[Lewis Thomson (OP)]

Donald has once again presented the Naked Scientists with a series of marine based questions.

"Most aquatic animals in the ocean still require oxygen for metabolism. The air breathers have lungs with a large surface area. But most have gills. How much oxygen is there in the ocean? How can so little gill surface area acquire oxygen such that tuna can speed thru the ocean? That is, are gills more effective/efficient than lungs in oxygen transfer? Or is it easier to transfer oxygen if it is already dissolved? Or do filled creatures have much lower oxygen requirements?"

Leave your answers in the comments below...