For ancient deep-sea plankton, a long decline before extinction

A new study of nearly 22,000 fossils finds that ancient plankton communities began changing in important ways as much as 400,000 years before massive die-offs ensued during the first of Earth’s five great extinctions. The research suggests that the effects of environmental degradation can be subtle until they reach a tipping point, at which dramatic declines in population begin.
Paleontology News — ScienceDaily