It took us about a week to get there, and years of preparation to be ready for the journey that awaited us once we arrived. Alas, after a few plane rides, a few days loading the boat with all our gear, and 5 days sailing across the infamously rough Drake Passage, Palmer Station came into sight from the bow of the R.V. Lawrence M Gould. And the work was just about to start.
Why were we traveling to the Antarctic?
Our purpose stretched far beyond checking off the last continent from our travel agenda. Myself and the project SWARM field team were there to investigate a question that has been intriguing ocean scientists for decades: what leads to the “patchy” distribution of prey in the ocean? [1,2,3]
Admits other objectives, the research questions we were there to explore that eventually motivated the creation of this manuscript were:
- How do local foragers, like penguins, locate patches of prey in their dynamic ocean environment?
- Do coastal ocean currents concentrate planktonic prey, making them easier for foragers to find?
- How do ocean currents effect predator-prey interactions?
Building an Ocean Observatory
To tackle these questions, team SWARM built an ocean observing system around a known penguin foraging area, Palmer Deep Canyon, which is about halfway down the Western Antarctic Peninsula. This began with three High Frequency Radars which use radio waves backscattered off the ocean surface to measure surface ocean currents. But these weren’t just any High Frequency Radars. These were specifically designed to be disassembled, transported, and assembled in remote locations, with no one piece of equipment weighing more than 100 pounds (45 kilograms).
To build each radar, the skillful crew aboard the R.V. Lawrence M Gould “parked” the 230 foot (70 meter) long boat nearby a remote island. Our shipboard team then loaded gear from a shipping container into small zodiac boats with a large crane. The zodiac boats then carried the gear over to the island where are shore team unloaded the boat and carried the equipment to our building sight.
Assembly of each radar took 4-8 days, depending on how much snow and ice we had to clear. Once all three radars were built, we had hourly observations of surface currents in the area!
With the radars built, we moved onshore to Palmer Station from where we conducted small-boat surveys of the local ecology. Twice a week, the SWARM team would board a small boat to survey the region within our surface current measurements from the radars. The small boat towed an instrument through the water that measured optical properties, allowing us to detect how much chlorophyll-a, a pigment in all photosynthesizing organisms, there was in the water. This gives us a good estimate of how much phytoplankton biomass there was in the water. We also used an acoustic instrument that was mounted to the bottom of the boat to observe backscattering zooplankton, the main predators of phytoplankton.
While part of the SWARM team was on a small boat measuring phytoplankton and zooplankton, the other part of our team was visiting local penguin colonies to tag penguins with a GPS that would track their location and dive depths. From this GPS data, we were able to determine where the penguins were foraging for their food, zooplankton.
From these data, we were able to map each level of the food web onto the dynamic ocean surface currents! We found that penguins visit certain features of the ocean as if going to marine “grocery stores”. Their food is grown elsewhere and transported to these patches of increased food availability, their “grocery store”. Read our manuscript to learn more about how ocean currents concentrate prey patches into “grocery stores” that are then visited by penguins!
Life at Palmer Station
Days were long but time was short at Palmer! Team SWARM had about three months at Palmer Station to conduct all of our observations. Most days begin around 7:00 with breakfast in the galley and a team meeting. We then dawn all our layers and load the small boat with the equipment we will need for the day. After all the necessary safety checks and a quick stop in the kitchen to pack a lunch for the day, we set off for about 8 hours of sampling from the small boat. Upon our return to station, we unload the boat and clean our instrumentation while the marine technicians moor the boat. A highly anticipated hot dinner awaits us prepared by the incredible kitchen staff. After dinner we look at some of the data that we had collected.
We also had a little time for fun while at Palmer Station. Behind the four buildings that make up the station is the “backyard”- an area near the Marr glacier where station dwellers are able to recreate. We can rent out snow shoes, skis, and micro spikes to aid in our ascent of the glacier. For the daring, tents, sleeping bags, and other survival gear are available to spend the night on the wooden tent platforms built throughout the backyard.
There are also several events planned to keep morale high, including open mic nights, Saturday evening Happy Hours, art classes- anything that someone is willing to organize on station. The SWARM team even raided the costume closet to perform a custom sea shanty during our last open mic night! Making our own fun was an integral part of enjoying our stint away from friends, family and our usual routines while at Palmer Station.
Implications for Future Research
Findings of this study suggest that coastal currents transport and concentrate plankton into dense patches that are then targeted by upper trophic creatures, increasing their foraging efficiency. Now that this has been seen in the relatively short, and tightly coupled food web in Palmer Deep, similar methodologies can be applied to more complex ecosystems elsewhere in the world. Relationships between coastal currents and the food web can also be used to guide conservation strategies to protect prey accumulation zones and mitigate human impacts.
References:
1 Marquet, P. A. et al. in Patch dynamics 277-304 (Springer, 1993).
2 Cheriton, O. M. et al. Effects of mesoscale physical processes on thin zooplankton layers at four sites along the west coast of the US. Estuaries and coasts 30, 575-590 (2007).
3 Benoit-Bird, K. J. et al. Prey patch patterns predict habitat use by top marine predators with diverse foraging strategies. PloS one 8, e53348 (2013).