The effect of maternal exposure to contaminated sediment on the growth and condition of larval Fundulus heteroclitus.

We employed a factorial laboratory experiment to determine the single and combined effect of maternal and larval exposure to contaminated sediment from Elizabeth River, Virginia, a site contaminated with high concentrations of multiple pollutants. Females were exposed to either reference or contaminated sediment and the larvae from both groups of mothers were in turn transferred to either reference or contaminated sediment. We found a strong maternal influence on yolk area, length and RNA:DNA ratio at hatch. Further, the maternal exposure significantly influenced growth rate and RNA:DNA ratios of larvae 14 days after hatch and was a more important factor in determining these endpoints than larval exposure. We found that after 14 days larvae were larger and had higher survivorship when the maternal and larval exposures were the same. There also was no statistical difference with respect to growth and condition between larvae that had hatched from exposed mothers and remained in contaminated water and larvae that had hatched from reference mothers and were placed in either reference or contaminated sediment. However, larvae that hatched from exposed mothers and then were switched to reference sediment had significantly lower growth, lower RNA:DNA ratios, and were smaller despite being large at hatch size, indicating that there are fitness trade-offs in exchange for apparent resistance to contaminants which are provided by the mother. Maternal effects add complexity to ecotoxicological research and should be incorporated into studies to predict population level responses more realistically.

Toxic effects of PCB126 and TCDD on shortnose sturgeon and Atlantic sturgeon.

Exposure to chemical contaminants is often invoked to explain recruitment failures to populations of sturgeon worldwide, but there is little empirical evidence to support the idea that young sturgeon are sensitive at environmentally relevant concentrations. The authors used shortnose sturgeon (Acipenser brevirostum) and Atlantic sturgeon (Acipenser oxyrinchus) as models to investigate the sensitivities of sturgeon to early-life-stage toxicities from embryonic exposures to graded doses of polychlorinated biphenyl 126 (PCB126) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Survival to hatching of shortnose sturgeon decreased with increasing dose, although the duration of the embryonic period was not significantly altered by exposure in either species. Morphometric features of larvae of both species were affected by dose, including shortening of the body, reduction in head size, reduction in quantity of yolk reserves, and reduction in eye size. Eye development in both species was delayed with increasing dose for both chemicals. The persistence of larvae in a food-free environment decreased inversely with dose in both species, with sharp declines occurring at PCB126 and TCDD doses of ≥1 ppb and ≥0.1 ppb, respectively. Dose-responsive early-life-stage toxicities reported here are among the more sensitive found in fish and occurred at burdens similar to those found in situ in a sympatric bottom-dwelling bony fish in the Hudson River Estuary. The present study is among the first demonstrating the sensitivity of any sturgeon to the hallmark early-life-stage toxicities induced by aryl hydrocarbon receptor agonists.