132
S. Z. EL-SAYED and H. R. lITIS
I. Methods
1. Primary Production
Primary organic production was determined by the 14C uptake method of STEEMANN
NIELSEN (1952) as modified by STRICKLAND and PARSONS (1968). Both in situ and
simulated in situ 14C uptake experiments were carried out. Measurements of submarine
light penetrations were made about an hour before Local Apparent Noon (LAN), using a
wide-band photometer with a quantum-corrected response in the visible spectrum.
Water samples were collected by Niskin samplers at various depths in the euphotic zone.
These depths corresponded to 100, 50, 25, 12, 6 and 3% of the quantum energy falling
at the sea surface. Pyrex glass bottles (65 m!) were filled with sea-water and each bottle
inoculated with 1 ml of 10 f-lC of NaH 14 C03 and lowered to the depth from which the
sample was taken. The incubation period lasted between LAN and sunset. Concurrently
with the in situ 14C uptake experiments, simulated in situ experiments (using a deck
incubator and a set of blue glass filters) were carried out using identical technique to
that of in situ experiments.
2. Pigment Analysis
Water samples for pigment analysis were taken from the same water collected for
primary productivity studies. Chlorophyll a was estimated by 2 methods: a) spectrophotometrically (RICHARDS and THOMPSON, 1952; CREITZ and RICHARDS, 1955), and
b) fluorometrically, using a modification of the procedure described by HOLM-HANSEN
et al. (1965). The latter method was also used for the estimation of the phaeopigments,
phaeophytin and phaeophorbin.
3. Nutrients
Water samples were taken from the regular hydrocasts for the determination of silicates, phosphates and nitrates according to STRICKLAND and PARSONS (1968).
n. Results
1. Distribution of Temperature between Australia and Antarctica
The temperature profiles taken between 35
0
and 65
0
S latitude along a 115
0
E transect
(Fig. 2) show that the areas between Australia and Antarctica can be divided into 4 fairly
well-defined water masses, namely, the Subtropical, the Subantarctic, the Polar Front
(Antarctic Convergence) and the Antarctic surface water. The main transport of water
between 40° Sand 60° S is from west to east in what is known as the Circumpolar
Current. Superimposed upon the eastward circumpolar movement are north-south
components. Its northern limit, the Antarctic surface water, sinks beneath the less dense,
south-flowing Subantarctic water to form the Antarctic intermediate water. Close to the
Antarctic continent, bottom water is formed. Immediately above this water mass there
is an exceptionally thick, warm, water mass, the deep water, which is characterized by
high salinity and high nutrient salts. The Polar Front was crossed between stations 4
and 5 during the south-bound leg of the cruise. During the north-bound leg, stations 17
and 17 A were located in the Polar Front. Station 18 seemed to be situated on the Antarctic side of the Convergence.
S. Z. EL-SAYED and H. R. lITIS
I. Methods
1. Primary Production
Primary organic production was determined by the 14C uptake method of STEEMANN
NIELSEN (1952) as modified by STRICKLAND and PARSONS (1968). Both in situ and
simulated in situ 14C uptake experiments were carried out. Measurements of submarine
light penetrations were made about an hour before Local Apparent Noon (LAN), using a
wide-band photometer with a quantum-corrected response in the visible spectrum.
Water samples were collected by Niskin samplers at various depths in the euphotic zone.
These depths corresponded to 100, 50, 25, 12, 6 and 3% of the quantum energy falling
at the sea surface. Pyrex glass bottles (65 m!) were filled with sea-water and each bottle
inoculated with 1 ml of 10 f-lC of NaH 14 C03 and lowered to the depth from which the
sample was taken. The incubation period lasted between LAN and sunset. Concurrently
with the in situ 14C uptake experiments, simulated in situ experiments (using a deck
incubator and a set of blue glass filters) were carried out using identical technique to
that of in situ experiments.
2. Pigment Analysis
Water samples for pigment analysis were taken from the same water collected for
primary productivity studies. Chlorophyll a was estimated by 2 methods: a) spectrophotometrically (RICHARDS and THOMPSON, 1952; CREITZ and RICHARDS, 1955), and
b) fluorometrically, using a modification of the procedure described by HOLM-HANSEN
et al. (1965). The latter method was also used for the estimation of the phaeopigments,
phaeophytin and phaeophorbin.
3. Nutrients
Water samples were taken from the regular hydrocasts for the determination of silicates, phosphates and nitrates according to STRICKLAND and PARSONS (1968).
n. Results
1. Distribution of Temperature between Australia and Antarctica
The temperature profiles taken between 35
0
and 65
0
S latitude along a 115
0
E transect
(Fig. 2) show that the areas between Australia and Antarctica can be divided into 4 fairly
well-defined water masses, namely, the Subtropical, the Subantarctic, the Polar Front
(Antarctic Convergence) and the Antarctic surface water. The main transport of water
between 40° Sand 60° S is from west to east in what is known as the Circumpolar
Current. Superimposed upon the eastward circumpolar movement are north-south
components. Its northern limit, the Antarctic surface water, sinks beneath the less dense,
south-flowing Subantarctic water to form the Antarctic intermediate water. Close to the
Antarctic continent, bottom water is formed. Immediately above this water mass there
is an exceptionally thick, warm, water mass, the deep water, which is characterized by
high salinity and high nutrient salts. The Polar Front was crossed between stations 4
and 5 during the south-bound leg of the cruise. During the north-bound leg, stations 17
and 17 A were located in the Polar Front. Station 18 seemed to be situated on the Antarctic side of the Convergence.