THESIS APPROVAL
THESIS APPROVAL
THESIS APPROVAL
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In the laboratory, a first group of 500 worms was separated in a petridish<br />
containing tap water for studying morphological feature and biological behaviors. A<br />
second group of about 20,000 worms was acclimated in 20×30×15 cm 3 plastic box<br />
containing 2-3 cm depth of wet sieved sediment with >500 µm particles removed.<br />
This depth should allow for natural burrowing behavior of the worm (Dermott and<br />
Munawar, 1992). Water brought from the sampling site was used for rearing at a<br />
depth of approximately 8 cm. The worms were fed on weekly diet with decomposing<br />
ground fish food and maintained at room temperature under a daily photoperiod of<br />
12 h. The water body was gently aerated via a pipette positioned 2 cm above the<br />
sediment surface. The overlying water was changed manually once a week to avoid<br />
accumulation of organic material. The last group of 300 worms was divided into 3<br />
replicates and analyzed for their background naphthalene concentration by using the<br />
technique of HPLC (Filipowicz et al., 2007).<br />
1.2 Sediment<br />
Test sediment was collected from the same location described above using<br />
a small shovel. Extraneous materials and any organisms seen by naked eyes were<br />
removed using a forceps. A small fraction of sediments was divided into 3 replicates<br />
and characterized by determination of granular composition using wet sieving method<br />
(Zhang et al., 2004), TOM using loss on ignition method (Parsons et al., 1984), WC<br />
using oven-drying method (Gardner, 1986) and background naphthalene<br />
concentration using the technique of HPLC (Filipowicz et al., 2007). The remaining<br />
sediments were washed through 0.5 mm mesh sieve and a large plastic container was<br />
used to allow for the retention of sediment fines. After the suspended fines settled,<br />
the overlying water was decanted carefully. The particles were mixed, turned them<br />
back into the sediment, and stored in a refrigerator at 4 °C prior to use in the<br />
experiment.<br />
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