A completely new group of sponges has been discovered, which scientists believe could be a key indicator species in measuring future mining impact in a region targeted for deep-sea mining of polymetallic (metal-rich) nodules. They are likely to be the most abundant nodule-dwelling animal in the area.
The new discovery, described in the journal Systematics and Biodiversity, was made in the vast 5 million square kilometre region of the central Pacific Ocean known as the Clarion-Clipperton Zone (CCZ). This area is incredibly rich in useful metals in the form of polymetallic nodules, potato-sized accretions of mineral that sit on the seafloor at depths of 4000-5000m. The new sponges, Plenaster craigi Lim & Wiklund, 2017 are described from the eastern region of the CCZ in exploration zones licenced to UK Seabed Resources Ltd and Ocean Mineral Singapore.
The animals were found living attached to the metal-rich nodules on two expeditions to the region in 2013 and 2015. Sponge expert and lead author Swee-Cheng Lim from the National University of Singapore participated in the second expedition and commented, "The unique morphology of the star-shaped spicules convinced me that these were a completley new group of sponges never seen before". Dr Helena Wiklund of the Natural History Museum, London, confirmed this with a detailed DNA-based study that placed them as a new genus of sponge.
The new sponges, although small, are remarkably abundant on the food-poor abyssal seafloor at a depth of 4000m. Principal investigator of the Deep-Sea Research Group at the Natural History Museum, Dr Adrian Glover said, "We were simply astonished to discover that the most abundant animal living on the metal-rich nodules was not only a new species, but from a new genus as well, despite the region being subject to many surveys in the past. It is clear that our taxonomic knowledge of the biodiversity in this region is still very limited".
The scientists believe that because the species is relatively easy to identify and count (now that it has been described) it could be a useful 'indicator' species to measure future mining impacts. "The fact that this is a small filter-feeding animal sitting on these nodules just a few centimetres above the sediment makes it a clear target for impact from a deep-sea mining plume" said Dr Glover. The scientists are now undertaking more detailed genetic and population studies of the animal to better understand its potential response to deep-sea mining.
Plenaster craigi have been named after their abundant stars inside their bodes, Plenaster, and the leader of the two successful survey expeditions, Prof Craig Smith of the University of Hawaii.
- Read the full article online here: http://www.tandfonline.com/doi/full/10.1080/14772000.2017.1358218
Captions for images in order:
1 Aboard the Research Vessel Thomas G Thompson in the Clarion Clipperton Zone, where Plenaster craigi was discovered (Image credit Thomas Dahlgren, Adrian Glover)
2 Seafloor at 4000m depth, central Pacific Ocean where Plenaster craigi was discovered (Image credit Craig R Smith University of Hawaii)
3 A box core sample is brought on board the research vessel from 4000m depth, central Pacific mining frontier (Image credit Thomas Dahlgren, Adrian Glover)
4 Surface of a 4000m core sample 50x50cm which appears devoid of life on first inspection, but is rich in biodiversity (Image Adrian Glover)
5 The new sponge group is visible on the surface of a large polymetallic nodule (arrowed) but had never before been described - it could be an easy-to-count indicator species for mining impacts (Image credit Adrian Glover, Thomas Dahlgren, H Wiklund)
6 Detail of polymetallic nodules 3-4cm in size, each with a Plenaster craigi (arrowed on one nodule) from 4000m deep, central Pacific mining frontier (scale bar 3cm) (Image credit Adrian Glover, Thomas Dahlgren, Helena Wiklund)
7 Plenaster craigi, detail shot of live animal from polymetallic nodule just recovered from the central Pacific at 4000m depth (Image credit Adrian Glover, Thomas Dahlgren, Helena Wiklund)
Sampling methodologies including box core sampling: https://www.youtube.com/watch?v=Io7NlFKUmYI
Natural History Museum Deep-Sea Research Group: http://www.nhm.ac.uk/deep-sea
Natural History Museum Oceans Hub: http://www.nhm.ac.uk/discover/oceans
Systematics and Biodiversity