Oceans Damaged by Climate Change Take Thousands of Years to Recover

by News Staff / March 31, 2015

New research out of the University of California, Davis, shows that ocean ecosystems that experience rapid upheaval from climate change can take thousands of years to recover.

Recovery from climate change and the deoxygenation of seawater -- which can alter ocean ecology very quickly -- was previously thought to be on a 100-year scale. But the work, led by scientist Sarah Moffitt, proved that wrong.

Moffitt determined this by analyzing more than 5,400 invertebrate fossils, from sea urchins to clams, within a sediment core offshore Santa Barbara, according to a press release.

This core is essentially a tube of sediment that covers a period between 3,400 and 16,100 years ago, so it offers a before-and-after snapshot of what happened during the last major deglaciation -- a time of abrupt climate warming, melting polar ice caps, and expansion of low oxygen zones in the ocean.

Moffitt's approach to studying the core is what has shed new light on the recovery period. Previous studies primarily relied upon single-celled organisms versus multicellular life like invertebrates. Perhaps more telling, however, was that Moffitt took the entire core -- which was about 30 feet long -- and cut it up like a cake, sampling the whole thing.

"Because of that, I had the whole record,” she said in the press release.

And the record showed an initially abundant, diverse and well-oxygenated seafloor ecosystem, then a period of warming and oxygen loss in the oceans -- by between 0.5 and 1.5 mL/L over a period of less than 100 years -- followed by a rapid loss of diversity. The fossils, according to U.C. Davis, nearly disappeared during the reduced oxygen periods, showing that relatively minor changes in oxygen levels could cause dramatic changes and reorganizations for seafloor communities. 

“These past events show us how sensitive ecosystems are to changes in Earth’s climate — it commits us to thousands of years of recovery,” Moffitt said. “It shows us what we’re doing now is a long-term shift — there’s not a recovery we have to look forward to in my lifetime or my grandchildren's lifetime. 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.”