Vulnerabilities of Early Life-Stages of Atlantic Sturgeon and Shortnose Sturgeon to Contaminant and Thermal Stressors

Atlantic and shortnose sturgeon from several Atlantic Coast estuaries are exposed to high levels of polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins (PCDDs), and in combination with other stressors such as warming, hypoxia, and acidification.  We experimentally exposed embryos of both species to contaminant and thermal stressors.  Four coplanar PCB congeners (77, 81, 126, and 169), two Aroclors (PCB mixtures), and TCDD were administered in graded doses to embryos.  The constant thermal regimes implemented spanned the tolerances of each species and included ten temperature levels.  Survival to hatch and embryonic period duration decreased with TCDD > 10 ppb and PCB126 > 100 ppb.  Toxicity was evident as shortening of larval size at hatching (> 0.1 ppb), yolk-sac edema, and retarded eye development (> 0.1 ppb).  Post-hatching lifespan of larvae in food-free environments declined with increasing doses in both species (> 0.1 ppb).  Maximum survival to hatch occurred from 12 to 16 °C with precipitous declines above 16 °C.  Developmental rate was linearly related to temperature but a reduction in hatch size occurred above 15 °C.  These sturgeons may be at risk to direct effects of modest increases in their thermal habitat which could be a significant co-stressor with contaminants.