Silent Stressors: Sublethal Inorganic Contaminants in Pacific Scoters

Jessica L. Hallman, and Marjorie L. Brooks,


Jessica L. Hallman*,

and Marjorie L. Brooks, Southern Illinois University, 1125 Lincoln Dr., LifeSci II, MC 6501, Carbondale, IL 62901 USA, "Over the last 30 to 50 years, populations have declined by an estimated 60%. Until recently, surf scoters (SUSC;

Melanitta perspicillatta), and its two congeners white-winged scoters (WWSC; Melanitta fusca), and black scoters (Melanitta nigra) were censused together without interspecific distinction. Thus, it is unknown which of the three species is driving the decline. Focusing on surf and white-winged scoters in the Pacific Northwest, previous studies found that habitat quality did not entirely explain their body condition (as size and metabolic biomarkers). Clearly, other factors constrain body condition and may contribute to population dynamics. We investigated the potential correlation between chronic exposure to sub-lethal metals concentrations and the body condition of surf and white-winged scoters. Data analysis is ongoing. Initial findings show that because of high variance, there were no interspecific differences in male livers for either selenium (Avg + SD, SUSC: 238 +117 μMol/kg dw; WWSC; 275+ 91 μMol/kg dw) or mercury (Avg + SD, SUSC: 6.0 + 4.5μMol/kg dw; WWSC; 11.7 + 7.7 μMol/kg dw). However, the trend for mercury concentrations in SUSC to be approximately half that of WWSC suggests that their dietary shift to herring spawn may minimize their exposure to mercury. Generally high body burdens of contaminants indicate that industrial output in the region may be affecting the quality of critical wildlife habitat. Analyses are underway to compare mercury and selenium concentrations in blood samples comparing birds from the Puget Sound-Georgia Basin region to birds living in non-industrialized sites in Southeast Alaska." As I might have said to you before (while on my soapbox), one of the past issues in determining the "subletal effects" wasthe inability to measure or quantify them. Most of the time individuals with nonlethal contaminant loads or disease exposures look completely normal until they are stressed. Of stressors can take a variety of forms including weather, lower quality habitats or food, or even excess disturbance at times. The actual cause of death like predation or starvation often appears completely unrelated to the contaminants or disease load of the individual but is major contributing factor in that made that individual less alert or decreased it's foraging ability thus leading to it's demise. It would appear from the above abstract that some is at least attempting to develope a measure for some of most prevalent heavy metal contaminants. Guess "baby steps" are better than none!!