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Abstract Submission No. | ABS-2022-06-0121 |
Title of Abstract | Comparative study of the phytoplankton pigment composition, community structure and diversity in the Seas around India during the pre-monsoon season |
Authors | Aswathy Vijaya Krishna*, Anima Tirkey, Mini Raman, Arvind Sahay, Arvind Singh |
Organisation | Space Applications Centre (ISRO) |
Address | D9/03, Vikramnagar, DOS Housing Colony Ahmedabad, Gujarat, India Pincode: 380058 Mobile: 9895599413 E-mail: aswathyvk@sac.isro.gov.in |
Country | India |
Presentation | Oral |
Abstract | The seas surrounding the Indian subcontinent, known for its dynamic nature has an unexplored wealth of primary producers. The spatial and vertical distribution of phytoplankton pigments in the eastern and central Arabian Sea and western and central Bay of Bengal were studied during the pre-monsoon period (April-May) of 2017 and 2019, respectively. The pre-monsoon period over the northern Indian Ocean is associated with highly stratified and oligotrophic waters. The present study aimed to unravel the phytoplankton community structure and diversity through investigating the phytoplankton pigment composition using High Performance Liquid Chromatography (HPLC). Since pigment biomarkers are associated with phytoplankton size classes, diagnostic pigment information gathered from HPLC was used to classify phytoplankton community into pico, nano and microphytoplankton. Further, the data obtained from both the seas were compared to understand their similarities and differences. Based on the marker pigments and pigment ratios, the phytoplankton classes identified were prochlorophyceae, chlorophyceae, bacillariophyceae, dinophyceae, pelagophyceae, cryptophyceae, haptophyceae, dictyochophyceae and prasinophyceae. Among the classes identified, prochlorophyceae dominated the open ocean surface waters of both, the Arabian Sea (58-72 %) and Bay of Bengal (47-63 %) during pre-monsoon period, which was represented by the ubiquitous existence of divinyl chlorophyll a. Diatoms comprised less than 7% of the total phytoplankton diversity within the study area with exceptions observed over the continental shelf zones. Dinoflagellates occurred mostly in the northern regions of both the seas. While cryptophytes were detected in traces (less than 4%) in the Arabian Sea, they showed considerable presence at certain regions of Bay of Bengal (~24%). The vertical profiles of pigment composition revealed the dominance of picophytoplankton followed by nanophytoplankton in both the seas. Only the well-mixed, nutrient rich waters of the continental shelf regions of the Arabian Sea was dominated by microphytoplankton. Chlorophytes, pelagophytes, dictyochophytes and haptophytes showed a greater preference for subsurface euphotic water column. Since, phytoplankton primary production accounts for about 95% of global marine primary productivity, any change in their composition and abundance is bound to affect the overall functioning of ecosystems and their biogeochemical activities. The study, thus, provides prime knowledge about the distribution of major phytoplankton groups based on biomarker pigments, in the yet unexplored regions of the Indian Ocean. |