Mining the extensive accumulations of minerals on the seafloor of the deep ocean can provide important resources but also has the potential to lead to widespread environmental impacts. Some of these impacts are unknown but there are expected to be differences between the mining of the three main resource types: polymetallic nodules, seafloor massive sulphides and cobalt-rich crusts. Here we detail the mining processes as well as the expected impacts of mining and discuss their potential effects to deep-ocean ecosystems. We also highlight the missing evidence needed to underpin effective environmental management and regulation of the nascent deep-sea mining industry.The attached document is the author’s final accepted/submitted version of the journal article. You are advised to consult the publisher’s version if you wish to cite from it