• S G Prabhu Matondkar

      Articles written in Journal of Earth System Science

    • Distribution of dissolved carbohydrates and uronic acids in a tropical estuary, India

      Vishwas B Khodse Narayan B Bhosle S G Prabhu Matondkar

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      Carbohydrates including uronic acids are among the active components of dissolved organic carbon, and play an important role in biogeochemical cycling of organic carbon in marine environments. In order to understand their distribution, concentrations of total dissolved carbohydrate (TCHO), dissolved polysaccharide (PCHO), dissolved monosaccharide (MCHO), and dissolved uronic acid (URA) were measured in the Mandovi estuary, west coast of India during the monsoon and premonsoon seasons. The estuary experienced nearly fresh water condition during the monsoon season and marine condition during the pre-monsoon season. Concentrations of TCHO, MCHO and URA ranged from 17.7 to 67.3 𝜇M C, 4.1 to 15.5 𝜇M C and 2.3 to 10.8 𝜇M C, and their contribution to dissolved organic carbon (DOC) varied from ∼11 to 60%, 2.5 to 9.7%, and 1.8 to 5.3%, respectively. PCHO accounted for ∼52 to 92% of the TCHO. Generally, concentrations and yields of TCHO species were greater during the monsoon season. Phytoplankton abundance and bacterial cell numbers influenced the distribution of TCHO in the pre-monsoon season but not during the monsoon season. Transport of TCHO rich (11 to 60%) dissolved organic matter from the Mandovi estuary to the coastal waters during the monsoon season may affect ecosystem function by fueling biological activity of heterotrophic micro-organisms.

    • Fine-scale responses of phytoplankton to freshwater influx in a tropical monsoonal estuary following the onset of southwest monsoon

      Suraksha M Pednekar S G Prabhu Matondkar Helga Do R Gomes Joaquim I Goes Sushma Parab Vijaya Kerkar

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      In May of 2007, a study was initiated by the National Institute of Oceanography (NIO), Goa, India, to investigate the influence of monsoonal rainfall on hydrographic conditions in the Mandovi River of India. The study was undertaken at a location ∼2 km upstream of the mouth of this estuary. During the premonsoon (PreM) in May, when circulation in the estuary was dominated by tidal activity, phytoplankton communities in the high saline (35–37 psu) waters at the study site were largely made up of the coastal neritic species Fragilaria oceanica, Ditylum brightwellii and Trichodesmium erythraeum. During the later part of the intermonsoon (InterM) phase, an abrupt decline in salinity led to a surge in phytoplankton biomass (Chlorophyll 𝑎 ∼14 mg m−3), of a population that was dominated by Thalassiosira eccentricus. As the southwest monsoon (SWM) progressed and the estuary freshened salinity and Chlorophyll 𝑎 (Chl 𝑎) concentrations decreased during the MoN, Skeletonema costatum established itself as the dominant form. Despite the low biomass (Chl 𝑎 > 2 mg m−3), the phytoplankton community of the MoN was the most diverse of the entire study. During the postmonsoon (PostM), the increase in salinity was marked by a surge in dinoflagellate populations comprising of Ceratium furca, Akashiwo sanguinea, and Pyrophacus horologium.

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