152
S. Z. QASIM:
III. Chlorophyll a Cycle
Seasonal changes in the chlorophyll a concentration are given in Fig. 17. A comparison
of the chlorophyll cycle with that of primary production (Fig. 15) reveals that the two are
not synchronous. This may be due to the presence of dead and inactive chlorophyll from
detrital material and stirred-up sediment (QASIM and REDDY, 1967). The quantity of
15
Fig. 17. Average monthly values of chlorophyll a in the surface water of the backwater
chlorophyll, which was later found to be predominantly phaeophytin, was much greater
during the monsoon months when light penetration in the backwater was greatly
reduced (unpublished data).
IV. Assimilation Ratio
The ratio between 14C assimilation and chlorophyll a ranged from 0.6 in November to
14.8 in April (Fig. 18). Such a large variation in the ratio further indicates that the entire
observed chlorophyll may not be photosynthetically active. The presence of inactive
chlorophyll would make the monthly variations in the ratio somewhat different from the
seasonal rises and falls of the primary production.
15
~
{) 10
0\
E
< a.
. . 5
.c
U
0\
E 0
0
Fig. 18. Average monthly ratios of carbon assimilation to chlorophyll a in the surface water of the
backwater