Some like it cold as sea life moves south

Ocean species that used to live off Sydney half a century ago now inhabit the Southern Ocean as climate change drives fish, plankton and microbes to colder waters, a scientific snapshot of marine health has found.

The report by 80 scientists, led by the CSIRO, documents the southward migration of marine life, as well as ocean acidification and coral bleaching that are attributable to climate change.

The report, a round-up of the leading scientific papers of the past three years, is the most comprehensive study of the impact of global warming on Australia’s oceans today, the authors say. It “shows new evidence and greater confidence in the ocean changes” due to climate change.

It describes south-east Australia as “a global warming hot spot”, with southward migration of seaweeds, phytoplankton, zooplankton and fish.

A marine ecologist with the CSIRO and the University of Queensland, Anthony Richardson, said oceans absorb 40 per cent of carbon dioxide, while plankton produce about half the oxygen we breathe, and that changes to the oceans could have dramatic consequences.

“What we do know is that there are likely to be big changes that we can’t do much about. We can change our fishing practices but we can’t help microbes or plankton. Probably our biggest concern and our biggest unknown is how the productivity of the ocean will change. Microbes do a lot of the nutrient recycling and get rid of a lot of the pollution we produce.”

Evidence of changes in the ocean due to global warming had accumulated in the past three years, the authors say.

“The research shows that for many groups of plants and animals where there was no evidence for climate impacts in 2009, there is now striking evidence of extensive southward movements of tropical species in south-east Australia, declines in abundance of many temperate species, and the first signs of the effect of ocean acidification on marine species with shells,” the report states.

Climate change had also strengthened the East Australian Current by about 30 per cent since the 1950s, Dr Richardson said. This strengthening was helping to carry marine life south.

The report finds there could be indirect impacts on marine life from climate change through extreme weather events on land.

The Queensland floods for example washed sediment into the sea, killing many green sea turtles.

David Wroe, The Sydney Morning Herald, 17 August 2012. Article.

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