Reports

Microbial oceanography of northern Australia

Authors: Doblin, M.A.

Year: 2013

Publication: Voyage Summary SST03/2013, CSIRO Marine National Facility, Hobart, Australia, pp. 31.

Abstract

Microbial oceanography. The microbial portion of this transit voyage was relatively successful. We were able to complete 11 deckboard incubations to quantify phytoplankton community carbon and nitrogen fixation, 11 full depth profiles of primary productivity (9 with size fractionated surface communities), 11 experiments with surface communities, conduct 6 experiments to assess aggregate formation, a further 9 experiments to assess the active incorporation of silica into diatoms.

Global drifter program. One drifter was launched near the Kimberley IMOS array (27/07/2013 at 11:27 UTC at 17 35.339 S and 121 51.616 E) and 4 further east in the Arafura Sea. Tracking data collected by the drifters on surface current direction and velocity will provide the baseline parameters for developing a dispersal prediction model of derelict fishing gear.

Swath mapping around the GBR. The results of the ss2013_t03 swath mapping and Topas subbottom profiling were generally considered a success, with some minor exceptions (see daily diary in Appendix). Both systems, for the most part, worked well, however in the northern GBR/Cape York area between latitude 9° 49’S to 12° 33’S, incorrect EM300 swath settings in the SIS acquisition software resulted in limited across track coverage and noisy data until the correct settings were applied. Therefore the objective to understand the northern limit of the GBR submerged reefs was inconclusive. However, the southern limit of the GBR submerged reefs has been extended to at least latitude 22° 08’S, as numerous pinnacles 5-15 m high were observed to seaward to the Swains Reefs to depths of about 100 m. Therefore the GBR submerged reefs are currently observed over a distance of about 1000 km, certainly justifying their label as the world’s longest fossil.

Greenhouse gas measurement. To characterise the sources and sinks of the major greenhouse gases in the Australasian region, continuous in situ measurements of the key greenhouse gases methane, carbon dioxide, nitrous oxide, as well as carbon monoxide and ozone were successfully performed during the transit SS2013_t03. The data were collected by using a fully automated Fourier Transform Spectrometer for CH4, CO2, N2O, d13C, CO and a UV absorption instrument for O3. The time resolution was 3 min and 1 min, respectively. The preliminary data are shown in Appendix 3. Final calibration of the instrument once returned to Wollongong will allow finalization of the data.

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