In this research, we assessed the chronic toxicity of sediment-associated chemicals of potential concern(COPCs) on the sediment-dwelling organism. The measurement of survival/ growth/reproduction of H. azteca and growth/fecundity of Paramisgurnus dabryanus exposed to formulated sediment and field sediment were reported. Our results showed two whole sediment chronic toxicity experiments with an amphipods (H. azteca ; 42-day exposure) and cobitidae (Paramisgurnus dabryanus; two months exposure) for measuring effects on survival/growth/reproduction was successfully developed. In addition, the parameters including fish eggs fertilization rate, hatching rate and embryo development were also evaluated in the Paramisgurnus dabryanus sediment toxicity test. Our study observed that the amphipod survival was 80% greater than the minimum control survival for test acceptability. However, the procedures require further refinement to ensure the minimum variation. In addition, the evaluation of the sublethal effects of 20 samples (H1, H3, H10, S1, S2, 2, 4, 9, 49, 13, 22, 30, 33, SY1, SY11, YKR2,YKR5, LK-R-2, LKR4 and A1) collected from six watersheds using a 42-day whole-sediment toxicity test with the amphipod Hyalella azteca (28-day sediment exposure followed by a 14-day water-only exposure ) and a large-scale loach (Paramisgurnus dabryanus) were reported.
Toxic effects on 60% samples the amphipod survival rates were below 80% of 20 field-collected sediment samples. The lowest survival rate was only 12.5% observed in site S1 and the highest survival rate was found from the site 30. Weight and body length of amphipods after the 28-day exposure was reduced compared to the control group in 80% and 25% of the samples, respectively. The average reproduction ratio (number of young/female) of amphipods at Day 35 and 42 is 13.54 (offspring/ female) reduced relative to the control (14.15 offspring/ female) with the exception of one sample at site LKR2 .
As for the Paramisgurnus dabryanus sediment toxicity test, early life stage of loach results shown it has less tolerance toward contamination compared to the juvenile stage according to the egg fertilization rate and larval hatching rate which were more sensitive than the growth performance indicator of loach exposing to the field sediments. No negative impact on the indicators of reproduction and growth performance of loach was found with the exception of the sediment sample collected from A1 site. Sediment samples collected from the other nineteen sites are significantly affect the egg fertilization rate and larval hatching rate of loach. Furthermore, the 10 of above sediment samples, including S1, 2, 4, 30, 33, SY1, SY2, YK2, YK5 and LKR, have negative effect on the growth performance of loach compared to control group.
The results suggest the potential and sensitivity using these two species in sediment chronic toxicity tests and the application to the sublethal effects of contaminants in the sediments.