GEOCHEMICAL PROXIES TO INTERTIDAL AND MARSH FORAMINIFERA FROM THE EASTERN COASTALMARGIN OF BANGLADESH: AN APPROACH TO STUDY THE LOCAL CLIMATIC VARIABILITY

The present research has assessed the indicative values of foraminifera to depict the local climatic variability along the eastern coastal margin of Bangladesh based on some taxonomic, statistical, geochemical, and morphological parameters derived from the recorded species from Cox’s Bazar to Shamlapur area. A total of 31 species representing 22 genera and 22 families of stress-tolerant benthic taxa were recorded. The species distribution shows three clusters in the overall study area. The value of different diversity indices namely the Species Richness (SR), Shanon-Wener diversity index (H) and Simpson diversity index (S) show decreasing trends towards the environmentally stressed regions of Cox’s Bazar. The geochemical analysis of foram shells shows that the average content of the major constituents such as oxygen, Carbon and Calcium are lower than that of the standard average value. Some foreign elements such as Silicon (Si), Magnesium (Mg), Iron (Fe), Chlorine (Cl), Sodium (Na), Aluminium (Al), and Manganese (Mn), are also present in the samples as minor constituents. The deviation in chemical composition from the standard value has been archived by the foram shells in terms of morphological abnormalities.The recorded foram shells confirmed the inner shelf zone as their living suite in terms of correlation with the global standard diagram indicates the recorded microforams or dead shells once lived in the inner shelf zone and then deposited on the beach by the mutual actions of wave and tides along the coastline. Irregular clustering in species distribution, an abundance of stress tolerant taxa, spatial variation of diversity indices towards environmentally stressed zones, deviation of standard shell constituents from the standard value, and the morphological abnormality of recorded forams as a whole justify that the community of foraminifera recorded from the study bears the imprints of climatic variability in the inner shelf zone in a much localized scale and the anthropogenic impacts have a major role in this variability.