Streams Glossary

A

Aerobic

Living in the presence of oxygen. Most organisms are aerobic and must have oxygen available in order to survive.

Algae

Mostly aquatic, non-vascular plants that float in the water or attach to larger plants, rocks, and other substrates. Also called phytoplankton when floating in the water, these individuals are usually visible only with a microscope. They are a normal and necessary component of aquatic life, but excessive numbers can make the water appear cloudy and colored, which may discourage human use./p>

Alkalinity

The acid-neutralizing or buffering capacity of water. It is primarily a function of the carbonate, bicarbonate, and hydroxide content in water. The lower the alkalinity, the less capacity the water has to absorb acids without lowering pH, becoming more acidic.

Ammonia - NH3

A nitrogen-containing substance which may indicate recently decomposed plant or animal material.

Anaerobic

Living in the absence of oxygen. Some bacteria can survive and grow without oxygen present.

Anoxic

No oxygen present in the system; see anaerobic.

Average

The sum of a group of numbers divided by the total number of values in the group.

B

Benthic

Bottom area of the lake which hosts the community of organisms (benthos) that live in or on the sediment.

Benthic invertebrates

See Invertebrates.

Benthos

The communities of aquatic life which dwell in or on the bottom sediments of a water body.

Blue-green algae 

See Cyanobacteria.

C

Catchment Basin

See Watershed.

Chlorophyte (algae)

Bright green algae that occur in lakes as plankton, as well as forming tangled masses of filaments coming up from the lake bottom or near shorelines. This group does especially well in warm water and bright light and is usually abundant in summer. The species are very diverse, including several that look more like grassy aquatic plants than algae. One chlorophyte species, Botryococcus, turns bright orange under certain conditions, but is not toxic like the marine red tides.

Combined sewer overflow (CSO)

Discharges of combined sewage and stormwater into water bodies during very wet or storm weather. These discharges occur to relieve the sewer system as it becomes overloaded with normal sewer flow and increased storm run-off. The term is also used to denote a pipe that discharges those overflows.

Concentration

The amount of one substance in a given amount of another substance, such as the weight of a chemical in a liter of water or the number of animals in a cubic meter of space.

Conductivity

A measure of water's capacity to convey an electric current. It is related to the total amount of dissolved charged substances in the water. Therefore, it can be used as one general indicator of water quality. It is often used as a surrogate for salinity measurements.

Cyanobacteria

Bacteria living in lakes and streams that make their own food instead of decomposing dead organisms and are very similar to freshwater algae in lake ecosystems. Many cyanobacteria grow especially well in lakes with high phosphorus content and are sometimes used as indicators of change due to human impacts through watershed development. Several species can make toxins dangerous to humans and other mammals if ingested. High concentrations of these cells in the water can result in closure of lakes to recreation or domestic use of water, although this has been relatively rare in occurrence historically.

D

Dissolved Oxygen - DO

Oxygen that is dissolved in the water. Certain concentrations are necessary for life processes of aquatic animals. The oxygen is supplied by the photosynthesis of plants, including algae, and by aeration through contact of the surface water with the atmosphere and mixing. Oxygen is consumed by animals and plants at night when photosynthesis cannot take place, as well as bacterial decomposition of dead organic matter (plant matter and animal waste).

E

Ecosystem

Any complex of living organisms, along with all other factors that affect them and are affected by them. This includes plants, animals, the nutrients that sustain them, and all of the other environmental conditions necessary for successful maturation and reproduction.

Effluent

Liquids discharged from sewage treatment plants, septic systems, or industrial sources to surface waters.

Escherichia coli - E coli

A type of fecal coliform bacteria that lives in the intestines of humans and animals. While some strains of E. coli are harmless, others can cause illness if they are ingested, especially through contaminated food or water. They are counted as indicators of the possible presence of harmful bacteria. E. coli is generally regarded as a better indicator of fecal pollution than the broader group of fecal coliforms./p>

Eutrophication

The physical, chemical, and biological changes associated with enrichment of a body of freshwater due to increases in nutrients from a variety of sources.

F

Fecal coliform bacteria

Bacteria from the intestines of warm-blooded animals. Most of the bacteria are not in themselves harmful, but they are measured or counted as indicators of the possible presence of harmful bacteria.

G

Green Algae

See Chlorophyte (algae)

Groundwater

Water located and moving beneath the surface of the earth. The water in the ground is supplied by the seepage (percolation) of rainwater, snowmelt, and other surface water into the soil. Some groundwater may be found far beneath the earth surface, while other groundwater may be only a few inches from the surface. Groundwater discharges into lowland streams at a relatively constant rate, which maintains their baseflow during periods of dry weather such as Pacific Northwest summers.

H

Hydrology

The science dealing with the properties, distribution and circulation of water. The term usually refers to the flow of water on or below the land surface before reaching a stream or lake.

L

Limiting nutrient

The nutrient that is in lowest supply relative to the demand. The limiting nutrient will be the one that is exhausted first by algae, which require many different nutrients and light to grow. Increasing the amount of the limiting nutrient will result in increased algal production, but as soon as the limiting nutrient is exhausted, growth stops. Phytoplankton growth in lake waters of temperate lowland areas is generally phosphorus limited.

Limnology

The study of lakes and inland waters as ecosystems.

Loading

The total amount of material (sediment or nutrients) entering a water body via streams, overland flow, precipitation, direct discharge, or other means over time (usually considered annually). Recycling of nutrients among sediment, organisms and water is sometimes referred to as “internal loading.”

Loading rate

The rate at which of a substance is added to a water body. For example, streams add nutrients to lakes at various loading rates as in "500 kilograms per year (500 kg/yr)" or "227 pounds per year (227 lb/yr)."

M

Macrophytes

Rooted and floating aquatic plants, larger (macro-) than the phytoplankton and most often belonging to the higher, vascular plant groups./p>

Mean

A representative value for a group derived by summing a group of numbers and dividing by the total number of values in the group. See average.

Median

The datum in a set of numbers that represents the exact center of the group: half of the numbers are smaller and the other half are larger.

N

Nitrate, Nitrite (NO₃, NO₂)

Two types of nitrogen compounds. These nutrients are forms of nitrogen that algae may use for growth.

Nitrogen

One of the elements essential as a nutrient for growth of organisms. Nitrogen is most abundant on the earth in the form of N₂, comprising 80% of the atmosphere, but is usually taken up by plants in the forms NO₃, NO₂ and NH₃.

Non-point source pollution

Pollution from diverse sources difficult to pinpoint as separate entities and thus more complicated to control or manage. Examples of “nonpoint sources” include area-wide erosion (as opposed to landslides or mass wasting), widespread failure of septic systems, certain practices or forestry practices, and residential/urban land uses (such as fertilizing lawns or landscaping).

Nutrients

Any chemical element, ion, or compound required by an organism for growth and reproduction.

P

Pathogens

Microorganisms that can cause disease in other organisms or humans, animals, and plants. Pathogens include bacteria, viruses, fungi, or parasites found in sewage, in runoff from farms or city streets, and in water used for swimming. Pathogens can be present in municipal, industrial, and nonpoint source discharges.

pH

Measure of the acidity of water on a scale of 0 to 14, with 7 representing neutral water. A pH less than 7 is considered acidic and above 7 is basic, also sometimes called alkaline.

Phosphorus

One of the elements essential as a nutrient for the growth of organisms. In western Washington lakes, it is usually the nutrient in shortest supply relative to the needs of the algae (also referred to as the limiting nutrient). Phosphorus occurs naturally in soils, as well as in organic material. Various measures of phosphorus in water samples are made, including total-phosphorus (TP) and the dissolved portion of phosphorus-containing molecules (orthophosphate).

Photosynthesis

The production of organic matter (carbohydrates) from inorganic carbon and water, utilizing the energy of light. In general, plants are equipped to carry out this process, while animals cannot.

Phytoplankton

Free floating microscopic organisms that photosynthesize (includes both algae and cyanobacteria).

Point-source pollution

An input of pollutants into a water body from discrete sources, such as municipal or industrial outfalls.

Primary treatment

The first stage of wastewater treatment involving removal of debris and solids by screening and settling.

Productivity

The production and accumulation of organic matter, usually measured over a certain period of time.

Pump station

A structure used to move wastewater uphill, against gravity.

S

Salmonids

Salmon, trout, char and whitefish species of fish belonging to the taxonomic family Salmonidae./p>

Secondary treatment

Following primary treatment, bacteria are used to consume organic wastes. Wastewater is then disinfected and discharged through an outfall. Nutrient concentrations are not decreased with secondary treatment.

Sediment

Solid material deposited in the bottom of a lake over time, carried in by wind and water inputs, as well as that produced in the lake by plants and animals.

Sewage

That portion of wastewater that is composed of human and industrial wastes from homes, businesses, and industries./p>

Standard

A legally established allowable limit for a substance or characteristic in the water, based on measurable criteria. Enforcement actions by the appropriate agencies can be taken against parties who cause violations.

Stormwater

Water that is generated by rainfall and is often routed into drain systems.

T

Total suspended solids (TSS)

Particles, both mineral (clay and sand) and organic (algae and small pieces of decomposed plant and animal material), that are suspended in water.

Toxic

Causing death, disease, cancer, genetic mutations, or physical deformations in any organism or its offspring upon exposure, ingestion, inhalation, or assimilation.

Turbidity

Cloudiness in water caused by the suspension of tiny particles (algae or detritus).