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THE MAINE EVENT: FALL 2003 Predation by Gelatinous Zooplankton in the Gulf of Maine MISSION DISPATCH 4 • Saturday, September 13, 2003 Location: Georges Basin (42° 18'N, 67° 30'W) Dispatch by Harry Breidahl - Marine Education Society of Australasia [MESA] Last night gelatinous animals had sudden and unexpected impact on daily life aboard the R/V Seward Johnson. For a day or so, the ships engineers have been struggling to clean the seawater intakes for the vessel. That's where the gelatinous animals come in - literally. Seawater is used to cool the engines and is also utilized for the desalination system that provides our freshwater. Pipes 
that bring this seawater into the vessel have filters that are currently being clogged by
masses of surface-dwelling gelatinous zooplankton.
The first hint of a plankton bloom surprised us a couple nights ago when Whitley Saumweber collected seawater in a bucket. Whit needed the water for his research on copepod respiration. After first notifying the bridge and donning a life jacket (both critical safety precautions) he lowered a bucket over the gunnel. What he caught with the water was most interesting - a few mysid shrimps and a lot of little bluish creatures called salps. Not a great deal of attention was given to this discovery at the time because the sunlit surface waters of the Gulf of Maine are normally rich in planktonic life. That all changed last night when Assistant Engineer Erik Bergendahl came into the dry laboratory to show us filters clogged with blue gelatinous goop. Per Flood and Francesc Pages identified this slimy material as the remains of Thalia democratica, the same salp that had been collected by Whit. The fact that these creatures are fouling the seawater inlet filters means that we are suffering a "salp induced drought" on board and the use of fresh water has been restricted. 
Despite the water rationing, everyone is busy aboard R/V Seward Johnson. Early this morning a couple vertical plankton tows
literally brimmed with plankton, especially the prolific salps. Various creatures were scooped from the soupy collection to be
examined, photographed and eventually preserved in one way or another for future, more detailed studies of their genetic makeup
or chemical composition. The sub crew rebuilt one of the critter gitter pumps, which allowed us to collect dozens of Nanomia
colonies during day and night JOHNSON SEA-LINK II (JSL)
excursions into the depths of Georges Basin (dives 3442 and 3443). Based on in situ
observations by scientist Francesc Pages and sub pilot Craig Caddigan sitting in the sphere and undergraduate
Brennan Phillips
and sub-crew Jim Pierce in the aft chamber, it was clear that a portion of the Nanomia cara
population migrated nearly 200 m upward
during the night. Why? Our preliminary examinations suggest they move into shallower waters to dine on small copepods.
The last activity at this location was a CTD cast at midnight to obtain water samplers for fatty acid analyses.
We've spent only four days at this location and there is more to learn but the seas are calm and predicted to remain benign
for a few days. So, we've decided to steam to the southern edge of Georges Bank to gather comparative data on colonies that
live in the deep water canyons. Hopefully, we will be able to operate there for a few days before the impending storms prevent
submersible dives and over-the-side operations. In anticipation of our transit, all laboratory equipment and other odds and
sods have been strapped down or stowed away. We will steam for the next 16 hours. Our expectation for tomorrow is a 2,900 foot
(900 meter) plunge into Oceanographer Canyon and the chance to observe and collect a much different, more diverse community
of plankton.
Fun facts for the day • During discussions about Thalia democratica with Per Flood, I discovered that the brilliant blue color of these diminutive drifters may be an important part of their ability to survive in the uppermost sunlit layers of the ocean. It seems that this blue pigment probably provides protection against ultra violet radiation from the sun. Now that I think about it, most oceanic drifters are blue in color. Surface drifters, such as the Portuguese man-o-war, belong to what is commonly known as the 'blue fleet' or 'blue armada'. • While we are on the subject of the Portuguese man-o-war, it is worth noting that they are siphonophores, surface-dwelling relatives of Nanomia cara.   |  |
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