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THE MAINE EVENT: FALL 2002 Predation by Gelatinous Zooplankton in the Gulf of Maine MISSION DISPATCH 5 • 09/11/02 Today's Weather - images courtesy of NOAA & RSMAS Dispatch by Harry Breidahl - Marine Education Society of Australasia [MESA] 
The Fall 2002 Maine Event is now into its second week. The last five days, spent at Oceanographer Canyon,
were very productive. Balmy weather and smooth seas allowed us to complete 10 dives in
Johnson-Sea-Link I (JSL),
five
MOCNESS multi-net tows and 31 vertical deployments with the French video profiler (UVP).
On Monday we moved the R/V Seward Johnson II to Hydrographer Canyon at 400 02.9' N, 690 02.3' W. The weather remained benign and the research projects continued at a hectic pace. Unfortunately, the threat of an approaching tropical storm that was likely to merge with a cold front over the Georges Bank compelled us to head for shelter at Woods Hole and wait for rough sea conditions to abate. The return trip showed us how far from land we ventured as it took 15 hours to reach the dock. 
This dispatch is the second in a series of three messages detailing research techniques aboard the R/V Seward Johnson II
in the Gulf of Maine. This time the focus is on the MOCNESS multi-net system. Before submersibles such as
Johnson-Sea-Link allowed scientists to explore the mesopelagic zone of the ocean in person, remote devices such as
MOCNESS net systems were used to provide information about the vertical distribution and relative abundance of midwater
zooplankton and fishes.
The MOCNESS net system consists of nine separate plankton nets that are connected to a large rectangular metal frame. At the distal end of each net is plastic canister, called a cod end (a link to the fishing industry ancestry of the system). This is where the captured animals are retained. The apparatus is quite heavy and a crane must be used to lift the MOCNESS over the starboard side and then lower it into, and later hoist it out, of the water. These tasks are not easy, especially on a rolling deck. )
The close cooperation between the crane operators and those people on deck
is great to watch, partly because of the skill involved but also because of the lively hand signals used by the deck
crew to communicate with the crane operators above.
Once below the surface of the water, the MOCNESS system is towed slowly behind the vessel. A winch is used to lower and then raise the multi-net system to and from the required depth - that's the dull bit. The fun begins when the nets are landed back on deck and expectant scientists gather around the cod ends like children around a Christmas tree. Apart from canister number 1, which stays open throughout the tow, the remaining eight canisters can be opened and closed to allow samples to be collected at various depths. As soon as the MOCNESS frame is secured on deck, the scientists carefully decant the contents of each canister into consecutively numbered plastic buckets and take them to the wet lab on board the R/V Seward Johnson II. Many of the animals returned from the depths seem to other worldly. A variety of gelatinous creatures, )
mostly fragmented, several
fishes, especially jet-black myctophids (small deep-sea fishes commonly called lanternfish), a few red shrimps and an
occasional squid represent the deep water food webs.
Every now and then an animal that is new to science turns up in one of the buckets. Discoveries of a new siphonophore from the genus Lensia, and an undescribed appendicularian had both Francesc Pages and Marsh Youngbluth quite excited.  |  |
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