Discolored Foraminifera Around St. Kitts, Eastern Caribbean Sea, and Their Environmental Significance

Abstract

Discolored (chemically discolored) foraminiferal tests have long been known to occur in shallow-water, silici-carbonate sediments of the Caribbean, but their distributions and environmental significance have been little studied. To address this, nineteen sediment samples were collected from the shoreline around St. Kitts (<1 m), eleven from nearby coral reefs (6 – 27 m below sea level) and one from a shipwreck, the River Taw. Three species and one species-group were examined in detail: Amphistegina gibbosa, Archaias angulatus, Asterigerina carinata and Peneroplis spp. (= P. carinatus P. proteus). Discolored specimens were either gray or brown. The percentage of this group of species discolored per sample was calculated, as was the percentage of each species discolored per sample. The percentage of discolored miliolids was consistently greater than that of rotaliids. The mean percentage of discolored specimens along the shoreline exceeded that on the reefs, suggesting that discolored specimens have potential as a proxy for palaeodepth. It was, however, greatest around the River Taw. High percentages mark areas with either low rates of sediment reworking or high levels of iron and manganese associated with the chemical alteration of tests. Observations on the River Taw show that discolored foraminifera may be used to assess the impact of artificial reefs on marine ecosystems.