Properties of blood, porphyrins, and exposure to legacy and emerging persistent organic pollutants in surf scoters (Melanitta perspicillata) overwintering on the south coast of British Columbia, Canada

Abstract

The surf scoter (Melanitta perspicillata) is a little-studied species of North American sea duck. Estimates suggest it has experienced a precipitous decline in breeding numbers over the latter half of the past century. To investigate the potential role of contaminant uptake and toxicity in the population decline, this study undertook to measure blood chemistry, porphyrin concentrations, EROD, and organic contaminants in mature surf scoters wintering in the Strait of Georgia, BC, Canada. Hepatic organochlorine pesticide, polychlorinated dibenzo-p-dioxin, polychlorinated dibenzofuran, polychlorinated biphenyl (PCB), polybrominated diphenyl ether, and nonylphenol concentrations were relatively low; for example, SigmaTEQs (toxic equivalents) for PCBs, dioxins, and furans combined ranged from 4.7 ng/kg wet weight in reference-site (Baynes Sound) birds to 11.4 ng/kg wet weight in birds from Vancouver Harbour. Nonetheless, elevated EROD activity indicated that birds in Howe Sound were responding to an Ah-receptor-mediated stressor, which was also affecting hematocrit values and possibly vitamin A status. In addition, a low proportion of lymphocytes in individuals across locations in early spring samples was associated with poor body condition. The apparent loss of fitness just prior to the onset of northerly migrations to breeding grounds is of particular concern. Compromised health of mature birds at this point in the season might impact negatively on the productivity and survival of some individuals, particularly those overwintering in Howe Sound.

Fig. 1

The variable composition of hepatic concentrations of total porphyrins, expressed as proportion of protophorphyrin relative to proportion of coproporphyrin, in adult male surf scoters collected during the late fall 1998 (December) and early spring 1999 (2 March) in the Strait of Georgia, BC

Fig. 2

The geographic differences in hepatic EROD activity and hematocrit values of adult male surf scoters collected from three locations in the Strait of Georgia, BC, 1998–2001. The significant association between EROD and hematocrit values is expressed in the bottom graph (see results text for r and p-values). Bars with different letters above them represent significantly different least squares mean values. Error bars represent upper and lower confidence intervals. ** p < 0.01; *** p < 0.001

Fig. 3

Geographic differences in the differential white blood cell counts of adult male surf scoters collected from three locations in the Strait of Georgia, BC, in early spring (February–March) 1999. Bars with different letters above them represent significantly different least squares mean values (p-Values are given in the Results section). Error bars represent upper and lower confidence intervals. Geometric mean values for adult males collected from Vancouver Harbour in spring 2001 are shown for comparison but were not included in the statistical evaluations