Research project on deep-sea ccosystems in Antarctica

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The study of the diving behavior of air-breathing vertebrates evolved dramatically with the appearance of time-depth recorders. Many diving animals can dive deeper than photic zone and for longer time. These results propounded new scientific questions. First, how they can dive so deep and for long time? Secondly, why they dive so deep? To answer the questions, new technology was developed in the present study. Acceleration data logger provides us information on fine scale movement of diving animals. To detect the food intaking, oesophagus temperature of penguins was recorded. Geomagnetism data logger can record the head direction of seals, which was used to calculate three-dimensional diving paths of Weddell seals. Digital still picture logger was attached on free-ranging Weddell seals in Antarctica, and recorded some interesting pictures, which related with their prey distributions. Field experiments were conducted at subantarctic Crozet Island (king penguin) and some Antarctic regions such as Syowa Station (Adelie penguin, Weddell seal), Dumont d'Urville French Station (Adelie penguin) and McMurdo US Station (Weddell seal). Some interesting results were obtained through the project. For example, using a newly developed data logger to measure acceleration, we demonstrate that free-ranging king and Adelie penguins only beat their flippers as descending, and then stopped swimming as ascending, and took advantage of their natural buoyancy to glide back to the surface. Biomechanical calculations for data from freeranging penguins indicate that the air volume of the birds can provide enough buoyancy for the passive ascent. When comparing the passive ascents for shallow and deep dives, there is a positive correlation between air volume and the depth of the dive. This suggests that penguins regulate their air volume to optimize the costs and benefits of buoyancy.