Mercury trends in colonial waterbird eggs downstream of the oil sands region of Alberta, Canada.
Mercury levels were measured in colonial waterbird eggs collected from two sites in northern Alberta and one site in southern Alberta, Canada. Northern sites in the Peace-Athabasca Delta and Lake Athabasca were located in receiving waters of the Athabasca River which drains the oil sands industrial region north of Fort McMurray, Alberta. Temporal trends in egg mercury (Hg) levels were assessed as were egg stable nitrogen isotope values as an indicator of dietary change. In northern Alberta, California and Ring-billed Gulls exhibited statistically significant increases in egg Hg concentrations in 2012 compared to data from the earliest year of sampling. Hg levels in Caspian and Common Tern eggs showed a nonstatistically significant increase. In southern Alberta, Hg concentrations in California Gull eggs declined significantly through time. Bird dietary change was not responsible for any of these trends. Neither were egg Hg trends related to recent forest fires. Differences in egg Hg temporal trends between northern and southern Alberta combined with greater Hg levels in eggs from northern Alberta identified the likely importance of local Hg sources in regulating regional Hg trends. Hg concentrations in gull and Common Tern eggs were generally below generic thresholds associated with toxic effects in birds. However, in 2012, Hg levels in the majority of Caspian Tern eggs exceeded the lower toxicity threshold. Increasing Hg levels in eggs of multiple species nesting downstream of the oil sands region of northern Alberta warrant continued monitoring and research to further evaluate Hg trends and to conclusively identify sources.
Environment Canada, Science and Technology Branch, National Wildlife Research Centre, Carleton University , 1125 Colonel By Drive, Ottawa, Ontario, Canada K1A 0H3.
Craig E
CE
Hebert
David
D
Campbell
Rhona
R
Kindopp
Stuart
S
MacMillan
Pamela
P
Martin
Ewa
E
Neugebauer
Lucy
L
Patterson
Jeff
J
Shatford
D000393:Air Pollutants / Q000032:analysis; D000416:Alberta; D000818:Animals; D001572:Benzofurans / Q000378:metabolism; D001717:Birds / Q000378:metabolism*; D046091:Charadriiformes / Q000378:metabolism; D004784:Environmental Monitoring; D005843:Geography; D008628:Mercury / Q000378:metabolism*; D009587:Nitrogen Isotopes; D061329:Oil and Gas Fields; D010063:Ovum / Q000378:metabolism*; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives / Q000378:metabolism; D012822:Silicon Dioxide
D000393:Air Pollutants; D001572:Benzofurans; D009587:Nitrogen Isotopes; D000072317:Polychlorinated Dibenzodioxins; D012822:Silicon Dioxide; C023614:dibenzofuran; D008628:Mercury