THESIS APPROVAL

each experimental unit, a little portion of sediment from the E-WH and E-NH was
kept and divided into three subsamples for measuring initial TOM at the start of the
experiment (o h). When sediment settles, 100 worms were placed to each test beaker
except the E-NH. After the worms had burrowed into the substrates, the beakers were
kept on a table without aeration. Each test vessel was covered with a sheet of
polyvinylchloride cling film, which prevented the dissolve of oxygen pass into the test
medium. The experiment was carried out for 6 w with 6 test durations: 7, 14, 21, 28,
35 and 42 d. Three replications were set up for each treatment and each of test
duration. The organic matter was added to the sediment every week after water
renewal. The produced fecal pellets were removed from the sediment surface with a
pipette every day. The test was conducted at room temperature in a daily photoperiod
of 12 h. Light was provided from cool-white fluorescent lamps. Mean values of pH
in the overlying water measured during the experiment were 6.09±0.77.
3.3 Biological and Environmental Analyses
At the end of each 7 d interval, the overlying water in the E-WH and
E-NH was measured for DO concentration by penetrating the oxygen probe through a
sheet of polyvinylchloride cling film to locate the tip of the probe about 2 cm over the
sediment surface. Change in oxygen concentrations was measured by using oxygen
meter connected to the probe. After measurement, the oxygen probe was taken off,
the volume of the water was gently poured, and the sediment was spread in an
aluminum tray. A small part of sediment in the E-WH and E-NH was removed from
each of the experimental unit to estimate TOM using loss on ignition method (Parsons
et al., 1984). The remaining sediments of the E-WH and the whole sediments of the
E-WL and E-WN were wet sieved (0.5 and 0.25 mm mesh) and the worms were
sorted under stereo microscope. The number of individual worm in each test vessel
was counted and then measured total wet weight. Each animal was narcotized in 5%
magnesium chloride and size-estimated by measuring length (Raburu et al., 2002).
Thereafter, they were fixed and then preserved in 70% ethanol for the observation on
morphological characteristics under stereo microscope.
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