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Ocean Took Thousands of Years to Recover from Past Climate Change

08 April 2015

US - Ecosystem recovery from climate change and seawater deoxygenation can take thousands of years, according to a study led by Dr Sarah Moffitt from the University of California.

The researchers analysed more than 5,400 invertebrate fossils, from sea urchins to clams, within a sediment core from offshore Santa Barbara, California.

The revolutionary study explored multicellular life rather than single-celled organisms, in pursuit of a more complete picture of ocean ecosystem resilience, and is published in the journal PNAS.

"In this study, we used the past to forecast the future," said Dr Peter Roopnarine, from the California Academy of Sciences, who also worked on the study.

"Tracing changes in marine biodiversity during historical episodes of warming and cooling tells us what might happen in years to come.

"We don't want to hear that ecosystems need thousands of years to recover from disruption, but it's critical that we understand the global need to combat modern climate impacts."

The tube-like sediment core is a slice of ocean life as it existed between 3,400 and 16,100 years ago, and provides 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.

Dr Roopnarine said: "To truly understand the health of an ecosystem and the food webs within, we have to look at the simple and small as well as the complex.

"In this case, marine invertebrates give us a better understanding of the health of ecosystems as a whole."

The study's all-important sediment core revealed an ancient history of abundant, diverse, and well-oxygenated seafloor ecosystems, followed by a period of oxygen loss and warming that seems to have triggered a rapid loss of biodiversity. The study reports that invertebrate fossils are nearly non-existent during times of lower-than-average oxygen levels.

In periods of fewer than 100 years, oceanic oxygen levels decreased between 0.5 and 1.5 mL/L. Sediment samples during these periods show that relatively minor oxygen fluctuations can result in dramatic changes for seafloor communities.

The study results suggest that future periods of global climate change may result in similar ecosystem-level effects with millennial-scale recovery periods.

As the planet warms, scientists expect to see much larger areas of low-oxygen "dead zones" in the world's oceans.

"Folks in Oregon and along the Gulf of Mexico are all-too-familiar with the devastating impacts of low-oxygen ocean conditions on local ecosystems and economies," said Dr Roopnarine.

"We must explore how ocean floor communities respond to upheaval as we adapt to a 'new normal' of rapid climate change."

Further Reading

You can view the full report by clicking here.

TheFishSite News Desk

Top image via Shutterstock



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