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THE MAINE EVENT: FALL 2003 Predation by Gelatinous Zooplankton in the Gulf of Maine MISSION DISPATCH 7 • Tuesday, September 16, 2003 Location: Wilkinson Basin (42° 28'N, 69° 42'W) Dispatch by Harry Breidahl - Marine Education Society of Australasia [MESA] Our time at Oceanographer Canyon was unfortunately cut short by the impending arrival of 14 foot (4 meter) swells headed our way, courtesy of Hurricane Isabel. Immediately following last night's dive (JSL II dive 3446), gear was stowed away and we headed back )
to Wilkinson Basin. As this site is closer to shore and more sheltered, the science party had an opportunity to work one more day
before the transit to a safe harbor.
Two dives were completed today. JOHNSON SEA-LINK II (JSL) dive 3447 was hoisted from the aft deck at 2.30 pm and returned at 5.30 pm. Dive 3448 hit the water at 9.00 pm and landed on the aft deck at 11.45 pm. Although no colonies of Nanomia cara were seen on either dive, the undersea excursions were highlighted by collections of a few small and exquisitely delicate medusae - Ptychogena lactea and an unknown tiarannid (if you go back to Dispatch 5 you will find out that a medusa is what scientists call a jellyfish). Also collected were several ctenophores (including Bolinopsis infundibulum, Euplokamis dunlapae and Beroe cucumis). The swimming and feeding behaviors of most of these species were observed, oxygen consumption was measured, and tissues were preserved for molecular sequencing. 
The fact that fragile midwater organisms were brought to the surface in prime condition clearly highlights the collection
capabilities of the JSL submersibles and the proficiency of their pilots, in this case Craig Caddigan. The clear acrylic sphere
of a JSL sub provides an uninterrupted forward view for a scientist sitting beside a sub pilot who controls the nine electric
thrusters that maneuver the sub. A skillful sub pilot can approach and capture even the most delicate gelatinous midwater creature,
in either the 24 "critter gitter" canisters or in the 8 "detritus" samplers. While the critter gitter package is relatively easy
to maintain, the detritus samplers need constant maintenance and a special kind of subtle, but firm tinkering. That is one of the
tasks at which Chuck Jacoby excels
and, on this cruise, so does undergraduate marine engineering student
Brennan Phillips. These
two guys are absolute masters at keeping the temperamental detritus samplers functioning properly.
The hour or so before every JSL dive is always a hectic period of checking the all the critical control functions and outfitting
the sub with sampling chambers. Last minute adjustments are often needed before the sub is hoisted into the sea on schedule. Then
a period of three and a half hours elapses while the sub is diving. During this time some of the science party continue to work in
the shipboard laboratories on various projects. Others go below and roll into their bunks to catch an hour or two of sleep.
Activities continue 24 hours a day and so it is not uncommon to see scientists taking a brief nap in one of the labs or elsewhere
on board.
The R/V Seward Johnson is underway now heading for Gloucester, Massachusetts. If all goes to plan we will return to the sea on Saturday and continue The Main Event 2003 research program. New mission dispatches will resume at that time. Fun fact for the day • In these dispatches I quote times in the more usual format of am (morning, or before noon) and pm (afternoon), the program aboard SEWARD JOHNSON runs on a 24 hour clock. Using this system dive 3447 was launched at 1430 hours and recovered at 1730 hours, while dive 3448 hit the water at 2100 hours and was hoisted back onto the aft deck at 2345 hours. • Our return to shore was necessitated by the arrival of Hurricane Isabel. I remembered, with just a little irony, that Gloucester was the fishing town featured in the film The Perfect Storm.   |  |
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