I agree that we need to do be exploring all options, but we need to make sure not to destroy other parts of our environment in the process.
Massive algal blooms in the ocean gives me nightmares.
Massive algal blooms in the ocean gives me nightmares.
Why? How you you think much of the carbon at the bottom of the sea got there? Biological activity, most of small species that died and sank.
The pelagic ocean is pretty nutrient-poor, so anything you grow there is going to need to be farmed. I've been reading that used to be far more fertile before the ecosystem crashed as we decimated the whale population (there are experiments under way for basically adding "artificial whale poo" (as it was jokingly described to me by one of the participants) to try to form little regions of more fertile surface waters.
IMHO you do want to stay away from coastal waters which are a witch's brew of all sorts of things, from runoff to various organic processes. Some algal blooms in coastal regions have been of toxic species (e.g. "red tide" -- those algaes also show up in snow BTW) but most are not that kind at all, and as I note above, in the pelagic (open) ocean you'll have to be seeding it anyway.
You want it to die and sink, but of course it will be attractive to other species some of which will eat it, grow, eventually die and sink, but will probably breath some of that carbon out again. But in the end, you'd want most of it to sink.
Just like my code, I want to make sure I'm able to undo some change before making even seemingly small changes. I don't know how you "undo" a huge cloud of algae.
If its all in some tank and can't escape, then fine, I'm on board.
Once we are electrolysing lots of water for the hydrogen, dissolving the waste oxygen in river outflows could start to save the current dead zones. But restricting over-fertilization would have a bigger effect.