New-Zealand margin

In the framework of the RENEWZ project, an international team led by Dr Amy Baco-Taylor, from the Woods Hole Oceanographic Institution (WHOI) in Massachusetts (USA) and Dr Ashley Rowden from the New Zealand's National Institute of Water & Atmospheric Research (NIWA), have observed, for the first time, the bizarre deep-sea communities living around methane seeps off New Zealand's east coast.

Onboard NIWA's deepwater research vessel Tangaroa, the 21-member expedition – led by scientists from WHOI, NIWA, the Scripps Institution of Oceanography, and the University of Hawaii at Manoa (UH) – has spent two weeks exploring eight cold seep sites and other ‘chemosynthetic' ecosystems on the continental slope to the east of the North Island, lying at depths of 750–1050 m.

The team pinpointed potential seep sites using sophisticated sonar to map seafloor topography and substrate and to detect plumes of methane-enriched water. The scientists then lowered a towed video and still camera system over each site to identify seep organisms and the extent of the seafloor they covered.

A few cold seep sites were previously known along the New Zealand coast from geological and biogeochemical studies of the continental margin. But this is the first time the biodiversity of the animal communities living at these sites has been observed directly and thoroughly documented, providing the first discovery of cold seep communities in the entire southwest Pacific.

With the live video feed, the scientists observed 30–40 cm long tube worms emerging from beneath limestone boulders and slabs lying at the core of the seeps. Around the rocks were patches of blackened sediment and pockets of white bacterial mats. Most sites also had extensive shell beds consisting of live and dead shells of various types of clams and mussels. These were fringed with stands of another type of deep-sea tube worm that is also gutless and relies on symbiotic bacteria for its nutrition. Corals and, at two of the sites, numerous sponges, were also observed.

The discovery of so many sites suggests that cold seeps are very abundant along New Zealand's eastern continental margin. However, this expedition also revealed the extent to which these communities may face serious threats from human activities. At all of the seep sites, there was evidence of fishing damage in the form of trawl marks, lost fishing gear, and extensive areas of deep-sea coral rubble.

This voyage was jointly funded by the US National Oceanic and Atmospheric Administration's Office of Ocean Exploration (NOAA OE) and NIWA, with additional support from WHOI, Scripps, and University of Hawaii.