Primary Production in the Indian Ocean I
121
of South Africa and another more extensive one in the NW Arabian Sea. Conversely,
the areas to the north and south of the Equator, except in the immediate vicinity of the
equatorial current, stand out as regions of infertility; similar areas are known to exist in
the Atlantic and Pacific oceans.
The chlorophyll distribution chart for the June - September period (Fig. 4) presents
a very similar pattern to that of the preceding season. Extensive regions of very high
fertility with a chlorophyll concentration of over 0.5 mg m- 3 are seen along the west
Fig. 4. Average concentration of chlorophyll a in the surface layer of 0 - 50 m during June to
September
coast of India, the Somali coast (the Somali Current region) and the SE coast of the
Arabian Peninsula. The dynamic spiral motion of the monsoon currents of the Arabian
Sea brings up nutrient-rich water from about 300 m depth and enriches the surface layers
off the Somali coast. The SE coast of the Arabian Peninsula is also an area of intensive
upwelling of nutrient-rich bottom water. The upwelling along the west coast of India is
caused by wind-driven water movements during the monsoon seasons. Other fertile areas
of secondary importance are the west and north coasts of Australia and the Banda Sea
(south of Java to Timor).
From the limited amount of data on chlorophyll distribution available for the December- March period (no averages could be calculated for its distribution), it is dear that
the most fertile areas are the SE coast of the Arabian peninsula and the west coast of
India (chlorophyll concentration >0.50 mg m- 3 ) and a minor one off Mombasa (chlorophyll concentration> 0.30 mg m- 3 ). It is noteworthy that the vast and highly fertile
121
of South Africa and another more extensive one in the NW Arabian Sea. Conversely,
the areas to the north and south of the Equator, except in the immediate vicinity of the
equatorial current, stand out as regions of infertility; similar areas are known to exist in
the Atlantic and Pacific oceans.
The chlorophyll distribution chart for the June - September period (Fig. 4) presents
a very similar pattern to that of the preceding season. Extensive regions of very high
fertility with a chlorophyll concentration of over 0.5 mg m- 3 are seen along the west
Fig. 4. Average concentration of chlorophyll a in the surface layer of 0 - 50 m during June to
September
coast of India, the Somali coast (the Somali Current region) and the SE coast of the
Arabian Peninsula. The dynamic spiral motion of the monsoon currents of the Arabian
Sea brings up nutrient-rich water from about 300 m depth and enriches the surface layers
off the Somali coast. The SE coast of the Arabian Peninsula is also an area of intensive
upwelling of nutrient-rich bottom water. The upwelling along the west coast of India is
caused by wind-driven water movements during the monsoon seasons. Other fertile areas
of secondary importance are the west and north coasts of Australia and the Banda Sea
(south of Java to Timor).
From the limited amount of data on chlorophyll distribution available for the December- March period (no averages could be calculated for its distribution), it is dear that
the most fertile areas are the SE coast of the Arabian peninsula and the west coast of
India (chlorophyll concentration >0.50 mg m- 3 ) and a minor one off Mombasa (chlorophyll concentration> 0.30 mg m- 3 ). It is noteworthy that the vast and highly fertile