seagrass-Watch, Townsville) 58pp.

2. Coles, R. G., McKenzie, L. J., Rasheed, M. A., Mellors, J. E., Taylor, H., Dew, K., McKenna, S., Sankey., T. L., Cater, A. B. and Grech, A. (2007). Status and Trends of Seagrass Habitats in the Great Barrier Reef World Heritage Area. Report to the Marine and Tropical Sciences Research Facility. Reef and Rainforest Research Centre Limited, Cairns (122 pp).