Generation of biogenic hydrocarbons during a spring bloom in Newfoundland coastal (NW Atlantic) waters

• Published in: Organic geochemistry 1997-02, Vol.26 (3), p.207-218
• Main Authors: Bieger, T., Abrajano, T.A., Hellou, J.
• Format: Article
• Language: English
• Subjects: Applied sciences; compound-specific 13C; Crude oil, natural gas and petroleum products; Earth sciences; Earth, ocean, space; Energy; Exact sciences and technology; Fuels; Geology and geochemistry. Geological and geochemical prospecting. Petroliferous series; highly branched isoprenoid; Hydrocarbons; laboratory culture of diatoms; Marine; Newfoundland; Plankton blooms; Prospecting and exploration; Prospecting and production of crude oil, natural gas, oil shales and tar sands; Sedimentary rocks
• ISSN: 0146-6380; 1873-5290
• DOI: 10.1016/S0146-6380(96)00159-3

The distribution and carbon isotopic composition of biogenic hydrocarbons in spring bloom plankton, bottom sediments, and benthic macrobiota in Conception Bay, Newfoundland (NW Atlantic) were determined by gas chromatography/mass spectrometry and gas chromatography/combustion/isotope ratio mass spectrometry. Although individual hydrocarbons were generally depleted by at least 3‰ relative to bulk organic matter, significant variations and temporal fluctuations in compound-specific carbon isotopic compositions were documented in bloom samples and laboratory cultures. Marked 13C depletions in a suite of eight C 25 highly branched isoprenoid alkenes, as well as a temporal shift in the 13C composition of spring bloom n-alkanes are suggested to be related to changes in the growth rates of bloom organisms. The input of multiple sources of organic matter into deep bay sediments could be recognized in the isotopic compositions of sedimentary n-alkanes. Overall, the carbon isotopic composition appeared to be primarily a reflection of the carbon fixing pathway of source organisms, with superimposed variations caused by fluctuations in growth rates and [CO 2(aq)]. These findings highlight the need for more study of contemporary biogenic hydrocarbons; specifically of the influence of growth rate and timing of synthesis on the carbon isotopic composition of biomarkers over the course of phytoplankton blooms.