Discovery and biogeochemistry of asphalt seeps in the North São Paulo Plateau, Brazilian Margin

Abstract

An initial multiple biogeochemical dataset was acquired from the first discovered asphalt seeps in the Brazil margin during deep-sea dive surveys in 2013 using a manned submersible. These surveys were conducted on the outer escarpment of the North São Paulo Plateau. Sediment cores taken from the submersible were processed for pore water and sediment biogeochemistry. The silica concentration, as a chemical geothermometer, showed a steep gradient in the pore water, which indicates the possibility of an active brine system operating in the seepage area. Rare earth elements were used as powerful tracers of chemical processes. Low rare earth element concentrations in both asphalt and Fe-Mn oxyhydroxide-phase sediments suggests that rare earth elements were released during the oil fractionation and biodegradation processes and further depleted under the reducing environment. The main bacterial communities of the sediment were Proteobacteria in the asphalt sites, while at non-asphalt sites, the main bacterial communities of sediment were Firmicutes. Stable carbon and nitrogen isotopes were used to determine the food sources of the heterotrophs, and results suggest that asphalt probably provides a carbon source for these benthic animals. This study may provide useful information to clarify the impact of heavy hydrocarbon seepage on the marine ecosystem.

Dynamics of Live Oil Droplets and Natural Gas Bubbles in Deep Water

“…Comparison of TAMOC predictions with laboratory observations reported by Pesch et al23,37 for live and dead oil droplets (Experiments[1][2][3][4][5][6][7][8][9][10][11][12]. Also shown are model values when assuming suppressed aqueous dissolution of methane.…”

“…Petroleum fluids comprising gaseous and liquid phases may enter deep water through natural seeps, − small-scale leaks during industry operations, leaking abandoned wells, , or major accidents such as the Deepwater Horizon disaster . During such events, the coupled chemical and physical dynamics of the released gaseous and live liquid petroleum phases largely determine the trajectories and fates of these fluids in the environment.…”

Oil seepage and carbonate formation: A case study from the southern Gulf of Mexico

“…Most seeps at continental margins are dominated by the seepage of biogenic and thermogenic methane (Claypool & Kvenvolden, ; Suess et al ., ; Suess, ). However, many hydrocarbon seeps have been discovered that are characterized by expulsions of crude oil (Estes et al ., ; Kennicutt et al ., 1988a; MacDonald et al ., ; Kvenvolden & Cooper, ; Joye et al ., ; Körber et al ., ; Jiang et al ., ). Such seeps are ideally suited to study the impact of oil seepage on the diversity, activity and distribution of microbial communities, as well as the role of oil seepage and its subsequent degradation for carbonate authigenesis (Naehr et al ., ; Orcutt et al ., ; Birgel et al ., ; Schubotz et al ., 2011a).…”

Bacterial diversity in deep-sea sediments under influence of asphalt seep at the São Paulo Plateau

“…During the cruise that explored the deep seafloor of the North São Paulo Plateau in Espírito Santo Basin (2500-3600 m), asphalt seeps were found at a depth of 2,700 m colonized by non-chemosynthetic megafaunal organisms [12]. They also found that, in non-asphalt seeps areas, outcrops of mudstone were covered by black manganese oxide crusts and nodules were also present [12, 13, 14]. These two particular conditions of the study area may be important factors determining patterns of bacterial diversity.…”

“…A previous study carried out by the Iatá-Piúna consortium [13] using PCR-DGGE method found high and widespread dominance of Proteobacteria and Firmicutes at sediment samples, including asphalt seep area. The two predominant species were Erythrobacter citreu s strain VSW309 detected in hydrothermal vents and Thalossospira xianhensis strain MT02 a hydrocarbon-degrading marine bacterium.…”