Oil under Troubled Water: Australia’s Timor Sea Intrigue

Surficial marine sediments are an important source of nutrients for productivity and biodiversity, yet the biogeochemistry of these sediments is poorly known in Australia. Seabed samples were collected at >350 locations in Australia’s western, northern and eastern continental margins during Federal Government surveys (2007–14). Parameters analysed included measures of organic matter (OM) source (δ13C, δ15N and C:N ratios), concentration (percentage total organic carbon,%TOC, and surface area-normalised TOC, OC:SA) and bioavailability (chlorin indices, total reactive chlorins, total oxygen uptake, total sediment metabolism (TSM), sediment oxygen demand (SOD) and SOD and TSM normalised against TOC). The aim of the present study was to summarise these biogeochemical ‘baseline’ data and make contextualised inferences about processes that govern the observed concentrations. The OM was primarily from marine sources and the OC:SA broadly reflected water column productivity (based on Moderate Resolution Imaging Spectroradiometer, MODIS). Approximately 40% of sediments were organic poor by global standards, reflecting seawater oligotrophy; ~12% were organic rich due to benthic production, high water column productivity and pockmark formation. OM freshness varied due to pigment degradation in water columns and dilution with refractory OM in reworked sediments. δ15N values confirmed the importance of N2 fixation to Timor Sea productivity, and point to recycling of fixed nitrogen within food chains in Western Australia.

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Offshore Exploration Program Benefits fom Rolling PDC Cutter Technology, Timor Sea Australia

10.2118/170532-ms ◽

2014 ◽

Cited By ~ 1

Author(s):

Martin Giumelli ◽

Paul O'Shea ◽

Eni Australia ◽

Alberto Maliardi ◽

Paul Sosnowski ◽

...

Keyword(s):

Timor Sea ◽

Program Benefits

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Determinants of pelagic metabolism in the Timor Sea during the inter-monsoon period

Marine and Freshwater Research ◽

10.1071/mf10170 ◽

2011 ◽

Vol 62 (2) ◽

pp. 130 ◽

Cited By ~ 7

Author(s):

A. D. McKinnon ◽

J. H. Carleton ◽

S. Duggan

Keyword(s):

Gross Primary Production ◽

Vertical Mixing ◽

Community Respiration ◽

New Production ◽

Net Community Production ◽

Monsoon Period ◽

Hydrocarbon Seeps ◽

Timor Sea ◽

Waves And Tides ◽

High Production

The Timor Sea is a major conduit of the Indonesian Throughflow characterised by large internal waves and tides. To ascertain whether these result in high pelagic productivity, we conducted experiments to determine the metabolic balance between net community production (NCP) and community respiration (CR) on the Sahul Shelf, the Sahul Shoals and the Yampi Shelf, an area of active hydrocarbon seeps. The barrier to vertical mixing of subthermocline nutrients represented by the halocline allowed new production to dominate in March 2004, whereas production in June 2005 depended on recycled nutrients. CR was correlated with dissolved organic carbon (DOC) in 2004, but with chlorophyll in 2005, suggesting that respiration was dominated by microheterotrophs in 2004 but by autotrophs in 2005. Overall, area-specific CR averaged 120 ± 92 (s.d.), 101 ± 52 and 61 ± 6 mmol O2 m–2 day–1, NCP averaged 109 ± 85 (s.d.), 32 ± 41 and 57 ± 10 mmol O2 m–2 day–1, and average gross primary production (= CR+NCP) : R ratios were 1.9, 1.4 and 1.9 on the shelf, at the Sahul Shoals and the Yampi Shelf, respectively. We suggest that differences in water column structure and internal wave activity drive intermittent high production events in a predominantly oligotrophic sea.

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