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Rocking the MOC

12/05/2010, 10:07 PM by Lollie Garay
Antarctic Starfish<br/><br/>Credit: Tish Yager
Antarctic Starfish
Photo Credit: Tish Yager

Dec 5

Marguerite Bay

Rocking the MOC

Stephanie Wilson, Zooplankton Ecologist from Woods Hole MA is part of the ASPIRE zooplankton team. She has written today’s blog explaining her work using the MOCNESS.


“It is 2:30AM and we have just deployed our "midnight" MOCNESS (or MOC for short) tow for zooplankton. MOCNESS stands for Multiple Opening and Closing Net and Environmental Sampling System and consists of 9 mesh nets that can be sent down into the ocean and triggered to open and close at specific depth intervals so we can collect zooplankton at different depths throughout the water column. This is great for looking at which zooplankton live at which depth.


Zooplankton are tiny animals that drift with the currents and include krill, salps, larvae, other crustaceans and jellies. For the most part, the highest density of zooplankon live close to the surface, in the euphotic zone where light penetrates, and their numbers decrease with depth. Here in the Bay, we aim to do one "noon" tow and one "midnight" tow at each station because some of the zooplankton migrate from deeper waters at night to feed. 


Even though it is still somewhat light at night here in the Antarctic summertime, many zooplankton still keep their day/night migrating patterns throughout the year. Our goal with the MOC for this part of the cruise will be to look for the invasive crab larvae as well as get a feel for what other types of zooplankton reside in this area of the Antarctic.


The MOCNESS is highly temperamental and everything needs to work just right before we deploy it over the side. The engineers, technicians, and scientists work together to make sure the instruments on the net are functioning. At one point, an instrument called the CTD that measures salinity, temperature and density stopped working. It was snowing out and the CTD had frozen in the cold Antarctic air. The engineer on duty took the CTD off the net and placed it snugly in his jacket to warm it up before testing it out again. Now that's dedication!

Now that the MOC is deployed, a scientist and engineer will monitor the net on its entire journey down to around 800m when the second net will be triggered to open (the first net stays open all the way down). As the nets slowly come back up, the triggering of each net will go on for 8 depth intervals until it reaches the surface, a total time of just over 3 hours. Then the fun begins with checking out what we've caught! “


Thanks Stephanie! Samples from the plankton net are preserved in ethanol to be taken home and “keyed out” to species under a microscope. Although there are microscopes on the ship, the careful lab work is best done off a “moving” lab ☺ Hope to see more specimen photos!


After a midnight MOCNESS, the ASPIRE Team will depart the Marguerite Bay and spend about 3 days in transit along ~ 65°S before they turn south into the Amundsen Sea.


It is also possible that they will encounter the “undersea pirates” of the Antarctic Circle crossing!!!!  Tish says: “We are on the lookout! “


 Be careful everyone!   ARRRR,










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Question of the Day

  • What are Polynyas and why are they important to study?

    Polynyas, are recurring areas of seasonally open water surrounded by ice.

    Energy and material transfer between the atmosphere, polar surface ocean, and the deep sea in polynas provide polar ecosystems with just the right ingredients needed for high productivity and intense biogeochemical recycling.

    Polynyas may be the key to understanding the future of Polar Regions since their extent is expected to increase with anthropogenic warming.