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Climate change could disturb marine life for millennia

Endangered ecosystem Climate change may lead to disturbances in marine life that will take thousands of years to recover from, not hundreds of years as previously thought, say researchers.

The study, published today in the Proceedings of the National Academy of Sciences , is based on a section of fossilised ocean fauna found on the seafloor off the coast of California dating to between 3400 and 16,100 years ago.

"This investigation presents the first record to our knowledge of the disturbance and recovery of seafloor ecosystem bio-diversity in response to abrupt climate change," say the team of researchers led by Sarah Moffitt of the University of California, Davis.

The researchers sliced up the sediment for a before and after glimpse of how creatures were affected by climate change during the last major deglaciation, when polar ice caps melted abruptly and low oxygen zones expanded in the ocean.

Ice melt and ocean dead zones are an increasing concern today, as scientists study the warming planet and trends that are driven by the burning of fossil fuels that send greenhouse gases into the atmosphere.

The researchers analysed more than 5400 invertebrate fossils, such as sea urchins and clams, and found that they "nearly disappeared from the record during those times of low oxygen."

Levels of oxygen in the ocean dropped by between 0.5 and 1.5 millilitres per litre over a period of less than 100 years, a relatively minor changes that resulted in "dramatic changes and reorganisations for seafloor communities," they report.

"This archive reveals that global climate change disturbs seafloor ecosystems on continental margins and commits them to millennia of ecological recovery."

Climate change in the future could have similar effects, and could take a similar time scale for ocean life to rebound, on the order of thousands, not hundreds of years, say the researchers.

"There's not a recovery we have to look forward to in my lifetime or my grandchildren's lifetime," says Moffitt.

"It's a gritty reality we need to face as scientists and people who care about the natural world and who make decisions about the natural world."

Related: Acidic shift may be fastest in 300 million years