April 5th, 2003; Leg 4, Day #2

Today's update is provided by Susan Von Thun.

Today we hope to find animals living along the Guaymas Transform Fault. We are searching for cold seeps.  Only a few other times have scientists seen animals in this area, the most recent in 1994. Samples from the previous expeditions revealed interesting evolutionary relationships between these animals and other cold seep fauna, including those in Monterey Bay.

We are working into the wee hours of the night processing all of the samples we collected today.  We are sure that all of our hard work will pay off, since we've already found surprises.

This morning we were in the water at 7:00 a.m., after a 22- hour steam from La Paz.  ROV Tiburon reached the bottom, a depth of 1,760 meters, in only 84 minutes.  The dive was 11 hours in duration.  That may seem like a long time, but we were glued to our seats every minute.  

Unexpectedly, during our dive, the diversity (within an 800 m transect) was striking, and far greater than any other seep site we have ever seen. We collected three types of vestimentiferan tubeworms, five species of clam, including six individuals of an unusual genus of bivalve called Solemya, and numerous gastropods, polychaetes, and brachiopods.

We also collected push cores over bacterial mats within the cold seeps. These push cores smelled strongly of sulfide (rotten eggs) and crude oil, which is actually a good sign that interesting microbes will be living within these cores.  Microbiologists and chemists aboard the cruise will process these sediment cores (see image above of Pete and Jean) and measure the bacterial diversity and chemical nature of the pore fluids within them.  They hope to find correlations between the nature of the bacterial community and the deep-sea environment.  Surprisingly, we also found gas bubbling from seeps as well as chunks of clathrate (methane ice). We know many chemists and geologists will be interested in that news!