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Abstract

Future supplies of rare minerals for global industries with high-tech
products may depend on deep-sea mining. However, environmental standards
for seafloor integrity and recovery from environmental impacts are
missing. We revisited the only midsize deep-sea disturbance and
recolonization experiment carried out in 1989 in the Peru Basin nodule
field to compare habitat integrity, remineralization rates, and carbon
flow with undisturbed sites. Plough tracks were still visible,
indicating sites where sediment was either removed or compacted.
Locally, microbial activity was reduced up to fourfold in the affected
areas. Microbial cell numbers were reduced by similar to 50% in fresh
"tracks" and by <30% in the old tracks. Growth estimates suggest that
microbially mediated biogeochemical functions need over 50 years to
return to undisturbed levels. This study contributes to developing
environmental standards for deep-sea mining while addressing limits to
maintaining and recovering ecological integrity during large-scale
nodule mining.