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Glossary
Biocriteria Links
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).
Aquatic Assemblage: an organism group of interacting populations in a given waterbody, for example, fish assemblage or a benthic macroinvertebrate 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.
Attribute: a measurable component of a biological system.
Benthic marcroinvertebrates: see benthos.
Benthos: animals without backbones, living in or on the sediments, a size large enough to be seen by the unaided eye, and which can be retained by a U.S. Standard No. 30 sieve (28 openings/inch, 0.595-mm openings). Also referred to as bentic macroinvertebrates, infauna, or macrobenthos.
Bioavailability: degree to which chemicals can be taken up by organisms.
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 Assessments or Bioassessments: evaluation of the biological condition of a waterbody using biological surveys and other direct measurements of resident biota in surface waters.
Biological Criteria or Biocriteria: narrative or numeric expressions that describe the biological condition (structure and function) of aquatic communities inhabiting waters of a designated aquatic life use. Biocriteria are based on the numbers and kinds of organisms present and are regulatory-based biological measurements.
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 Survey or Biosurvey: collecting, processing, and analyzing a representative portion of the resident aquatic community to determine its structural and/or functional characteristics.
Bioregion: any geographical region characterized by a distinctive flora and fauna (see also ecoregion).
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.
Community: all the groups of organisms living together in the same area, usually interacting or depending on each other for existence.
Criteria: statements of the conditions presumed to support or protect the designated use or uses of a waterbody. Criteria may be narrative or numeric.
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.
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).
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.
Historical Data: data sets from previous studies, which can range from handwritten field notes to published journal articles.
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.
Index of Biological Integrity (IBI): an integrative expression of site condition across multiple metrics. An index of biological integrity is often composed of at least seven metrics. The plural form is either indices or indexes.
Macroinvertebrates: animals without backbones of a size large enough to be seen by the unaided eye and which can be retained by a U.S. Standard No. 30 sieve (28 meshes per inch, 0.595 mm openings).
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.
Microinvertebrates: animals without backbones that are not large enough to be seen by the unaided eye; they will not be retained by a U.S. Standard No. 30 sieve (28 meshes per inch, 0.595 mm openings).
Minimally Impaired: sites or conditions with slight anthropogenic perturbation relative to the overall region of the study.
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.
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.
Numeric Biocriteria: numerical indices that describe expected attainable community attributes for different designated aquatic life uses.
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.
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.
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.
Use Attainability Analysis (UAA): analysis that describes factors limiting designated use of waterbodies.