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March 16, 2003: Leg 3, Day #5

Guaymas Basin
Today's update has been provided by Karen Osborn.

Another great day at sea! It was a day of firsts for the entire midwater science crew. We were exploring the water column above the hydrothermal vents in Guaymas Basin. We slowly worked the ROV Tiburon down stopping to identify animals as we came across them. Mar16_Munnopsis.jpg (24913 bytes)Unlike most of our other dives so far, there were no "spider" firsts today. However, the afterglow of finding hundreds of Munnopsis (a.k.a. "spiders" like the one seen here hanging in the water column) feeding like daddy-long-legs on the sea floor two days ago and yesterday, finding the feather-foot "spider" Munneurycope carrying around and chewing on larvacean sinkers, was enough to keep me riveted to my seat in case something else popped up. 

Seeing rather bizarre stomatapod (mantis shrimp) larvae at 200 meters was exciting because they are so unusual. On our way down we passed through a layer thick with the small, lobate Thallasocalyce and another with abundant Phialidium medusae. "Spiders" were less abundant than other dives here but still more abundant than we generally see in

Monterey Bay. We collected several Munnopsis that will be used: to illustrate the new species description, for molecular phylogenetic work, and for gut content analysis. That should ensure I don't make it to bed before at least midnight.  

You may have noticed my bias and figured out that I work on "spiders," otherwise known as munnopsid isopods, and am loving the chances to observe and study the group in an area where they are so plentiful. We have never seen them this abundant in Monterey Bay. Because of the increased abundance, the chances of observing interesting behaviors and using it to determine how they fit into the midwater community are greatly increased here. I am in my second year of working on my doctoral dissertation through University of California, Berkeley and MBARI on the natural history of munnopsid isopods.  

But now, back to our day… As we got closer to the sea floor and the vents, we saw the nutrient-rich smoke plumes typical above the hot vents. We are particularly interested in the animals that are found in these plumes. Will there be different animals here than found in non-vent areas, or will there be higher, lower, or similar numbers of animals found above the vents?  

Mar16_ventworms.jpg (79031 bytes)As we neared the bottom, swimming sea cucumbeMar16_cuc.jpg (44384 bytes)rs like the one shown here (see right) became numerous, and the ROV control room filled with all the science crew. Finally we began to see the hot vents and the huge clumps of tubeworms living around them (see left) for the first time in our lives—it was astonishing! After surveying the animals found around the vents, like the octopus seen here, and looking for the "spiders" we've quickly grown accustomed to seeing all over the bottom, we headed back up to run video transects in shallow water. 

As soon as the ROV was on deck, the ship's crew helped us set out the trawl net. Despite my best efforts searching through the trawl bucket, there were no spiders in either of the trawls we completed—they were too shallow. Luckily, that is not what we were looking for. Instead, Bruce Robison and Jeff Drazen are comparing the fish diversity and abundance to identical trawls carried out in this area 30 years ago by Bruce. The trawls also turned up numerous interesting pteropod and squid species, which Brad Seibel is using to measure respiration rates on.  

I better head to my bunk because we are in the water again at 6:30 a.m., and I don't want to miss anything. The really amazing thing about midwater work with the ROV is that you just never know when something new or unusual is going to turn up, so you never want to look away from the screen. It makes for long, but very interesting days, especially when you are exploring a little-studied area like this.   

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