10.3 Wildlife toxicology and biomonitoring
4 min read•august 7, 2024
Wildlife toxicology examines how pollutants impact animals in nature. It's crucial for understanding environmental health and protecting ecosystems. and are key processes that concentrate toxins in food chains.
and 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
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- 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 due to biomagnification
- Can lead to 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
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
- (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 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
- are conducted to determine the adverse effects of contaminants on wildlife species
- measure the lethal effects of a substance over a short period (48-96 hours) and determine the LC50 ( for 50% of test organisms)
- evaluate sublethal effects (growth, reproduction) over a longer period (weeks to months) and determine the NOEC ()
- 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, , 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 , 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 , 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
Key Terms to Review (20)
Acute toxicity tests: Acute toxicity tests are experimental procedures designed to assess the harmful effects of a substance over a short period, typically 24 to 96 hours, to determine the concentration that causes significant adverse effects or mortality in test organisms. These tests are crucial for understanding the immediate impact of toxic substances on wildlife and ecosystems and play a pivotal role in assessing risks associated with chemical exposures.
Bioaccumulation: Bioaccumulation is the process by which organisms accumulate contaminants in their bodies over time, often from their environment or food sources. This phenomenon can lead to higher concentrations of harmful substances in the tissues of an organism compared to the surrounding environment, significantly impacting health and ecological dynamics.
Bioindicators: Bioindicators are organisms or biological responses used to assess the health of an ecosystem, particularly in relation to pollution and environmental changes. They serve as a signal for the presence of harmful substances and provide insight into the overall condition of aquatic and terrestrial environments. Bioindicators are crucial in monitoring ecological integrity, particularly in unique ecosystems like aquatic systems, where specific species respond sensitively to changes in water quality and pollution levels.
Biomagnification: Biomagnification is the process by which the concentration of toxic substances increases as they move up the food chain, affecting organisms at higher trophic levels more severely. This phenomenon connects various aspects of ecological interactions and highlights the importance of understanding how pollutants behave in ecosystems and impact wildlife health.
Chronic toxicity tests: Chronic toxicity tests are assessments designed to evaluate the long-term effects of substances on living organisms, typically over extended periods, often spanning weeks to months. These tests help identify harmful effects that may not be evident in short-term acute tests, such as impacts on growth, reproduction, or behavior. Chronic toxicity is crucial for understanding how pollutants affect ecosystems and informs risk assessments for wildlife and human health.
Contaminant accumulation: Contaminant accumulation refers to the buildup of harmful substances in organisms, ecosystems, or food webs over time. This process can lead to increased toxicity in wildlife and can affect biodiversity and ecosystem health. As contaminants are introduced into the environment, they may be absorbed by living organisms, where they can magnify in concentration through various biological processes, impacting not just the individual but also the entire food chain.
Dose-response models: Dose-response models are mathematical representations that describe the relationship between the dose of a substance and the magnitude of its effect on an organism. These models are crucial in understanding how different levels of exposure can lead to varying biological responses, enabling scientists to assess the risks associated with environmental contaminants and their impacts on wildlife health.
Effects assessment: Effects assessment refers to the process of evaluating the potential adverse impacts of a stressor on ecological systems, including both wildlife and their habitats. This evaluation plays a critical role in understanding how pollutants or other environmental stressors can affect organisms, populations, and communities within ecosystems. It integrates various lines of evidence to determine the severity and nature of effects, informing management and regulatory decisions.
Endocrine disrupting chemicals: Endocrine disrupting chemicals (EDCs) are substances that interfere with the normal functioning of hormones in the endocrine system, which regulates various physiological processes. These chemicals can mimic, block, or interfere with natural hormones, leading to adverse health effects in both wildlife and humans. The impact of EDCs is significant, particularly regarding sublethal effects that can alter behavior and reproduction in organisms, as well as their role in biomonitoring efforts to assess the health of ecosystems.
Environmental Fate Models: Environmental fate models are tools used to predict the behavior and distribution of chemical substances in the environment, factoring in processes like transport, transformation, and bioaccumulation. These models help researchers and environmental scientists assess how pollutants interact with wildlife and ecosystems, aiding in the understanding of potential toxic effects on various organisms over time.
Indicator Species: Indicator species are organisms whose presence, absence, or abundance reflects specific environmental conditions, serving as a measure of the health or quality of an ecosystem. These species can help detect changes in the environment, indicating pollution levels, habitat quality, and biodiversity status.
Lethal concentration: Lethal concentration refers to the specific amount of a toxic substance in a given volume of water that results in the death of a certain percentage of organisms within a specific time frame. This measurement is crucial for understanding the impact of pollutants on wildlife and helps in assessing the safety of aquatic environments, making it a key concept in wildlife toxicology and biomonitoring.
Mechanism of action: Mechanism of action refers to the specific biochemical interaction through which a substance, such as a chemical or toxin, produces its effects on living organisms. This includes understanding how a toxicant interacts at the molecular level, such as binding to receptors or enzymes, leading to physiological changes. In wildlife toxicology and biomonitoring, knowing the mechanism of action helps identify potential risks to animal populations and ecosystems, enabling better assessment of environmental health.
No Observed Effect Concentration: No observed effect concentration (NOEC) is the highest concentration of a substance in which there are no significant effects observed in a given organism or population compared to a control group. This term is vital in understanding the potential impacts of pollutants and chemicals on wildlife, allowing scientists to identify safe exposure levels and assess ecological risks.
Persistent Contaminants: Persistent contaminants are toxic substances that remain in the environment for extended periods without breaking down or degrading significantly. These contaminants can accumulate in the tissues of organisms and may biomagnify through food webs, leading to adverse effects on wildlife and ecosystems, especially when monitored over time.
Population-level effects: Population-level effects refer to changes in the characteristics of a population, such as size, distribution, or genetic diversity, that occur as a result of environmental stressors, including pollution and habitat alteration. These effects are important in understanding how contaminants impact wildlife and ecosystems, influencing species survival, reproductive success, and long-term population viability.
Secondary Poisoning: Secondary poisoning occurs when a predator or scavenger consumes prey that has accumulated toxic substances in its body, leading to harmful effects on the predator. This phenomenon highlights the interconnectedness of food webs and the potential for toxins to move through ecosystems. It underscores the importance of understanding how contaminants can affect not just individual species but entire populations and communities in an ecosystem.
Sentinel species: Sentinel species are organisms used to detect risks to humans by providing advance warning of danger through their health and behavior. These species are sensitive to environmental changes and pollutants, making them crucial for monitoring ecosystem health and assessing the impact of contaminants on wildlife and human health.
Toxic effects: Toxic effects refer to the adverse biological responses that occur when organisms are exposed to harmful substances, resulting in physiological, behavioral, or ecological changes. These effects can vary widely depending on factors such as the type of toxin, dose, duration of exposure, and the species affected. Understanding toxic effects is essential in wildlife toxicology and biomonitoring, as it helps assess the impact of pollutants on wildlife populations and ecosystems.
Wildlife toxicity tests: Wildlife toxicity tests are scientific assessments designed to evaluate the harmful effects of various pollutants and chemicals on wildlife species. These tests help determine the safety and environmental impact of substances by observing how they affect different organisms, which can indicate the potential risks to ecosystems. The results from these tests can inform regulatory decisions and conservation efforts aimed at protecting wildlife and their habitats.