Climatic Influences on Deep-Sea Ostracode Species Diversity for the Last Three Million Years

Ostracodes (small, bivalved crustaceans) are preserved in deep-sea sediment cores with sufficient abundance to allow high resolution analysis of faunal diversity patterns during climatic and oceanographic changes. We present a synthesis of patterns and possible causes of species diversity variation in benthic deep-sea ostracodes at several Deep-Sea Drilling Program (DSDP 607, 610) and Ocean Drilling Program (ODP 925, 982, 1055) sites in the North Atlantic Ocean, which together cover the last 3 million years of climatic evolution from relatively stable warmth to high-amplitude glacial-interglacial cycles. Faunas from mid-latitude cores on the Mid-Atlantic Ridge show a positive correlation between warm temperatures and high species diversity. In the subpolar regions of the Rockall and Iceland Plateaus, this pattern is reversed for the last 200 thousand years when the highest diversity occurs during major glacials represented by Marine Isotope Stages (MIS) 2-4 and 6. Spikes in subpolar benthic diversity during glacial periods may be caused by ice rafting during Heinrich events, which would have less influence in the lower-latitude North Atlantic. Heinrich events reduce North Atlantic surface temperatures and salinity every ~6-12 ka, dramatically decreasing surface productivity. Higher diversity during Heinrich events may be explained either by surface productivity changes or benthic habitat disturbance by ice-rafted debris.