A cool window on the world
by Veronika Meduna
It’s possibly the most beautiful place on the planet to call your office.
Iceberg, Terra Nova Bay. Photograph by Dave Allen on 21 February 2015.
New Zealand and Australian scientists working off the Antarctic coast have been treated to a spectacular set of summer days as they research the complex food webs and top predators in the Southern Ocean.
This week the team reached Terra Nova Bay, a 64-km-long stretch of coastline between Cape Washington and the Drygalski Ice Tongue – and a hotspot for Antarctic silverfish.
Richard O’Driscoll, a fisheries scientist with the National Institute for Water and Atmosphere (NIWA) and one of the voyage leaders, said the tiny fish were a keystone species in the Ross Sea, providing one of the major links between zooplankton and predators like seals, penguins, seabirds and toothfish.
He said silverfish eggs and larvae were abundant in Terra Nova Bay during spring, but no adult fish had been found there during that season.
Pictured right: Silverfish. Photo: Dave Allen.
“In the spring when the ice clears out of Terra Nova Bay we see the eggs and the larvae of silverfish in this area, but we don’t know whether the adults actually swim in there and spawn during the winter when it’s covered with ice or whether the eggs and larvae just drift in.”
To find out whether there is a mass winter migration of silverfish to coastal spawning sites or whether their eggs are spawned elsewhere and accumulate under the ice, the team moored an underwater echo-sounder in Terra Nova Bay, which is 550 metres deep.
The echo-sounder was floating about 150 metres above the seabed, looking upwards towards the surface. It had been programmed to switch on come May 15, when it would start collecting data for 200 days throughout winter, until December. Once it had completed its mission, the instrument would be recovered by Italian colleagues in January.
The experiment would fill an important gap in observations of the lives of silverfish and help predict future changes in their spawning success and abundance in the Ross Sea as ocean temperatures rose.
Since NIWA’s research vessel RV Tangaroa departed from Wellington at the end of January, the scientists have recorded blue and humpback whales, as well as studying the abundance of bottom-dwelling fish to determine the potential ecosystem effects of the commercial toothfish fishery in the Ross Sea.
Gallery
Photos: NIWA/Dave Allen.
The images in this gallery are used with permission and are subject to copyright conditions.
