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Secrets of the abyss: deep-sea biodiversity, deep-sea mining and deep-sea biodiscovery in the world's largest exploration frontier
When HMS Challenger took the first dredge samples from the central Pacific abyssal plain in September 1875, the naturalists on board remarked that they ‘did not yield a very large number of deep-sea animals’. Instead, they enthused about the collections of the remarkable manganese nodules - potato sized mineral accretions of iron and manganese that we now call polymetallic nodules. Almost 100 years later, in the mid-1970s, the first large scale attempts to mine polymetallic nodules took place in the same region. Attention was paid to the economic and technical challenge of mining the nodules; almost none to the environmental consequences. Even in the 1980s, environmental reports dismissed the abyssal plain as a region generally devoid of life – a haven only for insignificant tiny worms and crustaceans of little value to anyone. We now know and think rather differently. The abyssal benthic ecosystem, in particular that in the central Pacific, is notable in that it is a system with extremely low abundance but relatively high biodiversity. The diversity is driven by a high degree of rarity – species that are recorded only a few times and in many cases only once. We have spent that last twenty years trying to figure out if this is a sampling artefact or a real pattern, and are still some way from figuring that out, or what is driving the high diversity. In the meantime, we have done a lot of taxonomic and phylogenetic work describing the many new species. We have been asked what is the value of the biodiversity in the abyss, given it may be competing with the cobalt-rich nodules for survival if deep-sea mining goes ahead. This is rather an important question as without some data on it, society cannot compare mining the deep sea with mining somewhere else in terms of impact. To make a start on this, we commenced a new project in collaboration with the University of Aberdeen and University of Strathclyde in 2022 called DEEPEND, supporting a new NERC Highlight Topic project SMARTEX studying the deep Pacific abyss. We have just returned from a remarkably successful sampling survey of the abyssal Pacific this year, where many incredible new species were discovered. I will provide an overview of this, and the entire complex story of deep-sea mining and biodiversity and show how we need to showcase the importance of biodiversity as a critical resource like any other.