Characterization of El Niño, La Niña, and normal conditions through planktonic foraminifera (2006–2007) in the southeastern Pacific

Nathalie Gajardo,Humberto E González,Margarita Marchant

doi:10.7773/cm.v39i3.2177

Nathalie Gajardo, Humberto E González + Show 1 more

Open Access

https://doi.org/10.7773/cm.v39i3.2177

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Abstract

We conducted a study to characterize the foraminiferal association off south-central Chile under positive (January to December 2006), neutral (January to June 2007), and negative (July to September 2007) thermal anomalies, which coincided approximately with El Niño (EN), normal (NC), and La Niña (LN) conditions, respectively, using samples collected in a sediment trap located off Concepción at 2300 m depth. During the three environmental conditions, total species richness was 19, with 18 species present during EN, 14 during NC, and 14 during LN. Moreover, a typical association of subantarctic waters was observed during NC and LN, but not during EN, when we found a mixture of cold and warm water species as well as higher foraminiferal and calcium carbonate fluxes. However, diversity was very similar under the three conditions. We observed significant differences in foraminiferal and calcium carbonate fluxes between NC and EN, with higher values during the warm phase.

Highlights

The Humboldt Current System (HCS) belongs to one of the regions of the Eastern Border Current Systems (EBCS), which correspond to the most productive oceanic areas in the world
During January and June 2007, temperatures tended towards resuming the normal levels for Concepción Bay (14–15 oC), and between July and September 2007, they continued to decrease to lower than the records for 2006, coinciding with the La Niña (LN) condition
During LN, the fauna association was similar to normal conditions (NC) with the presence of N. incompta (76%), G. glutinata (10%), G. bulloides (8.5%), G. scitula (1.5%), and Globorotalia truncatulinoides (~1%); they represented 97% of the total and the remaining nine species only 3%

Summary

Introduction

The Humboldt Current System (HCS) belongs to one of the regions of the Eastern Border Current Systems (EBCS), which correspond to the most productive oceanic areas in the world. This system consists of a northern current (the PeruChile Current) and a southern current (the Cape Horn Current) (Berger et al 1989, Strub et al 1998, Silva et al 2009). Desplazándose de norte a sur se encuentra la contracorriente de Perú-Chile, que es de alta productividad biológica a escala global (Shaffer et al 1995, Silva et al 2009)

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