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CADDIS Volume 1

Aquatic Stressors that Can Potentially Cause Biological Impairment

Stressors that Can Potentially Cause Biological Impairment

  • Dissolved oxygen (DO) regime alteration
  • Hydrologic regime alteration (includes flow or depth conditions; timing, duration, frequency, etc.)
  • Nutrient regime alteration
  • Organic-matter regime alteration
  • pH regime alteration
  • Salinity regime alteration
  • Bed sediment load changes, including siltation
  • Suspended solids and/or turbidity alteration
  • Water temperature regime alteration
  • Habitat destruction
  • Habitat fragmentation (e.g., barriers to movement, exclusion from habitat)
  • Physical crushing and trampling
  • Toxic substances
    • Herbicides and fungicides
    • Halogens and halides (e.g., chloride, trihalomethanes)
    • Fish-killing agents (e.g., rotenone)
    • Insecticides
    • Lampricides
    • Metals
    • Molluscicides
    • Organic solvents (e.g., benzene, phenol)
    • Other hydrocarbons (e.g., dioxins, PCBs)
    • Endocrine disrupting chemicals
    • Mixed, cumulative effect
  • Interspecies competition
  • Complications due to small populations (e.g., inbreeding, stochastic fluctuation, etc.)
  • Genetic alteration (e.g., hybridization)
  • Overharvesting or legal, intentional collecting or killing
  • Parasitism
  • Predation
  • Poaching, vandalism, harassment, or indiscriminate killing
  • Unintentional capture or killing (e.g., artillery explosions, roadway casualties)
  • Vertebrate animal damage control (includes trapping, shooting, poisoning)
  • Radiation exposure increase (e.g., increased UV radiation)


  • Adapted from Richter BD, Braun OP, Mendelson MA, Master LL (1997) Threats to imperiled freshwater fauna. Conservation Biology 11:1081-1093.

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