DECIPHERING PALEO CORAL REEF DYNAMICS USING THE FORAM INDEX IN ST. MARTIN’S ISLAND, BANGLADESH
Abstract:
Coral reefs at St. Martin’s Island represent a vital coastal ecosystem in Bangladesh and are increasingly threatened by a variety of anthropogenic and climatic stressors. The present study investigates the paleoenvironmental conditions associated with fossil coral reefs on the St. Martin’s Island using FORAM Index (FI) and foraminiferal assemblages. Coral fossil samples were collected from the island at different depths, and subjected to 14C dating. Sediments were also analyzed for foraminiferal composition and FI calculation. The obtained results specify two distinct phases of coral development on the island. The first phase occurred in between 2058 and 1866 BP, while the second phase sustained from 1290 to 797 BP. Hallock’s FI was calculated for both phases of corals development to evaluate the water and sediment quality of the coral habitat. The obtained result shows that the value of the first cycle is 2.71, indicating marginal environmental conditions for reef growth. In contrast, FI values for the second cycle are 1.74-1.98, suggesting conditions unfavorable for reef development and recovery. Among the three functional groups of foraminifera, Heterotrophic were most abundant (>80%) followed by Opportunistic (6-17%) and Symbiont Bearing (2-10%) in both the cycle. The decreasing FI values over time signify a gradual deterioration in environmental conditions in the coral habitat. The findings elucidate the paleoenvironmental history of St. Martin's Island and illustrate the utility of benthic foraminiferal assemblages and the FI in reconstructing past reef conditions.
Journal of the Asiatic Society of Bangladesh (Science)
52(1)
Editor: Professor Dr. A S M Woobaid Ullah
Associate Editor: Professor Dr. Upama Kabir
Published At: June 2026
Journal of the Asiatic Society of Bangladesh (Science) - Vol. 51(1) Articles
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DOI: 10.64298/jasbsci.v52i.001
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