Deep-sea discoveries

New insights into biodiversity of the Southwest Pacific Ocean

Dense bamboo corals at a depth of 2100 m off the Cook Islands.

In 2016 and 2017, NOAA ran a programme of exploration on seamounts in the Central Pacific Ocean. Termed “CAPSTONE”, the programme aimed to explore the biology and geology of Pacific seamounts. As the NOAA vessel Okeanus Explorer was going to be working in American territories with transits through waters of the Tokelau Islands and Cook Islands, New Zealand scientists associated with the Ecosystem Management and Deep-Sea Mining Group were provided an opportunity to conduct multibeam mapping and ROV research in these regions. Two ROV (see Figure A) dives were completed on Tokelau seamounts in March, and two in northern Cook Island waters at the beginning of May 2017.

One of the dives, on a deep ridge off the Cook Islands, termed Te Kawhiti, was startling in the abundance of corals. The transect came up the side of the ridge from 2200 m depth. Large bamboo corals dominated almost the full length of the 5 hour dive-they were very dense in places, packed onto most exposed rock surfaces (see Figure B). Their branches were host to numerous feather stars and brittle stars. The corals were sometimes over 3 m in height and were very fragile. Another highlight was a new species of glass sponge, resembling a transparent hairy vase in the genus Walteria (see Figure C).

The dives enabled the shipboard team and online scientists to record a wide range of benthic fauna, and improve understanding of the distribution and biogeographic patterns of species in the general region. These data can help characterise the environment of areas with potential for mineral resources (cobalt-rich crust on Tokelau seamounts, manganese nodules on Cook island abyssal plains) and better inform environmentally sustainable management of future human activities in the area. The local scientists and managers involved in these dives are very appreciative to NOAA and the Okeanos Explorer team.

Malcolm Clark and Kevin Passfield


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