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First published online September 14, 2007
Journal of Experimental Biology 210, 3344-3355 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.008730

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To what extent might N₂ limit dive performance in king penguins?

A. Fahlman^1,2,*, A. Schmidt³, D. R. Jones², B. L. Bostrom² and Y. Handrich³

¹ North Pacific Universities Marine Mammal Research Consortium, UBC Marine Mammal Research Unit, ROOM 247, AERL, 2202 Main Mall, Vancouver, BC, V6T 1Z4, Canada
² Department of Zoology, The University of British Columbia, 6270 University Blvd., Vancouver, BC, V6T 1Z4, Canada
³ Centre d'Ecologie et Physiologie Energétiques, C.N.R.S., 23 rue Becquerel, 67087, Strasbourg, Cedex 02, France

View larger version (13K): [in this window] [in a new window]   Fig. 1. Ambient pressure (red broken lines), measured (solid blue circles) (Ponganis et al., 1999) and estimated (solid and dotted black lines) mixed venous N2 tensions (PN2) during hyperbaric exposures to (A) 102 m, (B) 68 m and (C) 34 m depth. Estimated PN2 assumed a blood flow distribution of 60% to central circulation, 26% to muscle, 10% to brain and 4% to fat, as in model 0 in Table 3 (solid lines) and 36%, 52%, 10% and 2%, respectively (dotted lines).

View larger version (14K): [in this window] [in a new window]   Fig. 2. Model sensitivity analysis comparing (A) central circulation, (B) muscle, (C) brain and (D) fat PN2 levels against diving tissue time constant (tiss1/2). Results shown are predicted compartment values at the time the bird reaches the surface after the last dive in a dive bout (black circles), or after deep (>50 m, red triangles) or shallow (50 m, green squares) dives.

View larger version (12K): [in this window] [in a new window]   Fig. 3. Model sensitivity analysis comparing (A) central circulation, (B) muscle, (C) brain and (D) fat PN2 levels against surface tissue time constant (tiss1/2). Results shown are predicted compartment values at the time the bird reaches the surface after the last dive in a dive bout (black circle) or after deep (>50 m, red triangle) or shallow (50 m, green square) dives.

View larger version (17K): [in this window] [in a new window]   Fig. 4. Estimated blood and tissue N2 tensions (PN2) during a single dive for a 12 kg king penguin. Dive duration (133 s), dive depth (54 m) and surface interval (46 s) were mean values of all dives during the foraging bout. Note that PN2 for the fat compartment is on a different scale. Initial conditions are those of model I in Table 3.

View larger version (58K): [in this window] [in a new window]   Fig. 5. (A) Ambient pressure (Pamb), and (B–D) estimated N2 tensions (PN2) for (B) central circulation and mixed venous blood, (C) brain and muscle and (D) fat in a 12 kg king penguin. Data used to estimate PN2 are from an actual dive bout for bird 3 (see Table 2). Initial conditions are those for model I (Table 3).

View larger version (26K): [in this window] [in a new window]   Fig. 6. Estimated subcutaneous fat N2 tensions (PN2) for birds 1–4 during an entire foraging trip with several diving bouts. Black and red circles show, respectively, the start and end of a dive bout. Initial conditions are those for model I (Table 3).

View larger version (14K): [in this window] [in a new window]   Fig. 7. Ambient pressure (Pamb, ATA) and estimated mixed venous supersaturation [(PN2venous–PN2amb)·PN2amb–1] for a bird performing short and shallow dives (red dots) or resting at the surface (green dots) during an interbout interval. Initial conditions are those for model I (Table 3).