When fluids seep out of the seafloor, they provide chemical substrates to fuel both microbial and macro-biological communities. Even hyper-salty brine seeps are “oases” of life along the seafloor. While the salt content of some seafloor brines can create challenges for macro-organisms, microbial life thrives in brines.
At the venting center of a brine flow, numerous bubbles of gas and drops of oil are apparent in the water column. At some sites, these vents may occupy a small area (2 x 2 m) while at others, the vents occupy large areas (50 m long x 3 m wide faults where bubbles explode from the subsurface). Along with dissolved gases, the venting fluids deliver nutrients (mainly nitrogen and bioactive trace metals) and dissolved organic carbon to the seafloor; these materials can fuel microbial processes that further promote growth and proliferation of macro-biological communities. Away from the main vent, brine flowing along the seafloor can look rather strange, often there is a lighter colored, ropey structure to the brine flows, and because they are dense, they flow down slope (see image gallery below). The areas adjacent to brine lakes or pools is often home to diverse animal life, ranging from tube worm bushes, mussels, holothurians (sea cucumbers), heart urchins, clams, pogonophorans and microbial mats to various other invertebrates (see image gallery below).
We collected brine and sediment samples from around various animal habitats to evaluate how variations in geochemistry and microbial activity alter the animal habitats. Some might find the diversity of animal life around these brine seeps shocking. Microbial mats are abundant (1st image gallery below). Meadows of holothurians (better known as "sea cucumbers") and heart urchins are abundant along the edges of brine lakes and pools (2nd and 3rd image gallery below). Mussel beds are home to a diverse variety of associated fauna including fish, crabs, invertebrate worms and snails (4th image in the gallery). We're moving next to the Orca Basin, which promises to be one of the most interesting sites we visit during this cruise!