14 August, 2003
Much of the focus of this cruise has been on what's below the surface. The scientists on board are primarily interested in chemical and physical properties such as dissolved oxygen, salinity, temperature, chlorophyll, and nutrients in the seawater. There is one exception, however, as everyone loves the mammals, and seeing polar bears, walrus, and whales is a high priority for many aboard. Indeed, when word gets out that a bear is near, phones ring, radios call, doors knocked, and before you know it, a crowd of wildlife watchers have gathered on the Palmer's bow with cameras and videos in hand.
So I was somewhat puzzled by one observer's comment to my enthusiastic heads-up, "look, there's a seal!" A short pause later, his response was simply "how about a bear?" "No, I don't see any," I chuckled, "although the bearded seal at two o'clock on the starboard side is pretty cool." But my companion on the Palmer's bow wanted bears, for after all, as he logically noted, "Bears eat seals, so there must be one around nearby." And that's how it went for much of the trip whenever seals were sighted. Responses often ranged from a respectful "oh, really?" to an indifferent "that's nice."
Perhaps I exaggerate a little bit, for there are three people in parcticular that are very, very, very interested in seeing seals - or at least in counting them. Actually, the three scientists of the Marine Mammal Survey Team really love these hairy flippered pinnipeds. So much so that two of them have largely made the study of seals and their kin their life's work and the third may do the same.
Dr. John Bengtson of the National Marine Mammal Laboratory has been researching the ecology and behavior of marine mammals for nearly 30 years from Antarctica and Central America to Florida and the Arctic. By chance, I happened to come across a photograph up on the bridge that showed John as the Chief Scientist during an Antarctic cruise on the Palmer not long ago. Needless to say, this guy gets around, and he is well known and highly respected among marine mammal scientists. Recently he gave a presentation to many of us on board about his work on Antarctic seals. John's pictures, research, and humorous anecdotes made for a highly interesting and entertaining program. And John's sharp eye for spotting seals helped him as well to spot the cruise's first Ivory Gull, the significance of which is explained in the journal entry for the first of August.
Dr. Mike Cameron, also with the marine mammal lab in Seattle, Washington, has been working with seals and their population dynamics for the past 11 years. Until now, all of Mike's previous research was in Antarctica where he found it easier to study seals. For one, he explained, Antarctic seals do not have to worry about polar bears; in fact, they are most vulnerable when they are in the water where Leopard Seals and Orcas are the top predators. And unlike their northern counterparts, Antarctic seals have largely not been hunted by humans. This enabled Mike to walk right up to a seal, which of course, greatly facilitated his work. Still, after just a few minutes of visiting with Mike about his current project, it's easy to share in his excitement for having this opportunity to study marine mammals in the Arctic which he intends to do for the next few years.
Heather Smith, a graduate student in Dr. Glenn VanBlaricom's laboratory at the University of Washington, completes the marine mammal team. Although she is technically only a student, Heather brings a wealth of field experience to the team. She assisted in a marine mammal survey for the Marine Mammal Research Group in Victoria, BC, for example, and later radio-tracked manatees in southern Florida. Heather also spent a field season on Midway Island where she assisted with the tagging, radio-tracking, and population monitoring of Hawaiian Monk seals as well as research on the reproductive success of various seabirds. After that, Heather studied fat. Well, blubber, really. Heather recently completed her Master's degree at Texas A&M University where she examined the fatty acid composition of Common Dolphin blubber. There's an old saying that goes "you are what you eat," and that seems to hold true for marine mammals. By studying the fatty acids in their blubber, it may be possible to determine what these creatures have been feeding on. Heather plans to complete a similar analysis on samples of Beluga blubber that she collected last summer in Point Lay, Alaska. When she returns to school after the cruise, this highly talented wildlife biologist hopes to develop a research project examining the food habits of ice seals.
How do these adventurous wildlife biologists study seals? According to John (in his words) the most effective way to conduct this work is by flying aerial surveys from the helicopter aboard the Palmer. Surveys are flown during mid-day (2 hours either side of local noon) when the greatest proportion of seals are expected to be hauled out. As conditions allow, helicopter survey tracks are set out perpendicular to bathymetric and sea ice gradients, which are thought to influence seal distribution. An observer positioned at each of the windows on the right and left sides of the aircraft counts seals seen during the flight Perpendicular distance of seals from the survey line is measured by sighting along six fixed 10 degree vertical angles (0 degree - 60 degree from the horizon in 10 degree increments) on a Plexiglas strip attached to the helicopter's window. The perpendicular distance interval is then computed from the helicopter's altitude and the assigned angle category. The area beneath the aircraft (60 degree- 90 degree) is not visible to the observer, so this survey strip is monitored by a downward-looking digital video recorder. When weather conditions are not suitable for flying, we can also conduct surveys from the Palmer's ice tower as the ship moves through the pack ice.
And exactly what are they looking for, and why? John goes on to explain: The shelf, slope, and basin zones of the western arctic provide productive habitats for polar marine mammals. Determining the seasonal patterns of seal and whale abundance and distribution is the key to understanding the ecological interactions involving these apex predators and the ecosystem "hotspots" where they are often found. Different marine mammal species integrate the environment across variable spatial and temporal scales, with the composite result reflecting oceanographic primary and secondary productivity derived from transport processes and mesoscale oceanographic features. Although abundance and distribution data on all marine mammal species observed is being recorded, our main focus is on two species of seals in the sea ice zone: Bearded Seals (benthic foragers), and Ringed Seals (fish and crustacean predators). Our principal research objectives are to determine marine mammal distribution, relative abundance and habitat associations via visual surveys, and to relate these patterns with measures of oceanographic structure and potential prey availability.
So certain species are found in parcticular environments at various times of the year. And that is what they have seen: bearded seals (bottom feeders) above the continental shelf in relatively shallow water, for example, while ringed seals have been in the deeper water where the shelf drops-off steeply into the ocean basin. Perhaps the most surprising aspect of their surveys has been the lack of ice. This doesn't bode well for the sealsí future if the melting continues, or for that matter, bears and any species that are adapted to the ice, which is all the more reason for scientists to get a handle on what's going on up here. From what I have seen, intrepid scientists like John, Mike, and Heather are surely up to the task.
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