New light on marine life and climate change

Posted on May 3, 2012

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Dr Strugnell inspects a Megaleledone Octopus

Ground-breaking research by geneticist Dr Jan Strugnell has helped explain the origin and global distribution of deep-sea marine life, providing critical insights into climate change.

Her work was highlighted at a celebration of 100 years of Australian Antarctic science when she delivered a keynote address on marine biodiversity in the Southern Ocean.

About 250 local and international experts met in Canberra in May to discuss the state of Antarctic science since Sir Douglas Mawson led Australasia’s first Antarctic Expedition in 1911-1914. 

Dr Strugnell is also lead author of a new international study that reveals how the genes of a fairly sedentary Antarctic octopus provide a clue to the risk of sea-level rise if world temperatures keep climbing.

Published in the journal ‘Molecular Ecology’ and reported on Britain’s Natural Environment Research Council ‘Planet Earth’ website, the study found that the genetic make up of Turquet’s octopus was startlingly similar in both the Weddell and Ross Seas.

As these two bodies of water are some 10,000 kilometres apart, on opposite sides of Antarctica separated by the West Antarctic Ice Sheet, researchers think such strong genetic similarity is only possible if there had been a previous collapse of the ice sheet, maybe as recently as 200,000 years ago.

This suggests that scientists’ concerns about the state of today’s ice sheet could well be justified. Planet Earth says while a previous study, in 2010, provided the first evidence of a trans-Antarctic seaway connecting the Ross and Weddell Seas, the findings by Dr Strugnell’s team are the first genetic evidence of such a connection.

‘Ocean currents both facilitate and hinder the flow of genes,’ says Dr Strugnell. ‘But the Antarctic Circumpolar Current almost certainly wouldn’t have facilitated so much dispersal by octopuses that two populations would have almost identical genetics if the ice sheet had been in place.’

Off to work on the British research vessel James Ross

Ten year census of marine life

A former Rhodes Scholar, Dr Strugnell made world headlines with the results of her research into the evolution of deep-sea octopuses. She says modern molecular studies have revealed that the Southern Ocean is teeming with a huge diversity of previously unknown marine life.

Her study was part of the first Census of Marine Life, a ten year project involving more than 2,000 scientists from 82 nations. She was lead scientist of a team that studied marine life from ocean floors that had never been sampled before. 

In addition, genetic material from marine life from the project was brought together and made available to Dr Strugnell for DNA studies, who was then working at Queen’s University Belfast.

The work revealed that all octopuses found in deep oceans world-wide originated in the waters around the South Pole about 33 million years ago. They spread into other oceans around 15 million years ago, as the Antarctic cooled and eventually froze over.

Climate change at ocean’s depth

As a result, there was an outflow from Antarctica of cold, nutrient-rich water with high levels of salt and oxygen, creating a north-bound freeway along which octopuses travelled to their new habitats.

Striped pyjama squid

‘We think that if octopuses colonised the deep sea by this route, it’s very likely that other organisms did so as well,’ says Dr Strugnell.

She says her research also demonstrates that climate change can have profound effects on biodiversity, with impacts extending into habitats as remote as our deep oceans.

Originally from Swan Hill in Victoria, Dr Strugnell’s doctoral study at Oxford was the first to use molecular and fossil evidence to estimate dates of divergence for octopus, squids and cuttlefish.

Impacts on abalone industry

Since joining La Trobe’s Department of Genetics in 2010, she is also investigating the molecular basis of stress and disease in abalone, shellfish whose export is worth more than $200 million annually to the Australian economy.

Dr Strugnell says mass mortality disease of farmed abalone during the summer, related to high water temperatures, is likely to increase with predicted global warming. Her ARC funded research aims to develop an early warning test for stress and stress resilience for the abalone industry.

She is also continuing her studies into population and molecular evolution of Antarctic and deep-sea marine animals in the context of past climatic and geological change.

From deep sea to high heaven

Polar studies of space weather

La Trobe University research in Antarctica goes back to the 1960s.

Over the years University programs in radio, magnetic and optical remote sensing have attracted students keen to combine research with winter on the frozen continent.

The University has built and operates two pieces of scientific equipment in Antarctica, one at Mawson and one at Davis. Called Fabry Perot Spectrometers, these measure wind and temperature in the thermosphere.

La Trobe scientists have also designed and installed a key radar research facility TIGER – the Tasman International Geospace Environment Radar – which straddles Australia, Antarctica and New Zealand. 

The University operates TIGER on behalf of a consortium that includes the Australian Antarctic Division and other universities. Part of the international SuperDARN (Dual Auroral Radar Network) this project monitors the aurora. 

Other biological sciences’ studies have included research into the recovery of fur seals on Macquarie Island.