Radke, L; Nicholas, T; Thompson, PA; Li, J; Raes, E; Carey, M; Atkinson, I; Huang, Z; Trafford, J; Nichol, S (2017). Baseline biogeochemical data from Australia's continental margin links seabed sediments to water column characteristics. MARINE AND FRESHWATER RESEARCH, 68(9), 1593-1617.
Abstract
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 (delta C-13, delta N-15 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 Spectro-radiometer, MODIS). Approximately 40% of sediments were organic poor by global standards, reflecting seawater oligotrophy; similar to 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. delta N-15 values confirmed the importance of N-2 fixation to Timor Sea productivity, and point to recycling of fixed nitrogen within food chains in Western Australia.
DOI:
10.1071/MF16219
ISSN:
1323-1650