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Biological productivity of the Indian Ocean

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Title Biological productivity of the Indian Ocean
 
Creator Qasim, S. Z.
 
Description 122-137
Oceanographic data, largely collected during the International Indian Ocean Expedition (IIOE), are used to study the biological productivity of the Indian Ocean. The factors studied are light, nutrients and the rates of production at the primary, secondary and tertiary levels of the food chain. The euphotic zone or the compensation depth (1% of the surface illumination) has been determined. Similarly, values of phosphate-phosphorus and nitrate-nitrogen up to 100 m depth are integrated and plotted for the entire Indian Ocean. Euphotic zone varies between 40 m and 120 m. Both phosphorus and nitrogen show a similar pattern of distribution. Rates of primary production for the surface (1 m depth) and column (up to the depth of 1% illumination) are calculated separately. Surface production per unit area in the Bay of Bengal is higher than that of the Arabian Sea. This is probably because of greater cloud cover over the Bay of Bengal during the year than that of the Arabian Sea. The Bay of Bengal also seems to receive a high load of nitrate-nitrogen from the riverine system which enhances the nitrogen concentration at the surface resulting into a greater primary production. Column production in the Arabian Sea, on the other hand, is much greater than that of the Bay of Bengal. The total column production for the Indian Ocean amounts to 4.42 x 109 tonnes of carbon/yr or 94 tonnes of carbon/km2/yr or 258 mgC/m2/day. Secondary production computed from the zooplankton biomass gives the value of 69.27 x 106 tonnes of carbon/yr. From the primary and secondary production rates, tertiary production or the potential exploitable yield for the Indian Ocean has been estimated as 15 and 17 million tonnesjyr respectively. Transfer coefficient for the Indian Ocean or the ratio between the yield from one trophic level to the other is much lower than 10%. Potential yield for the Indian Ocean based on published data of catch and effort is estimated to be about 14ยท25 million tonnes. The reliability of various estimates has been discussed. Recent figures of pelagic, demersal and crustacean resources from the different regions indicate that the annual catch for the Indian Ocean is about 3 million tonnes. Hence to bring the catch close to the potential yield, nearly 3-4 time increase is possible annually.
 
Date 2016-12-30T06:23:33Z
2016-12-30T06:23:33Z
1977-12
 
Type Article
 
Identifier 0975-1033 (Online); 0379-5136 (Print)
http://nopr.niscair.res.in/handle/123456789/39365
 
Language en_US
 
Rights CC Attribution-Noncommercial-No Derivative Works 2.5 India
 
Publisher NISCAIR-CSIR, India
 
Source IJMS Vol.06(2) [December 1977]