Aquatic 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)

References

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