Global warming causing changes in ocean life
Melbourne: Profound changes are taking place in marine life around the planet in response to global warming, an international team of scientists has found.
The study took in research from all the world`s oceans, with a particular focus on what is happening on the east and south coasts of Australia, both US coastlines, the European Atlantic and Mediterranean.
Researchers found phytoplankton, which provide the basic food for all life in the seas, are now blooming an average of six days earlier in the season, compared with land plants. Baby fish appear to be hatching around 11 days earlier in the season.
Marine species - including fish, shellfish, crustaceans, plankton, mangroves and seagrasses - are now shifting the areas they inhabit at an average rate of 72 kilometres per decade as a result of one degree of planetary warming.
Some species have moved up to 470 kms in a decade, according to the report in the journal Nature Climate Change by scientists from Australia, Germany, South Africa, the UK, the US, Denmark, Spain and Canada.
This contrasts with an average 6 km movement by life on land. Most of the movement is towards the poles as sea life searches for cooler waters.
Sea creatures are now going into their seasonal breeding cycles an average of 4.4 days earlier - almost twice as early as land animals - in response to warmer waters, the study found.
The team analysed 208 reports on marine life and fisheries, covering 857 different marine species or groups from around the world for changes in their normal distribution, abundance, breeding cycles, community composition, shell formation and age structure.
"The results were quite a shock. We found that changes in sea life attributable to a one degree increase in the Earth`s overall temperature appear much greater than those seen in life on land so far," said co-author Professor John Pandolfi of the ARC Centre of Excellence for Coral Reef Studies and University of Queensland.
The oceans are estimated to have absorbed 80 per cent of the extra heat put into the Earth system by human use of fossil fuels, but have nevertheless warmed more slowly than the land owing to their huge mass, he said.
"This makes the very large changes in the behaviour of sea life all the more surprising. We put it down mainly to the fact that marine organisms often produce substantial numbers of floating larvae that are easily dispersed by ocean currents," he added.
The researchers cautioned that these big shifts in the timing of major events could produce disruption to ocean food webs. This has implications for all sea life, as well as for humans who depend on the sea for food, said Pandolfi.
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