A joint Japanese-New Zealand scientific research voyage leaves Tonga this week to explore underwater mountains and volcanoes about 1000km northeast of New Zealand.
Scientists from the National Institute of Water and Atmospheric Research (NIWA), GNS Science (GNS) and the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) will be aboard the Japanese research vessel Yokosuka to learn about the ecosystems of the Louisville Seamount Chain and northern Kermadec Arc.
A feature of the voyage will be five dives by the human-operated vehicle Shinkai 6500, one of the world's most advanced deep diving submarines, capable of going to depths of 6.5km below the ocean surface. It is the deepest manned submersible for academic research and can accommodate two pilots and a researcher on dives that typically last eight hours each.
NIWA fisheries scientist Dr Malcolm Clark said the Louisville Seamount Chain is one of the longest in the world, stretching about 4300km from the Pacific-Antarctic Ridge north-west to the Tonga-Kermadec Trench where it is thrust under the Australasian plate. The seamounts can rise up to 4000m from the seafloor – higher than Aoraki-Mt Cook.
The dives by the Shinkai 6500 will be the first detailed biological investigation of the area. Dr Clark, who is taking part in the voyage and will be aboard the Shinkai 6500 for one of its dives, said they expect to find species that have not previously been seen.
"You never know what to expect in the deep sea, animal life on the seamounts could be sparse, or there could be rich diversity and abundant new communities. There is a strong element of discovery about the trip, as we will be diving in unknown areas and to greater depths than most research activities around New Zealand."
The scientists will also look at the role seamounts can play in the distribution of life in the deep sea. Dr Clark said it is thought that some animals use the seamounts as "stepping stones" across the ocean by establishing communities on one before moving to the next. The team also wants to determine whether the seamounts, as they are dragged deeper and deeper into the trench, sustain communities that normally would only exist in shallower waters.
Dr Clark said the Louisville Chain also supports extensive trawl fisheries for orange roughy. Previous scientific modelling has predicted corals and other sensitive habitats may occur on the seamounts, and so more information is needed on their biology to establish if they are vulnerable to fishing operations.
The other focus of the expedition will be two dives on volcanoes along the northern part of the Kermadec Arc, which extends from White Island up towards Tonga. The scientists will dive on hydrothermal systems (seafloor hotsprings) known to exist on two of these volcanoes to sample the hot water being discharged from chimneys, or vents on the seafloor, together with any mineralization and animals.
GNS principal scientist Dr Cornel de Ronde said "these hydrothermal systems are likely to host significant minerals deposits, in keeping with those discovered in the southern part of the Kermadec Arc. Confirmation of their existence will have strategic importance for New Zealand considering the number of volcanoes along the 1300km length of Kermadec Arc that sits within New Zealand's territorial waters."
Habitats located at these vent sites often host unique animals adapted to survive in extreme temperature and chemical conditions that are hostile to most life forms.
Dr Clark said he and the New Zealand science team were excited to be working with JAMSTEC on this collaborative project that brings together experts from both countries and further develops long-term cooperation in science, technology and innovation.
