Production in the Indian Ocean and the Transfer from the Primary to the Secondary Level 483
of hauls made in each square. Some hauls made during the period of the NE monsoon
were not used because, when compared with the primary production, they yielded transfer
coefficients (see below) greater than 40%. Some horizontal hauls were made during the
expedition and it is possible that they have been included. Whatever the true reason for
the aberrant transfer coefficients, it has led to a shortage of observations in the Arabian
Sea during the NE monsoon period.
Secondary production as gC m- 2 180 day-I is illustrated in Figs. 4a and b. There are
not enough observations for the detailed analysis by region which was made for the
distributions of primary production. However, secondary production appears to be
highest off the coasts of southern Arabia, Somalia, the Malabar coast of India, off Ceylon
and the northern part of the Bay of Bengal, as might be expected from the distribution of
upwellings. Direct comparison with primary production can be made with the use of the
charts of gC m- 2 180 day-I at both trophic levels (Fig. 2 in primary production and Fig. 4
in secondary production). The average secondary production during the SW monsoon is
7.3 gC m- 2 180 day-I that during the NE monsoon is 7.0 gC m- 2 180 day-I. The
difference is very much less than might have been expected from the very marked
difference in primary production between the two monsoons. The sampling in the NE
monsoon is poor in the central part of the ocean as compared with that in the SW
monsoon, so perhaps a better sampling of secondary production during the NE monsoon
would yield a lower average.
The estimate of secondary production depends upon the duration of copepodid
generations, the mortality rates are unknown. It is assumed that copepods are the
dominant herbivores, or that the generation time of other herbivores can be described by
the same rule. VINOGRADOV and VORONINA (1962) described a cruise of the "Vityaz" in
the northern and equatorial part of the Indian Ocean. They show that the maximum
abundance of herbivorous copepods is found in the South Equatorial Current and in the
eastern tropical ocean; the ship did not go into the Arabian Sea proper or the Bay of
Bengal. Hence it is likely that copepds are the dominant herbivores, supported by
euphausids in some regions, as in the other oceans.
3. Tertiary Production
The figures of tertiary production are taken, by squares, from those of primary and
secondary production. Because more samples were taken of the primary production, the
charts in Figs. 5 a and b are based more on the production of algae. During the period of
the SW monsoon (Fig. 5 a), there are four high points, off the coast of Arabia, off
Zanzibar, and off the Malabar coast of India and in the northernmost part of the Bay of
Bengal. Here the tertiary production is greater than 40 .10 5 tons wet weight per 50 square
per 180 days. But the most remarkable feature of the chart is the extensive area of tertiary
production, between Arabia and Madagascar, of 20 - 40 . 10 5 tons wet weight per 50
square per 180 days; there are other patches at the same level in the Bay of Bengal and in
the eastern tropical ocean. Further, there is a fairly heavy level of production all over the
northern and equatorial parts of the ocean. Only in the centre of the southern subtropical anticyclone is there a really low production, < 5 . 10 5 tons wet weight per 50
square 180 day-I.
During the NE monsoon, the areas of low production are very much more extensive.
However, there is still a high patch off southern Arabia and east Africa, with a relatively
of hauls made in each square. Some hauls made during the period of the NE monsoon
were not used because, when compared with the primary production, they yielded transfer
coefficients (see below) greater than 40%. Some horizontal hauls were made during the
expedition and it is possible that they have been included. Whatever the true reason for
the aberrant transfer coefficients, it has led to a shortage of observations in the Arabian
Sea during the NE monsoon period.
Secondary production as gC m- 2 180 day-I is illustrated in Figs. 4a and b. There are
not enough observations for the detailed analysis by region which was made for the
distributions of primary production. However, secondary production appears to be
highest off the coasts of southern Arabia, Somalia, the Malabar coast of India, off Ceylon
and the northern part of the Bay of Bengal, as might be expected from the distribution of
upwellings. Direct comparison with primary production can be made with the use of the
charts of gC m- 2 180 day-I at both trophic levels (Fig. 2 in primary production and Fig. 4
in secondary production). The average secondary production during the SW monsoon is
7.3 gC m- 2 180 day-I that during the NE monsoon is 7.0 gC m- 2 180 day-I. The
difference is very much less than might have been expected from the very marked
difference in primary production between the two monsoons. The sampling in the NE
monsoon is poor in the central part of the ocean as compared with that in the SW
monsoon, so perhaps a better sampling of secondary production during the NE monsoon
would yield a lower average.
The estimate of secondary production depends upon the duration of copepodid
generations, the mortality rates are unknown. It is assumed that copepods are the
dominant herbivores, or that the generation time of other herbivores can be described by
the same rule. VINOGRADOV and VORONINA (1962) described a cruise of the "Vityaz" in
the northern and equatorial part of the Indian Ocean. They show that the maximum
abundance of herbivorous copepods is found in the South Equatorial Current and in the
eastern tropical ocean; the ship did not go into the Arabian Sea proper or the Bay of
Bengal. Hence it is likely that copepds are the dominant herbivores, supported by
euphausids in some regions, as in the other oceans.
3. Tertiary Production
The figures of tertiary production are taken, by squares, from those of primary and
secondary production. Because more samples were taken of the primary production, the
charts in Figs. 5 a and b are based more on the production of algae. During the period of
the SW monsoon (Fig. 5 a), there are four high points, off the coast of Arabia, off
Zanzibar, and off the Malabar coast of India and in the northernmost part of the Bay of
Bengal. Here the tertiary production is greater than 40 .10 5 tons wet weight per 50 square
per 180 days. But the most remarkable feature of the chart is the extensive area of tertiary
production, between Arabia and Madagascar, of 20 - 40 . 10 5 tons wet weight per 50
square per 180 days; there are other patches at the same level in the Bay of Bengal and in
the eastern tropical ocean. Further, there is a fairly heavy level of production all over the
northern and equatorial parts of the ocean. Only in the centre of the southern subtropical anticyclone is there a really low production, < 5 . 10 5 tons wet weight per 50
square 180 day-I.
During the NE monsoon, the areas of low production are very much more extensive.
However, there is still a high patch off southern Arabia and east Africa, with a relatively