Cruise preparation, part 1

Hi Everybody! This is the first in a series of blog entry updates on a R/V Atlantis cruise to the Gulf of Mexico. Rich Viso and I (Rick Peterson) will be boarding Atlantis on November 6th to embark on a 29 day cruise with researchers from the University of Georgia, University of North Carolina, Florida State University, University of Southern Denmark, Woods Hole Oceanographic Institute, and Harvard University.

The primary objective of the cruise is to examine brine seeps in the Gulf of Mexico. When the Gulf was an evaporative basin through geologic history, large salt deposits were precipitated on the sea floor and subsequently overlain by sediments. As seawater circulates through those sediments today, it slowly dissolves those salt layers, thereby opening fissures and faults through the salt layers. These fissures allow underlying hypersaline groundwaters to discharge into the bottom waters of the Gulf of Mexico. These hypersaline waters are substantially denser than the bottom waters, so they form dense pools lying on the seafloor. As with more oceanic extreme environments, it is likely that some biological communities have adapted to living in these pools. The goals of this cruise are to (1) characterize the diversity and activity of the microorganisms living in these environments, (2) understand the biogeochemical scenarios by which those communities can thrive, and (3) examine the interaction of these microbes with the brine pools.

Rich and I are primarily responsible for determining the discharge rates of groundwater into these brine seep pools. We plan to measure radon and radium isotopes as indicators of this benthic fluid discharge around these discharge points. Using the natural radioactive decay of these isotopes, we can determine the amount of time for each sample since discharge, and therefore work out the discharge rate.

To help with these efforts, the human-occupied vehicle (HOV) Alvin will perform 24 dives throughout this cruise. Alvin will be key to collecting individual water samples in these brine pools and giving the human eye an opportunity to observe these environments as they appear naturally. These brine pools are located ~2000 m deep, so each Alvin dive will last for approximately 8 hours.

We left CCU on Wednesday, November 3rd and drove our shipboard equipment to the University of Georgia in Athens. Here, we loaded our gear on a larger truck headed for the ship in Galveston, TX and toured the laboratory facilities here at UGA. We will board the ship on Saturday (Nov. 6th) and leave port on Monday (Nov. 8th).

Field Note Event: