Biotic response to late Quaternary rapid climate switches in Santa BarbaraBasin: Ecological and evolutionary implications

Benthic foraminiferal assemblages from Santa Barbara Basin exhibit major fa unal and ecological switches associated with late Quaternary millennial- to decadal-scale global climate oscillations. Repeated turnovers of entire fa unas occurred rapidly (<40-400 yr) without extinction or speciation in conj unction with Dansgaard-Oeschger shifts in thermohaline circulation, ventila tion, and climate, confirming evolutionary model predictions of Roy ct al. Consistent faunal successions of dysoxic taxa during successive interstadia ls reflect the extreme sensitivity and adaptation of the benthic ecosystem to the rapid environmental changes that marked the late Quaternary and poss ibly other transitional intervals in the history of the Earth's ocean-atmos phere-cryosphere system. These data support the hypothesis that broad segme nts of the biosphere are well adapted to rapid climate change.