A Magical World of Brittle Stars Is Under Threat

A Magical World of Brittle Stars Is Under Threat

In its surveys, the team found 42 species, most of which had never been seen before. Several belong to entirely new lineages, and perhaps a new family—a group of brittle stars that’s only distantly related to those that have been cataloged. “It’s thought that in the abyssal plain you don’t get a lot of biodiversity, but there are all these species that look very different,” Christodoulou says. “They’re beautiful.”

For perspective, about 2,000 brittle-star species have been identified, and the team increased that tally by about 2 percent, by exploring a football field’s worth of seafloor. What else awaits? “That the relatively small number of samples collected to date, representing an extremely minute fraction of the CCZ and Peru Basin, should reveal so much diversity within the brittle stars is exciting,” says Cindy Lee Van Dover, a deep-sea biologist at Duke University. That variety will doubtless be mirrored in other animal groups that are less visible.

Three of the new brittle-star lineages that the team discovered don’t even exist in surface waters, and have been living and evolving in the deep for more than 70 million years. This contradicts the long-standing idea that the deepest ocean is simply an evolutionary sink—a retirement home for shallower species. The brittle stars reveal that it’s also a place where new species are born, independently of what occurs on the surface. The abyss is both cradle and crucible.

Most of the brittle stars were found among or upon the CCZ’s manganese nodules, perhaps because they are “the only hard substrate on which that kind of animal can live,” says Sabine Stöhr, a brittle-star expert at the Swedish Museum of Natural History. The nodules “create a more varied environment, which in turn allows a more varied fauna to evolve.” It is unfortunate, then, that those same life-creating nodules have attracted the attention of prospectors.

In international waters, all deep-sea mining must be licensed by the International Seabed Authority, the Jamaica-based body that is writing a code for mineral exploitation in the high seas. No such operations have begun, but 29 exploratory licenses have been issued to state-sponsored companies that want to trial mining technology like the failed nodule-collecting robot. There’s so much wealth on the ocean floor—including minerals necessary for making cellphones and other modern technologies—that Christodoulou thinks mining is all but inevitable. “We can’t prevent it, but we can try to do it in the most sustainable way,” she says.

At minimum, that means better understanding what exists in the deep, and what stands to be destroyed. Food is scarce so far from the ocean’s surface, so “deep-sea species often have low population densities, and are easily eradicated,” Stöhr says. Life may be diverse down there, but it is slow to grow. In a recent study, Ann Vanreusel of Ghent University in Belgium looked at nodule-rich parts of the CCZ that were subject to experimental mining simulations up to four decades ago and found that they have thus far failed to recover.

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