Separate and Combined Effects of Anthropogenic Co-Stressors in the Early Life-Stages of Atlantic and Shortnose Sturgeons

Atlantic sturgeon (Acipenser oxyrinchus) and shortnose sturgeon (A. brevirostum) live in coastal and riverine waters along the Atlantic Coast and spawn in upper reaches of these estuaries.  Many estuarine inhabitants are subjected to anthropogenic stressors including contaminants, low dissolved oxygen (DO), and elevated temperatures.  We address the impact of these stressors on sturgeon early life-stages by exposing embryos and pre-feeding larvae to graded does of PCBs; low levels of DO, and elevated temperatures singly and in pairwise combinations.  Survival to hatch, embryonic period duration, and the size and condition of larvae at hatching were scored.  Survival decreased with increasing contaminant concentration and sublethal effects included a shortening of larval size at hatching, yolk-sac edema, retarded eye development, and reduced post-hatching lifespan in food-free environments.  Survival to hatch declined precipitously above 16 °C.  Developmental rate was linearly related to temperature but a reduction in hatch size occurred above 15 °C.  The impact of constant (low and high) and diel fluctuating DO regimes on these same responses will be quantified this spring-summer.  Results show these sturgeons to be at risk to direct effects of modest increases in their thermal habitat which magnify effects of other co-stressors.