In biology, things aren't always that clean. Does whale poo release the iron in a way which is more accessible to other life forms vs dead krill? Perhaps one of

In biology, things aren't always that clean. Does whale poo release the iron in a way which is more accessible to other life forms vs dead krill? Perhaps one of these floats better than the other, or diffuses more evenly, or through some other mechanism makes it easier for the phytoplankton to access the iron. The shameful thing is that we have learned how to commercially harvest krill and sell it as animal feed. Which means we are strip-mining this resource also from the ocean. Which before too long will lead to starving the whales to death, followed by the collapse of the krill populations because we just take, we don't give back. 'animal feed' includes pet food.