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posted by martyb on Thursday November 03 2016, @03:12PM   Printer-friendly
from the old-salts dept.

New Frontier in Ocean Exploration: The E/V Nautilus and NOAA Ship Okeanos Explorer 2015 Field Season (22.1 MB PDF, starts on page 30):

During two cruise legs of the 2015 E/V Nautilus field season, the remotely operated vehicle (ROV) Hercules was deployed to examine some of the cold seep features of the deep Gulf of Mexico. Cold seeps are locations where hydrocarbons that are normally trapped deep beneath the seafloor escape into the water column. The hydrocarbons are forced out from the depths by the movement of large salt bodies that developed over the course of several million years as water evaporated from an ancient shallow Gulf of Mexico (Brooks et al., 1987). Shifting of these salt layers produces cracks in the oil-bearing shale that provide pathways for upward migration of oil and gas.

At some seep sites, deep within the sediments, the interaction of porewater and salt results in a highly saline fluid (brine) that can be more than four times more saline than seawater. When this brine is expelled from the sediments, it is far denser than the overlying seawater and does not mix very easily with it. In some cases, the brine forms large pools, or even rivers, as we discovered on one of the ROV dives at a site called Garden Banks 903. [...] At active seep sites where methane and hydrogen sulfide are expelled at the sediment-water interface, large mussel beds can form (reviewed in Cordes et al., 2009). Here in the deep sea where food is generally scarce, bacterial symbionts in the mussels' gills allow them to use dissolved gases being emitted at the seafloor as a source of energy.

[...] On the last leg of these seafloor hydrocarbon community investigations, we focused on a larger brine pool dubbed the "Jacuzzi of Despair," in reference to its warm temperature (19°C) and high salt content—which can be fatal to many macrofauna unlucky enough to fall in (we observed large dead isopods and crabs that had been preserved along the edge of the brine pool). This crater-like, circular, brine-filled pool rose 3 m above the surrounding seafloor, and brine was spilling out on one side in a spectacular "waterfall."

Also at Los Angeles Times and the Houston Chronicle .


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