Abstract
GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS,
VOL. 13,
Q01015,
17 PP., 2012
doi:10.1029/2011GC003595
Reconstructing past upwelling intensity and the seasonal dynamics of primary productivity along the Peruvian coastline from mollusk shell stable isotopes
- Methodological advance for the use of mollusk geochemistry in paleoceanography
- New shell d13C and d18O interpretation model
- New perspectives for the study of long-term variability in coastal upwellings
School of Ocean and Earth Science, National Oceanography Centre, Southampton, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH, UK
Institut des Sciences de l'Evolution de Montpellier, Université Montpellier 2-CNRS-IRD, CC061, Pl. Eugène Bataillon, F-34095 Montpellier, France
Institut des Sciences de l'Evolution de Montpellier, Université Montpellier 2-CNRS-IRD, CC061, Pl. Eugène Bataillon, F-34095 Montpellier, France
Department of Earth and Space Sciences, University of Washington, Box 351310, Seattle, Washington 98195, USA
Oceanografia Quimica, IMARPE, Cruce Esq. Gamarra y Gral Valle s/n Callao, Callao 01, Peru
Laboratorio Costero de Ilo, IMARPE, Ilo, Callao 01, Peru
Institut des Sciences de l'Evolution de Montpellier, Université Montpellier 2-CNRS-IRD, CC061, Pl. Eugène Bataillon, F-34095 Montpellier, France
Department of Archaeology, History, Culture and Religion, University of Bergen, Postbox 7805, N-5020, Bergen, Norway
Institut des Sciences de l'Evolution de Montpellier, Université Montpellier 2-CNRS-IRD, CC061, Pl. Eugène Bataillon, F-34095 Montpellier, France
Institut des Sciences de l'Evolution de Montpellier, Université Montpellier 2-CNRS-IRD, CC061, Pl. Eugène Bataillon, F-34095 Montpellier, France
IPSL/LOCEAN, UPMC/CNRS/IRD/MNHN, Centre IRD France Nord, 32 ave. Henri Varagnat, F-93143 Bondy CEDEX, France
School of Ocean and Earth Science, National Oceanography Centre, Southampton, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH, UK
School of Oceanography, University of Washington, Box 355351, Seattle, Washington 98195, USA
We present here a potential new method to evaluate past variations of the mean intensity of Peruvian coastal upwelling and of the seasonal timing of phytoplankton blooms. This method uses a combination of the monthly carbon and oxygen isotopic signals preserved in fossil mollusk shells, and a series of corrections to extract the variations of the dissolved inorganic carbon (DIC) δ13C. Based on the analysis of five shell samples (85 shells in total) from the southern Peruvian coast, we suggest that the mean coastal upwelling intensity can be determined from a linear relationship between average values of corrected shell δ13C and δ18O. This new potential proxy would bring additional independent information valuable to interpret paleoproductivity changes reconstructed from marine sediment of the nearby continental shelf. Results obtained on fossil samples from the middle Holocene show an increase in upwelling intensity during this period associated to a spatial reorganization of upwelling centers along the South Peruvian coast. At the seasonal scale, corrected shell δ13C enrichment indicates a phytoplankton bloom. Seasonal timing of phytoplankton blooms can be estimated by the lag with the annual temperature cycle reproduced by shell δ18O monthly variations. The results obtained with two modern shell samples indicate phytoplankton blooms occurring during summer and fall, consistently with in situ productivity observations. Our method relies on revisited assumptions about the influence of temperature and metabolism in mollusk shell δ13C. We further discussed the validity of these assumptions and the potential implications for the interpretation of similar data sets.
Received 1 March 2011; accepted 2 December 2011; published 27 January 2012.
Citation: (2012), Reconstructing past upwelling intensity and the seasonal dynamics of primary productivity along the Peruvian coastline from mollusk shell stable isotopes, Geochem. Geophys. Geosyst., 13, Q01015, doi:10.1029/2011GC003595.
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