3.4. Study 3 water quality and BOD
Mean TAN and chlorophyll a concentrations in ponds did not differ
significantly by sample date, but salinity increased significantly over
time (Table 6). Mean coefficient of variation for measured DO
concentrations for replicate samples at each time period was low
and averaged 2.6%. A representative DO consumption curve for
replicate pond and canal samples is shown in Fig. 2. The mean BOD
:
BOD
88–94
ratio was 0.35. The BOD
for the harvest sample was
significantly lower than for the 30- and 61-d samples, which did not
differ. Pond BOD
88–94
5
for the harvest and 61-d samples was
significantly lower than for the 30-d sample. Computed UBOD,
however, did not differ significantly among sample dates, and
averaged 61.30 mg L
−1
. The mean decomposition rate constant was
0.071 d
−1
. The computed UBOD and BOD
in pond water were
linearly related (R
2
(d) (kg ha
5
−1
d
−1
) (kg ha
=0.899). The increment in BOD that resulted from
shrimp culture was calculated using the water supply canal BOD
because no estuarine BOD data was available. The water supply canalBOD at day 61, which was higher than for the pond likely because of
the high phytoplankton biomass, was not used in calculating
incremental BOD. After 30 d of culture, incremental BOD
was
57.8 mg L
−1
was 39.7 mg L
, but at harvest (70–72 d of culture) incremental BOD
−1
.
88
94