New deep-sea sponge could play a starring role in monitoring ocean health

Plenaster craigi grows on metal-filled rocks that are a target for mining

DEEP-SEA STAR  This fuzzy white sponge — identified as a new species, thanks in part to star-shaped skeletal parts — encrusts metal-filled rocks that could be a target for deep-sea mining.

S.-C. Lim et al/Systematics and Biodiversity 2017, published by Taylor & Francis

The deep waters of the East Pacific hold an unprepossessing treasure trove: potato-sized lumps of rock that contain valuable metals such as manganese, cobalt and copper. Turns out, such “manganese nodules” are home to another kind of goody: a species of sponge never before seen, researchers report online September 24 in Systematics and Biodiversity. These newly discovered nodule-dwellers may help scientists monitor the impact of future deep-sea mining.

Little is known about life in the abyssal depths of the ocean, 4,000 to 6,000 meters down. But the prospect of mining in those depths is looming: For example, the United Nation’s International Seabed Authority has granted 16 exploration contracts for mining manganese nodules. To track how mining will affect deep-sea ecosystems over time, scientists are eager to establish a baseline of existing biodiversity in regions such as the Clarion-Clipperton Zone (CCZ), an area in the eastern Pacific Ocean littered with the nodules.

The new sponge species may be the key to that baseline. Zoologist Swee-Cheng Lim of the National University of Singapore and colleagues examined samples of manganese nodules retrieved from the CCZ in 2015 that were covered in snow-white patches of sponge. Based on the sponges’ unusual star-shaped spicules — skeletal parts that support the sponge’s soft tissues — the team suspected they’d found a new species. DNA analyses confirmed it. Dubbed Plenaster craigi, this species’ proximity to the nodules may make it the perfect canary in the coal mine.

Carolyn Gramling is the earth & climate writer. She has bachelor’s degrees in geology and European history and a Ph.D. in marine geochemistry from MIT and the Woods Hole Oceanographic Institution.

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