Wildlife and landscape science research topics: contaminants and wildlife

Various natural and anthropogenic chemicals and compounds can pose a risk to wildlife. Each contaminant has different characteristics and can affect wildlife in different ways. Understanding these different properties, pathways and effects, alone and in combination, is necessary to understand the impacts of contaminants on wildlife and ecosystem health.

The science produced by wildlife and landscape researchers has been used in many programs and policies to help inform decision making and conservation efforts to protect Canadian species and ecosystems against harmful legacy substances.

Ongoing research is continually identifying new chemicals of concern and ensuring that robust science informs decisions about new and emerging contaminants.

Endocrine disruptors are substances that mimic hormones and can interfere with the body’s normal physiological and metabolic processes that regulate growth, development, tissue function, reproduction and behaviour.

These substances have different life spans and consist of drugs, pesticides, industrial chemicals, metals and natural compounds often found in municipal, textile, mining and pulp and paper effluents.

Some examples are:

• Dioxins, furans
• Polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (DDE), polycyclic aromatic hydrocarbons (PAHs) and flame retardants like polybrominated dipheynl ethers (PBDEs) and hexabromocyclododecane (HBCD)

Increased exposure can reduce an organism’s ability to respond adequately to stressful situations, disrupt hormone flow, alter sexual characteristics, reduce birth rate, cause birth defects and impair development.

These factors may affect wildlife at the individual, population and community levels, thereby impacting the structure of biological communities and possibly reducing biodiversity.

Current research on endocrine disruptors focuses on:

• Understanding and investigating the ecotoxicology of contaminant and metabolite exposure on species and ecosystems
• Investigating the sub-organismal effects of contaminant exposure
• Conducting assessments of species and overall ecosystem health
• Investigating the effects of endocrine disrupting compounds and metabolites on the reproductive, immune and other systems of various wildlife species including polar bears, marine mammals, mink, amphibians, snapping turtles, bald eagle, peregrine falcon, herring gulls, and many other avian species
• Conducting multi-generational laboratory investigations of the subtle effects of exposure to chemicals at early life stages, using model species such as the zebra finch
• Examining the fate and pathways of endocrine disruptors in marine and aquatic food webs
• Examining soil and water interactions to better understand the pathways of transport for nutrients and contaminants
• Studying the chemical composition in suspected sources of endocrine disruption including industrial effluents and land use-agriculture practices
• Species specific, contaminant-mediated enzyme induction and associated mechanistic pathways of contaminant metabolism/biotransformation leading to endocrine-disrupting products in wildlife
• An in vitro competitive binding assays using e.g., recombinant thyroid hormone transport proteins from a bird and mammalian models to understand the structure-activity relationships and relative potencies of chlorinated, brominated or fluorinated compounds, and especially phenolic metabolites and complex mixtures from wildlife, to influence e.g., circulating thyroid hormone status

Some examples are:

• Pesticides: dichlorodiphenyltrichloroethane (DDT), aldrin, dieldrin
• Industrial chemicals: polychlorinated biphenyl (PCBs), hexachlorabenzene, polybrominated diphenyl ethers (PBDEs), other organic flame retardants, compounds, polyfluoroalkyl acids and their precursors
• By-products and contaminants: dioxins, furans, persistent metabolites such as halogenated phenolic metabolites of PCBs and PBDEs

POPs bioaccumulate mainly in the fatty tissue of living organisms and produce a number of harmful effects in wildlife including reproductive dysfunction, eggshell thinning, metabolic changes, birth defects, cancer, immune system suppression and endocrine disruption.

These effects, alone or in combination, can leave individuals and populations vulnerable to diseases and predation, and can be a contributing factor in population declines.

In the 1970s, Great Lakes monitoring programs alerted scientists to the fact that the eggs of fish-eating birds were becoming so thin that they would crack during incubation. This was a result of DDT exposure, and once banned, levels declined by 10 times and the health of local birds improved.

Researchers have determined that since regulatory actions have been taken against legacy POPs, levels in general have declined by about half, and in some indicator species, such as the herring gull, drastic reductions have occurred.

Considerable work in this field has centered on northern and Arctic regions, where atmospheric processes deposit POPs originating from southern sources.