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| Abstract Submission No. | ABS-2022-05-0372 |
| Title of Abstract | Seasonality in the characteristics of fluorescent dissolved organic matter along the eastern Arabian Sea |
| Authors | N.V.H.K.Chari*, G.V.M.Gupta |
| Organisation | CMLRE, Kochi |
| Address | CMLRE, LNG road Kochi, Kerala, India Pincode: 682508 Mobile: 9491789436 E-mail: harinaroju@rediffmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | Eastern Arabian Sea experiences various seasonal physical processes viz. convective mixing induced Arabian Sea High Salinity water (ASHSW) formation, intrusion of the Bay of Bengal water mass, warm pool, coastal upwelling, etc. which greatly affects the distribution and characteristics of dissolved organic matter. To address these seasonal changes, basin scale six cruises were undertaken between January and September 2018 with seven to ten coast-offshore transects along the eastern Arabian Sea as part of the project ⿿Marine Ecosystem Dynamics of eastern Arabian Sea (MEDAS)⿿. Source characterization of colored dissolved organic matter (CDOM) was done by three dimensional Excitation Emission Matrix (EEM) fluorescence spectra combined with parallel factor analysis. The surface waters of entire study showed five fluoropores viz. C1 (phytoplankton derived), C2 (phytoplankton degradation), C3 (microbial reworking), C4 (degraded protein) and C5 (lignin degraded). Between January and May (non-monsoon), their abundance followed the order C1>C2>C3>C4 with no presence of C5. While the same during June-September (summer monsoon) was C4>C1>C3>C2>C5. The intensity of humic like fluoropores (C2 and C3) was high in the northern and southern regions during January-February due to winter convective mixing and intrusion of Bay of Bengal water, respectively. But with the setting of warm pool conditions in May, the intensity of these high molecular weight compounds reduced due to photodegradation. With the change of season to the summer monsoon, these fluoropores with shorter emission maxima (low molecular weight compounds) were found with large north-south and coast-offshore variations; the upwelling induced phytoplankton production along the entire eastern Arabian Sea has increased the tryptophan protein like fluoropores (C1). Consequent to withdrawal of upwelling, the phytoplankton degraded fluoropores (C2) increased in south in September. But Phenylalanine like fluoropore (alias C5), which is an end product of protein degradation, has been found abundantly in the centre and northern regions during September may be due to late phase of upwelling when phytoplankton production is relatively reduced. Keywords: Eastern Arabian Sea; Excitation emission matrix fluorescent spectra; Parallel factor analysis; Humic and protein like fluoropores |