Halimeda
Halimedia exposed at low tide, growing in the shallows of south east of Thursday Island.
by Eric Lawrey (AIMS)Halimeda is a green macroalgae, that is composed of a string of jointed calcified green segments. They are abundant in shallow seas in the tropics. Substantial Halimeda banks exist inside the Ribbon Reefs passages of the northern GBR but also in the central northern GBR. Dominated by a live veneer of the calcareous green algae Halimeda which dies to forms banks, typically up to 20 metres thick, on the seafloor usually in waters 40 metres or more deep. Their distribution is determined by “a complex interaction of outer-shelf geometry, regional and local currents, coupled with the morphology and depth of continental slope submarine canyons determining the delivery of cool, nutrient-rich water upwelling through inter-reef passages”. Recent work by McNeil et al. (2016) reveals the morphology is far more complex than previously thought. They describe three morphological sub-types distributed in a cross-shelf pattern of reduced complexity from east to west. The northern GBR bioherms cover an area of 6095 km2, three times larger than the original estimate, exceeding the area and volume of calcium carbonate in the adjacent modern shelf-edge barrier reefs. Also recently mapped was a 1740 km2 bioherm complex north of Raine Island not previously recorded, extending the northern limit > 1° of latitude (McNeil et al. 2016).
This map shows the connectivity of Halimeda in the Great Barrier Reef and its surrounding areas: Torres Strait, Coral Sea and Great Sandy regions. The arrows indicate the strength and nature of the connection between the regions. This map is intended to identify where one region is dependent on a neighbouring region.
Additional notes: There is no data for the Great Sandy region.
The data for this map was developed based on expert opinion (Guillermo Diaz-Pulido).
by NESP TWQ 3.3.3, Guillermo Diaz-PulidoReferences
McNeil M. A., Webster J. M., Beaman R. J., Graham T. L. (2016) New constraints on the spatial distribution and morphology of the Halimeda bioherms of the Great Barrier Reef, Australia. Coral Reefs 35:1343-1355. DOI 10.1007/s00338-016-1492-2
Pitcher R., Doherty P., Gribble A. N., Hooper J. (2009) Seabed Biodiversity on the Continental Shelf of the Great Barrier Reef World Heritage Area 2003 - 2006 (CRC Reef, CSIRO) [Dataset]. Commonwealth Scientific and Industrial Research Organisation, Australian Institute of Marine Science, Queensland Department of Primary Industries, Queensland Museum [producer]. Restricted license [License]. eAtlas Repository [distributor]. http://eatlas.org.au/data/uuid/6f61137b-8baa-40fa-bde1-670655254afa
