Phytoplankton fix loads of CO2, especially where there are plenty of nutrients, but most of it gets recycled in the surface ocean (and so back into the atmosphere), only a small fraction gets down to deep layers. Copepods, being heavier, help some to sink through, so it seems they’re proposing to study more what makes these thrive, but it’s not clear from linked info what’s specifically new in this project, nor that there is any practical intervention proposed.

Once I had a tank with marine plankton which brought the CO~2~ in the headspace above down to just 5ppm…, sometimes the most revealing experiments are not the ones you intend.