Ocean ecosystems that have been affected by climate change could take thousands of years to recover.
A recent study provides the first record of "disturbance and recovery" of ecosystems existing on the seafloor, UC Davis reported. The findings demonstrate that climate change and deoxygenation of seawater can trigger rapid and dramatic changes in these ecosystems that would take thousands of years to reverse.
A team of researchers looked at more than 5,400 invertebrate fossils found within a sediment core from offshore Santa Barbara. The sediment demonstrates a "snapshot" of a time period ranging from between 3,400 and 16,100 years ago. This period corresponds with the last major deglaciation, which was characterized by abrupt climate warming and expansions of low oxygen zones in the ocean. Past studies on historical climate changes have relied primarily on single-celled organisms, called foraminifera; the recent study provides new insight by looking at multicellular life.
"After the initial sampling at sea, I took the entire core, which was about 30 feet long," said Sarah Moffitt, a scientist from UC Davis Bodega Marine Laboratory and Coastal and Marine Sciences Institute. "I cut it up like a cake, and I sampled the whole thing. Because of that, I had the whole record."
The findings revealed a period of rich diversity and high sea oxygenation, followed by a period of warming, oxygen loss, and reduced diversity in ocean ecosystems. During this time oceanic oxygen levels fell by between 0.5 and 1.5 mL/L over a period of less than 100 years, suggesting even small changes could trigger a big change in ocean ecosystems.
"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."
The findings were published in a recent edition of Proceedings of the National Academy of Sciences.
