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Abstract Submission No. | ABS-2022-06-0299 |
Title of Abstract | Phytoplankton diversity at surface and Deep Chlorophyll Maxima in Arabian Sea and Bay of Bengal during pre-monsoon season |
Authors | Anima Tirkey*, Aswathy Vijaya Krishna, Arvind Sahay, Arvind Singh, Mini Raman, Hitesh Solanki |
Organisation | Department of Botany, Gujarat University, Ahmedabad |
Address | GUJARAT UNIVERSITY GIRLS HOSTEL, NAVRANGPURA, AHMEDABAD AHMEDABAD, GUJARAT, India Pincode: 380009 Mobile: 9726171791 E-mail: animatirkey20@gmail.com |
Country | India |
Presentation | Oral |
Abstract | Arabian Sea and Bay of Bengal, the two wings of the Indian Ocean, is known for its oligotrophic existence during the pre-monsoon season. Studies comparing the phytoplankton diversity at surface and Deep Chlorophyll Maxima (DCM) in the Indian Ocean are sparse. DCM reflects the depth of absolute maxima of Chlorophyll-a concentration among the deep ocean vertical profiles. In a stratified ocean, DCM usually forms near the nutricline and the bottom of the euphotic zone. The objective of this study was to understand the phytoplankton community structure at the surface and DCM in the Arabian Sea and Bay of Bengal during pre-monsoon season. Phytoplankton diversity was studied using microscopy and High Performance Liquid Chromatography (HPLC). The phytoplankton cell count observed using microscopy ranged from 1.44 x 10 3 l -1 to 3.14 x 10 5 l -1 and 4.07 x 10 3 l -1 to 25.21 x 10 5 l -1 at surface and DCM, respectively in Arabian Sea and 1.16 x 10 3 l -1 to 3.23 x 10 6 l -1 at surface and 3.68 x 10 3 l -1 to 3.32 x 10 6 l -1 at DCM in Bay of Bengal during the pre-monsoon season. Microscopic study, thus, showed dominance of diatoms in both Arabian Sea and Bay of Bengal at surface and DCM depth followed by dinophyceae, and other algal classes like dictyochophyceae, cyanophyceae and prymnesiophyceae. Similar phytoplankton species were observed to occur at both the surface and DCM depths of respective sampling points, provided that the cells identified at DCM were larger in size with higher chloroplast content. Also, chain forming species were observed to have greater cell numbers per chain at the DCM depth. The most abundant diatom genera identified in the study were Chaetoceros, Pseudo-nitzschia, Bacteriastrum, Rhizosolenia, Proboscia, Leptocylindrus, Guinardia, Coscinodiscus, Lauderia and Thalassiosira. Among dinoflagellates Ceratium, Scrippsiella, Protoperidinium, Dinophysis and Oxytoxum were common genera observed in both the Seas. In contrast, HPLC derived phytoplankton pigment analysis revealed the study area to be dominated by pico and nanophytoplankton during the pre-monsoon season. Prochlorophytes, Pelagophyltes, Prymnesiophytes and Chlorophytes were observed to be the major contributors towards phytoplankton community according to pigment data analyzed using HPLC. As a consequence of using both techniques, eleven classes of phytoplankton were identified during the study period Bacillariophyceae, Dinophyceae, Dictyochophyceae, Cyanophyceae, Chrysophyceae, Prymnesiophyceae, Prasinophyceae, Chlorophyceae, Prochlorophyceae, Pelagophyceae and Euglinophyceae in both Arabian Sea and Bay of Bengal. The present work thus shows that in order to understand the phytoplankton diversity as a whole, both microscopy and HPLC techniques should be treated complementary to each other. |