Biotic effects of abrupt paleocene and cretaceous climate events

In the last 125 million years, a series of substantial environmental perturbations had major impacts on the composition, distribution, and stability of marine and terrestrial ecosystems. This interval was marked by particulary radical changes in the protistans. Groups such as the diatoms and planktic foraminifera became fundamental parts of marine food chains during this time. Other groups such as the calcareous nannoplankton and radiolarians underwent wholesale changes in species composition and assemblage structure. The underlying causes the long-term (millions of years, or m.y.) evolutionary changes are complex (see summary in kie et al., review). Research over the last decade has established that these groups also were transformed by environmental changes that took place over short time scales (thousands of years. ork.y.). In particular, short-lived global warming events led to dramatic changes in the nature of global carbon cycling while sparkling significant biotic turnover (e.g., Kennett and Stott, 1991; Erba, 1994; Erbacher and Thurow, 1997; Leckie et at al., in review). We focus here on the biotic consequences of a major warming event in the late paleocere and ocean-wide anoxic events in the Cretaceous. Recent efforts of the Ocean Drilling Program (ODP) have led to significant advances of our understanding of both these intervals.