Toxins in Osprey Eggs an indicator of contaminants in the Fraser and Columbia River basins

What is Happening?

Ospreys (Pandion haliaetus) are a good indicator species of aquatic ecosystem health. Because they eat large fish, Ospreys are directly exposed to pollutants that accumulate in aquatic food chains. It is also known from past studies that Osprey egg shell quality and egg viability has been reduced by exposure to organochlorine contaminants such as DDE. Since Ospreys typically lay an extra egg that is rarely fledged, it can be removed for analysis with minimal population effects. Their nests are found throughout the Fraser and Columbia River basins.

Since 1991, Environment Canada has monitored the levels of three toxin groups found in Osprey eggs: industrial organochlorines (dioxins, furans and PCBs), organochlorine pesticides (DDE, dieldrin, chlordane and toxaphene) and mercury.

Industrial Organochlorines

Since dioxins, furans and PCBs all have similar physiological effects on birds, Environment Canada uses a system known as toxic equivalents (TEQs) to measure the combined effect of these compounds. As shown in the graphs below, the contribution of dioxins and furans to total TEQs in Osprey eggs collected from the Fraser and Columbia River basins decreased substantially between 1991 and 1997. This decline was most evident downstream of pulp mills, such as the areas downstream of Kamloops and Castlegar. PCB TEQs were variable but persistent.

Source: Elliott et al. 1998 and L. Wilson. 2003. Environment Canada, Canadian Wildlife Service, Delta, British Columbia.

GRAPH DATA

Organochlorine Pesticides

About one quarter of the osprey eggs collected from 120 nests in the Fraser and Columbia River basins between 1991 and 1997 had concentrations of DDE exceeding 4 mg/kg wet weight. Several had burdens above 10 mg/kg. Eggshell thinning is known to occur at DDE concentrations of 4.2 mg/kg (Wiemeyer et al. 1988) and improper embryo development at 10 mg/kg (Poole 1989). After 1997, none of the eggs measured had levels of DDE above 4 mg/kg suggesting that DDE levels are slowly declining in these aquatic ecosystems. However, in some glacial-fed reservoirs and in areas where past pesticide use was heavy like the South Okanagan, Osprey eggs still have elevated levels of DDE.

Source: Elliott et al. 2000, Elliott et al. 2002 and L. Wilson. 2003. Environment Canada, Canadian Wildlife Service, Delta, British Columbia. Levels of DDE are expressed as geometric means (blue bar) with range (black vertical line). The data are from various locations within the basins.

GRAPH DATA

Two other organochlorine pesticides, chlordane and dieldrin, are also found in the Fraser and Columbia aquatic ecosystems. Levels of these toxins in Osprey eggs peaked in 1993 before dropping off.

Source: Elliott et al. 2000. Levels of chlordane and dieldrin pesticides are expressed as geometric means. The detection limit for dieldrin is 0.1 µg/kg wet wt. The * asterisk denotes non-detection.

GRAPH DATA

Although there are few reports of the organochlorine pesticide, toxaphene, in avian tissues, low levels were measured in Osprey chick plasma from both the Fraser and Columbia River basins. This is consistent with recent findings which document atmospheric deposition of toxaphene and other persistent organochlorines into alpine mountain and northern regions of British Columbia and Yukon (Blais et al. 1998 and Kidd et al. 1995). In Alberta, elevated levels of toxaphene were found in fish (Donald et al. 1993) and in Osprey chick plasma from high elevation Rocky Mountain lakes.

Source: Elliott et al. 2002. Total toxaphene levels are expressed as geometric means (µg per kg wet weight).

GRAPH DATA

Mercury

As illustrated in the graph below, there has been no discernible trend in mean concentrations of total mercury found in Osprey eggs from various locations in the Fraser and Columbia River basins.

Source: Elliott et al. 2000, Elliott et al. 2002 and L. Wilson. 2003. Environment Canada, Canadian Wildlife Service, Delta, BC. 2003. The level of total mercury is expressed as a geometric mean (red bar) with range (black vertical line). The data are from various locations within the basins.

GRAPH DATA

Mean mercury concentrations in Osprey eggs from the Fraser and Columbia River basins are similar to those in Osprey eggs collected elsewhere from rivers and naturally formed lakes (Hughes et al., 1997). No differences were found between Osprey eggs taken from sites downstream or upstream of pulp mills indicating that past releases of mercury at those sites is not evident. Although not directly comparable, mercury levels accumulated in the livers of River Otters and Mink from both the Fraser and Columbia River basins were approximately 10 times those in Osprey eggs (Harding et al. 1998).

Why is it Happening?

There are two general sources for the toxic contaminants found in Osprey from the Fraser and Columbia River basins. One is from nearby sources which include industrial sites and sites of past use where residues remain. The other is from distant sources. Distant sources include long-range atmospheric dispersal from Asia and elsewhere in North America and potentially from dietary prey items at the osprey's wintering grounds in Latin America.

Nearby Sources

Levels of some organochlorines in Osprey eggs reflect the level of industrialization and toxic pollution in local waters as well as persistent historic residues in sediments. In the Fraser River Basin, levels of industrial organochlorines are generally lowest at Prince George, intermediate at Quesnel and Kamloops, and highest near Vancouver (Elliott et al. 1998, 2000 and 2001). Industrialization increases in the lower reaches of the Basin and contaminants also tend to accumulate there.

Figure 1. Location of pulp mills and major cities in the Fraser River Basin.

A 1994 study of Tree Swallows in the Fraser Basin also documented the effects of industrialization on ecosystem health. As shown in the graph below, industrial organochlorines (expressed as TEQs) in Swallows were 3-6 times greater downstream of large pulp mills and industrial centres. Tree Swallows pick up these contaminants from the aquatic ecosystem as they forage on emerging insects above the water surface.

Source: Harris and Elliott 2000.

GRAPH DATA

In agricultural areas where DDT was historically used in large quantities the primary source of DDE in Osprey probably originates from historic soil residues. This explanation is supported by elevated DDE levels measured in Osprey eggs collected near Pitt River, which is adjacent to an area of intensive horticultural activity in the Lower Fraser Valley. Even higher levels have been measured in fish (burbot) tissues in lakes near agriculture (e.g. Nicola Lake) (Macdonald et al.1998).

In 1989, the provincial government implemented legislation that restricted the amount of dioxin (2378-TCDD) that could be discharged from pulp and paper mills. The decline in dioxin (2378-TCDD) levels that occurred between 1991 and 1997 reflected changes made in bleaching technology at pulp mills. As a result, between 1989 and 1998, there was a 97% decline in the amount of dioxin (2378-TCDD) and a 99.5% decline in the amount of furan (2378-TCDF) discharged from Fraser River Basin pulp mills.

GRAPH DATA

Most uses of DDT were banned in Canada by 1974 and the use of PCBs was severely restricted in 1977. After implementation of these regulations, sharp declines of these organochlorines were observed in Osprey as well as other indicator species monitored in the Fraser River Basin (Great Blue Heron and Double Crested Cormorant).

Distant Sources

Ongoing low levels of PCBs and DDE in osprey eggs may also be a result of contamination from dietary prey items at wintering grounds and atmospheric dispersal from distant sources, including Asia. Many contaminants, including organochlorine pesticides such as DDE and toxaphene, PCBs and mercury are volatile and therefore enter the atmosphere, where they disperse. These contaminants often condense out of the atmosphere in cooler climates, such as arctic and alpine ecosystems. As a result, some of the most remote ecosystems in the world are among the most contaminated. In BC and Yukon, many alpine glaciers have elevated toxin levels and this is reflected in high contaminant levels in fish from some alpine lakes (Macdonald et al. 1998 and Kidd et al. 1995). With climate change these compounds can be released through melting and runoff and be bioaccumulated in alpine aquatic food chains.

In order to examine the impact of alpine contaminants on wildlife, Osprey eggs and prey fish were collected at a variety of elevations in BC and Yukon over a three year period (1999-2001)(Elliott et al. 2002). The highest concentrations of DDE in fish were measured in rainbow trout (215 µg/kg) from Upper Jade Lake, located at 1800 m in Revelstoke National Park, where there is no history of local application. Other Osprey prey fish collected from large mid-elevation reservoirs such as the Kinbasket, Revelstoke and Upper Arrow Lakes, all of which have greater than 50% of their drainage basins at higher than 1500 m, contained a wide range of chlorinated hydrocarbon contaminants at low levels.

Figure 2: Locations of fish and osprey samples collected in British Columbia and the Yukon for the Elliott et al. 2002 study.

However, analysis of Osprey eggs from eleven locations found no apparent contaminant concentration gradient with elevation (see graph below). This may be because Ospreys largely nest at low and mid elevations where alpine contamination is diluted by runoff from lower elevation sources.

Source: Elliott et al. 2002. DDE concentration expressed as geometric mean and range.

Because historic use of DDT was minimal in most of the upper Fraser Basin (Elliott et al. 2000) most of the breakdown product, DDE, acquired by Ospreys is likely from long-range atmospheric transport. This is supported by the similarly high concentrations of pesticides found in trout and burbot from remote alpine headwater lakes (Donald et al. 1993 and Macdonald et al. 1998). Pesticides have also been measured in Vancouver Island marmots living only in remote sub-alpine meadows (Lichota et al. 2003).

Another potential distant source of DDE in Osprey from the upper Fraser is contaminant exposure from dietary prey while on their wintering grounds. Radio telemetry carried out by the Canadian Wildlife Service with Mexican and American agencies tracked Ospreys nesting in the Fraser Basin to areas of intensive agriculture in Mexico and other Central American countries (see maps below).

Figure 3. Satellite telemetry of ospreys tagged in BC showing migration routes to wintering sites on the Pacific Coast of Mexico and in Central and South America from Elliott et al. 2002. Results above are from 8 transmitters mounted on Osprey in BC, 1996-2001. Click on images to enlarge.

To determine whether wintering sites could be a source for contaminants, osprey prey fish were collected and tested at 16 wintering sites. At 15 of the tested sites, however, DDE concentrations in fish were low (below 0.1 mg/kg).

DDE concentrations in Osprey eggs collected between 1999 and 2001, including those from females known to winter in Mexico, were with one exception lower than those collected in the early 1990s. Based on DDE:DDT ratios, which give an indication of the time since DDT was used, there is no indication of recent DDT accumulation suggesting that exposure on wintering grounds was from historic rather than recent DDT use.

Other recent scientific evidence has also shown the importance of distant sources of toxic contaminants. PCBs which were found to accumulate in sockeye salmon during their ocean life were released into their natal waters when their spawned carcasses decomposed. The levels in adult sockeye were such that the total toxic load from a million sockeye was comparable to the amount of fugitive PCBs released annually from hazardous waste incinerators (Krümmel et al. 2003). Further evidence of long range transport of some contaminants comes from the fact that the pesticides found in alpine dwelling marmots are also those used in distant areas of North America and/or Asia.

Why is it Significant?

DDT, PCBs and dioxins and furans are chlorinated contaminants that have caused widespread reproductive failure and population declines in raptors throughout the world. DDT, in particular, caused eggshell thinning among Ospreys during the 1960s and 1970s before it was banned in North America.

Breeding Bird Surveys conducted between 1968 and 2002 suggest Osprey numbers in BC increased by 5.4% per year, mostly in the southern portion of the province. Across Canada, Osprey populations increased by nearly 4.6% per year during this same period. These increases likely reflect the recovery of this species from the impacts of chlorinated contaminants such as DDE and PCBs. 

The toxin levels measured in Ospreys have important implications for other wildlife. For example, Mink and River Otters are extremely sensitive to PCBs. Any increases in PCB concentrations measured in Osprey eggs may have a more significant effect in other wildlife.

Since Ospreys feed on several sport fish species, ongoing monitoring of contaminant levels in Ospreys may also provide an early warning about toxins potentially consumed by humans. Climate change in the region may exacerbate these risks when toxins that have accumulated over many decades are released as glaciers melt. For example, total PCB concentrations in coastal snowpack are up to 2.17 ng/L (Blais 1998), well above the current Canada Drinking Water Guideline of 1.0 ng/L.

What is Being Done?

During the early 1990s, Environment Canada initiated the Fraser River Action Plan to assess the environmental health of the Fraser Basin. As shown on the map below, assays for toxic contaminants were conducted throughout the Basin on wildlife, sediment and fish. This created a baseline against which future changes could be measured. Rather than continue to monitor all ecosystem components for toxic contaminants, certain species have been selected as indicators of overall ecosystem health. Ospreys serve as a sentinel species for the Fraser and Columbia basins with monitoring continuing on an ongoing basis.

Figure 4: Sampling sites and reaches used for the Fraser River Action Plan research in the Fraser River Basin.

For many years Ospreys did not breed in the Vancouver region, due to high levels of industrialization and chemical contamination. However, after implementing pollution regulations and restoring lost and degraded habitat, Ospreys have returned to Maplewood Flats, in North Vancouver. The return is celebrated annually with the Return of the Osprey Festival. Creston, on the Columbia River, celebrates the densest Osprey population in Canada with an annual Osprey Festival. These festivals not only provide some commerce for local businesses, but they also foster an awareness of and appreciation for Ospreys and other wildlife.

The Canadian Wildlife Service continues the monitoring of contaminants in areas of interest including industrial sites and alpine areas. To assess the proportion of contaminants that come from southern wintering areas, bird migration and wintering patterns are also under study using satellite transmitters. Since mercury is known to accumulate in food chains in flooded lands including hydro reservoirs, federal and provincial environmental agencies are working with BC Hydro to monitor mercury concentrations in both fish and fish-eating wildlife. Because of global concern about long range atmospheric deposition of mercury, primarily from coal burning power plants, Environment Canada scientists and regulators are also taking part in international level processes to identify sources and track trends. Where feasible, actions to reduce contaminant risks are being taken.

Canada has established a $20 million Persistent Organic Pollutants (POPs) Fund to help developing countries and those countries with economies in transition to reduce or eliminate the release of POPs. Canada also continues to work with Mexico and the US under the North American Commission on Environmental Cooperation established under the Free Trade Agreement. Regional action plans on POP substances such as chlordane, DDT, PCBs, dioxins, furans and hexachlorobenzene are being established.

For more information contact:  John.Elliott@ec.gc.ca or Laurie.Wilson@ec.gc.ca

Check the following sites for additional information on this indicator:

• Hinterland's Who's Who - Osprey
• Canadian Bird Trends Database for Osprey
• Environment Canada's S&E Bulletin - High-Altitude POPs and Alpine Predators
• Mercury and the Environment
• Persistent Organic Pollutants - POPs
• PCB - Polychlorinated Biphenyls
• Endocrine Disrupting Substances (EDS)
• Chlorinated Substances Action Plan
• ARET: Accelerated Reduction/Elimination of Toxics
• Pollution Prevention Fact Sheets
• National Office of Pollution Prevention
• Species at Risk - Vancouver Island Marmot
• Department of Fisheries and Oceans - Marine mammals as sentinels

The following Web sites are not under the control of Environment Canada (EC) and they are provided solely for the convenience of users. Environment Canada is not responsible for the accuracy, currency or the reliability of the content. Environment Canada does not offer any guarantee in that regard and is not responsible for the information found through these links, nor does it endorse the sites and their content. Users should be aware that information offered by non Government of Canada sites that are not subject to the Official Languages Act, and to which Environment Canada links, may be available only in the language(s) used by the sites in question.

• Georgia Basin-Puget Sound Ecosystem Indicators - Persistent organic pollutants in harbour seals
• Centre for Alpine Studies - See Mountain science highlights - Contaminants
• Consult the Fraser River Action Plan Report List for reports on toxic contaminants
• UNEP Global Programme of Action - POPs Chemicals - Persistent Organic Pollutants in the Marine Environment
• World Wildlife Fund - Toxic Chemicals and Wildlife
• World Wildlife Fund. Persistent Organic Pollutants (POPs)
• USGS - Osprey Species Account
• British Columbia Wildlife Watch
• Wild Bird Trust
• North American Commission for Environmental Cooperation
  • North America eliminates use of chlordane
  • Mercury hot spots of North America

For references used for this indicator click here.