Relationship between Bottom Water Oxygen Concentration and Palmitic Acid Preservation in Saanich Inlet, BC and Hood Canal, WA

Abstract

The global carbon cycle in the ocean is closely associated with dissolved oxygen in the surface ocean. Phytoplankton produce oxygen, and the oxygen in the atmosphere and surface seawater diffuses down to the seafloor. Dead phytoplankton, at the same time, contribute to respiration in the bottom water, consuming the bottom water oxygen (BWO). In this study, palmitic acid (C16:0) commonly found in autotrophic and heterotrophic organisms are examined to find out its relationship to the BWO. Surface sediment samples and dissolved oxygen samples were obtained in the seafloors of Saanich Inlet, BC and Hood Canal, WA. Winkler titration and Gas Chromatography- Mass Spectrometry (GC-MS) methods were conducted on the samples. Our results demonstrate that palmitic acid preservation is more efficient with increasing BWO in Hood Canal. It is suggested that sedimentation rate, presence of benthic organism, population of bacteria, and aggregation of organic carbon have more influence on the preservation of C16:0 in sediment than the available BWO directly above the seafloor. If a correlation between BWO and the preservation of palmitic acid is found from surface seafloor samples, its regression line could be used to reconstruct BWO in the past. It would require sediment cores containing palmitic acid preserved in the past, which may provide clues on how organic carbon made its way into the sediment in the past.