SHE Analysis for Biozone Identification among foraminiferal sediment assemblages on reefs and in associated sediment around St. Kitts, Eastern Caribbean Sea, and its environmental significance

Abstract

Abstract Sixteen nearshore (≤ 1 m water depth) sediment samples, termed Sample Set 1, were collected from the eastern and south-western coasts of the South East Peninsula (SEP) of St. Kitts. Twelve samples termed Sample Set 2 were taken from nearby fringing (6–17 m) and offshore (~ 18–25 m) reefs. The sample sets were analysed separately using SHE Analysis for Biozone Identification (SHEBI), α and β diversities and complementarity. SHEBI is a statistical technique that determines abundance biozones (ABs) using the entire vector of species abundances in samples, species richness S , the information function H , and the equitability index E . Alpha diversity expresses the diversity within an AB, while β diversity quantifies diversity changes between adjacent ABs. Complementarity assesses the permeability of AB boundaries. SHEBI divided Sample Set 1 into five ABs but did not distinguish separate bays. Beta diversities reflected the highest and lowest α diversities at Mosquito Bay and South Friar's Beach\Frigate Bay respectively. Complementarity was highest between two ABs in South Friar's Bay, indicating a close relationship between shoreline sediment and material marginally farther offshore. It was lowest between Whitehouse and South Friar's Bays. The assemblages along this transect were rich in Discorbis rosea . For Sample Set 2, samples were accumulated for SHEBI by depth. SHEBI distinguished four ABs (three on the fringing reefs) characterised by differing percentages of Asterigerina carinata , Archaias angulatus and Amphistegina gibbosa . Comparison between Sample Sets 1 and 2 indicates that during storms sediment moves shoreward from the fringing reefs. Foraminifera show that there is less movement of sediment > 63 μm from the shoreline (Sample Set 1) to the fringing and deeper reefs.