• P V Bhaskar

      Articles written in Journal of Earth System Science

    • Dynamics of transparent exopolymeric particles (TEP) and particle-associated carbohydrates in the Dona Paula bay, west coast of India

      P V Bhaskar Narayan B Bhosle

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      Surface seawater samples were collected over a period of 27 months at a shallow water station in Dona Paula bay from 1998–2000. The samples were analyzed to assess the seasonal variations, inter-annual variability and the contributions of:

      •transparent exopolymeric particles (TEP) concentration,

      •two forms of particle-associated carbohydrates — 1.5 M NaCl/saline extracted (Sal-PCHO) and 10 mM EDTA-extracted (CPCHO) and

      •total bacterial abundance (TBA) to particulate organic carbon pool.

      A distinct inter-annual variability was observed with an increase in the bacterial abundance, chlorophylla (Chl a), TEP and Sal-PCHO and their greater contribution to particulate organic carbon during May 1998–1999 than in June 1999–July 2000. Overall, there was no statistically significant correlation of TEP with phytoplankton biomass (Chl a), Sal-PCHO, CPCHO and hydrodynamic conditions. A weak inverse correlation was observed between TEP and TBA (r = −0.397;p < 0.05) but the role of TEP as a C-source for bacteria was not evident. Both Sal-PCHO and CPCHO appeared to be two distinct forms of carbohydrates. Unlike CPCHO, Sal-PCHO concentrations showed a positive trend with Chla and significant linear correlation with bacterial abundance (r = 0.44,p < 0.007,n = 48), indicating that Sal-PCHO as carbon source might have supported bacterioplankton abundance. The mean %TEP-C contribution to the annual average organic carbon for 1998–2000 was 6.9% ± 5.8%, next only to phytoplankton-C (33.1 ± 22.1%) and greater than bacterial-C (4.6% ± 4.6%) or carbohydrate-C (< 3.8%). Despite its greater contribution to the organic carbon pool, the contribution of TEP-C to the benthic carbon demand and its fate in the study area could not be ascertained in this study.

    • Identification of non-indigenous phytoplankton species dominated bloom off Goa using inverted microscopy and pigment (HPLC) analysis

      P V Bhaskar Rajdeep Roy Mangesh Gauns D M Shenoy V D Rao S Mochemadkar

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      An unusual phytoplankton bloom dominated by unidentified green coloured spherical algal cells (∼5 𝜇 m diameter) and dinoflagellates (Heterocapsa, Scripsiella and Gymnodinium) was encountered along the coast of Goa, India during 27 and 29 January, 2005. Pigment analysis was carried out using both fluorometric and HPLC methods. Seawater samples collected from various depths within the intense bloom area showed high concentrations of Chl 𝑎 (up to 106 mg m−3) associated with low bacterial production (0.31 to 0.52 mg C m−3 h−1) and mesozooplankton biomass (0.03 ml m−3). Pigment analyses of the seawater samples were done using HPLC detected marker pigments corresponding to prasinophytes, dinoflagellates and diatoms. Chlorophyll 𝑏 (36–56%) followed by peridinin (15–30%), prasinoxanthin (11–17%) and fucoxanthin (7–15%) were the major diagnostic pigments while pigments of cryptophytes and cyanobacteria including alloxanthin and zeaxanthin formed > 10%. Although microscopic analysis indicated a decline in the bloom, pheaophytin concentrations in the water column measured by both techniques were very low, presumably due to fast recycling and/or settling rate. The unique composition of the bloom and its probable causes are discussed in this paper.

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