Whole-sediment toxicity tests are increasingly being used in ecological risk assessments of contaminants in sediments. Standardized sediment toxicity tests in the environmental and ecological risk assessment process have played a major role in quantifying the harmful effects that chemical analyses alone cannot. In this project, we developed and used two chronic sediment toxicity tests in order to predict the sublethal effects of chemicals of potential concern (COPCs) on a sediment-dwelling amphipod (Hyalella azteca) and a cobitid (Paramisgurnus dabryanus). The sensitivity of and toxicological effects on the two test organisms were evaluated by exposing them to different concentrations of a heavy metal (copper) and three polycyclic aromatic hydrocarbons (naphthalene, phenanthrene, and pyrene). Standardized experimental designs for spiking methodologies were developed for two chronic toxicity tests (survival and growth) and to obtain information on the accumulation of these materials during different life stages to reveal whether the information derived is adequate. Spiked sediment results showed that copper, naphthalene, phenanthrene, and pyrene required 7-14 d, 28-35 d, 28-35 d, and 35-42 d, respectively, to reach equilibrium in sediment. In copper, phenanthrene, and pyrene spiked sediment toxicity tests, LC50 values for H. azteca were 64.80, 4.061, and 5.198 mg/kg, respectively, based on dose-response relationships. Significant growth (length and weight) differences were observed between formulated sediment and experimental groups at concentrations of 200 mg/kg Cu and 5 mg/kg pyrene (p < 0.05), respectively. Significant weight differences were observed between the formulated sediment and experimental groups at concentrations of 0.014 and 0.5 mg/kg for naphthalene and phenanthrene, respectively. The bioaccumulation of spiked copper (30 mg/kg) and pyrene (1 mg/kg) in H. azteca was significantly higher than in controls, indicating that these contaminants accumulate easily in organisms (BSAF>1) and at rates that are positively related to exposure concentration. Moreover, our study observed that growth performance, survival rate, and feed efficiency of Paramisgurnus dabryanus were significantly decreased when exposed to 100 mg/kg Cu, 0.7 mg/kg phenanthrene, and 50 mg/kg pyrene, and that 100% mortality occurred at concentrations of 200 and 400 mg/kg Cu. Similarly, 100% mortality was found at concentrations of 200 and 400 mg/kg pyrene in sediment. Nevertheless, no physiological parameters of growth in P. dabryanus were affected by exposure to naphthalene and phenanthrene in sediment due to lower concentrations of these two PAHs. In addition, the values of the bioaccumulation factor (BAF) of copper and biota-sediment accumulation factor (BSAF) of pyrene in P. dabryanus were 0.16 and 1.04 × 10-4, respectively. This means that copper and pyrene are considered not bioaccumulative to P. dabryanus because both factors’ values were < 1. Whole-sediment toxicity tests are increasingly being used in ecological risk assessments of contaminants in sediments. Standardized sediment toxicity tests in the environmental and ecological risk assessment process have played a major role in quantifying the harmful effects that chemical analyses alone cannot. In this project, we developed and used two chronic sediment toxicity tests in order to predict the sublethal effects of chemicals of potential concern (COPCs) on a sediment-dwelling amphipod (Hyalella azteca) and a cobitid (Paramisgurnus dabryanus). The sensitivity of and toxicological effects on the two test organisms were evaluated by exposing them to different concentrations of a heavy metal (copper) and three polycyclic aromatic hydrocarbons (naphthalene, phenanthrene, and pyrene). Standardized experimental designs for spiking methodologies were developed for two chronic toxicity tests (survival and growth) and to obtain information on the accumulation of these contaminants (copper and pyrene) during different life stages to reveal whether the information derived is adequate. Spiked sediment results showed that copper, naphthalene, phenanthrene, and pyrene required at least 14 d, 35 d, 35 d, and 42 d, respectively, to reach equilibrium in sediment. In copper-, phenanthrene-, and pyrene-spiked sediment toxicity tests, LC50 values for H. azteca were 64.80, 4.061, and 5.198 mg/kg, respectively, based on dose-response relationships. Significant growth (length) differences were observed between formulated sediment and experimental groups at concentrations of 200 mg/kg Cu and 5 mg/kg pyrene (p < 0.05). Weight differences were also observed between the formulated sediment and experimental groups at concentrations of 0.014 and 0.5 mg/kg for naphthalene and phenanthrene, respectively. The highest concentrations of spiked copper (300 mg/kg) and pyrene (20 mg/kg) in H. azteca indicated that bioaccumulation of these contaminants in organisms is unlikely (BAF<1000). Moreover, our study demonstrated that growth performance, survival rate, and feed efficiency of Paramisgurnus dabryanus were significantly decreased when exposed to 139±31 mg/kg Cu, 0.7±0.12 mg/kg phenanthrene, and 43.6±2.5 mg/kg pyrene, and that 100% mortality occurred at concentrations of 200 and 400 mg/kg Cu and pyrene. Nevertheless, no physiological parameters of growth in P. dabryanus were affected by exposure to naphthalene in sediment due to the highest measured concentrations being only 0.28 mg / kg, despite the huge difference between spiked and equilibrated concentration. In addition, the values of the copper bioaccumulation factor (BAF) and pyrene biota-sediment accumulation factor (BSAF) in P. dabryanus were 0.16 and 1.04 × 10-4, respectively. Copper and pyrene factor values (BAF<1000, BSAF<1) means that both are considered not bioaccumulative to P. dabryanus. Overall, the case demonstrated herein using a biological chronic toxicity test in an ecological risk assessment may provide helpful information to agencies in remediation decision-making.

Sediment toxicity, Sediment-dwelling organism, metals, polycyclic aromatic hydrocarbons, Bioaccumulation