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Another update from austral graduate student Karen:

This research cruise is part of a Long Term Ecological Research Program (LTER), an NSF-funded project to study long-term change in a diverse set of ecosystems.  Palmer Station and the LTER cruise are the primary components of the Antarctic LTER.  Long-term research is expensive to support and does not turn out a lot of results in the short-term.  However, without it, people would have no way of knowing how the world is changing over time.  It is therefore exceedingly important.

LTER science covers many aspects of the ecosystem.  There are people studying gases and trace metals in the ocean, bacteria, phytoplankton (plant plankton), zooplankton (animal plankton), birds and whales.  Carbon flux is a major focus that crosscuts many of the different project teams.  

The group that I work with studies zooplankton and their role in the Antarctic carbon cycle.  Dr. Deborah Steinberg, from the Virginia Institute of Marine Science (VIMS), runs the project.  We conduct different kinds of net tows to sample the zooplankton at different locations and at different depths around the peninsula.  In addition, some of us are conducting experiments to look at fecal pellet production, gut evacuation rates and development rates.  Each of these aspects of zooplankton ecology directly relates to carbon cycling.
The rockin' zooplankton team working their magic aboard the LMG, LTER 2012.

Carbon cycling is important because carbon is one of three primary elements that simulate the growth of life in the sea; the other two are nitrogen and phosphorus.  In addition, carbon in the ocean can exist as carbon dioxide (CO2), a major player in greenhouse gas warming.  It is therefore of utmost importance to understand how carbon moves in the marine system, and under what conditions it remains in the sea versus exits into the atmosphere.  
The way we catch zooplankton is with large nets that are towed behind the boat.  We use nets made of different sized meshes to catch different sized organisms.  
Our two meter "metro" net is deployed off the stern of the ship.  We typically tow this net down to 120 meters.  For every regular sampling station, we take a tow with this net, and another with a smaller (one meter) net down to 300 meters.

Once we have our zooplankton samples onboard, we sort, identify and count all of the animals that we have caught; this takes quite a long time!  Some examples of animals that we typically catch include: krill, salps, amphipods, copepods and chaetognaths.  We also occasionally catch larval and juvenile fish and squid.
Kate and Miram take a gander at what we have caught in our latest tow.
A mélange of zooplankton swim around in a large beaker after being brought inside the lab; here you can see different ages and species of krill, chaetognaths and more.

We are not the only ones out here trying to catch zooplankton; whales are a great indicator of large numbers of krill in the area.  In fact, when we do a net tow in the presence of whales, we usually find big healthy-looking krill in the sample.
The head and dorsal fin of a humpback whale feeding near one of our sampling stations.
Humpback whale flukes- the patterns on the underside of humpback whale flukes are used to identify individual animals.  The longest animal migration on record was recorded after a humpback known to frequent American Samoa was sighted in Antarctica.  

The zooplankton community changes with the oceanographic conditions in different areas.  Nearshore, the water contains more phytoplankton, while offshore, the waters are less phytoplankton-rich.  We tend to find large schools of krill inshore, where phytoplankton is most abundant.  Offshore, less krill are seen but we also catch more salps, a type of gelatinous zooplankton.  Salps tend to be found in nutrient-poor waters, potentially indicating ecosystem niche-differentiation from krill.  

While tiny, zooplankton are an incredibly important component of the Antarctic ecosystem.  They are the link between the organisms converting sunlight into useable energy, and all higher trophic levels here. ¬ There is evidence that as the climate warms and ice conditions change, major changes in the zooplankton community will follow.  LTER scientists are seeking to describe and understand these changes, as they occur. 

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Karen's blog prompted some discussion between me and Nick:

Andy--(to Karen) Awesome. I love the krill pics. FYI--Arctic terns kick the crap out of Samoan humpbacks, at least in terms of migration.

Nick--Yeah, do you mean the largest humpback migration? That doesn't seem that far to me.

Andy--Samoa to Antarctica?--Whatever. I bet Pete could swim that.

NIck--I'm pretty sure he has already swum it. On a bicycle.

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This page contains a single entry by Andy Pershing published on January 14, 2012 8:46 AM.

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