New constraints on the spatial distribution and morphology of the Halimeda bioherms of the Great Barrier Reef, Australia

McNeil, Mardi A., Webster, Jody M., Beaman, Robin J., and Graham, Trevor L. (2016) New constraints on the spatial distribution and morphology of the Halimeda bioherms of the Great Barrier Reef, Australia. Coral Reefs, 35 (4). pp. 1343-1355.

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Halimeda bioherms occur as extensive geological structures on the northern Great Barrier Reef (GBR), Australia. We present the most complete, high-resolution spatial mapping of the northern GBR Halimeda bioherms, based on new airborne lidar and multibeam echosounder bathymetry data.

Our analysis reveals that bioherm morphology does not conform to the previous model of parallel ridges and troughs, but is far more complex than previously thought. We define and describe three morphological sub-types: reticulate, annulate, and undulate, which are 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. We have mapped a 1740 km² bioherm complex north of Raine Island in the Cape York region not previously recorded, extending the northern limit by more than 1° of latitude.

Bioherm formation and distribution are controlled 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.

Distribution and mapping of Halimeda bioherms in relation to Great Barrier Reef Marine Park Authority bioregion classifications and management zones are inconsistent and currently poorly defined due to a lack of high-resolution data not available until now.

These new estimates of bioherm spatial distribution and morphology have implications for understanding the role these geological features play as structurally complex and productive inter-reef habitats, and as calcium carbonate sinks which record a complete history of the Holocene post-glacial marine transgression in the northern GBR.

Item ID: 45289
Item Type: Article (Research - C1)
ISSN: 1432-0975
Keywords: Halimeda bioherm, geomorphology, reticulate, habitat complexity, Holocene
Funders: University of Sydney, Australian Research Council (ARC)
Projects and Grants: ARC DP1094001
Date Deposited: 31 Aug 2016 05:07
FoR Codes: 37 EARTH SCIENCES > 3705 Geology > 370504 Marine geoscience @ 80%
31 BIOLOGICAL SCIENCES > 3103 Ecology > 310305 Marine and estuarine ecology (incl. marine ichthyology) @ 20%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 100%
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