I am not sure how large a carbon sink the
oceans are but I have got the idea the
creatures grow carbonate shells which fall to
the ocean bottom on death. So Wow! this must
be important for removing CO2. And I do not
think the creatures get off lightly when
the props of a supertanker or freightliner
pass. Think of the forces involved in moving
such masses against their drag in the water!
Surely this question has been looked at
quantitivly.