Baseline biogeochemical data from Australia’s continental margin links seabed sediments to water column characteristics

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 (2007-2014). Parameters analysed included measures of organic matter (OM) source (δ13C, δ15N and C:N-ratios), concentration (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 to TOC). The aim of this study is to summarise these biogeochemical ‘baseline’ data, and make contextualised inferences about processes that govern the observed concentrations. The OM was mainly from marine sources and OC:SA broadly reflected water column productivity (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.

Citation: Radke Lynda, Nicholas Tony, Thompson Peter A., Li Jin, Raes Eric, Carey Matthew, Atkinson Ian, Huang Zhi, Trafford Janice, Nichol Scott (2017) Baseline biogeochemical data from Australia’s continental margin links seabed sediments to water column characteristics. Marine and Freshwater Research 68, 1593-1617. https://doi.org/10.1071/MF16219