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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.
secchi depth<sub> </sub>
|Abstract:||Surface concentration of gelbstoff and vertical structure of chlorophyll-<i>a</i> (chl-<i style="">a</i>) and pheophytin-<i>a</i> were determined in coastal waters off Orissa along five transects. Depth-dependent concentrations of NO<sub>3</sub><sup>-</sup> and PO<sub>4</sub><sup>3-</sup> at several stations along the Paradip transect (Tr.), Tr.-IV were also studied. The concentration of chl-<i>a</i> 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-<i>a</i> both NO<sub>3</sub><sup>-</sup> and PO<sub>4</sub><sup>3-</sup> 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-<i>a</i> constituted mostly less than 5-7 % of the total chl-<i style="">a</i> 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-<i>a</i> value for validation of the satellite derived values for the pigment. The study also indicated that chl-<i>a</i> retrieval from the satellite image need not be corrected for the presence of pheophytin-<i>a</i> because of its low presence in the surface waters, but must be corrected for interference by the presence of high concentration of the gelbstoff.|
|Appears in Collections:||IJMS Vol.32(2) [June 2003]|
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