First of all, I think you are missing my point. These kinds of experiments (i.e. the introduction of variables to "improve" an environment) have a long and sordid history. The Cane Toad is a cautionary tale: it was supposed to eat pests, but instead it took over large swaths of Australia and caused devastation.

What this person is trying to do is seed plankton. Plankton, as anyone who grew up near a coast can attest, commit mass suicide as they over-bloom. This is called the red tide and it caused me to spend a lot of evenings after beach days itchy with watery eyes. It also kills enormous numbers of fish, whales, jellyfish, etc.

EDIT: I can't reply, but I saw your comment that "unlike the cane toad, iron can't reproduce." Unfortunately, you're in error. Iron, like a lot of metals and toxins, can bioaccumulate in the food chain, pass from prey to predator and from gestating mother to fetus, and persist in ways that cause all kinds of havoc [1]

[1]http://www.sciencedirect.com/science/article/pii/S0147651311...