490
D. ]. TRANfER:
Fig. 2 this volume). The nitrate: phosphate ratio of the water is not constant but shows a
gradual decline towards the surface (Fig. 3): reflecting biological differences in the history
of these two major nutrients through the food web (GRILL and RICHARDS, 1964; BEERS,
1966; THOMAS, 1966). The boundary between the tropical and subtropical zones lies
near latitude 18
0
S. (ROCHFORD, 1962, 1969). South of this, a strong shallow thermocline
(25 -75 m) develops in late summer, dividing the mixed layer into an upper and a lower
stratum.
The subtropical area is essentially the eastern part of a large anti-cyclonic gyre, as in
the Pacific and Atlantic, lying between the zonally oriented equatorial waters and the
subantarctic cyclones (REID, 1962; WYRTKI, 1973, this volume). Within such anti-cyclonic
gyres, surface waters converge and sink. To the north and to the south, surface waters
diverge and upwelling tends to occur.
The tropical zone is dominated by the SE monsoon winds (= SE trades) for a large
part of the year (May to November). These reinforce the South Equatorial Current which
flows strongly across the section line north of about 15
0
S. (HAMON, 1965). During the
SE monsoon season (southern winter) the stream lies further to the north and flows at
maximum strength. In the opposite season, corresponding to the southern summer, the
stream lies further to the south and its flow is weaker.
III. Standing Stocks
The general level (concentration) of various biological properties and their variations
with depth, latitude, and time have been described by ROCHFORD (1969), JIlTS (1969),
HUMPHREY and KERR (1969), NEWELL (1969), TRANTER and KERR (1969), and LEGAND
(1969). The distribution of these properties, in relation to latitude and time, is shown in
Figs. 4-10. These distributions are based on column averages. Primary productivity is
10 0
15 0
200
25 0
SEPT
INORGANIC PHOSPHATE
100111
1M2
NOV
0
1M'
JAN
"".AA.
.. AV
J .... y
< 0 .'
0.3-0 S
05 - 10
Fig. 4. Inorganic phosphate distribution (100 m) with respect to latitude and month.
(After ROCHFORD, 1969)
D. ]. TRANfER:
Fig. 2 this volume). The nitrate: phosphate ratio of the water is not constant but shows a
gradual decline towards the surface (Fig. 3): reflecting biological differences in the history
of these two major nutrients through the food web (GRILL and RICHARDS, 1964; BEERS,
1966; THOMAS, 1966). The boundary between the tropical and subtropical zones lies
near latitude 18
0
S. (ROCHFORD, 1962, 1969). South of this, a strong shallow thermocline
(25 -75 m) develops in late summer, dividing the mixed layer into an upper and a lower
stratum.
The subtropical area is essentially the eastern part of a large anti-cyclonic gyre, as in
the Pacific and Atlantic, lying between the zonally oriented equatorial waters and the
subantarctic cyclones (REID, 1962; WYRTKI, 1973, this volume). Within such anti-cyclonic
gyres, surface waters converge and sink. To the north and to the south, surface waters
diverge and upwelling tends to occur.
The tropical zone is dominated by the SE monsoon winds (= SE trades) for a large
part of the year (May to November). These reinforce the South Equatorial Current which
flows strongly across the section line north of about 15
0
S. (HAMON, 1965). During the
SE monsoon season (southern winter) the stream lies further to the north and flows at
maximum strength. In the opposite season, corresponding to the southern summer, the
stream lies further to the south and its flow is weaker.
III. Standing Stocks
The general level (concentration) of various biological properties and their variations
with depth, latitude, and time have been described by ROCHFORD (1969), JIlTS (1969),
HUMPHREY and KERR (1969), NEWELL (1969), TRANTER and KERR (1969), and LEGAND
(1969). The distribution of these properties, in relation to latitude and time, is shown in
Figs. 4-10. These distributions are based on column averages. Primary productivity is
10 0
15 0
200
25 0
SEPT
INORGANIC PHOSPHATE
100111
1M2
NOV
0
1M'
JAN
"".AA.
.. AV
J .... y
< 0 .'
0.3-0 S
05 - 10
Fig. 4. Inorganic phosphate distribution (100 m) with respect to latitude and month.
(After ROCHFORD, 1969)