Habitats and Benthos at Hydrographers Passage, Great Barrier Reef, Australia
January 02, 2012

Authors: Beaman, R.J., Bridge, T., Done, T., Webster, J.M., Williams, S., Pizarro, O.

Year: 2012

Publication: Harris, P.T., Baker, E.K. (Eds.), Seafloor Geomorphology as Benthic Habitat: GeoHab Atlas of Seafloor Geomorphic Features and Benthic Habitats. Elsevier, Amsterdam, Netherlands, pp. 425-434.


Hydrographers Passage lies on the shelf-edge of the central Great Barrier Reef in north-eastern Australia. The survey location is approximately 800 km2 in area and ranges in depth from 14 m to 300 m. The mapped geomorphic features (>1 km) include a broader-scale slope, terrace and platform, with smaller reefs and dune features.

Sediment grabs from two cross-shelf transects show a generally similar composition of poorly-sorted, muddy sand and Fe-stained carbonate gravel. In contrast, dune sediments are a well-sorted sand with no Fe staining. Images from two AUV transects provide the data for a hierarchical clustering of substrate types into five Substrate Groups: Sand, Gravel, Rubble, Sediment-covered limestone; and Reef.

The AUV imagery reveals a clear distinction between the benthos associated with hard substrates and soft substrate habitats at a finer-scale than can be shown within the broader-scale geomorphic features. Maximum entropy modelling is used to generate a habitat preference map for azooxanthellate, filter-feeding octocorals.

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