Just to be clear, the energy source for the bacteria is "photodetritus", i.e. dead algae and other photosynthetic organisms from higher up in the water column.
CO2 isn't an energy source, ever. It's a building block, not food for the construction workers who do the building. There's quite a significant difference.
It is interesting that there's another potential path to CO2 mineralization that we haven't known about before. However, the carbonate/bicarbonate content of the oceans and the CO2 concentration in the atmosphere are things we can measure, have measured and continue to measure. We already know that the CO2 concentration in the atmosphere a) is increasing, b) is the highest it has been in the past 3 million years or so, c) rose from a level around 280 ppm where it was stable for at least 1000 years, started climbing around 1700, and is now 405 ppm with a bullet, so to speak d) the isotopic balance of the CO2 in the atmosphere is consistent with the new, extra CO2 being of fossil origin and e) only about 1/2 of the CO2 we've emitted by the burning of fossils and the roasting of carbonate rocks to make cement and lime etc. has ended up in the atmosphere- the other 1/2 has been taken up by the biosphere and the oceans. Those points aren't in dispute, nor does this new sink bring any of them into question.