CES Ecological Risk Assessment & Biodiversity 3 — Questions and Answers
Question 1: Which of the following stressors is considered a 'chemical stressor' in the ERA stressor characterization phase?
- Altered flow regime in a river
- Polychlorinated biphenyls (PCBs) in sediment (Correct answer)
- Invasive species introduction
- Deforestation causing habitat fragmentation
Correct answer: Polychlorinated biphenyls (PCBs) in sediment
PCBs are chemical contaminants that constitute a chemical stressor category in ERA, distinct from physical or biological stressors.
Question 2: Under the Endangered Species Act, which agency has jurisdiction over marine and anadromous species?
- U.S. Fish and Wildlife Service (USFWS)
- National Oceanic and Atmospheric Administration (NOAA) (Correct answer)
- U.S. Environmental Protection Agency (EPA)
- Bureau of Land Management (BLM)
Correct answer: National Oceanic and Atmospheric Administration (NOAA)
NOAA Fisheries (NMFS) has ESA jurisdiction over marine mammals and anadromous fish, while USFWS covers terrestrial and freshwater species.
Question 3: A bioaccumulation factor (BAF) differs from a bioconcentration factor (BCF) in that BAF:
- Is measured only in laboratory settings
- Includes dietary and waterborne exposure routes (Correct answer)
- Applies only to sediment-bound contaminants
- Is always lower than BCF for lipophilic compounds
Correct answer: Includes dietary and waterborne exposure routes
BAF reflects accumulation from all exposure routes including diet, while BCF is measured only from waterborne exposure in lab settings.
Question 4: The concept of 'umbrella species' in conservation biology refers to a species whose protection:
- Covers the habitat needs of many other co-occurring species (Correct answer)
- Acts as an early warning indicator of ecosystem degradation
- Provides economic justification for conservation funding
- Controls populations of prey species across multiple trophic levels
Correct answer: Covers the habitat needs of many other co-occurring species
Umbrella species have large habitat requirements such that protecting them simultaneously protects many other species within their range.
Question 5: In the Habitats Directive (EU), 'favorable conservation status' for a species requires all EXCEPT which of the following?
- Population dynamics indicate long-term viability
- Natural range is not declining
- Sufficient habitat exists to maintain populations long-term
- The species is present in every member state (Correct answer)
Correct answer: The species is present in every member state
Favorable conservation status requires stable/expanding population, adequate habitat, and stable range — but not presence in every EU member state.
Question 6: Which mathematical model is commonly used to describe logistic population growth in ERA population-level risk assessments?
- Lotka-Volterra competition model
- Leslie matrix model
- Verhulst logistic equation (Correct answer)
- Ricker stock-recruitment model
Correct answer: Verhulst logistic equation
The Verhulst logistic equation (dN/dt = rN[(K-N)/K]) models density-dependent population growth approaching carrying capacity (K).
Question 7: During ERA problem formulation, a conceptual site model (CSM) primarily serves to:
- Quantify contaminant concentrations in environmental media
- Illustrate exposure pathways linking stressors to ecological receptors (Correct answer)
- Establish cleanup standards for contaminated sites
- Determine the statistical approach for data analysis
Correct answer: Illustrate exposure pathways linking stressors to ecological receptors
The CSM visually depicts the relationships among stressor sources, exposure pathways, and ecological receptors to guide the risk assessment.
CES Ecological Risk Assessment & Biodiversity 3
Which of the following stressors is considered a 'chemical stressor' in the ERA stressor characterization phase?