Algae (phytoplankton): Simple, rootless plants that grow in bodies of water in relative proportion to the amounts of nutrients available. Blue-green algae are primitive algae, typically found in water high in phosphorus that form scum blooms that congregate at the water's surface. Diatoms are algae that have silica in their cell walls.
Algal Bloom: An unusual or excessive abundance of algae.
Bacteria: Single celled organisms having no cellular nucleus. Pathogenic bacteria are capable of causing disease. Coliform bacteria are prolific in the intestines of warm blooded animals and are used as an indicator of fecal waste pollution.
Bioaccumulation: Build-up of toxic substances through the food chain. The result of bioaccumulation is contaminants found at higher concentrations in predators. A concern exists with build-up in fish tissues and passing the toxins on to human and other animal consumers.
Chlorophyll-a: The primary photosynthetic pigment in plants, used to measure the concentration of algae in lakes.
Clean Water Act: The Federal Water Pollution Control Act of 1948, amended beginning in 1956 to become the Federal Water Pollution Control Act of 1972. Congress passed the original Clean Water Act in 1972 and amended it with the Water Quality Act of 1987. The major impact of the 1987 amendments was to include a permitting process and requirements for municipal storm water discharges.
Clean Water Partnership Program: Program administered by the Minnesota Pollution Control Agency to improve water quality by providing matching funds and technical assistance to local units of government.
Combined Sewer Overflow (CSO): A system of combined sanitary and storm sewers that directs effluent to a sewage treatment plant during low flows. During rain events excess storm water and sewage is diverted away from the treatment plant to a river or stream. In the late 1940's Minneapolis embarked on a 40year $160 million Combined Sewer Overflow project to guarantee treatment of all sanitary flow and prevent untreated sewage from entering surface waters.
Detention basin: Impoundments constructed to retain storm water for extended periods of time and allow for the retention of pollutants in the pond through deposition of sediments and attached pollutants.
Ecoregion: An environmental area characterized by a specific land use, soil type, land surface form and natural vegetation.
Erosion: The wearing away of land surface by water or wind which occurs naturally from weather or runoff, but is often intensified by human activities.
Eutrophic Lake: A nutrient-rich lake - usually shallow with large amounts of algae or rooted plants and with limited oxygen in the bottom layer of water.
Eutrophication: The aging process by which lakes are fertilized with nutrients. Natural eutrophication changes the character of a lake very gradually. Cultural eutrophication is the accelerated aging of a lake resulting from human activities.
Impervious Surface: Waterproof ground cover that does not allow for infiltration of water (e.g., roofs, parking lots, roads) and which increases the volume and speed of runoff after a rainfall.
Internal Cycling: Transformation of nutrients such as nitrogen or phosphorus from biological to inorganic forms through decomposition, occurring within the lake itself. Most often refers to movement of nutrients from lake sediments into lake water due to chemical processes.
Limnology: Scientific study of fresh water, especially the history, geology, biology, physics and chemistry of lakes. Also termed freshwater ecology.
Loading: The total amount of material (sediment, nutrients and oxygen-demanding material) brought into a lake by inflowing streams, runoff, direct discharge through pipes, groundwater, the air (aerial or atmospheric load) and other sources over a specific period of time (often annually).
Mesotrophic: Lake condition in which nutrient levels are between eutrophic and oligotrophic levels. A mesotrophic lake has fairly good water quality and may be used for recreational activities.
National Pollutant Discharge Elimination System (NPDES): Created in 1972 under the Clean Water Act to authorize discharges to local receiving waters only pursuant to government permits, in an effort to reduce point source pollutants.
Nationwide Urban Runoff Program (NURP): An US EPA program aimed at characterizing the composition of storm water runoff and its impacts upon receiving waters and assessing best management practices. The program was undertaken in 28 US cities in the early 1980s.
Nonpoint Source: Nutrient and pollution sources not discharged from a single point, e.g. runoff from agricultural fields, feedlots or urban streets.
Nutrient Budget: Quantitative assessment of nutrients (e.g., nitrogen or phosphorus) moving into, being retained in, and moving out of an ecosystem; commonly constructed for phosphorus because of its tendency to control lake trophic status.
Nutrient: Elements or compounds essential to growth and development of living things (e.g., nitrogen, potassium, phosphorus).
Oligotrophic Lake: A relatively nutrient-poor lake, typically clear and deep with bottom water high in dissolved oxygen.
Parts Per Billion (ppb): One pound per billion pounds of water.
Parts Per Million (ppm): A common basis of reporting water analysis. One part per million (ppm) equals one pound per million pounds of water.
Pollution: The process of contaminating air, water and land with impurities to a level that is undesirable and results in a decrease in usefulness of the environment for beneficial purposes.
Retention Time: The length of time water, nutrient, or other chemical substances remain in a lake.
Secchi Disk: A device used to measure the depth of light penetration in water.
Trace metals: Inorganic chemical compounds normally found in low concentrations in the natural environment. Include such elements as lead, mercury, arsenic, cadmium, chromium and selenium.
Trophic State Index (TSI): The trophic state index was developed in 1977 to provide a convenient measure of water quality. The scale is 1 to 100 and uses the three parameters of total phosphorus, chlorophyll a and Secchi disk depth to categorize lake water quality.
Trophic Status: The level of growth or productivity of a lake as measured by phosphorus content, algae abundance, and depth of light penetration.
Water Budget: The movement of water into and out of a lake as described by a balance equation in which the change in storage of water equals the rate of inflow from all sources minus the rate of loss.
Water Quality: A state of lake water represented by a combination of productivity, chemistry, cleanliness and recreational potential.
Watershed: The surrounding land area that drains into a lake, stream, river or river system.
Wetlands: Low-lying areas inundated or saturated by water at a frequency and duration sufficient to support wetland vegetation (e.g. wetlands include such areas as swamps, marshes and wet meadows). Wetlands remove pollutants through a series of chemical, physical and biological mechanisms.
Zooplankton: Microscopic animals that float freely in lake water, graze on detritus particles, bacteria and algae, and may be consumed by fish. Daphnia are a large (2mm in size) zooplankter that can consume large amounts of algae.