<i>Trichodesmium</i> Phenomenon
NOPR - NISCAIR Online Periodicals Repository
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Title |
Trichodesmium Phenomenon
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Creator |
Devassy, V. P.
Bhattathiri, P. M. A. Qasim, S. Z. |
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Description |
168-186
Trichodesmium phenomenon was studied during the seasons of 1975, 1977 and 1978 in the Arabian Sea (nearshore waters of Goa, west coast of iIndia). This Iphenomenon occurred in the 'form of blooms of T. erythroeum every year with a marked periodicity from February to April. During this period the sea was calm with little wave action and had high temperature, high salinity and maximum periods of sunshine. High inorganic PO4-P, NH4-N and NO3-N were found in the sea associated with the blooms. The values of all these nutrients went up with every pulse of the bloom. Each year the bloom occupied many square kilometres of the near-shore water. It was generally spread out in long bands probably because of convective circulation prevailing in the region during the premonsoon months. In association with the patches of bloom, 44 different algae were recorded during the 1975 season when the bloom was in great profusion. In the 1977 season, 39 different algae were recorded besides Trichodesmium species and these did not attain as high counts as in the 1975 season. During the bloom, 14C uptake was largely contributed by Trichodesmium. Similarly, high chI. 0 and particulate organic carbon (POC) coincided with dense bloom. At times, pheophytin was higher than chI. 0 probably because of the presence of a large number of physiologically inactive ftiaments. During the bloom seasons, other phytoplankton organisms were abundant and some diatoms appeared in profusion in association with the bloom. Zooplankton organisms were fairly abundant in bloom patches as in non-bloom areas. Many zooplankton organisms were found llving in patches of dense bloom. Fish catches taken in areas of the bloom were largely composed of •trash fish' showing no marked dissimllarity from those of the non-bloom areas. Trichodesmium is not much favoured as food by the fishes or other animals although the bloom is totally non-toxic. No mortality of fish or any other animal was ever found in association with the bloom. During the 3 seasons, the intensity of the bloom was highly variable not only from year to year but from day to day. Bloom patches kept appearing and disappearing with the state of the sea. Slightly turbulent conditions made the bloom disappear from the surface and calm conditions made it reappear. The bloom was largely confined to the surface. In its early stages, the bloom had the appearance of sprinkled saw-dust over the sea surface, but as the season advanced, it began to impart reddish brown colour to the water. Laboratory experiment with natural blooms gave a clear evidence that Trichodesmium plays a very important role in the enrichment of water by releasing phosphorus and nitrogen. The ability of Trichodesmium to fix nitrogen enhances its role in enrichment. With the disintegration and decay of the bloom, NH4-N becomes very high in the water. Growth of unialgal culture is enhanced in lower concentrations of the medium in which the bloom decays. In each season, Trichodesmium phenomenon makes a substantial contribution to the total nutrient budget of the sea. |
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Date |
2017-01-02T09:06:35Z
2017-01-02T09:06:35Z 1978-09 |
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Type |
Article
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Identifier |
0975-1033 (Online); 0379-5136 (Print)
http://nopr.niscair.res.in/handle/123456789/39490 |
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Language |
en_US
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Rights |
CC Attribution-Noncommercial-No Derivative Works 2.5 India
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Publisher |
NISCAIR-CSIR, India
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Source |
IJMS Vol.07(3) [September 1978]
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