Distribution of smaller benthic foraminifera in the Chagos Archipelago, Indian Ocean

Abstract

Abstract. The Chagos Archipelago is a series of atolls situated in the centre of the Indian Ocean close to the equator. The area experiences small tides and periods of strong winds. The combined effects of these is to cause relatively high energy conditions to exist in the shallow waters around the reefs, therefore the bottom sediments are coarse grained and mobile. Although the coral faunas are diverse, seagrasses are rare. The total benthic foraminiferal assemblages have low to high species diversity and are dominated by hyaline taxa. On the oceanic side of the atoll reefs, the dominant foraminiferan is Amphistegina lessonii, with subsidiary miliolids. Planklonic tests form up to 20% of the combined benthic and planktonic component. In the lagoon, the assemblages are dominated by Calcarina calcar, with subsidiary miliolids. Planktonic tests are relatively uncommon. Some post-mortem transport and damage to tests has taken place but the distribution patterns are believed to be representative of the original living ones.