2002-2003 Science Planning Summary

Biology & Medicine

Dr. Polly Penhale
Program Manager


NSF/OPP 01-30417
Station: McMurdo Station
RPSC POC: Curt LaBombard
Research Site(s): Sea ice camp

Effects of foraging on the lipid biochemistry of freely diving Weddell seals
Dr. Michael A. Castellini
University of Alaska Fairbanks
Institute of Marine Sciences
Dr. Lorrie Rea
Alaska Department of Fish and Game

Deploying Team Members: Michael A Castellini . Leslie Cornick . Shawn Harper . Susan Inglis . Tamara L Mau . Lorrie D Rea . Stephen J Trumble
Research Objectives: Freely diving Weddell seals in Antarctica offer a unique opportunity to follow the biochemistry and physiology of nutrient utilization in a large carnivore.

A study of the in vivo nutritional biochemistry of foraging in a free-ranging, large mammalian carnivore has never been attempted because of the logistics of obtaining multiple blood samples, conducting turnover studies, and measuring digestive chemistry while the animal is actively foraging. Although such studies can be conducted in laboratory or zoo settings, they are limited to captive animals whose feeding times and diets are typically constrained by humans.

A unique opportunity exists in the Antarctic. For several decades, the Weddell seal has been the focus of natural diving physiology studies using isolated holes through the sea ice near McMurdo Station. The seal has access to a single ice hole where it routinely returns to breathe, sleep, digest, and so on. With the use of blood-sampling catheters, this group has been able to collect serial samples whenever the seal returns to the surface between dives. During such experiments, these seals actively catch and digest their prey. However, all previous studies have focused on diving physiology per se because they were designed to examine how the animals tolerated long periods of holding their breath. Any observations on nutritional chemistry were incidental and not part of the study design.

This season, researchers will take this method in a new direction by examining how Weddell seals process nutrients while foraging. Like all seals, Weddell seals rely primarily on lipid metabolism for daily energy. Therefore, this group will examine the kinetics of lipid uptake and utilization during active foraging bouts. They will obtain blood samples from freely diving animals and use labeled traced experiments to quantify lipid turnover rates and separate the lipid pool into its various components. They will also compare lipid uptake and utilization in adult seals and in pups, which are biochemically adapted for massive and rapid lipid utilization while nursing.

This project will provide important insights into mammalian biochemistry. These data will be important not only to antarctic ecosystem studies, but also to the entire field of lipid metabolism in mammals and the study of carnivore biology.

Field Season Overview:
Project team members will establish a sea-ice camp a few miles from McMurdo Station. A hole will be drilled in the ice and a hut erected over it. Seals will be captured at another location along the coastline and brought back to the camp. There, they will be allowed to dive through a hole in the sea ice under the hut. Since there is no nearby access to the surface, the seals must always come back to the hut to breathe and rest. The seals naturally hunt for fish and squid under these conditions and blood samples can be taken whenever the seal is at the surface. Researchers hope to study six adults (non-lactating females) in each of the first two seasons. Blood samples will also be collected from five seal pups after they have nursed in order to follow lipid disappearance curves.