Abstract: Zooplankton and Western Antarctic Peninsula Water Masses

Thanks for stopping by my blog! To begin, I have some explaining to do, because the timing of my project is a little unusual. While most Monroe scholars are currently taking spring classes and getting ready to carry out their research in the summer months, I am working on mine right now.

The Antarctica Peninsula can be seen at the southern end of the map

The Antarctica Peninsula can be seen at the southern end of the map

On December 26th I jumped on a plane in Washington, DC and flew all the way down to Punta Arenas, Chile. But that was only the start of my journey. I was joining Dr. Debbie Steinberg’s zooplankton team on the 2015 Palmer Antarctica Long Term Ecological Research cruise (PAL LTER). For the 23rd consecutive year, a group of scientists from around the country spent over a month at sea off the Western Antarctic Peninsula (WAP) working around the clock to learn as much as possible about this rapidly warming marine ecosystem. In addition to our group studying zooplankton this project has teams of researchers focusing on the physical oceanography, microbial biogeochemistry, phytoplankton, seabirds, and marine mammals of the region. I landed back home on February 13th and still had six weeks until my spring classes began at Friday Harbor Laboratories, the University of Washington’s marine lab. I turned that chunk of free time into my Monroe Project.

The 2015 PAL LTER cruise track until the crossing back to Chile. Note the pattern along the Peninsula, the PAL LTER cruise has run similar transects annually since 1993

The 2015 PAL LTER cruise track until the crossing back to Chile. Note the pattern along the Peninsula, the PAL LTER cruise has run similar transects annually since 1993

My goal is to determine how the zooplankton community in the WAP is influenced by specific water masses.

What the heck are zooplankton and why does anyone care? Zooplankton are animals that float in the ocean and are unable to swim against currents. They serve a key role in the WAP ecosystem as the primary grazers of phytoplankton (plants that drift in the ocean) and the main prey for higher trophic level organisms such as penguins, seals, and baleen whales. There is also a growing extractive industry for the species Euphausia superba (Antarctic krill), which is processed and sold as an omega-3 fatty acid supplement.

And what are water masses? Water masses are distinct bodies of water defined by a unique range of temperature and salinity characteristics. We have an idea of where they are located consistently, but the boundaries of these water masses migrate over time. They can highly influence zooplankton distribution, because the currents that are driving these water masses also transport animals. Additionally, the presence/absence of certain water masses will determine whether zooplankton sensitive to temperature and salinity conditions can thrive in a given location.

ARSV Laurence M. Gould, our home and office for the 2015 Palmer Antarctica LTER cruise

ARSV Laurence M. Gould, our home and office for the 2015 PAL LTER cruise

I will investigate whether water mass dynamics could influence the distribution of zooplankton species throughout the WAP by analyzing data from PAL LTER cruises dating back to 1993. For 23 consecutive years the PAL LTER cruises have sampled the zooplankton community in the WAP using 2-m2 nets towed to a depth of 120m. These tows are located at specific stations on a sampling grid that runs along the peninsula. The catch from each of these tows is analyzed for the presence and abundance of zooplankton taxa. Additionally, CTD casts are used to measure the temperature and salinity throughout the entire water column at the same stations where zooplankton tows were performed. If I know the temperature-salinity definitions for WAP water masses, then I will be able to match every tow with a specific water mass. This will allow me to search for trends and relationships between zooplankton taxa abundance within different water masses throughout the sampling grid over the entire study period.