- Dona Paula, Goa, India.
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| Abstract Submission No. | ABS-2022-05-0107 |
| Title of Abstract | Characterization of Colored Dissolved Organic Matter along the western continental shelf of India during the south west monsoon |
| Authors | Albertina Dias*, Siby Kurian |
| Organisation | CSIR-National Institute of Oceanography |
| Address | HNo 1176, Segundo Bairro, Santa Cruz, Tiswadi Panaji, Goa, India Pincode: 403005 Mobile: 9763551033 E-mail: albertina.dias8@gmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | In recent years the number of hypoxic zones in the world are rising, which has been attributed to the increase in nutrients and organic matter along with anthropogenic activities. Here we present results on the variations in absorption and fluorescent characteristics of colored dissolved organic matter (CDOM) along the western continental shelf of India (WCSI) during south-west monsoon (SWM). WCSI hosts world⿿s largest, natural, seasonal hypoxic zone covering 180000 km2. The water samples were collected along 4 transects off Kochi, Mangalore, Karwar and Goa during SWM (June - July 2018). In addition, the Goa In recent years the number of hypoxic zones in the world is rising, which has been attributed to the increase in nutrients and organic matter along with anthropogenic activities. Here we present results on the variations in absorption and fluorescent characteristics of colored dissolved organic matter (CDOM) along the western continental shelf of India (WCSI) during the southwest monsoon (SWM). WCSI hosts the world⿿s largest, natural, seasonal hypoxic zone covering 180000 km2. The water samples were collected along 4 transects off Kochi, Mangalore, Karwar, and Goa during SWM (June - July 2018). In addition, the Goa transect was sampled during late SWM (September - November 2016 and September 2018). The onset of upwelling was observed on the hydrographical parameters with low temperature and dissolved oxygen (DO) at the subsurface waters along the Kochi transect. The surface DO concentration increased from south (Kochi) to north (Goa). DO decrease with depth, and was hypoxic to suboxic in the bottom waters (except the nearshore waters off Goa). The waters along the Goa transect were highly stratified during the late SWM (September 2018) with low saline waters at the surface (due to heavy rainfall), with the development of hypoxia in the bottom waters. In general, high CDOM absorption (ag412 m-1) with low spectral slopes was observed in the bottom waters which coincided with hypoxic conditions. Three fluorescent DOM components were identified from PARAFAC analysis. Component 1 (C1) and 2 (C2) were humic-like with emissions in the longer wavelength, while component 3 (C3) was protein-like with excitation and emission in the UV region. CDOM absorption (ag412) and humic-like fluorescent component (C1) showed a positive correlation with apparent oxygen utilization (AOU) (r2 = 0.55 and r2 = 0.64 respectively), attributing the production of marine humic-like DOM during microbial remineralization. Laboratory experiments also shed light on the production of CDOM in low oxygenated waters. This study gives insight into understanding the cycling of dissolved organic matter under varying oxygen conditions observed in these waters. |