Our echo sounder, or DT-X as its manufacturer Biosonics call it, sends sound waves out at a frequency of 120 kilohertz (kHz). The sound waves bounce off animals, like krill, in the water and return to the echo sounder. The acoustic returns are logged and later analyzed.
The data we get from the echo sounder allow us to figure out what is in the water and how much of it is there. For every acoustic return we have a date and time stamp as well as latitude and longitude coordinates.
Our target animal is the Antarctic krill (Euphausia superba), and we are trying to understand what drives its distribution patterns and densities near Palmer Station. One of the reasons we are interested in this is because the Adélie penguins that breed on the islands here feed on Antarctic krill.
We’ve had an exciting week here at Palmer Station! First and foremost, the ‘polar plunge’ was completed as the Laurence M. Gould pulled away. All participants stripped down into bathing suits and jumped from the boating pier into the freezing Southern Ocean. Your whole body instantly goes numb so the water doesn’t feel that cold—but running through the snow to the hot tub was a little chilly.
After waiting for the sea ice to move out and the winds to calm down, we were finally able to have our Boating II course! It was my first time driving a Zodiac so I was really excited. We practiced driving around, landing at islands, and working the GPS. In addition our boating coordinator put on an immersion suit and flung himself into the water several times so that we could practice “man overboard” drills and retrieve him.
On Saturday Kim and I went out on our Zodiac (Miss Chippy) to calibrate the echo sounder. After making it through some brash ice (accumulation of floating ice chunks) we set to work trying to calibrate, but without much success due to currents and wind. We ended up moving back into a part of the brash ice that was slushy—this allowed us to stay still enough to retrieve some data. So although sea ice is normally a nuisance with boating, it proved to be helpful!
To help us suspend our echo sounder off the side of the Zodiac, it attaches to the bottom of a wood structure shaped like a whale, complete with a dorsal fin. This year, the whale needed a new paint job. Kim and I started off by sanding away the old paint and then I spent a few days adding new coats. We decided to decorate it as a leopard seal, complete with spots and teeth, however the dorsal fin proved to be a little bit of a problem – so I painted it orange and we’re claiming it’s a leopard seal in disguise.
After 9 days of traveling, I finally arrived at Palmer Station, Antarctica! I flew from Dulles International Airport down to Santiago, Chile and then landed in Punta Arenas, Chile to await my voyage by sea, aboard the Laurence M. Gould research vessel. I am working on a zooplankton acoustics project with a Post-Doctoral student Kim Bernard from the Virginia Institute of Marine Science. I will be living at Palmer Station until I return home at the end of December.
Before heading to the ship, I made sure to rub the toes of a statue in the main square of Punta Arenas. It is a local tradition to ensure safe passage across the Drake (waters separating South America and Antarctica). One observation I had about the city, is that it is ruled by dogs. They are everywhere, roaming around in packs, sitting at street corners and outside shops, and occasionally escorting you as you walk through their turf. The city even has trashcans marked only for food scraps, specifically at dog height.
While going across the Drake Passage, all of us helped deploy Expendable Bathy-Thermograph (XBT) and Expendable Conductivity Temperature Depth (XCTD) probes. XBT probes measure water temperature, while XCTD probes tell us water temperature and conductivity. A group of scientists is studying the ocean currents in the passage, and hope to release these probes for the next 50 years to obtain data. Some of the ship crew joke that by the end of the project, there will be stepping-stones across the Drake where the probes were dropped. The procedure is to shoot the probe out and let it transmit data for a few minutes, which is then repeated every 30-45 minutes.
Additionally we obtained seawater samples, to measure oxygen content and nutrients in the water. Here I am in the process – I really was excited to be helping, I must have that face on because I had left my hat inside (it was around -13 degrees Celsius with the wind chill).
Our fifth day at sea, we stopped at the King George Island to unload researchers and supplies to the Copacabana (Copa for short) field camp there. I was a ‘sherpa’, which meant I helped load supplies off the zodiacs and onto land. It was a lot of work, but nice to be so active after a few days at sea. We were able to see penguin colonies hanging out around the field camp, and a few even wandered over to see what we were doing on the beach.
So far at the station I’ve gone hiking up the glacier in our backyard, and will soon learn how to drive and operate Zodiac boats. I’m excited to get the season started!
VIMS post-doctoral research associate Kim Bernard will be returning to the U.S. Palmer Research Station on the Antarctica Peninsula for another field season beginning in mid-October. Traveling with her is W&M undergraduate Domi Paxton.
Their research, part of the ongoing Palmer Long-Term Ecological Research Project (PAL-LTER), focuses on the distribution patterns of Antarctic krill in nearshore waters, and on how these patterns change across time and space. They relate their findings to physical drivers, such as tidal phases, and to the foraging ranges of Adelie penguins. Krill are an important part of the Antarctic marine food web, providing the main source of energy for marine mammals, penguins, seabirds, and fish.
During the upcoming field season, which will stretch into February 2012, Bernard and her colleagues will use acoustics to detect krill aggregations and to estimate their abundances and biomass. They will also try to collect krill samples from net tows to measure length frequencies of the krill in the area. Most of the work will be done from a Zodiac fitted with an echo-sounder—the researchers will go out every day during a diurnal tide and then for up to 5 days into the following semi-diurnal tide to monitor how the tides affect krill distribution patterns. (The Antarctic Peninsula is one of a few places in the world that experiences both tidal types.) She expects to see 4 or 5 series of diurnal to semi-diurnal tides and will attempt to sample all of these.
Bernard will also be going out on the research vessel Laurence M. Gould to conduct an acoustic survey of the head of the Palmer Deep Canyon (which is too far offshore to reach using a Zodiac from Palmer Station).
Bernard says that her work will “contribute to the PAL-LTER through improving our understanding of the physical drivers of krill distribution patterns, and will provide important information in terms of key penguin foraging areas.”