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THE MAINE EVENT: FALL 2002 Predation by Gelatinous Zooplankton in the Gulf of Maine MISSION DISPATCH 4 • 09/09/02 Today's Weather - images courtesy of NOAA & RSMAS Dispatch by Harry Breidahl - Marine Education Society of Australasia [MESA] 
Sunday, September 8 signaled the start of the second week of the Maine Event for Fall 2002. Sunday night
was also the time when we moved from our first major survey location, Oceanographer Canyon, to the second
at Hydrographer Canyon.
This report is the first in a series of three dispatches about major research techniques aboard the R/V Seward Johnson II in the Gulf of Maine. It focuses on Johnson-Sea-Link I (JSL) and its role as one of the Maine Event's primary research tools. This adaptable submersible allows two scientists to spend about four hours underwater on a given dive. Sunday night's plunge, number 4479 for Johnson-Sea-Link I and the tenth for this cruise, reached the maximum working depth of 3,000 feet (984 meters). Usually two JSL dives are scheduled every day. The first splashdown is at 1.30 pm and the recovery winds-up on deck around 5 pm. Our 5.30 to 6.30 pm dinner is often a rushed affair because this is the time when the sub crew and scientists prepare JSL for the second dive of the day. The night dive begins around 8.30 pm and concludes close to midnight. There are certainly no Cinderellas on this voyage because midnight is far from the end of a typical Maine Event day. If anything, midnight signals the start of a hectic few hours for many on board. As JSL lands 
on the deck both sub crew and scientists swarm over the vessel once again. The sub crew recharges batteries,
fills air tanks and completes many other well-rehearsed maintenance tasks. The scientists expectantly check
the 32 collecting buckets for specimens.
Living colonies of Nanomia cara from the eight detritus samplers mounted in front of the JSL sphere are destined for Andrew Opatkiewicz, who is measuring rates of oxygen consumption and nitrogen excretion of this deep-sea siphonophore. Colonies of Nanomia preserved at the moment of capture are offloaded from the upper rotary sampler that holds 12 critter gitter buckets. In the lab the gastrozooids (= stomachs) are carefully dissected to determine the kinds and amounts of prey consumed. 
Each of the 12 critter gitter buckets in the lower sampler can also used to collect living Nanomia, or
other interesting animals that the sub pilot is able to slurp down the collection funnel. Here's where
the excitement lies. The mesopelagic zone of the ocean is such an inaccessible environment to humans that
many the specimens observed and collected are either totally new to science or rarely encountered.
The specimens, video tapes and environmental data logged on each JSL dive therefore result in a great deal of follow-up work in the science labs on the R/V Seward Johnson II. This investigation will continue for months after the cruise as the specimens, videos and other records are processed ashore. Stay tuned for details of the French underwater video profiler (UVP) and the more traditional MOCNESS multi-net system.  |  |
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