Post by VIMS graduate student Lori Price
Shortly after leaving Palmer Station we reached our first oceanographic sampling station and began our science! We are part of the Palmer Long-Term Ecological Research project (PAL-LTER) which has been sampling the marine ecosystem along the Western Antarctic Peninsula for about 20 years now.
There are several scientists involved in this project—a physical oceanographer who studies the water masses and currents, a bacterial guy who studies, yes … bacteria, a phytoplankton guy who also operates gliders, Debbie the zooplankton person, and people that study the seabirds. Gliders are autonomous underwater vehicles—a fancy phrase for a torpedo-shaped vehicle that glides in the water, collecting information on water quality. It’s the latest, greatest piece of technology being used by oceanographers.
Each scientist has their own team of technicians and graduate students that help out with the research and do some side projects on their own. At each regular sampling station (which takes about 7 hours to complete), each group has their own task to perform to collect samples, which becomes like routine clockwork after the first few stations (unless something goes wrong or breaks … knock on wood). These stations are laid out like a grid along the Peninsula from north to south, extending about 200 kilometers (120 miles) offshore. We sample the same stations every year, providing a nice long-term dataset.
At each regular station our zooplankton group collects critters using three different nets—a very large square-frame net (2m x 2m) to collect larger zooplankton like krill and salps (gelatinous animals, kind of like jellyfish that don’t sting), a smaller square-frame net (1m x 1m) to collect smaller animals (like copepods), and a small ring net (0.5 m) to collect microzooplankton (very tiny single-celled zooplankton). The nets are attached to a cable and towed behind the ship to a certain depth. There is a bucket (called a cod end) at the end of the net that collects all of the zooplankton. When the net is brought on board we dump everything that we catch into a big tub. All of the animals we catch in the two larger nets are sorted and counted live on the ship. Most of the critters are large enough that we can easily identify them, although sometimes microscopes are needed for the slightly smaller zooplankton that we catch. The contents of the small net are preserved immediately and processed in the lab back home.
At three stations called “process study stations” spaced out along the grid close to penguin feeding areas, we stay for about three days and do more in-depth sampling. Our zooplankton group does day and night MOCNESS tows at these stations. MOCNESS stands for Multiple Opening and Closing Net Environmental Sensing System and is a large, complicated frame that can hold ten nets at a time. The nets can be triggered to open and close at different depths so that we can sample the zooplankton community at specific depths. We do day and night tows because some zooplankton are known to vertically migrate. This means that they are found in the surface waters at night in the cover of darkness to feed, and then they migrate deeper during the day to avoid being eaten by some predators that rely on their eyesight to hunt and feed in the surface waters. Using the MOCNESS, we can sample specific depths during the day and night to see if any of the zooplankton species show this behavior.
In addition to the MOCNESS and our regular net tows, I do experiments for my thesis research at these process studies. I do two experiments, called dilution experiments, that measure microzooplankton grazing on phytoplankton and bacteria. They are very time-consuming to set-up and take down, but I always have someone to help me to make things go quicker and also to make it more fun. Dilution experiments are kind of tricky to do and don’t always work exactly how you would like them to, so I’m keeping my fingers crossed that this year they will go well. I’ll keep you posted.
Our group also does fecal-pellet production experiments to measure how much the krill and salps are pooping. Not only do we measure how much they poop, but we also do sinking rate experiments to measure how fast the krill and salp poop pellets sink. That literally involves putting a piece of poop in a clear tube of seawater and timing how long it takes to fall a certain distance. We have poop races sometimes. This might sound a little bit ridiculous, but it’s actually very important. The ocean removes a lot of the carbon dioxide that’s in the atmosphere, which phytoplankton use when they photosynthesize (if you remember your Intro to Bio class, plants use CO2 for photosynthesis, removing it from the atmosphere). Zooplankton eat the phytoplankton, packaging them into fecal pellets that they poop out. Some of the fecal pellets break down in the surface waters and the carbon in them in released, but some fecal pellets make it to the ocean floor and the carbon in them is buried by sediment. This cycling of carbon by zooplankton, part of the “biological pump,” removes carbon from the atmosphere and puts it in the deep ocean. So, poop really is important!! Especially today with the ever-rising CO2 concentrations in the atmosphere. And we think it’s fun playing with poop sometimes too!