Planktonic foraminifera from the eastern Indian Ocean: Distribution and ecology in relation to the Western Pacific Warm Pool (WPWP)

J. Ignacio Martinez, Lynda Taylor, Patrick De Deckker*, Timothy Barrows

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Faunal assemblages, principal component (PCA), canonical correspondence (CCA), and factor analysis are applied to planktonic foraminifera from 57 core-top samples from the eastern Indian Ocean. The foraminiferal lysocline occurs at ~2400 m north of 15°S where carbonate dissolution is induced by the Java upwelling system, and occurs deeper south of 15°S where carbonate dissolution is characteristic of the oligotrophic regions in the Indian Ocean. Dissolution effects, the February standing stock at the time of collection of the plankton-tow material, and different production rates explain the different foraminiferal assemblages found between plankton-tow and core-top samples. Core-top samples are differentiated by PCA into four groups - Upwelling, Western Pacific Warm Pool (WPWP), Transitional, and Southern - that are related to environmental variables (temperature, salinity and nutrients); all environmental variables follow a strong latitudinal component as indicated by the CCA analysis. Similarly, three assemblages are recognized by factor analysis: Factor 1 (dominated by Globigerinoides sacculifer, G. ruber, Globigerinita glutinata and Globorotalia cultrata), factor 2 (dominated by Globigerina bulloides and Globorotalia inflata) and factor 3 (dominated by Neogloboquadrina duttertrei) explain more than 92% of the variance, and are related to sea-surface temperature, thermocline depth and nutrient levels. The seasonal influence of the Java upwelling system supplies nutrients, phyto- and zooplankton to the oligotrophic eastern Indian Ocean (factor 1). South of ~24°S, a deep chlorophyll maximum, a deep euphotic zone, a deep thermocline, SSTs below ~22°C, and brief upwelling pulses seem to explain factors 2 and 3. The ratio of G. sacculifer and N. dutertrei, two mutually excluding especies, appears to indicate the southern boundary of the WPWP. This ratio is applied to core Fr10/95-11 to demonstrate past shifts of the southern boundary of the WPWP.

    Original languageEnglish
    Pages (from-to)121-151
    Number of pages31
    JournalMarine Micropaleontology
    Volume34
    Issue number3-4
    DOIs
    Publication statusPublished - 1 Sep 1998

    Keywords

    • Carbonate dissolution
    • Core-tops
    • Indian Ocean
    • Lysocline
    • Planktonic foraminifera
    • Principal Component Analysis
    • Western Pacific Warm Pool

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