| 英文摘要 |
Chemical contaminants discharged into estuaries and coastal areas often attach to sediment particles and are deposited on the sea bed. Contaminant-laden sediments may pose potential threats to coastal ecosystems, the sustainability of aquatic resources, and human health (via the food chain). The main purpose of this project was to establish toxicity test protocols for two saltwater benthic invertebrates (an amphipod and a polychaete) and compare their suitability for toxicity testing through a review of the literature. We selected the local amphipod Ptilohyale barbicornis and polychaete Perinereis aibuhitensis as our experimental benthic organisms. We established 10 d / 28 d survival and growth for Ptilohyale barbicornis as the acute and chronic toxicity endpoints. In addition, 10 d / 28 d survival and bioaccumulation effects were evaluated for Perinereis aibuhitensis. The toxicity protocols that we developed were applied using 10 estuarine field sediments collected along the coast of Taiwan in order to understand the sensitivity of the two selected organisms to different estuarine sediments. This information will be used to elucidate the biological effects of long-term exposure to contaminated estuarine sediments.
The optimal conditions for Ptilohyale barbicornis estuarine sediment toxicity tests were determined to be 19‰ salinity, 25 ºC water temperature, feeding frequency of three times per week, sandy sediments, and 2.5-4.5 mm body length. Optimal conditions for the Perinereis aibuhitensis toxicity tests were muddy sediment, 1.5 ~ 3.0 g body weight, salinity of 20‰, and temperature of 20 ºC. Under these conditions, a 96 hr LC50 value of 0.98 mg/L (CV = 7.5%) was obtained when Perinereis aibuhitensis was exposed to copper.
In copper-spiked sediment toxicity tests, the LC50 value for Ptilohyale barbicornis was 24.56 mg/kg based on dose-response relationships for 10 d sediment acute toxicity. Significant survival differences were observed between formulated sediment and experimental groups at a concentration of 34 mg/kg Cu. In a long-term exposure (28 d) experiment, the LC50 value for Ptilohyale barbicornis was 32.72 mg/kg. Growth (body length) showed no significant differences with controls when Ptilohyale barbicornis was exposed to 10 mg/kg and 34 mg/kg, while there was no survival when exposed to a concentration of 64 mg/kg. The Perinereis aibuhitensis acute toxicity (10 d) test showed that survival rates at sediment concentrations of 196 mg/kg or higher were significantly different from controls (p <0.05). Significant weight differences were observed between formulated sediment and experimental groups at a concentration of 72 mg/kg Cu (p <0.05). The bioaccumulation of spiked copper (72 mg/kg) in Perinereis aibuhitensis was significantly higher than in controls, indicating that Cu accumulates easily in organisms and at rates that are positively related to exposure concentration.
We completed the metal analysis at ten collected estuarine sediment samples and conducted 10 d sediment acute toxicity and 28 d chronic toxicity tests of Ptilohyale barbicornis and Perinereis aibuhitensis. The metals lead, zinc, nickel, chromium, and arsenic were detected in all samples, the highest average detected concentration was found to be zinc, and cadmium was not detected. In Ptilohyale barbicornis acute toxicity tests, survival at sites DC, LG, CL, CT, AGD, HJ, CJ, and LP was significantly different from controls (p <0.05). Growth (body length and weight) for Ptilohyale barbicornis was mostly inhibited compared to controls, body lengths in particular being significantly different from controls (p <0.05) when exposed to field sediments. Overall, these contaminant levels affected the survival or growth of these small benthic aquatic organisms. In Perinereis aibuhitensis, survival showed no statistically significant differences between controls and all sampling sites (p >0.05). The 28 d sediment chronic toxicity test showed that 80% of the individuals had lower survival rates than controls, but this was not statistically significant (p >0.05). Bioaccumulation test results showed that there was a significant difference (p <0.05) between the concentration of copper in the organism and in controls. However, the concentrations of metals in environmental samples had bioaccumulation factor (BAF) and biota-sediment accumulation factor (BSAF) values <1.
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