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April 7th, 2003; Leg 4, Day #4

Today's update is provided by Chief Scientist, Bob Vrijenhoek.

Area of Study: Guaymas Basin

Site: Rebecca�s Roost

We returned today to the Rebecca's area to do some more fine-grained sampling of the small animals associated with tubeworm clumps. On the way to the target site, we came across a short sulfide mound covered with Riftia tubeworms. On closer inspection, we saw that most of the tubes were empty, but a few tubes had some very �unhappy looking� worms draped out of them. This was a dying tubeworm colony (see right). There was no venting water, and the temperatures at the base of the colony were as cool as the surrounding seawater, about 2� C. The tubeworm tubes were covered with small white Munidopsis, squat lobsters that are found everywhere in the deep sea. These Munidopsis were scavengers cleaning up the remains of a once viable tubeworm colony and its associated animals. Munidopsis are very difficult to catch. Just one flick-of-the-tail and they shoot away. Then they drift passively back down to the bottom like little parachutes.

Satisfied that we got a good look at the senescent colony, we moved on to a taller chimney near Rebecca's Roost. It had healthy colonies of tubeworms and, as you can see from the accompanying photo, no Munidopsis. We took temperatures in and around the worms (see left) and got high temperatures of 35� C (that's about 95� Fahrenheit) among the palm worms and bacterial mat where the temperature probe is located. In general, temperatures around the tubeworms ranged from about 5 to 25� C. They typically are not found in the hotter water.

Once we were done with the temperature readings, we used a small vacuum cleaner (Dave Clague's glass sampler) to collect the small animals from the tubeworm clumps (see below). These tubeworms were relatively clear of the scale worms seen on the other nearby tubeworm clumps. Scale worms seem to prefer the cooler temperatures. The palm worms are more common in the higher flow areas with warmer water. Tomorrow we will sample some more hot vents and clumps of worms to see how well this idea holds up.

The Guaymas Basin area has some of the most picturesque hydrothermal vents I have visited anywhere in the world. The Riftia tubeworms are very large here and sulfide chimneys forming around the smokers take many forms. Some are typical mounds formed from the buildup of crumbling chimneys. They usually have one or more little smokers at or around the top. Some mounds grow lateral flanges that look like bracket fungi growing on a tree, except the flanges are large. Very hot water, often over 300� C, pools up under the flanges and trickles upward along the perimeter where you find little clumps of tubeworms and palm worms.

Tomorrow I hope to get another look at a wonderful "crystal garden" area that I visited in 1990. Slender chimneys grow several meters high and create a garden of small spires that cover the area. It looks a lot like the crystal gardens you ordered from the back of a comic book and grew in a jar. I had one of those colorful crystal gardens when I was a kid. Somehow this kind of science brings the kid back out in most of us. It's a good feeling.

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