Hot seas altered nitrogen cycle, delaying recovery by millions of years
Out-of-reach nutrients could help explain why life on Earth took so long to bounce back from the worst extinction of all time.
Analyzing the chemical changes that followed the Permian extinction 252 million years ago, geologists propose that hot sea surface temperatures led to conditions that trapped nitrogen far below the ocean’s sunlit, life-filled layers. The resulting deficiency of the key nutrient helps explain why marine ecosystems took 5 million to 9 million years to recover, millions of years longer than for other mass extinctions, the researchers propose online August 5 in Geology.
“It’s equivalent to a farm,” says study coauthor Stephen Grasby, a geochemist at the Geological Survey of Canada in Calgary. “If you’re not throwing fertilizer on the field, the soil becomes nutrient limited and you get less and less plant growth.&rdquo