But that should be good news for the penguins, who are in trouble now. We'd thought it was because of human-caused climate change and the melting of the sea ice, but also because the mean old whales were eating up all their krill. Never mind that much larger populations of whales had been coexisting with penguins for an awfully long time.
Krill need iron to grow and reproduce. But most of the iron is at the bottom of the ocean. And the krill
Here's another oddity. There used to be plenty of free iron in the ocean. But when the first photosynthetic plants devised themselves, way back when, they pooped out oxygen. The oxygen attached itself to all the iron in the ocean and the resulting rust sank to the bottom until the iron was all used up. Pretty much all the iron we ever mine today comes from that original band of iron oxide on the ocean floor, from that first photosynthesis event. And when the rust settled, the free oxygen had no place to go but the atmosphere. That was called the Great Oxygenation Catastrophe because almost all the nascent life that had burgeoned in the absence of oxygen failed in its presence. It was a major extinction event--wiped out almost everything. That's what happens when something causes conditions to change drastically.
Here's another oddity. We're right in the middle of another major extinction event right now. Damn the luck, huh?
Thanks to Joan Campbell for pointing me in this direction.