Follow Dr. Shana Goffredi on her research cruise from April 17-25, 2015 to sample benthic organisms from deep-sea hydrothermal vents and hydrocarbon seeps in the Gulf of California.
The Gulf of California (between the Baja California peninsula and mainland Mexico) is unique in that seafloor spreading occurs at ~6 cm per year along short ridge segments separated byactive transform faults, as opposed to a long continuous ridge. This presents an opportunity to examine the biological communities along these independent transform faults, which likely experience unique chemistries due to influences from both underlying geological venting and shallow subsurface biological production of gases. The seafloor in the GoC region also experiences very rapid sedimentation of organic-rich material. As a consequence, the transform faults are studded with sites of methane gas and sulfide-rich fluid seepage, hosting rich chemosynthetic bacterial and animal communities. A few of these sites were explored by us previously in 2003, and we discovered vestimentiferan tubeworms, vesicomyid clams, lepetodrilid limpets, cladorhizid sponges, foraminifera, and multi-colored bacterial mats, to name a few. In some cases, slight sediment temperature anomalies were noted, possibly the result of nearby volcanic activity. Habitat heterogeneity and patchiness were high, due to carbonate structures and animal-materials (i.e. tubes and shells), suggesting that total organismal diversity is also likely to be high and that community composition will be unique from the more well-studied hot vents to the east (GUY) and south (21°N). During this cruise, we hope to expand our geographic sampling ranges to include sites previously identified as areas of interesting geology and chemistry, including some in the Pescadero, Farallon, and Carmen Basins at ~ 3000 m depth (from south to north; ~25°-27°N).
Our main biological questions concerning this area include :
- Do biological communities differ between the transform faults and those along the Carmen, Farallon, or Pescadero faults, the latter of which are the most southern by 150 nautical miles (~ 25°N) and may experience influx of species from the southern hot vents.
- Will a more thorough sampling of the smaller community members (i.e. snails, polychaetes, crustaceans) at the transform faults reveal affinities to the nearby hot vents, or a hybrid community spanning seeps and vents, as was shown for a similar hydrothermal seep off of the Costa Rica margin.
- Is there an influence of the amount of seepage on community structure, as it diminishes with distance from the ridge crests.
- Do other dominant invertebrate hosts (i.e. sponges, animals with epibionts) reveal bacterial symbiont differentiation on spatial and geochemical scales, as was previously observed for transform fault tubeworms.
Ship and Submersible
We’ll be aboard the RV Western Flyer, owned and operated by the Monterey Bay Aquarium Research Institute. The Western Flyer is a 117-foot oceanographic research vessel designed specifically for deploying, operating, and recovering tethered submersibles. In order to visualize and sample the seafloor, we’ll be using the 10,000 lb remotely-operated vehicle ROV Doc Ricketts, built in 2009.
