Journal of the Marine Biological Association of India

Benthic foraminiferal response to the bottom water oxygenation of the
Southern Bay of Bengal during the last 44 kyr BP

Volume 66 Issue 1

Kavya Aravind, N. R. Nisha, Veena G. Viswam and Naveen Gandhi

10.6024/jmbai.2024.66.1.2454-01

Abstract

In this study, we record the benthic foraminiferal response to the bottom water oxygenation of the Southern Bay of Bengal during the last 44 kyr BP. Benthic responses to deep water ecological conditions are rarely documented in the Southern Bay of Bengal. We analysed the downcore variation of benthic foraminifera, their microhabitat preferences (epifauna and infauna), and morphotype variations (plano- convex/trochispiral and tapered/cylindrical) to reconstruct the past bottom water oxygen conditions. The benthic foraminiferal records revealed that the core site was well-oxygenated during the Holocene compared to the last glacial period. The dysoxic species Chilostomella oolina is absent during the Holocene, showing its appearance from 12 kyr BP and a rapid increase is noticed in its abundance at 32-33 kyr BP due to the depletion of bottom water oxygen. The benthic foraminiferal records show that the last glacial period is characterized by low species abundance and low-moderate oxygenation. Our records also show that epifaunal and plano-convex/trochispiral taxa prefer high- oxygen and warm climate conditions (Holocene). In contrast, infaunal and tapered/cylindrical taxa prefer low-oxygenated water and cold periods (Heinrich events). In the southern Bay of Bengal, the tapered/ cylindrical and plano-convex benthic foraminiferal morphotypes and microhabitat (epifauna/ infauna) preferences show major changes in glacial/interglacial periods. The Holocene is marked by well-oxygenated water whereas the last glacial period, where the infauna-tapered/ cylindrical and dysoxic forms dominate has moderate to low oxygen conditions.

Keywords

Benthic foraminifera, microhabitat, morphology, oxygenation, Southern Bay of Bengal

Date : 29-04-2024