THESIS APPROVAL

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