Dispersion and cycling of organic matter from the Sepik River outflow to the Papua New Guinea coast as determined from biomarkers

Burns, Kathryn A., Hernes, Peter J., Brinkman, Diane, Poulsen, Anita and Benner, Ronald (2008) Dispersion and cycling of organic matter from the Sepik River outflow to the Papua New Guinea coast as determined from biomarkers. Organic Geochemistry, 39 12: 1747-1764. doi:10.1016/j.orggeochem.2008.08.003

Author Burns, Kathryn A.
Hernes, Peter J.
Brinkman, Diane
Poulsen, Anita
Benner, Ronald
Title Dispersion and cycling of organic matter from the Sepik River outflow to the Papua New Guinea coast as determined from biomarkers
Journal name Organic Geochemistry   Check publisher's open access policy
ISSN 0146-6380
Publication date 2008-12-01
Sub-type Article (original research)
DOI 10.1016/j.orggeochem.2008.08.003
Volume 39
Issue 12
Start page 1747
End page 1764
Total pages 18
Place of publication Oxford, U.K.
Publisher Pergamon Press
Language eng
Subject 0402 Geochemistry
Abstract The Sepik River is a major contributor of water, sediment and associated organic loads to the coastal waters of northern New Guinea. With a narrow continental shelf and strong coastal currents, much of this exported material is available for long distance transport into the Bismarck Sea and beyond. CTD casts and associated instrument data showed that the river signature was visible in optical measurements of deep profiles from the Sepik Canyon. Discrete water samples were collected in clean Niskin bottles for organic analysis. Additional high volume samples for lipid classes were collected with Infiltrex samplers deployed on a floating mooring, along with two sediment trap arrays set at 100 and 260 m depth. The Infiltrex samplers were set at 55, 180, 200 and 220 m depth in an effort to target the surface layers and those of westward flowing water in the New Guinea Coastal Undercurrent (NGCUC). The samplers allowed analysis of lipid classes in both dissolved and particulate phases. Analyses of lignin phenols, hydrocarbons, fatty acids, sterols, and n-alcohols in the samples were used to estimate the cycling of the organic input from the river system to the coastal waters and possible entrainment in the NGCUC. The molecular biomarkers confirmed the Sepik River as a significant source of reduced carbon in the near coastal zone influenced by the plume. They indicated that ca. 90% of the organic carbon delivered to the coastal zone is dispersed or degraded, with only about 10% of terrestrial carbon being deposited on to the narrow shelf of coastal sediments. The dissolved lignin phenols provided evidence for desorption of organics from particles with increasing depth. However, this desorption process did not change the C/N ratio of the dissolved organic carbon (DOC) in the deep water of the Sepik Canyon. The hydrocarbons, sterols and fatty acids showed the change from lipid content dominated by phytoplankton in surface layers to zooplankton and bacterial biomarkers in deeper waters. The organic biomarkers provided evidence that some of the dissolved organic input from the Sepik River was injected into fast moving undercurrents. However, concentrations of terrestrial biomarkers were diluted and/or degraded to non-detectable levels within 100 km of the source.
Keyword Papua New Guinea
Organic matter
Sepik River
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ
Additional Notes Special Section on Stable Isotopes in Biogeosciences (II)

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
National Research Centre for Environmental Toxicology Publications
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