A multiproxy reconstruction of biological productivity and oceanography inthe eastern equatorial Pacific for the past 30,000 years

Surface ocean biological productivity was reconstructed for oxygen isotope stages 1 and 2 in 5 cores from the eastern equatorial Pacific using a newly developed proxy based on assemblages of benthic foraminifera. Along the eq uator and in the South Equatorial Current there was a drop in productivity during the early to mid-Holocene, a peak during the later stages of the gla cial-interglacial transition, and full glacial values lower than those of t he present. There was a decrease in biological productivity (new production ) on the order of 25% along the equator during the last full glacial. The w est to east productivity gradient in the east equatorial Pacific was mainta ined in glacial times, but was reduced compared to the present. In contrast , values to the south and north of the equatorial belt of high productivity may have increased modestly during the glacial. The equatorial decrease in surface ocean biological productivity during the Ice Age was rested using multispecies benthic foraminiferal carbon isotope data and carbonates prese rvation indices. These tests support the faunal interpretations. The paleop roductivity results presented here conflict with those based on the record of organic carbon in deep sea sediments. The nature of this conflict and re asons for it are examined. Finally, the results here may be compatible with geochemical reconstructions of surface water nutrient concentrations, nutr ient utilization, paleo-pH estimates and CO2 efflux in the eastern equatori al Pacific. However, the nutrient reconstructions are not supported by plan ktonic foraminiferal multispecies; carbon isotope values, and an alternativ e model of glacial age circulation and plankton communities may be needed t o account for all the data. (C) 1999 Elsevier Science B.V. All rights reser ved.