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THE MAINE EVENT: FALL 2004 Predation by Gelatinous Zooplankton in the Gulf of Maine MISSION DISPATCH 5 • Saturday, September 18, 2004 Dispatch by Chuck Jacoby - University of Florida 
Last night's weather forecast had a gale passing through the area late today, so the start time for
afternoon sub dive was moved up to 1200 in an attempt to beat the
weather. Between 1000 and 1130,
the sub and science crews readied the
Johnson Sea-Link submersible. Unfortuantely, the wind speed
picked up and sea state conditions became too rough for diving. A decision was made to avoid the
worst of the weather by running to the northwest for more sheltered water.
With the winch for the MOCNESS out-of-action, the Swedish team, Ulf, Calle, Sofie and Ebba, designed and set up new experiments to determine how much oxygen free-floating or planktonic plants and animals use in a given time and how much ammonia and phosphate they excrete. Oxygen is consumed to fuel the activity, growth and reproduction of plants and animals through a process called respiration. Ammonia and phosphate are byproducts of respiration that become toxic in high concentrations. Animals, including people, remain healthy by releasing these substances through a process called excretion. 
In the oceans, much of the ammonia and phosphate excreted by animals gets recycled.
Small, free-floating plants, called phytoplankton, use the nitrogen in ammonia and phosphorus in
phosphate during photosynthesis. In essence, the ammonia and phosphate act as fertilizer supporting
phytoplankton growth and reproduction. Animals also need the nutrients nitrogen and phosphorus, and
they get them through a food web, that is, by eating phytoplankton or other animals. Phytoplankton
contribute to the cycle in another important way. Photosynthesis creates the oxygen needed for
respiration. The Swedish team is looking at how this cycle varies in an effort to describe key
ecological processes in the canyons of Georges Bank.
One series of respiration experiments form the basis for Sofie's thesis. These experiments involve taking water from CTD casts and filtering out everything but microplankton. In this case, that's plants and animals smaller than 47 millimeters or 0.02 inches. Sofie is looking for differences in oxygen use and excretion of ammonia and phosphate among microplankton found at different depths. Some depths have more microplankton than others, so respiration, excretion and recycling may be higher. 
Ebba's experiments and her thesis will focus on oxygen consumption and excretion by krill.
Krill or euphausiids are significant members of the planktonic community in many parts of the world's oceans, including
Oceanographer Canyon. Measuring the rates of respiration and excretion for these common animals
will contribute another piece to the ecological puzzle for the canyons of Georges Bank.
Well, it's time to hunker down and survive the rough weather that's coming our way. 
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