Research Projects

The geological record offers long-term evidence for climatic and oceanographic variability in the form of physical, chemical and biological signatures, from where the past perturbations in the environmental conditions can be studied directly. To better understand the present ocean acidification and future trends, past knowledge of ocean acidification is a prerequisite. The pteropod shells contained in sediments can provide a large amount of information by incorporating the geochemical signature from the environment in which they form and indicating the physical and chemical conditions of their habitat, providing access to qualitative or quantitative reconstructions of environmental parameters. An increased interest in studying this faunal group has arisen from recent findings on the vulnerability of aragonite shell preservation to human-impacted water column chemistry changes. The seasonality and magnitude of several processes during the monsoon, such as ocean warming, dissolved oxygen depletion, freshwater runoff, biological productivity, formation of oxygen minimum zones (OMZ) etc., control the pH in the Indian Ocean, as against other global oceans. The thermohaline circulation is another process that continuously affects the water chemistry in the Indian Ocean and has varied strength over glacial-interglacial cycles. Despite this pivotal role the Indian Ocean plays, only a few studies of pteropod preservation and abundance records with time have been conducted. Hence, compiling all the records on pteropods from different parts of the northeastern Indian Ocean will help assess the variability of processes and effects. India is primarily surrounded by oceans, understanding the impacts of changes in ocean chemistry is vital as ocean acidification may directly or indirectly affect many organisms and ecosystems, which may also hold significant economic value to the Indian community. The samples (surface and core samples) from the northeastern Indian Ocean will explore for the present study by analyzing pteropod shells preserved in the geological record. Their abundance variability is a proxy for carbonate preservation. However, additional techniques viz shell size variations, Limacina Dissolution index, Productivity indicators (both pteropods species and planktonic foraminifera), and geochemical analyses of pteropods shells, and geochemistry of sediments will be carried out. Analyzing stable isotopes and elemental ratios gives indications of ocean acidification, productivity, current circulations, Aragonite Compensation Depth, and OMZ reconstructions. It is worth exploring how long Indian ocean pteropods are preserved, the factors controlling their preservation, the reconstruction of water column chemistry, and the strength of OMZ using aragonite (pteropods) and calcite (planktonic foraminifera) zooplanktons from the northeastern Indian Ocean.