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Title: Spatio-temporal variation of optically active substances in the coastal waters off Orissa from Rushikulya to Dhamra (east coast of India)
Authors: Mishra, R. K.
Shaw, B. P.
Keywords: Chl-a;Orissa coast;gelbstoff;nitrate;pheophytin-a;phosphate;secchi depth
Issue Date: Jun-2003
Publisher: CSIR
Abstract: Surface concentration of gelbstoff and vertical structure of chlorophyll-a (chl-a) and pheophytin-a were determined in coastal waters off Orissa along five transects. Depth-dependent concentrations of NO3- and PO43- at several stations along the Paradip transect (Tr.), Tr.-IV were also studied. The concentration of chl-a differed greatly between various sampling stations. Along a transect the concentration of the pigment was mostly higher in the near-shore waters (station depth ≤ 20 m) than in the offshore waters (station depth > 20 m). And irrespective of the depth of the sampling stations and the transects, the pigment was more concentrated towards the bottom than towards the surface (0 m) and sub-surface (10/15 m) layers of the water column. Similar to chl-a both NO3- and PO43- were found to be more concentrated towards the bottom than towards the surface of the water column, but none of them really regulated the growth of phytoplankton. Pheophytin-a constituted mostly less than 5-7 % of the total chl-a value in the surface waters, and the concentration of gelbstoff differed greatly in time and space. Secchi-disc transparencies indicated one attenuation depth (for light) of around 4 m and 7 m for the near-shore and the offshore waters, respectively, suggesting the use of only the surface chl-a value for validation of the satellite derived values for the pigment. The study also indicated that chl-a retrieval from the satellite image need not be corrected for the presence of pheophytin-a because of its low presence in the surface waters, but must be corrected for interference by the presence of high concentration of the gelbstoff.
Page(s): 133-140
ISSN: 0379-5136
Appears in Collections:IJMS Vol.32(2) [June 2003]

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