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

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.

► SHEBI discerns ABs among reefal foraminifera around St. Kitts.
► The shore zone (< 1 m depth) comprises ABs arrayed along shore, dominated by Discorbis rosea.
► Deeper areas contained ABs arrayed by depth.
► Foraminifera indicate that most sediment transport is from fringing reefs shorewards.
► Little sediment > 65 μm is transported from the shore to the reefs.