Zooplankton — Bary 
23 
TABLE 3 
Species’ Groups, as Determined from the 
T-S-P Diagrams, and the Waters of 
Which They Are Indicators 
species’ group 
water 
Subantarctic 
Water of Subantarctic 
origin 
i. Southern Subantarctic 
from 8°C. 
species 
ii. Northern Subantarctic 
11°C. and higher 
species 
Subtropical Species 
From, or due to, the influ- 
ence of subtropical water 
Coastal Species 
Coastal water — an admix- 
ture of subantarctic, sub- 
tropical and fresh waters 
reason, and for lack of any published evidence 
to the contrary, the Tasman Sea water and the 
waters northward of the subtropical con- 
vergence to the east of New Zealand are con- 
sidered together as "water of subtropical 
origin” in this study. Whether in fact the 
physical and faunistic properties of the two 
areas will prove to be identical, or nearly so, 
has yet to be demonstrated. For the purpose 
of the present investigation the T-S charac- 
teristics of this water are included in Figure 3 
for two reasons. First, they provide a contrast 
across the subtropical convergence with the 
water originating in the subantarctic; second, 
they delineate the mass from which the warm 
saline water (and a warm-water fauna) that 
influences southern and north-eastern South 
Island is being derived. 
Subantarctic (West Wind Drift) water 
moves mostly toward the east, but with a 
northerly component. It has a strong influ- 
ence on the waters of southern and eastern 
South Island (Garner, 1954) and perhaps also 
in some measure on those of the west coast. 
Some is also believed to pass into Foveaux 
Strait from the west. The temperature at Sta- 
tion 921 (Fig. 2) was 8.2°C.,and it increases 
northwards to about 13°C. at the conver- 
gence. Salinity ranged between 34.0 and 
34.3 °/oo in the colder waters and 34.3 and 
34.7 °/oo in the warmer (northern) waters. 
Such values are within those described for 
subantarctic water by Deacon (1937). The 
properties of these waters are summarised in 
Table 2 and their relationships illustrated in 
the T-S diagram, Figure 3. 
Waters of subtropical and subantarctic ori- 
gins meet in the subtropical convergence, a 
zone usually described as of variable width 
which is believed to migrate northwards in 
winter, southwards in summer. The existence 
of the convergence eastwards of New Zealand 
is undoubted, from evidence discussed by 
Deacon (1937) and Garner (1954). Evidence 
from the present survey indicates that it was 
crossed twice, with biological and hydrologi- 
cal samples being obtained during the first 
traverse. Data from surface waters from the 
cruise of March 21-22, 1951 (see Series 6, pp. 
47, 48, and Figs. 4^, 19^, 2Qb), show that 
near Station 330 there was an abrupt increase 
northwards of 2°C. and of 0.3 to 0.4 / oo 
salinity (over subantarctic salinities as at Sta- 
tions 341, 342). The section constructed on 
the basis of bathythermograph records to 450 
feet (approximately 138 m.) from between 
Wellington and Dunedin (Fig. Aa) shows 
that towards the north cool water was sub- 
merged beneath a layer 35 to 60 m. deep of 
warmer water. Immediately north of Station 
330 this cool water reaches the surface. South 
of Station 330, and including Station 337, is 
a second body of warm water which is of 
coastal origin (Figs. 19^, 20^) and which 
overlies, and is mixing with, subantarctic wa- 
ter. On the second crossing on April 18, a 
surface thermograph trace (Fig. Ab) recorded 
a temperature drop from 16.8° to 12.8°C. in 
a position approximately 45 miles seaward on 
a bearing of 96° from Station 330 (Fig. 19^). 
These data are typical of those associated with 
a convergence of warm and cold waters, and 
it is believed they are attributable to the sub- 
tropical convergence. This would fit in with 
Garner’s interpretation of these and other 
data, and, if so, the crossings herein discussed 
were of the southern extremity of a south- 
going tongue of subtropical water which was 
