Persistent organic pollutant effects on middle Mississippi River Scaphirhynchus sturgeon reproduction and early life stages
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Pallid sturgeon (Scaphirhynchus albus) and shovelnose sturgeon (Scaphirhynchus platorynchus) populations have been in decline over the past century and contaminants may be a contributing factor. Two studies were designed to assess if POP contaminants, specifically polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs), could be affecting reproduction and development in wild and hatchery-reared Scaphirhynchus sturgeon. The first were egg exposures with two of the most potent POPs, 3,3',4,4',5-pentachlorobiphenyl (PCB-126) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The second was a reproduction assay using wild-caught Middle Mississippi River shovelnose sturgeon along with egg contaminant analysis and H4IIE bioassay. Pallid and shovelnose sturgeon were similar in sensitivity to PCB-126 (LD50 values of 159 and 191 ng/g egg for pallid and shovelnose sturgeon, respectively) and TCDD (LD50 values of 12 and 13 for pallid and shovelnose sturgeon, respectively). No PCB-126 or TCDD dose-related effects on percent fertilization or hatch were observed in either species. Similar pathologies were present in both species. Concentrations of PCBs, OCPs, and PBDEs in shovelnose sturgeon eggs were highly correlated in eggs from the reproduction assay. No relationship between bioassay derived potencies and POP concentration was observed. However, associations between increased embryological and larval mortality and decreased percent hatched were observed with increasing POP concentration. These results indicate that shovelnose sturgeon are suitable surrogates for assessing contaminant related effects on pallid sturgeon and that POP contaminants are likely one factor limiting recruitment in wild and hatchery- reared Scaphirhynchus sturgeon.