Benthic foraminiferal assemblages as proxies for paleoenvironmental indicators in the Indo-Pacific (Indonesia)

Abstract. This study tests the hypothesis that benthic foraminiferal assemblages in Indonesian seas exhibit systematic depth zonation, with environmental controls shifting from physical factors in shallow waters to biochemical factors in deep waters. We established a comprehensive regional indicator set spanning six bathymetric zones (transitional, inner neritic, middle neritic, outer neritic, upper bathyal, and lower bathyal) based on 35 surface sediment samples collected from 0–4327 m water depths across the Indonesian seas. Statistical analysis, combining indicator value (IndVal), detrended correspondence analysis (DCA), and hierarchical cluster analysis using Bray–Curtis dissimilarity, successfully discriminated assemblages with 89 % classification accuracy based on bathymetric zones. Results demonstrate a systematic increase in the percentage of planktonic foraminifera in relation to the whole fauna (%P) from 0 %–0.6 % in transitional environments to > 90 % in lower bathyal settings. Benthic species richness peaked at middle-neritic depths (47 species per sample) before declining in deeper waters, while planktonic diversity increased continuously with depth. Primary indicator taxa show clear bathymetric segregation: Amphistegina and Sphaerogypsina dominate transported assemblages in transitional settings; substrate-dependent communities characterize inner neritic environments; Quinqueloculina and Pseudorotalia indicate middle-neritic environments; Brizalina, Gyroidina, and Cibicides mark outer neritic environments; while Uvigerina, Bulimina, and Globobulimina typify bathyal depths. The shift from physical to biogeochemical environmental controls appears to take place in outer neritic environments on the shelf and provides a robust, locally calibrated framework for paleobathymetric reconstruction in Indonesian seas.