Biological Impacts of Cenozoic Global Changes on the Deep-sea Ostracods fauna

Abstract:

The deep ocean floor is the largest and the least explored ecosystem on Earth. It has gradually become clear that it hosts high biodiversity. However, the evolution of deep-sea ecosystem remains poorly understood partially due to the poor fossil preservation of most benthic organisms. In this study, we aim to provide an important glimpse into deep-sea metazoan evolution by studying microcrustacean ostracods, the only metazoan group with abundant fossil records in the deep sea. We reconstructed global diversity and biogeographic changes of ostracods over the past ~72 million years based on assemblage data compiled from 77 deep-sea drilling sites. Our results showed that the global diversity patterns of ostracods closely corresponded to the changes in the global deep-sea oxygen isotopic records. The Cretaceous–Eocene “greenhouse” deep-sea fauna were characterized by high provincialism. Multivariate statistical analyses revealed that a globalization process in some deep-sea genera was initiated through the Eocene-Oligocene climate transition. The globalization of the deep-sea fauna might result from biological impacts of the global cooling, the contraction of oxygen minimum zones, and the enhancement episodes of the Antarctic Circumpolar Current and the Atlantic meridional overturning circulation. Our study demonstrated that the rich fossil records of ostracods provide critical insights for future deep-sea biological and paleontological macroevolution studies.