Sujatha, C H; Anu, Gopinath; Neema, Joseph; Nair, S M(Taylor & Francis, September 14, 2010)
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Abstract:
The distribution of three important dissolved forms of nitrogen, viz. nitrate, nitrite and urea in the surface and bottom
water samples collected from 27 selected hydrographic profiles, in the Arabian Sea, along the west coast of India is
described. Of the three forms, nitrate concentrations were the highest and comparatively higher concentrations were
observed in the bottom water. Decomposition of organic matter resulting in the release of the thermodynamically
stable nitrogen species, i.e. nitrate, may be the major factor resulting in higher nitrate concentrations at these
depths, where the water is also characterized by low values of dissolved oxygen and temperature. The significant
positive correlation between A.O.U. and nitrate of the bottom water samples emphasizes the role of oxidative
decomposition of organic matter which plays an active role in reducing the oxygen concentrations below the
theoretical values since at this depth ( 200 m) the net production is taken to be zero. This is also evidenced by
the negative correlation of nitrate with dissolved oxygen and temperature, for the bottom samples
Description:
Chemistry and Ecology, 2002, Vol. 18(3–4), pp. 233–244
Bijoy, Nandan S; Lathika, Cicily Thomas; Padmakumar, K B; Smitha, B R; Asha Devi, C R; Sanjeevan, V N(Polish Academy of Sciences, Institute of Oceanology, 2013)
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Abstract:
The phytoplankton standing crop was assessed in detail along the South Eastern
Arabian Sea (SEAS) during the different phases of coastal upwelling in 2009.During phase 1 intense upwelling was observed along the southern transects
(8◦N and 8.5◦N). The maximum chlorophyll a concentration (22.7 mg m −3) was
observed in the coastal waters off Thiruvananthapuram (8.5◦N). Further north
there was no signature of upwelling, with extensive Trichodesmium erythraeum
blooms. Diatoms dominated in these upwelling regions with the centric diatom
Chaetoceros curvisetus being the dominant species along the 8◦N transect. Along
the 8.5◦N transect pennate diatoms like Nitzschia seriata and Pseudo-nitzschia sp.
dominated. During phase 2, upwelling of varying intensity was observed throughout
the study area with maximum chlorophyll a concentrations along the 9◦N transect
(25 mg m−3) with Chaetoceros curvisetus as the dominant phytoplankton. Along
the 8.5◦N transect pennate diatoms during phase 1 were replaced by centric diatoms
like Chaetoceros sp. The presence of solitary pennate diatoms Amphora sp. and
Navicula sp. were significant in the waters off Kochi. Upwelling was waning during
phase 3 and was confined to the coastal waters of the southern transects with
the highest chlorophyll a concentration of 11.2 mg m−3. Along with diatoms,
dinoflagellate cell densities increased in phases 2 and 3. In the northern transects
(9◦N and 10◦N) the proportion of dinoflagellates was comparatively higher and was
represented mainly by Protoperidinium spp., Ceratium spp. and Dinophysis spp.