Wildlife toxicology examines how pollutants impact animals in nature. It's crucial for understanding environmental health and protecting ecosystems. Bioaccumulation and biomagnification are key processes that concentrate toxins in food chains.

Sentinel species and bioindicators help scientists detect contamination early. By studying these organisms, we can assess ecosystem health and identify potential threats to wildlife populations and human health.

Bioaccumulation and Biomagnification

Contaminant Accumulation in Organisms

• Bioaccumulation occurs when an organism absorbs a substance at a rate faster than it is lost, leading to an increase in the concentration of the substance in the organism over time
  • Can happen through direct exposure (skin, gills, lungs) or by ingesting contaminated food or water
  • Lipophilic substances (DDT, PCBs) are more likely to bioaccumulate due to their affinity for fatty tissues
• Biomagnification is the increasing concentration of a substance in the tissues of organisms at successively higher levels in a food chain
  • Top predators (eagles, polar bears) tend to have the highest concentrations of persistent contaminants due to biomagnification
  • Can lead to toxic effects in top predators even when environmental concentrations are low

Exposure Pathways and Non-target Effects

• Wildlife can be exposed to contaminants through various routes including ingestion of contaminated food or water, inhalation, and dermal absorption
  • Exposure can be acute (short-term, high dose) or chronic (long-term, low dose)
  • Bioavailability of the contaminant influences the extent of exposure and potential for toxicity
• Non-target species, those not intended to be affected by a chemical (pesticide), can suffer adverse effects due to bioaccumulation and biomagnification
  • Insecticides (neonicotinoids) can accumulate in nectar and pollen, impacting pollinators (bees, butterflies)
  • Rodenticides (anticoagulants) can bioaccumulate in predators (hawks, owls) that consume poisoned rodents, leading to secondary poisoning

Sentinel Species and Bioindicators

Using Organisms to Detect Environmental Contamination

• Sentinel species are organisms used to detect the presence of contaminants or to monitor changes in environmental quality
  • Mussels and oysters are commonly used as sentinels for coastal pollution due to their ability to accumulate contaminants from water
  • Birds (swallows, sparrows) can serve as sentinels for air pollution by monitoring contaminant levels in their eggs or tissues
• Bioindicators are species or communities that reflect the ecological health of an environment and can signal changes in environmental conditions
  • Lichens are sensitive to air pollution (sulfur dioxide) and can indicate air quality based on their abundance and diversity
  • Aquatic invertebrates (mayflies, stoneflies) are indicators of water quality as they are sensitive to pollution and habitat degradation

Endocrine Disruption and Population-level Effects

• Endocrine disrupting chemicals (EDCs) can interfere with the normal functioning of the endocrine system, leading to adverse effects on development, reproduction, and behavior
  • EDCs (PCBs, BPA) can mimic or block natural hormones, disrupting normal signaling pathways
  • Exposure to EDCs has been linked to reproductive abnormalities in fish (intersex), amphibians, and reptiles
• Contaminants can have population-level effects on wildlife by reducing survival, reproduction, or altering behavior
  • Eggshell thinning in birds (eagles, pelicans) due to DDT exposure led to population declines in the mid-20th century
  • Feminization of fish populations near wastewater treatment plants due to exposure to estrogenic compounds (birth control pills)

Wildlife Toxicity Assessment

Evaluating the Toxicity of Contaminants to Wildlife

• Wildlife toxicity tests are conducted to determine the adverse effects of contaminants on wildlife species
  • Acute toxicity tests measure the lethal effects of a substance over a short period (48-96 hours) and determine the LC50 (lethal concentration for 50% of test organisms)
  • Chronic toxicity tests evaluate sublethal effects (growth, reproduction) over a longer period (weeks to months) and determine the NOEC (no observed effect concentration)
• Toxicity tests can be conducted on various wildlife species including birds (quail, mallard), mammals (mice, rats), and aquatic organisms (fish, invertebrates)
  • Species selection considers ecological relevance, sensitivity to the contaminant, and ease of testing
  • Extrapolation from test species to wild populations involves uncertainty and requires careful consideration of species differences and environmental factors

Ecological Risk Assessment

• Ecological risk assessment is a process used to evaluate the likelihood of adverse ecological effects occurring as a result of exposure to contaminants
  • Involves problem formulation, exposure assessment, effects assessment, and risk characterization
  • Considers multiple stressors (chemical, physical, biological) and their interactions
• Exposure assessment estimates the concentrations of contaminants in the environment and the potential for wildlife exposure
  • Uses environmental fate models, monitoring data, and exposure scenarios
  • Considers bioavailability, bioaccumulation, and biomagnification potential
• Effects assessment evaluates the potential adverse effects of contaminants on wildlife based on toxicity data and exposure-response relationships
  • Uses dose-response models, species sensitivity distributions, and ecological models
  • Considers acute and chronic effects, direct and indirect effects, and population-level impacts
• Risk characterization integrates exposure and effects information to estimate the likelihood and magnitude of adverse ecological effects
  • Uses risk quotients (exposure/toxicity), probabilistic methods, and weight of evidence approaches
  • Communicates risks to decision-makers and stakeholders for risk management and mitigation