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THE MAINE EVENT: FALL 2003 Predation by Gelatinous Zooplankton in the Gulf of Maine MISSION DISPATCH 5 • Sunday, September 14, 2003 Location: Oceanographer Canyon (40° 17'N, 68° 7'W) Dispatch by Harry Breidahl - Marine Education Society of Australasia [MESA] The 16 hour transit from Georges Basin to Oceanographer Canyon (our third area of operation) began early this morning. Along the way the weather was fine and low swells made for a smooth passage. After almost a week at sea the transit provided us with a brief break in the hectic daily shipboard schedule. Because time at sea is limited, scientists on board must pack as much as they can into every day. In other words, all of the scientific party must adjust their sleep patterns to fit a 24 hour program of field work (sub diving, MOCNESS net towing, CTD deploying) and laboratory work (sorting, preserving, counting, photographing, measuring, and monitoring with stereo microscopes, video/still cameras, and data-logging computers). Coming from Australia, the added time difference of 14 hours has made this adjustment especially tough for me, it is hard to tell night from day. 
R/V Seward Johnson reached Oceanographer Canyon at 4.15 pm. Clear oceanic blue waters surrounded us and we look forward
to exploring a water column three times deeper than Georges Basin, down to 980 meters. At Georges Basin, we had been drifting
in a bloom of surface dwelling salp aggregates. Here at Oceanographer Canyon, we were introduced to a beautiful medusa known
as Pelagia noctiluca when graduate student
Brian Ortman netted a specimen and
brought it into the dry lab in a bucket.
That night we were surrounded by these beautiful creatures but thankfully they were too large to clog the vessel's saltwater
intakes and drifted peacefully by.
The R/V Seward Johnson has several laboratories on-board. Some are permanent while others are temporary, specialized labs housed in shipping containers fixed (very firmly) to the vessel's decks. One of the permanent labs is called the wet lab because anything that requires working with seawater is conducted there. On this voyage a peculiar piece of equipment in the wet lab is the circular, upright aquarium, called a plankton kreisel. It has been used to take photographs of Pelagia noctiluca and will be utilized again for imaging other gelatinous zooplankton from tonight's dive. 
JOHNSON SEA-LINK II (JSL) dive 3444 was a night dive and our first at
a deep canyon site for this year's Maine Event.
Marsh Youngbluth and sub pilot
Tim Askew Jr. were in the forward sphere, while the aft compartment was occupied by research assistant
Helen Mayoral and sub crew
Alan Fuller. The dive began at 8.30 pm and reached a depth of 2,700 feet (820 meters). Three and a half hours later (at midnight),
the well rehearsed routine of recovering the sub was witnessed by the usual collection of expectant scientists.
The return of JSL II to the aft deck is always a much anticipated event and on this occasion the waiting scientists were in for a treat. In addition to the usual cargo of Nanomia cara colonies, Marsh and Tim captured a deep-sea cranchid squid and a midwater cirrate octopus (Stauroteuthis syrtensis) at 800 m. The 20 cm long squid had two large and darkly pigmented eyes but the most striking feature was the animal's ability to be almost transparent one moment and highly freckled in the next. This feat was accomplished by a rapid concentration 
and dispersal of pigment in special cells called chromatophores. The 30 cm octopus was
a vivid reddish-orange color, had a membranous web of skin between its tentacles and possessed two small flipper fins just behind
the eyes (hence the common name of dumbo octopus). This animal is one of only two octopus species in the world that are known to
bioluminesce. The suckers along the arms have evolved into light-emitting organs that glow blue-green in the perpetual darkness
of its habitat.
Fun facts for the day • Jellyfish, siphonophores, corals and sea anemones all belong to a single animal group - the Phylum Cnidaria. The term medusa refers to the typical bell-shaped cnidarian form that we commonly call a jellyfish. • The noctiluca in Pelagia noctiluca means night light and that is just what this beautiful medusa does - it glows in the dark. Unfortunately, the powerful lights that flood the aft deck of R/V Seward Johnson prevented us from seeing this phenomenon. • A kreisel is also called a plankton wheel. It is an upright circular aquarium with a pump that continuously moves water in a clockwise direction. The currents are gentle and serve to keep plankton suspended in the water. This feature allows scientists to observe and photograph planktonic organisms.   |  |
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