Patrick L. Parker

Land-derived organic matter in surface sediments from the Gulf of Mexico

Abstract Lignin oxidation products and 13C/12C ratios were compared as indicators of land-derived organic matter in surface sediments from the western Gulf of Mexico. Whole sediments were reacted with cupric oxide to yield phenolic oxidation products that indicated the types and relative amounts of the lignins that were present. Measurements of lignin concentration and carbon isotope abundances both indicated a sharp offshore decrease of land-derived organic matter in most areas of the western Gulf. This decrease results primarily from mixing of terrestrial and marine organic matter. The terrestrially derived material in these sediments has a lignin content similar to that of grasses and tree leaves. Flowering plants contribute most of the sedimented lignin compounds. These lignins apparently occur in the form of well-mixed plant fragments that are transported to sea by rivers and deposited primarily on the inner continental shelf.

Hydrocarbons of Blue-Green Algae: Geochemical Signfficance

The hydrocarbon compositions of 11 species of blue-green algae are simple and qualitatively similar. Three marine coccoids contain only monoenoic and dienoic C19 hydrocarbons. Hydrocarbons of the remaining eight species are C15 to C18. Hydrocarbons of higher molecular weight (C20 or more) were not detected. Blue-green algae do not appear to be the source material for the longchain (greater than 20 carbons) hydrocarbons found in ancient sediments.

Geochemical implications of induced changes in C13 fractionation by blue-green algae

Abstract The photosynthetic fractionation of carbon isotopes by blue-green algae in laboratory culture is dependent in a non-linear fashion on the CO 2 concentration in the feed gas. For the three species tested, the minimum fractionation occurred at a CO 2 concentration of 0.2% in air and was approximately zero for the two marine species tested. Enrichment of C 12 in the reduced carbon is not an inevitable result of photosynthetic carbon fixation. Temperature and pH had no detectable effect on fractionation. The maximum fractionation observed in the laboratory cultures or in recent blue-green algal mats was 18‰. Differences in the isotope ratio of coexisting oxidized and reduced carbon in Precambrian stromatolites are as great as 31‰. Present carbon isotopic evidence is not consistent with the idea that blue-green algae were major contributors to the organic matter in Precambrian sediments.

Maximum carbon isotope fractionation in photosynthesis by blue-green algae and a green alga

Abstract The maximum carbon isotope fractionation occurring in photosynthetic fixation of carbon dioxide in pure cultures of blue-green algae was −23.9%. and for a green alga was −22.6%., Maximum fractionations were obtained where cell densities were low and carbon dioxide concentrations were greater than 0.5%. Fractionation was reduced at higher temperatures using a thermophilic blue-green alga. For filamentous blue-green algae wherein clumping occurs and localized cell concentrations were high, fractionation was also lower. Fractionations reported in literature for Precambrian organic materials are comparable to the maximum fractionations reported here. This suggests that the early photosynthetic organisms developed under conditions of high carbon dioxide availability, i.e. slow growth rates and/or low population densities.

Seep Oil and Gas in Gulf of Mexico Slope Sediment

Concentrations in Gulf of Mexico slope sediment of material soluble in methanol and benzene as high as 4.5 percent are shown to be attributable to biodegraded petroleum. Associated carbonate deposits and organic sulfur are the products of the microbial oxidation of petroleum and sulfate reduction. The results of chemical and carbon isotope analyses indicate that high concentrations of hydrocarbon gases, from methane to pentane, are petroleum rather than microbiologically derived. These hydrocarbons, believed to have been produced thermally at depth, probably reached the surface through faults and fractures associated with salt diapirs.

Sterols in Recent Marine Sediments

Sterolic fractions have been isolated from Recent marine sediments representing two different environments. The fractions were characterized by infrared spectroscopy and thin-layer chromatography. The major sterols in the fractions were identified by gas chromatography and mass spectrometry. The demonstrated survival of these common plant and animal sterols for several thousand years suggests that these molecules will be useful geochemical indicators.

Resuspension of oil: probable cause of brown pelican fatality

Coastal ecosystems are vital nesting and wintering areas for numerous bird populations. Increasing growth in costal areas, particularly development related to the recovery and transportation of oil, poses severe threats to coastal and marine bird species. The devastating effects of oil spills on waterbirds are now well documented; large numbers of marine birds die each year as a result of oil spills. Most mortality occurs within a few days after the spill; however, our recent observations in Texas indicate that mortality may occur at least 6 weeks after the original spill.

Stable Isotopes As Tracers In Ocean Sciences

By making use of differences in stable carbon isotope ratios, which have resulted from chemical isotope effects, for carbon reservoirs large scale tracer experiments have been observed. These natural experiments have been used to quantify ocean pollution, sediment sources and duck food-webs.