Super impressed by the units used on that map: Mm3/d = millions of cubic meters per day

Edit: Largest average effusion rate is 12Mm3/d which is 138 cubic meters per second. So if that were all in a single lava flow it could be as high as a person, as wide as a football field and moving at 2+ miles an hour. And basically unstoppable.

Random interesting fact

That's about the flow rate of mafic rock required to offset global CO2 emissions, if it went into the ocean mix layer (and dissolved).

Makes you wonder if all those evil villains blowing up volcanoes were really just maligned :).

As fertiliser for algae or in a direct chemical reaction that reacts with the CO2 in the water?

You could think of it as the latter.

It's ocean alkalinity enhancement (offsets ocean acidification, lets the ocean continue to take up CO2).