You’ve probably seen the Alaska SeaLife Center’s mission statement focused on generating and sharing scientific knowledge to promote understanding and stewardship of Alaska’s marine ecosystems. Why then do some of our scientists travel all over the planet, including extreme places such as Antarctica, in pursuit of scientific knowledge?
Well, there are several good reasons:
Paradoxically, some Antarctic animals may be more accessible to us than animals in arctic waters. For example, in arctic open waters of the marginal ice zone, ice seals may be difficult to approach in small inflatables requiring expensive large vessel support.
In Antarctica, some southern ice seals like the Weddell seal (Leptonychotes weddellii) occupy regions covered by hard ice (as opposed to pack ice or marginal ice), and do not experience predators when hauled out on the ice. As a result, they are relatively easily approached and worked with. We can drive snowmobile or larger tracked vehicles over the ice to a reasonable proximity of seal haul-outs or rookeries (this does require a permit!):
Even when seals dive under the ice, we can quite literally walk or drive over the top of their heads. This ease of access also makes it comparably easy to deploy and retrieve telemetry devices that can log information about what the animals do while they dive well beyond our direct observational reach. After all, we can dive, but they can dive so much better. Weddell seals are some of the most capable divers in the animal kingdom: they can dive to depths in excess of 650 meters (2,000 ft) and remain submerged for over an hour.
This is what things look like under the sea ice:
The Isolated Hole: In Antarctica, we can study these animals using very unique experimental setups like the ‘isolated hole’ setup, and apply what we learn from these to other settings. The isolated hole setup is a classic experimental design: the annual sea ice near McMurdo is surveyed, and a large area is identified that does not have any cracks or holes in it, and a 1.5m diameter hole is drilled through it. Then a seal is captured in a nearby rookery and transported to the experimental site by sled. There it is released near the hole. The seal can now dive at will, but has to return to this hole as the sole breathing and in/out opportunity in range. Here too, we can literally walk on top of the seals head as it dives. We can work with the seal between each and every dive. We can put a small transparent dome over the hole and measure the seals breathing gases, conducting respirometry to determine metabolic rate. We have also placed small temporary catheters on these seals (for example into the extradural intervertebral vein), that allow us to draw a small venous blood sample from a seal after every dive. We can analyze these samples for blood gases or metabolites. The seals are so mellow, we can even reach into the hole and quickly detach or exchange small dive recorders temporarily attached to the seals back. After a few days, once the seal hauls out from diving and hunting for fish beneath the ice, it is transported back to the original capture location and released.
Noted pinniped physiologist Dr. Gerald L. Kooyman used this classic experimental design to experimentally determine what he called the ‘Aerobic Dive Limit’ or ADL in a free-diving seal. He defined the ADL as the dive duration associated with the onset of blood lactate accumulation, presumably resulting from anaerobic energy production following oxygen depletion in some tissue. Standby for a forthcoming blog entry on the ADL, and on what tricks of the trade allow diving, air-breathing vertebrates to perform such amazing feats, and what still limits such performance.
This classic isolated hole experimental design is unique, in that it combines many of the important characteristics of a controlled laboratory environment, with the less biased behavior and physiological response we get from an animal in the wild. The controlled aspect derives from our ability to collect data from and work with the animal between every single dive. The reduced bias comes from the fact that the animal can determine when, how deep and how long it will dive. In a laboratory simulation, even with animal holding tanks as large as our biggest at the ASLC (about 280,000 liters) an animal could never dive to hundreds of meters of depth. In the isolated hole setup we have observed dives to 500m depth and beyond, and easily for 30 – 50 minutes in duration.
How cool is that? Well, if you want a very literal answer to that question, here is a link to a paper we published in 2015 in the journal Animal Biotelemetry, from the 2011-2012 Weddell seal study, with the title: Estimating total body heat dissipation in air and water from skin surface heat flux telemetry in Weddell seals. This Open Access article is freely downloadable.
Now that you know why we go to Antarctica for our research, I’ll be honest and let you know about another reason: it’s one of the most amazing places on earth, and one of the few or maybe even the only place where one might get a feeling for what it could be like to be on a completely different planet. We’ll finish this blog entry with an amazing video created by Henry Kaiser while diving under Antarctic ice as part of our project in 2012. This lengthy, but incredibly spectacular video also features some of Henry’s own music, as well as natural vocalizations by Weddell seals.
This video and soundtrack were created by Henry Kaiser, on assignment to the B470 research team under NSF award 1043779. Filmed on multiple locations in McMurdo Sound, Antarctica. Though no research activities are shown, all research by team B470 was conducted under Antarctic Conservation Act permit #2012-003 and Marine Mammal Protection Act NMFS permit #15748.
Written by: Markus Horning, PhD