Stressors and Pollutants

Biological impairments can be caused by altered habitats or impacts from other organisms. Linking biological effects with their causes is particularly complex when multiple stressors impact a waterbody. Investigation procedures are needed that can successfully identify the stressor(s) and lead to appropriate corrective measures through habitat restoration, point and non-point source controls, or invasive species control.

Flow

(1) The movement of water. (2) The rate of water discharged from a source given in volume with respect to time.

Hydrologic Impacts

Hydrologic impacts due to urbanization are reported to cause water quality problems such as sedimentation, increased temperatures, habitat changes, and the loss of fish populations. These problems are caused by increased runoff volumes and velocities from urbanization and associated increases in watershed imperviousness, but much of the reported information has been anecdotal.
http://www.epa.gov/OWOW/NPS/urbanize/report.html#03

Invasive Species

The term "invasive species" can refer to any plants, animals, or other viable biological material that enter an ecosystem beyond its historic range. Other terms include: "alien species," "invasive species," "nonnative species," "aquatic nuisance species," "introduced species," "exotic organisms," "xenobiotic organisms," and probably other terms as well. Invasive species can successfully invade any terrestrial or aquatic ecosystem, and may enter through a wide variety of introduction mechanisms. Human activities, both intentional and non-intentional, are the chief cause of invasive species introductions. http://www.epa.gov/owow/invasive_species/

Mercury

Mercury (Hg): Heavy metal that can accumulate in the environment and is highly toxic if breathed or swallowed. (See: metals.)

Metals

Metallic elements with high atomic weights (heavy metals - e.g., arsenic, chromium, cadmium, lead, mercury, nickel and zinc). Although many are necessary nutrients, these metals can damage living things at low concentrations, tend to accumulate in the food chain and can be toxic to life in high concentrations.

Multiple Pollutants

Many of EPA's exposure analyses and risk assessments focus on a single pollutant, a single source or category of emissions, or a single environmental medium (such as water). In reality, people tend to be exposed through multiple pathways to numerous pollutants originating from a variety of sources. Multiple pollutants may have cumulative impacts.

Nonpoint Sources

Diffuse pollution sources (i.e., without a single point of origin or not introduced into a receiving stream from a specific outlet). The pollutants are generally carried off the land by stormwater. Common nonpoint sources are agriculture, forestry, urban, mining, construction, dams, channels, land disposal, saltwater intrusion, and city streets.
http://www.epa.gov/owow/nps/index.html

Nutrients

Any substance that is assimilated (taken in) on organisms and promotes growth. Nutrients of concern for water bodies are typically nitrogen and phosphorous; one is often the "limiting nutrient" and limiting its discharge can reduce nuisance growth of algae, other micro-organisms or rooted aquatic growth.
http://www.chesapeakebay.net/stressor1.htm

Pathogens

A disease-causing microorganism. A disease-producing agent; usually applied to a living organism. Generally, any viruses, bacteria, or fungi that cause disease.

Pesticides

Any substance or chemical designed or formulated to kill or control weeds or animal pests.
http://www.epa.gov/compliance/
http://www.epa.gov/oppbead1/methods/

pH

A measure of the relative acidity or alkalinity of water. Water with a pH of 7 is neutral; lower pH levels indicate increasing acidity, while pH levels higher than 7 indicate increasingly basic solutions.

Point Sources

Any discernible confined and discrete conveyance, including, but not limited to, any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding operation, landfill leachate collection system, vessel, or other floating craft from which pollutants are or may be discharged. This term does not include return flows from irrigated agriculture or agricultural stormwater runoff.
http://cfpub2.epa.gov/npdes/

Salinity

The relative concentration of dissolved salts, usually sodium chloride, in a given water. A measure of the concentration of dissolved mineral substances in water.

Sediment

Usually applied to material in suspension in water or recently deposited from suspension. In the plural the word is applied to all kinds of deposits from the waters of streams, lakes, or seas. The problems associated with sediment can be two fold, i.e . Sediments can carry other pollutants, e.g. nutrients, biochemical oxygen demand (BOD) or toxic metal and organic concentrations, hence the term contaminated sediments. Sediment transport can smother benthic communities and change the sediment oxygen demand (SOD).
http://www.chesapeakebay.net/stressor1.htm

Suspended Solids

Suspended solids are not in true solution and can be removed by filtration or settling. Such solids usually contribute directly to turbidity. These small particles resist separation by conventional methods.

Water Temperature

From a water quality engineering point of view, the temperature of a body of water is of particular significance for three principal reasons: (a) the discharge of excess heat from industrial or municipal effluents may positively or negatively affect the aquatic ecosystem, (b) temperature influences all biological and chemical reactions, and (c) variations in temperature affect the density of water and hence the transport of water (Thomann and Mueller, 1987).

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