Shoreline foraminiferal thanatacoenoses around five eastern Caribbean islands and their environmental and biogeographic implications

Abstract

Foraminiferal thanatacoenoses were examined around five islands in the Caribbean Sea, which forms a single biogeographic province with respect to nearshore (<3 m water depth) foraminifera, which live primarily on marine vegetation. On death, they become incorporated into the sediment. The assemblage at a site reflects the live assemblage and post mortem affects such as dissolution and transport during storms. Reefal species ( Amphistegina gibbosa, Asterigerina carinata) are transported towards shore during storms. Foraminiferal thanatacoenoses were examined in 65 nearshore sediment samples from around five eastern Caribbean islands: St. John (US Virgin Islands), St. Kitts, Nevis, Bequia and Tobago. Cluster and principal components analyses distinguished the following environments (indicator species in parentheses): 1. Sediment associated with mangroves ( Ammonia sobrina), 2. Bays subject to organic matter enrichment ( Quinqueloculina poeyana, Triloculina rotunda, T. trigonula), 3. Areas subject to moderate sediment flux during storms ( Quinqueloculina auberiana, Nodobaculariella mexicana, Peneroplis proteus, Archaias angulatus), 4. Locations subject to high sediment flux during storms ( Amphistegina gibbosa), 5. Sites little stressed by organic matter enrichment or storms ( Discorbis rosea). The majority of samples were from sites in the last category. The data from this study could form the nucleus of a catalogue of Caribbean beaches and their environmental influences.