396
M. SAKTHIVEL:
V. The Distribution of Limacina inflata in Relation to
Thermocline
During the HOE RRS "Discovery" collected zooplankton samples from 62 stations
in the area of the western half of the Indian Ocean for the study on distribution of
plankton in relation to the thermocline (Fig. 5 A). Fig. 12 shows that Limacina inflata is
abundant at night above and below the thermocline in the 200 m water column. During
the day the population of this species is very poor above the thermocline and less
abundant below the thermocline (Fig. 12). The mean number of organisms above and
below the thermocline in terms of unit haul and in terms of number per m 3 are given in
Table3.
240
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Fig. 12. The distribution of Limacina inflata in relation to the thermocline (in terms of unit haul).
For cruise tracks see Fig. 5
Table 3. Diurnal variation in the mean number of Limacina inflata in relation to the depth of
thermocline in terms of unit haul and number m- 3
Limacina inflata
Mean number per unit haul
Mean number per m 3
Day
Thermocl.
200 m -
- 0 m
Thermocl.
3.83
0.07
34.96
0.16
Night
Thermocl.
200 m -
- 0 m
Thermocl.
72.17
1.12
+52.06
-0.55
Of the 6 cruise tracks, tracks C, E and F show relatively high abundance of Limacina
inflata which perhaps might be due to the influence of the SW monsoon during June and