ABSTRACT: Raja Ampat (Indonesia) is a remote archipelago west of Papua mainland and situated at the eastern edge of the Coral Triangle. The archipelago is considered one of the species-richest and most pristine localities and home to the world’s most diverse coral reefs. For centuries, reefs of Raja Ampat have enjoyed natural protection and remained largely untouched due to their isolated location. The region represents a key area for evaluating richness and biogeographic patterns of tropical shallow-water organisms, yet the foraminiferal fauna of Raja Ampat is virtually unexplored. Benthic foraminifera are an integral part of the reef fauna, prolific carbonate producers and essential for reefal accretion and substrate stability. Previous studies on Indo-Pacific benthic reef foraminifera indicate that diversity is highest in the Central Indo-Pacific and broadly correlates with diversity patterns of other tropical marine taxa. This report presents the first illustrated catalog and comprehensive analysis of the structure, composition, and diversity of the species-rich benthic foraminiferal biotas of the Raja Ampat Archipelago including an assessment of local reef vitality with the Foraminifera in Reef Assessment and Monitoring (FoRAM) Index. We examined shallow-water sediment samples from fringing reefs, reef platforms, sheltered bays and reef-associated environments to cover the full range of existing micro- and macrohabitats. Atotal number of 421 species were recovered, among them five new species and one newly described genus of the porcelaneous Miliolida. The fauna is dominated by hyaline taxa but the Miliolida represent the species-richest order and are especially diverse in fine-grained sediments of deep fore-reef slopes. Extraordinary high diversity of the benthic foraminiferal communities indicates that the waters of Raja Ampat probably represent one of the world’s biologically richest locations in reefs.We identified a total of 35 species of larger symbiont-bearing benthic foraminifera, a number that is among the highest reported so far for reefs in modern oceans. The analysis of the FoRAM Index revealed that water quality at all sites examined is suitable for reef growth and recovery. The results of our study show that the Raja Ampat Archipelago harbors unique and particularly diverse assemblages of modern benthic foraminifera and provides a protistan perspective for the hotspot of diversity in the Central Indo-Pacific.


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