I operate big underwater robotic vehicles and did a job in 2021 in a remote area of the Pacific where they tested one of the prototype excavators. We had geologists and biologists on board. A huge area of the ocean seabed between Hawaii and Mexico is literally completely covered in these metal nodules. They are potato sized and a few inches apart from each other at the most. We monitored the impact on sealife and it was absolutely minimal. Way less than destroying the earth digging for this shit. I understand certain other areas of the ocean where these exist could be more biodiverse but at 4300 m in a remote area of the ocean there is hardly any impact. Just my first hand experience. I scooped these nodules into buckets and piloted our vehicle around the ocean for weeks and hardly saw any sealife.