For years oceanic biologists have studied the potential of the oceans to absorb more CO2 and convert it into carbon through its normal biological life. It turns out that iron plays an important role in the metabolism of pythoplankton limiting it to a large extend. It is found that adding even a small amount of iron can increase life in some parts of the ocean significantly.
Apart from this finding its also found that increasing sulfur and nitrogen can increase ocean life.
iron fertilization
https://en.wikipedia.org/wiki/Iron_fertilization
https://www.frontiersin.org/articles/10.3389/fmicb.2018.03190/full
https://aslopubs.onlinelibrary.wiley.com/doi/abs/10.4319/lo.2002.47.4.0997
https://www.sciencedirect.com/science/article/pii/002209817990011X?via%3Dihub
https://phys.org/news/2019-06-mystery-atmospheric-carbon-dioxide-ice.html
https://journals.ametsoc.org/doi/full/10.1175/2009JTECHO679.1
https://www.bco-dmo.org/project/2051
Patents (should be irrelevant but ok)
https://patents.google.com/patent/US4597360?oq=ocean+upwelling