> Doesn’t surface mining also do that?

No, surface mining doesn't "suck up and kill seabottom creatures". :)

More sympathetically: yes, surface mining can have habitat loss issues (i.e. land use changes), but the bigger issue erosion and sediment control, the management of which is a major component of any modern mine in a well regulated country. Maybe there are ways to mitigate subsea sediment migration, but they definitely haven't been studied to nearly the same extent as surface issues and mitigations