The zooming vehicle spits out a plume of sediment behind it, covering whatever is down there with a blanket of mud. More sediment is sucked up the tube with the nodules. That sediment is then pumped back into the water column thousands of feet above the mined area. The two plumes are a big concern to marine researchers because nobody knows much about the life forms down there or how they interact with the rest of the ocean’s chemical and biological systems.