Updates From Sea | Cruise 2007
February 4th
By Eric Simms, Education Outreach Coordinator
Vent Biology is Booming After the Eruption
Tim, Kate and Breea eagerly inspect samples collected from today's dive. Photo © E. Simms
When Dr. Tim Shank saw the first pictures of the seafloor at the East Pacific Rise (EPR) last May, almost six months after a large eruption, he wasn't quite sure how he should feel. After all, Tim had been studying the hydrothermal vent animals at this area of the mid-ocean ridge for twelve years. But almost overnight, the same area of the seafloor that Tim knew in great detail looked completely different - most of the animals and vents had been completely covered by up to several meters of fresh lava. "I felt like I went on vacation and came home only to find that all the furniture in my house was rearranged," remarked Tim, "I had a hard time recognizing anything down there." Although he was excited at the opportunity to study what happens after a new eruption, Tim also felt some disappointment that the sites and animals that he had studied for so long were now simply gone. But he knew too that vents are very dynamic environments, and quickly shifted gears to take advantage of this unique research opportunity.
In the last year, Tim and a team of biologists from Woods Hole Oceanographic Institution and Rutgers University have returned to the EPR several times to begin to document the order in which animals arrive at new vent sites. On this cruise the team visited both old and new vent sites to see what animals are present and collect samples for analyses. And, of course, they are also interested in how the chemistry of the vent fluids relates to the animals found there.
Click here for pictures of the Biology lab group at work.
Tevnia tubeworms appear to be early settlers. Photo © E. Simms
One animal the group has found plenty of at many of the new vents is Tevnia, a species of tubeworm. It appears that the larvae of these worms arrive early at new vents and within a year can reach their adult size of up to 50 centimeters. Based on chemical measurements where the Tevnia are found, it appears they prefer to live at vents where there are high levels of hydrogen sulfide in the fluids. This is interesting because scientists suspected a similar pattern after a large eruption at EPR in 1991, even though they weren't able to sample as extensively then as they are now. The group is also curious to see how long the Tevnia at the vents will survive before other animals arrive and compete for the limited space around the vents. There weren't many Tevnia at the vents several years after the 1991 eruption, so it is believed they may eventually decrease in numbers over time after the recent eruption. Other animals that were fairly abundant around the vents on this cruise included crabs, fish, and swarms of amphipods (small crustaceans a few millimeters long).
Other animals that were abundant at the vents before the eruption include large Riftia tubeworms and mussels, but very few of these animals appear to have survived. Scientists believe that these animals usually arrive at vents later than others after an eruption. However, some juvenile Riftia were found at a few new vents, indicating that conditions might be favorable in some places for these worms to start returning.
Bythidid fish - a face only a scientist could love! Photo © E. Simms
A very exciting part of the biological studies on this cruise involves the collection of deep-sea Bythidid fish by graduate student Kate Buckman and Alvin pilot Gavin Eppard. Although scientists often see these fish at the vents, almost nothing is known about them, including what they eat, and how and when they reproduce (by the way, one of the fish collected had developing fish inside, and this has only been found one other time!). With some help, Kate and others dissected all but one of the fish collected and took samples of their liver, muscle, gills, and digestive and reproductive systems. Kate will analyze all of these samples when she gets back to shore to learn much more about these fascinating fish.
The hundreds of samples and thousands of images taken of the animals found at the vents during this cruise will help Tim and his team of scientists better understand these animals, how they interact with each other and their environment, and how the communities of vent animals change over time after an eruption. It promises to be an exciting story.
