Reports

Carbon chemistry of the Great Barrier Reef

Authors: Tilbrook, B., Matear, R.

Year: 2008

Publication: Voyage Summary SS09/2008, CSIRO Marine National Facility, Hobart, Australia, pp.17.

Abstract

Large-scale carbonate chemistry of the Great Barrier Reef waters: A major aim of the voyage was to characterise the carbonate chemistry through the reef region and compare this to the carbonate chemistry of the offshore source waters in the Coral Sea. Inshore-offshore sections and stations along the length of the GBR lagoon and offshore were used to characterise gradients in carbonate chemistry. Water samples during the voyage were obtained using Niskin bottle mounted on a CTD rosette and ship’s underway seawater supply. These samples were be analysed onboard for total dissolved inorganic carbon, titration alkalinity, macronutrients, oxygen and salinity. Continuous underway measurements of O2/Ar ratio (net community production estimate) and the surface partial pressure of carbon dioxide (air-sea CO2 flux estimate) were also made.

Bathymetry: The ships EM300 multibeam swath mapper and Topas sub-bottom profiler were run for the entire duration of the voyage from Cairns to the arrival at Gladstone, with down-time restrictions in accordance with the GBRMPA permit for the survey. The collection of the bathymetry data was coordinated and run by Dr Robin Beaman, James Cook University.

Benthic samples: On the current voyage, brittle star sampling was carried out when the ship transited through Hydrographers Passage. Previous AUV images over the dune field provide targeted locations for sampling the brittle star beds with a Smith-MacIntyre sediment grab device. Similarly, Halimeda mound sampling was carried out in the LADS Passage region after suitable sites were identified using the ships swathmapper and sub-bottom profiler. Underwater video transects over these sites were used to provide additional ground-truthing of the seabed habitats and sample site selection. The grab samples were organised by Dr Robin Beaman in collaboration with Dr Jodie Webster (James Cook University) and Prof. Maria Byrne (Sydney University).

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