Of all the planet hacking possibilities floated as last-minute ways to stave off a climate catastrophe (building a solar shade for the Earth, injecting the atmosphere with sunlight-reflecting aerosols, etc.), iron seeding seems one of the more practical and feasible ideas. The scheme calls for the fertilization of patches of ocean with iron to spur blooms of plankton, which eventually die, sink, and sequester carbon at the seafloor. However, worries over the consequences of tinkering with the ocean ecosystem have held up plans to attempt this. And now, in a study in the Proceedings of the National Academy of Sciences, researchers claim that such a plan could risk putting a neurotoxin into the food chain. Iron seeders have targeted the large swaths of ocean surface with high levels of nitrate and low chlorophyll, where an injection of iron could potentially turn a dearth of plankton into a bloom.