Journal of the Marine Biological Association of India

Volume 16 Issue 3

Distribution of dissolved organic phosphorus and nitrogen in the Bay of Bengal

V. Chalapati Rao and T. S. Satyanarayana Rao

Data on dissolved organic components presented in this paper deals with values obtained in the inshore waters of Bay of Bengal off the coast of Waltair for a period of two years (1961 and 1962) and also from the different regions of the Bay of Bengal obtained during March-April 1963 on board R, V. ANTON BRUUN 'm the International Indian Ocean Expedition. Dissolved organic matter described herein constitutes the compounds of nitrogen and phosphorus present in sea water that pass through a 0.5 Iµ filter.

Dissolved organic nitrogen is seen to accumulate to the extent of 0.28 mg/1 in 1961 and 0.23 mg/1 in 1962 in the surface waters a few weeks after the phytoplankton bloom during March-April period. High Dissolved Organic nitrogen (Don) value of 0.36 mg/1 in 1961 and 0.22 mg/1 in 1962 recorded in November are attributed partly to contribution from rivers waters and partly to phytoplankton production.

High values of dissolved organic phosphorus (Dop) are encountered during May, June, July 1961 (2.63,1.99, and 3.08 /µg. at/1 respectively) in the surface water off the Waltair Coast and this fraction constitutes between 80-90% of the total phosphorus. Dissolved organic phosphorus is inversely related to phytoplankton production.

Average values in the surface water of the different regions of the Bay of Bengal during March-April 1963 reveal high Don content off the coast of Burma and in the rest of the Bay when compared to the Nicobar-Andaman Sea. Dop values in the central bay are high and this area has been shown to be very low in productivity from chlorophyll and primary productivity values during March-April period.

The vertical distribution of Dop reveals high values in the upper layers of the sea and exhibit a gradual decrease with depth and no Dop was noticed around and below 1000 metres. Between 2000 and 3000 metres values ranging from 0.18 lµg. at/1 to 0.3 /µg. at/1 are encountered.

Date : 31-12-1974