Planktonic Foraminifera Proxies Calibration Off the NW Iberian Margin: Nutrients Approach

Friday, 19 December 2014: 10:20 AM
Emilia Salgueiro1,2, Carmen G Castro3, Diana Zuniga1,2, Pamela A Martin4, Jereon Groeneveld5, Francisco de la Granda3, Nicolas Villaceiros-Robineau3, Fernando Alonso-Perez3, Ana Alberto1, Teresa Rodrigues1,2, Marta M. Rufino1, Fatima F G Abrantes1,2 and Antje H L Voelker1,2, (1)Instituto Português do Mar e da Atmosfera (IPMA), Divisão de Geologia e Georecursos Marinhos, Lisbon, Portugal, (2)CIMAR, Associated Laboratory, Porto, Portugal, (3)Instituto de Investigacións Mariñas – CSIC, Vigo, Spain, (4)Indiana University–Purdue University, Departments of Geology and Geography, Indianapolis, IN, United States, (5)University Bremen, Faculty of Geosciences, Bremen, Germany
Planktonic foraminifera (PF) shells preserved in marine sediments are a useful tool to reconstruct productivity conditions at different geological timescales. However, the accuracy of these paleoreconstructions depends on the data set and calibration quality. Several calibration works have been defining and improving the use of proxies for productivity and nutrient cycling parameters. Our contribution is centred on a multi-proxy calibration at a regional coastal upwelling system. To minimize the existing uncertainties affecting the use of trace elements and C stable isotopes as productivity proxy in the high productivity upwelling areas, we investigate the content and distribution of Ba/Ca and δ13C in the water column, its transference into the planktonic foraminifera shells, and, how the living planktonic foraminifera Ba/Ca and δ13C signal is related to the same planktonic foraminiferal species preserved in the sediment record. This study is based on a large data set from two stations (RAIA - 75m water depth, and CALIBERIA - 350m water depth) located off the NW Iberian margin (41.5-42.5ºN; 9-10ºW), and includes: i) two year monthly water column data (temperature, salinity, nutrients, chlorophyll a, Ba/Ca, and δ13C-DIC); ii) seasonal Ba/Ca, δ13C in several living PF species at both stations; and iii) Ba/Ca and δ13C in several PF species from a large set of core-top sediment samples in the study region. Additionally, total organic carbon and total alkenones were also measured in the sediment. Our results showed the link between productivity proxies in the surface sediment foraminifera assemblage and the processes regulating the actual phytoplankton dynamics in an upwelling area. The understanding of this relationship has special relevance since it gives fundamental information related to the past oceanic biogeochemistry and/or climate and improves the prevision of future changes against possible climate variability due to anthropogenic forcing.