Glossary
Acclimation - response by an animal that enables it to tolerate a change in a single factor (e.g. temperature) in its environment.
Adaptation - adjustments made by animals in respect of their environments. The adjustments may occur by natural selection, as individuals with favorable genetically acquired traits breed more prolifically than those lacking these traits (genotypic adaptation), or they may involve non-genetic changes in individuals, such as physiological modification (e.g. acclimatization) or behavioral changes (phenotypic adaptation).
Algal biomass - The weight of living algal material in a unit area at a given time (Wetzel 1983).
Allochthonus - An organism or substance foreign to a given ecosystem (Atlas and Bartha 1993); describes organic matter reaching an aquatic community from the outside in the form of organic detritus or organic matter adsorbed to sediment (Wetzel 1983).
Anion – a negative ion, i.e., an atom, or complex of atoms, that has gained one or more electrons and thereby carries a negative electric charge (e.g., Cl -, OH -, and 
. It is so called because when an electric current is passed through a conducting solution the negative ions present in the solution are attracted to the anode (the positive electrode).
Aquatic Assemblage - an organism group of interacting populations in a given waterbody, for example, fish assemblage or an algal assemblage.
Aquatic Biota - collective term describing the organisms living in or depending on the aquatic environment.
Aquatic Community - association of interacting assemblages in a given waterbody, the biotic component of an ecosystem (see also aquatic assemblage).
Aquatic Life Use - a beneficial use designation in which the waterbody provides suitable habitat for survival and reproduction of desirable fish, shellfish, and other aquatic organisms.
Ash-free Dry Weight - An algal biomass measurement that measures the standing crop of algae to estimate net production (APHA 2000).
Attribute - a measurable component of a biological system.
Autochthonus - Microorganisms and/or substances indigenous to a given ecosystem; the true inhabitants of an ecosystem; refering to the common nicrobiota of the body or soil microorganisms that tend to remain constant despite fluctuations in the quantity of fermentable organic matter (Atlas and Bartha 1993); describes organic matter originating within a waterbody / aquatic community (Wetzel 1983).
Authotrophic Index (AI) - A means of determining the trophic nature of the periphyton community; calculated by dividing the biomass (ash-free weight of organic matter) by chlorophyll a. High AI values indicate heterotrophic associations or poor water quality (APHA 2000).
Benthos/benthic - The assemblage of organisms associated with the bottom, or the solid-liquid interface of the aquatic system. Generally applied to organisms in the substrata (Wetzel 1983).
Biocriteria - (biological criteria) Narrative or numeric expressions that describe the desired biological condition of aquatic communities inhabiting particular types of waterbodies and serve as an index of aquatic community health. (USEPA 1994).
Biodiversity - Refers to the variety and variability among living organisms and the ecological complexes in which they occur. Diversity can be defined as the number of different items and their relative frequencies. For biological diversity, these items are organized at many levels, ranging from complete ecosystems to the biochemical structures that are the molecular basis of heredity. Thus, the term encompasses different ecosystems, species, and genes.
Biological Integrity - the ability of an aquatic ecosystem to support and maintain a balanced, adaptive community of organisms having a species composition, diversity, and functional organization comparable to that of natural habitats within a region.
Biological Monitoring or Biomonitoring - use of a biological entity as a detector and its response as a measure to determine environmental conditions. Toxicity tests and ambient biological surveys are common biological monitoring methods.
Biological Oxygen Demand (BOD) - Oxygen required to break down organic matter and to oxidize reduced chemicals (in water or sewage) (APHA 2000).
Biological Survey or Biosurvey - collecting, processing, and analyzing a representative portion of the resident aquatic community to determine its structural and/or functional characteristics.
Cation – An ion that carries a positive electrical charge (e.g., the metallic element of salt compounds). A cation can combine with certain anions (which have negative charges).
Clean Water Act (CWA) - An act passed by the U.S. Congress to control water pollution (formerly referred to as the Federal Water Pollution Control Act of 1972). Public Law 92-500, as amended. 33 U.S.C. 1251 et seq.
Clean Water Act Section 303(d) - annual report to Congress from EPA that identifies those waters for which existing controls are not sufficiently stringent to achieve applicable water quality standards.
Clean Water Act Section 305(b) - biennial reporting requires description of the quality of the Nation's surface waters, evaluation of progress made in maintaining and restoring water quality, and description of the extent of remaining problems by using biological data to make aquatic life use support decisions.
chlorophyll a - A complex molecule composed of four carbon-nitrogen rings surrounding a magnesium atom; constitutes the major pigment in most algae and other photosynthetic organisms; is used as a reliable index of algal biomass (Darley 1982).
Cladophora - A common nuisance filamentous green alga (Dodds et al. 1997).
Community - all the groups of organisms living together in the same area, usually interacting or depending on each other for existence.
Community metabolism - The relationship between gross community production and total community respiration (Odum 1963).
Criteria - statements of the conditions presumed to support or protect the designated use or uses of a waterbody. Criteria may be narrative or numeric.
Cultural enrichment - Human activities that result in increased nutrient loads to a waterbody.
Density-Dependence - regulation of the size of a population by mechanisms that are themselves controlled by the size of that population (e.g. the availability of resources) and whose effectiveness increases as population size increases.
Designated Use - classification specified in water quality standards for each waterbody or segment describing the level of protection from perturbation afforded by the regulatory programs. The designated aquatic life uses established by the state or authorized tribes set forth the goals for restoration and/or baseline conditions for maintenance and prevention from future degradation of the aquatic life in specific waterbodies.
Detritus - Unconsolidated sediments comprised of both inorganic and dead and decaying particulate organic matter inhabited by decomposer microorganisms (Wetzel 1983).
Diatom - microscopic algae with cell walls made of silicon and have two separating halves.
Ecological Integrity - the condition of an unimpaired ecosystem as measured by combined chemical, physical (including physical habitat), and biological attributes.
Ecoregions - a relatively homogeneous ecological area defined by similarity of climate, landform, soil, potential natural vegetation, hydrology, or other ecologically relevant variables (see also bioregions).
Eutrophic - Abundant in nutrients and having high rates of productivity frequently resulting in oxygen depletion below the surface layer (Wetzel 1983).
Eutrophication - The increase of nutrients in [waterbodies] either naturally or artificially by pollution (Goldman and Horne 1983).
Existing uses - The use that has been achieved for a waterbody on or after November 28, 1975 (USEPA 1994).
Flowpath - Conveys water between points in the stream system. Examples of flow paths are a stream channel, canal, storm sewer, or reservoir (http://il.water.usgs.gov/proj/feq/feqdoc/chap3_1.html).
Habitat - a place where the physical and biological elements of ecosystems provide a suitable environment including the food, cover, and space resources needed for plant and animal livelihood.
Heterotrophic - Describes organisms that need organic compounds to serve as a source of energy for growth and reproduction (Atlas and Bartha 1993).
Historical Data - data sets from previous studies, which can range from handwritten field notes to published journal articles.
Hypolimnetic - Characteristic of the hypolimnion, the deep, cold, relatively undisturbed stratum of a lake (Wetzel 1983).
Hydrologic Unit Codes - An 8-digit code, determined by the U.S. EPA, that is used as a standard method for watershed identification throughout the United States.
Hyporheic zone - The subsurface zone where stream water flows through short segments of its adjacent bed and banks (Winter et al. 1998).
Impact - change in the chemical, physical (including habitat) or biological quality or condition of a waterbody caused by external sources.
Impairment - detrimental effect on the biological integrity of a waterbody caused by an impact that prevents attainment of the designated use.
Lentic - Relatively still-water environment (Goldman and Horne 1983).
Lotic - Running-water environment (Goldman and Horne 1983).
Macrophyte - (also known as SAV-Submerged Aquatic Vegetation) Larger aquatic plants, as distinct from the microscopic plants, including aquatic mosses, liverworts, angiosperms, ferns, and larger algae as well as vascular plants; no precise taxonomic meaning (Goldman and Horne 1983).
Macroinvertebrate - Small benthic organisms which are retained on sieves with a mesh size >2 mm (Thorp and Covich 1991).
Mesotrophic - Having a nutrient loading resulting in moderate productivity (Wetzel 1983).
Metric - A calculated term or enumeration representing some aspect of biological assemblage, function, or other measurable aspect and is a characteristic of the biota that changes in some predictable way with increased human influence. A multimetric approach involves combinations of metrics to provide an integrative assessment of the status of aquatic resources.
Minimally Impaired - sites or conditions with slight anthropogenic perturbation relative to the overall region of the study.
Morphological characteristics - The morphological characteristics of a waterbody are the characteristics that comprise the shape of the waterbody. In stream systems, morphology usually refers to the shape of the stream channel.
Multimetric - analysis techniques using several measurable characteristics of a biological assemblage.
Multivariate Community Analysis - statistical methods (e.g. ordination or discriminant analysis) for analyzing physical and biological community data using multiple variables.
Narrative Biological Criteria - general statements of attainable or attained conditions of biological integrity and water quality for a given designated aquatic life use.
Nitrogen (N) – an element that is essential to all plant and animal life. It is found reduced and covalently bound in many organic compounds, and its chemical properties are especially important in the structures of proteins and nucleic acids.
Nitrogen Cycle – a description of the balance, changes, and nature of the nitrogen-containing compounds circulating between the atmosphere, the soil, and living matter.
Nitrogen Fixation – the reduction of gaseous molecular nitrogen and its incorporation into nitrogenous compounds.
Non-Point Source Pollution - pollution that occurs when rainfall, snowmelt, or irrigation runs over land or through the ground, picks up pollutants, and deposits them into rivers, lakes, and coastal waters or introduces them into ground water.
NPDES - National Pollutant Discharge Elimination System. The EPA program that regulates point source discharges through the issuance of permits to discharges and enforcement of the terms and conditions of those permits.
Numeric Biocriteria - numerical indices that describe expected attainable community attributes for different designated aquatic life uses.
Nutrient Cycle – a biogeochemical cycle, in which inorganic nutrients move through the soil, living organisms, air, and water, or through some of these (e.g., nitrogen as NO 3 and NO 4, etc.). The use of the term ‘mineral’ can cause confusion because although some nutrients (e.g., potassium, magnesium, etc.) are derived originally from minerals in the strict sense, minerals are involved in the cycle only as sources of replenishment.
Oligotrophic - Trophic status of a waterbody characterized by a small supply of nutrients (low nutrient release from sediments), low production of organic matter, low rates of decomposition, oxidizing hypolimnetic condition (high DO) (Wetzel 1983).
Parafluvial - Sediments within the active channel, outside the wetted stream; lateral sandbars (Holmes et al. 1994).
Periphyton - Associated aquatic organisms attached or clinging to stems and leaves of rooted plants or other surfaces projecting above the bottom of a water body (USEPA 1994).
Phosphorus (P) – An element that is an essential nutrient for all living organisms. Plants require it in the oxidized form, as orthophosphate 
. The growth of phosphorus-deficient plants is usually reduced and their leaves become dark green or blue-green and a reddish pigment may develop.
Point Source - origin of a pollutant discharge from a discrete conveyance typically thought of as an effluent from the end of a pipe.
Population - aggregate of individuals of a biological species that are geographically isolated from other members of the species and are actually or potentially interbreeding.
Primary production - Quantity of new organic matter created by photosynthesis or chemosynthesis, or stored energy which that material represents (Wetzel 1983).
Probability sampling - A sampling process wherein randomness is a requisite (Hayek 1993).
Production/respiration ratio - The primary production to respiration ratio is a measure of community or whole system metabolism. This measurement can be used to assess ecosystem health and determine if the system is heterotrophically or autotrophically dominated.
Q10 - The estimated discharge of ten year flood (USEPA 1994).
Random sampling - Generic type of probability sampling, randomness can enter at any stage of the sampling process (Hayek 1993).
RTAG (Regional Technical Assistance Group) - Group of technical experts assembled at the EPA Regional level to assist in establishing criteria for States, Tribes and nutrient ecoregions.
Reference Condition - set of selected measurements or conditions of unimpaired or minimally impaired waterbodies characteristic of a waterbody type in a region.
Reference Site - specific locality on a waterbody which is unimpaired or minimally impaired and is representative of the expected biological integrity of other localities on the same waterbody or nearby waterbodies.
Regionalization or Ecoregionalization - procedure for subdividing a geographic area into regions of relative homogeneity in ecological systems or in relationship between organisms and their environment.
Riparian - Riverside , usually referring to vegetation (riparian vegetation) (Goldman and Horne 1983).
Secchi disk - A white or black and white disk used to measure transparency of a waterbody. The Secchi disk transparency is measured as the mean depth of the point where a weighted white (or black and white) disk, 20 cm in diameter, disappears when viewed from the shaded side of a vessel, and that point where the disk reappears upon raising it after it has been lowered beyond visibility (Wetzel 1983).
Secondary production - New organic material created by an organism that uses organic substrates (i.e. uses material from primary producers) (Wetzel 1983).
Seston/sestonic - organic matter suspended in the water column generally comprised of phytoplankton, bacteria and fine detritus (Thorp and Covich 1991).
STORET - EPA’s computerized water quality database that includes physical, chemical, and biological data measured in water bodies throughout the United States (USEPA 1994).
Stratification, stratified random sampling - Type of probability sampling where a target population is divided into relatively homogenous groups or classes (strata) prior to sampling based on factors that influence variability in that population (Hayek 1993). In stratified sampling, a heterogenous environment is divided into homogenous strata or parts. Analysis of variance can be used to identify statistically different parameter means among the sampling strata or classes. The strata are the analysis of variance treatments ( Poole 1972).
Stressors - physical and biological factors that adversely affect aquatic organisms.
Taxa - a grouping of organisms given a formal taxonomic name such as species, genus, family, etc.
Total Maximum Daily Loads (TMDLs) - calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards and an allocation of that amount to the pollutant's source.
Trophic – pertaining to nutrition.
Trophic state - The trophic status of a waterbody (Carlson 1977).
Turbidity - Cloudiness or opaqueness of a suspension. In our context, refers to the amount of suspended matter in the water column, usually measured in nephelometric turbidity units (NTUs) (Atlas and Bartha 1993).
TVSS (Total Volatile Suspended Solids) - Volatile particulate matter suspended in the water column.
Use Attainability Analysis (UAA) - analysis that describes factors limiting designated use of waterbodies.
Watershed - The area of land that drains water, sediment, and dissolved materials to a common outlet at some point along a stream channel. In American usage, watershed is synonymous with the terms drainage basin and catchment (Dunne and Leopold 1978).
