Scientists from the University of Aberdeen and New Zealand have sent cameras to a depth of 7000 metres (4.5 miles) to record rarely seen creatures on the floor of the New Hebrides Trench in the South Pacific. The researchers say they had expected to see more variety in the previously unexplored trench and believe climate change could be having an impact even in the deepest reaches of the ocean.
NEW HEBRIDES TRENCH, SOUTH PACIFIC OCEAN (NOVEMBER/DECEMBER, 2013) (UNIVERSITY OF ABERDEEN) - The New Hebrides Trench lies between New Caledonia and Vanuata to the West of the Coral Sea in the South Pacific. It's approximately 750 miles (1200 km) long and 45 miles (70 km) wide, plunging to a depth of 7600 metres (4.7 miles) in places.
The scientists say their findings came as surprise, as the footage revealed a much sparser and less diverse range of life than expected. Large red prawns and Cusk eels were abundant with arrow-tooth eels and smaller crustaceans also present but despite a total of 27 different camera deployments little else was spotted.
The researchers suggest that changing water temperatures higher up in the ocean are having a knock-on effect at the ocean floor.
Voyage leader Dr Alan Jamieson, of the University of Aberdeen's Oceanlab said: "We set out to investigate whether the patterns of biodiversity in these medium depth trenches could be predicted by trends that we have observed in the really deep trenches that we've already studied elsewhere in the Pacific Rim, but what we found was an entirely different deepwater fish community. Fish were surprisingly few in number and low in diversity and not at all what we expected. The fish we would always expect to see, the grenadiers, were completely absent. The fish that dominated the area were a group called cusk eels which are far less conspicuous elsewhere."
The scientists say the New Hebrides Trench lies underneath tropical waters, which are typically less productive than the waters around the Pacific rim.
"The waters over a trench are what 'feeds' the deep sea community and in this case it appears that the prawns and cusk eels are specialists in low food environments. This means the huge expanses of the deep Pacific Ocean that span the tropical regions are likely to be largely inhabited by the cusk eels and prawns rather than the more diverse communities we see around the Pacific Rim. If that is the case it also means that these animals are far more widespread than previously thought," said Thom Linley, fellow marine biologist from Oceanlab.
The team says that any change in temperature at higher levels is likely to have a cascading effect on the deep sea community.
"The deep sea is potentially a kind of silent victim in the era of a changing climate," they said.