Toxic contaminants in Puget Sound wildlife

Studies on birds and marine mammals from around the world indicate that environmental contaminants have adversely affected wildlife. This is especially well documented for stable chlorinated hydrocarbon compounds, such as DDT (and its major metabolite DDE) and polychlorinated biphenyls (PCBs), that occur at higher concentrations at higher trophic levels. However, the role of contaminants in the causation of a variety of biological disorders observed in Puget Sound wildlife is not well understood. This report summarizes the current understanding and implications of toxic contaminants in Puget Sound wildlife and provides recommendations for future research and monitoring. A primary objective of this report is to provide technical guidance on research and monitoring that, where possible, integrates a variety of approaches to identify contaminants and their impact on wildlife. This guidance id designed to support local, state, and federal agencies that may conduct research or monitoring of wildlife in Puget Sound. These agencies include the Puget Sound Water Quality Authority, Washington Department of Wildlife (WDW), U.S. Fish and Wildlife Service (FWS), and U.S. Environmental Protection Agency.

The scope of this report has been kept limited. Only bird and marine mammal species that feed in marine areas of Puget Sound are considered. The geographic scope considered in this report includes Puget Sound proper (Puget Sound basin south of Admiralty Island), the Strait of Juan de Fuca, the San Juan Islands, and the northern Washington inland bays (Padilla, Samish, Skagit, and Bellingham bays).

Research on contaminant concentrations in Puget Sound birds has focused on great blue herons, pigeon guillemots, glaucous-winged gulls, and waterfowl (Riley et al. 1983; Henny et al., in press; Kendall et al. 1990; Speich et al., in preparation). Surf scoters and western grebes were found to have accumulated higher concentrations of contaminants after wintering in Puget Sound, compared to concentrations in mid-fall, after the birds had just arrived (Henny et al., in press). Concentrations of PCBs and DDT were highest in gulls from Tacoma and Seattle, compared to concentrations reported for other regions around Puget Sound (Speich et al, in preparation).

Only limited research has been conducted on potential health problems in Puget Sound birds as a result of contaminant exposure. Significant eggshell thinning was found in great blue herons and glaucous-winged gulls in Puget Sound, apparently as a result of exposure to DDE (Calambokidis et al. 1985; Speich et al., in preparation). The impact on the great blue heron populations caused by the eggshell thinning was not determined. Glaucous-winged gulls from sites in Puget Sound exhibited anomalous liver weights compared to liver weights reported in other regions. The potential role of contaminants in this phenomenon has not been determined.

Principal research on contaminant concentrations and impacts on marine mammals in Puget Sound has focused on harbor seals. This species is a common resident and breeds in Puget Sound. Concentrations of PCBs found in Puget Sound harbor seals in the 1970s were among the highest concentrations recorded in the world (Arndt 1973; Calambokidis et al. 1978, 1984). However, these levels have declined significantly since that time (Calambokidis et al. 1988, 1991c). PCBs may have played a major role in reproductive problems that were reported in Puget Sound harbor seals in the 1970s (Newby 1973; Arndt 1973). Currently, populations of harbor seals are increasing in Puget Sound (Calambokidis et al. 1985, 1988).

Research on contaminant concentrations in other Puget Sound marine mammals has been more limited. In addition to PCBs, high concentrations of chlorinated hydrocarbon contaminants and mercury have been found in the limited number of killer whales examined from the Puget Sound Region (Calambokidis et al. 1984, 1990a). Killer whale pods that feed on other marine mammals had the highest concentrations of contaminants, consistent with their position at the top of the marine food chain. The role of contaminants in gray whale deaths in Puget Sound has not been determined, despite a great deal of speculation on this issue reported in the media. Concentrations of most contaminants, with the exception of aluminum, identified in stranded gray whales have generally been low (Malins et al. 1984; NMFS 1990).

Existing research is insufficient to adequately assess the impacts of contaminants on wildlife species in Puget Sound. Some of the data gaps involve the status and trends of wildlife populations and contaminant levels in wildlife that will require long-term monitoring. Other data gaps may be addressed through discreet research projects that address specific questions or hypotheses regarding contaminant impacts on wildlife. Research areas identified in this report as having the highest priority include:

  • Sublethal effects of contaminants on harbor seals
  • Role of contaminants in gray whale mortality
  • Contaminant concentrations and impacts on killer whales
  • Role of contaminants in glaucous-winged gull liver abnormalities
  • Impact of eggshell thinning on great blue herons
  • Impact of consumption of seal carcasses on bald eagles

In addition to these research areas, baseline information on exposure (and potential impacts) to contaminants is needed for some species found in Puget Sound including harbor porpoises, Dall’s porpoises, river otters, belted kingfishers, loons, and some waterfowl species. For species that are most commonly the subject of past contaminant research, data gaps on levels of heavy metals, coplanar PCBs, polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and pentachlorophenol (PCP) should also be addressed.

Current monitoring plans for marine mammals under the Puget Sound Ambient Monitoring Program (PSAMP) include the examination of population trends, reproductive rates, mortality, and contaminant concentrations in harbor seals. Harbor seals are the best choice for initial monitoring of marine mammals because 1) they are resident and relatively sedentary in Puget Sound, 2) they are relatively easy to sample and have a population size adequate for sampling, 3) there is historical data on population size and contaminant concentrations, and 4) they are distributed at numerous sites around Puget Sound. Other species of marine mammals important for monitoring include killer hales, harbor porpoises, and gray whales.

Current and planned PSAMP monitoring of bird species provides valuable management and status information for a broad number of species. However, it does not provide information needed to examine contaminant-related problems in some of the species most likely affected by contaminants. In addition to the ongoing monitoring programs conducted by WDW and FWS, monitoring of populations and contaminants in several key resident species, including the great blue heron, belted kingfisher, and pigeon guillemot, is recommended. Shorebirds are not currently being monitored but represent an important group of species for ongoing study. Monitoring program recommendations focus on obtaining data on reproductive success and contaminant concentrations, as well as population status. 


Calambokidis, J., J.B. Buchanan, G.H. Steiger, and J.R. Evenson. 1991. Toxic contaminants in Puget Sound wildlife. Report EPA910/9-91-023 to the U.S. EPA, Region 10, Seattle, Washington. 96pp.