Warming oceans impact marine-life habits

The distribution, breeding patterns and habitat of marine life are rearranging in response to warming oceans, according to a three-year international study.

The international team, led by CSIRO’s Climate Adaptation Flagship and University of Queensland marine ecologists Dr Elvira Poloczanska and Associate Professor Anthony Richardson, identified more than 1700 changes in the geographic distribution of marine animals, including 222 records from Australia’s marine life.

The study, which was based on a synthesis of peer-reviewed literature from around the world, found that marine species are shifting their geographic distribution poleward and doing so much faster than their land-based counterparts.

“The leading edge or ‘front line’ of a marine species distribution is moving towards the poles at the average rate of 72 km per decade, which is considerably faster than terrestrial species moving poleward at an average of 6 km per decade,” said Dr Poloczanska.  “This is despite sea surface temperatures warming three times slower than land temperatures.”

The ocean absorbs 80% of the heat added to the global climate system. However, because of its large thermal capacity, surface waters have warmed three times slower than air temperatures over land.

“The rapid poleward shift of marine life tracks the poleward migration of isotherms across the ocean, and represents an effort of marine life to keep within the thermal regimes they are adapted to, avoiding warmer waters and those experiencing heat waves impacting on marine life,” said research team member Professor Carlos Duarte from The University of Western Australia’s Oceans Institute and School of Plant Biology.

Changes in the life cycle of species, such as breeding times, were found to be changing as the seas warm. 

The timing of breeding and migration were found, on average, to be advancing by 4.4 days each decade in marine species, which is also much faster than land-based species which are breeding around 2.3-2.8 days earlier each decade.

Although the study reported global impacts, there is strong evidence of change in the Australian marine environment.

Dr Poloczanska said that in Australia’s south east, tropical and subtropical species of fish, molluscs and plankton were shifting much further south through the Tasman Sea. In the Indian Ocean, there was a southward distribution of sea birds as well as loss of cool-water seaweeds from regions north of Perth.

“We are seeing widespread reorganisation of marine ecosystems, with likely significant repercussions for the services these ecosystems provide to humans,” Dr Poloczanska said.

The international team included 19 researchers from Australia, USA, Canada, UK, Europe and South Africa.

The work has been published in Nature Climate Change.