May 10th & 11th, 2003; Leg 5, Days #20 & 21

It’s Sunday afternoon, and the R/V Western Flyer is steaming to port at Pichilingue. The air is gradually getting warmer as we sail south into warmer waters. We had an entertaining display of dolphin acrobatics in front of the bow wake of the ship this morning. A few dolphins showed up and played for about an hour, spinning, twisting, leaping into the air. They whistled and squeaked with each other while putting on an entertaining performance.

The labs have been quiet for the most part today. Last minute analyses and calibrations have been completed, organizing and packing samples has begun. But after days of long intense hours in the control room and the labs, we’re ready for a break. It’s a sunny afternoon, and it is rumored that some of the science crew are sunning themselves on the Lido deck.

There were two dives yesterday, exploration and sediment coring in the morning, and more laser Raman measurements in the afternoon. We continued to explore the seafloor along the transform fault southeast of Pinkie’s Vent. For the past two dive days, we’ve targeted hilly areas on the seafloor to determine what creates these structures and to see if gas venting is occurring at their crests. We did not see any gas venting on the tops of these features, however, there were abundant small clusters of chemosynthetic communities, comprising bacterial mats and clams. Tube worms were also abundant, but they were primarily on the carbonate rock outcrops on the seafloor, not in the sediment. We have recovered rock samples with baby tube worms on them, which is a rare find. Mature tubeworms will grow to almost four meters in length, and growth rate measurements in the Gulf of Mexico have shown that these individuals may be as old as 400 years. The tops of the hill crests are covered with thick layers of fractured carbonate rock, which forms large blocks, boulders, and slabs. Sediment is thin on the tops of these outcrops, and it is found in isolated pockets across the rock surface. Rock samples from these hills show that the rock is comprised of shelly material cemented together with carbonate.

A solitary tubeworm appears on this freshly recovered rock sample. Tubeworms have “roots” that extend down into the rock through cracks and cleavage surfaces and are believed to be the way tubeworms mine the hydrogen sulfide that they need for their metabolism. They have large masses of sulfur- oxidizing bacteria in their troposome. The flared end of the tubeworm points up into the seawater and has a frilly structure called a fimbria, that filters oxygen from the water. Inside the troposome, the bacteria combine the oxygen and hydrogen sulfide and capture the energy from this chemical reaction to make sugars and other biomolecules that they and the tubeworm need to survive. The tubeworm provides shelter and the mechanisms for bringing the hydrogen sulfide and oxygen to the bacteria, and the bacteria provide the tubeworm with energy and food.

More tests of the laser Raman occurred during the afternoon. During most of these experiments conducted over the past week, Ed Peltzer has been collecting gas samples near the seafloor using his heated, gas-trapping funnel. The accompanying picture shows Ed in the lab with a set of gas samples cylinders that are filled with gas for analysis when he returns to MBARI.

A happy Ed Peltzer displays his "catch of the day."

The entire crew of the R/V Western Flyer would like to wish all of our moms out there a very Happy Mother’s Day. We love you!

Special greetings are sent by:

Patrick Mitts to his mom: Happy Birthday and Happy Mother’s Day!

Lynne Christianson: Happy Mother’s Day, and thanks for sending me the emails.

Sheri White: Hi Mom, sorry you’re home alone on Mother’s Day. We’ll take you out for steak next weekend. Happy Mother’s Day.

Ed Peltzer: Hi Mom!

Bill Ussler: Happy Mother’s Day!

Rendy Keaten: Happy Mother’s Day. See you soon. Love, Rendy.

Peter Walz: Hi Mom. Thanks for all your support over the years. Love and hugs to you!

Here is a group of very happy scientists at the end of Leg 5. We’re about to make landfall in Pinchilingue.

– Bill Ussler, reporting