Technology provides new insights to Antarctic blue whales and krill
Whales, krill, iron & ice
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The seven-week science voyage to East Antarctica on RV Investigator has been a major success.
Searching 200,000 km2 of the Southern Ocean, scientists found Antarctic blue whales by following their calls.
More than 250 underwater listening devices were deployed, capturing over 750 hours of underwater recordings.
More than 300 hours of search effort were logged.
36 blue whales were encountered, and 25 individually identified.This voyage was the first to also focus on the whales’ primary food source, Antarctic krill.
For the first time on an Australian research vessel, echo sounders built 3D pictures of giant krill swarms.
Several swarms extended over 1 kilometre in length and hundreds of metres across.
Scientists want to learn if iron-rich whale poo fertilises the ocean and helps grow more krill.
For the first time in the Southern Ocean, drones were used to take surface water samples.
Near icebergs where the ship couldn’t reach, drone missions dipped jars into the sea to collect water.
Vast amounts of other data about water chemistry were collected.
Every piece of the puzzle is important to better understand the ecology of the Southern Ocean.
Production: Mark Horstman, Simon Payne.
Vision: Alex Vail, James Cox.
This research is supported by a grant of sea time on RV Investigator from the CSIRO Marine National Facility.
Australian Antarctic Program scientists have used innovative technologies, including drones, to shed new light on the distribution of endangered Antarctic blue whales and their food source krill.
The CSIRO research vessel RV Investigator returned to Hobart today after a seven week voyage to the Southern Ocean, covering 200,000 square kilometres.
Voyage Chief Scientist Dr Mike Double said the researchers were looking at the complex relationship between Antarctic blue whales and krill, and their roles in maintaining the health of the Southern Ocean.
“This was an ambitious undertaking in an often hostile environment, and our achievements have exceeded all expectations,” Dr Double said.
The first challenge for the 28 scientists on the 13,000 kilometre journey was to find the rare Antarctic blue whales in the vast Southern Ocean.
Lead whale acoustician, Dr Brian Miller, said more than 250 underwater listening devices were deployed during the voyage to detect the low frequency calls of the whales.
“We monitored over 750 hours of underwater recordings and measured over 33,000 bearings to blue whale calls, which enabled us to home in on whale ‘hotspots’,” Dr Miller said.
Over 300 hours of search effort led to 36 encounters with blue whales and individually identifying 25. One was a whale which had previously been sighted on an expedition six years ago.
Krill ecologist with the Australian Antarctic Division, Dr So Kawaguchi, said this is the first time a survey of blue whales has been conducted together with a structured survey of their prey.
“This opens a window into understanding the relationship between the world’s largest animal and one of the world’s most abundant organisms, Antarctic krill,” Dr Kawaguchi said.
For the first time on an Australian research vessel, echo sounders were used to construct three-dimensional pictures of giant krill swarms. Several swarms extended over one kilometre in length and hundreds of metres across, containing many millions of krill.
“We’ve now got so much more information about the fine-scale three-dimensional structure of krill swarms that we can start to get a better idea of the sort of swarms Antarctic blue whales hunt,” he said.
Drones were used in more than 130 missions across a range of scientific applications, including the first size measurements and ‘blow’ sampling of blue whales in the Southern Ocean and a new method for trace metal surface water sampling.
Voyage Deputy Chief Scientist Dr Elanor Bell said biogeochemists conducted experiments on the water samples, to test the theory that whale faeces is an important source of iron in the Southern Ocean.
“It’s thought the whales’ iron-rich faeces may stimulate the growth of phytoplankton on which krill feed, which in turn becomes whale food,” Dr Bell said.
“We looked at the entire food chain from the smallest organisms on the planet to the largest – viruses to bacteria to phytoplankton to krill to Antarctic blue whales.”
The voyage’s multidisciplinary research will contribute to the improvement of ecosystem-based management of the Antarctic krill fishery and the conservation of endangered species such as Antarctic blue whales.
This research was supported by a grant of sea time on RV Investigator from the CSIRO Marine National Facility.
A large number of collaborating institutions and partners were involved in supporting this voyage including University of Tasmania, Murdoch University, University of Technology Sydney, University of Washington, University of Liverpool, Texas A&M University, University College Cork and the World Wildlife Fund.