Calcareous Nannoplankton Response to Surface-Water Acidification Around Oceanic Anoxic Event 1a

Abstract

Acidification of the Ancient Oceans Ocean acidification fueled by rising levels of atmospheric CO 2 is likely to become a major challenge for ocean ecosystems. Understanding how marine biota responded to similar events in Earth's history may provide clues as to what to expect—and what to prevent—in the future. To this end, Erba et al. (p. 428 ) present a detailed stratigraphic and geochemical characterization of 120-million-year-old marine sediments from a time when the oceans acidified because of a massive outgassing of volcanic CO 2 . Microscopic fossils in the sediments, such as calcareous nannoplankton, show evidence of having responded to this major disruption through species-specific adaptations like deforming and shrinking their cells. These changes allowed these abundant and diverse organisms to avoid extinction, even through a subsequent global depletion of ocean oxygen levels.