Aquatic Glossary

Aquatic life use
a beneficial use designation (in state water quality standards) in which the waterbody provides suitable habitat for survival and reproduction of desirable fish, shellfish, and other aquatic organisms.
an association of interacting populations of organisms in a given waterbody.
of the bottom of a waterbody.
Benthic macroinvertebrates
animals without backbones, living in or on sediments or other substrates, 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 openings per inch, 0.595-mm openings).
evaluation of the biological conditions of a waterbody that uses biological surveys of the resident plants, animals, and other living organisms that depend upon the aquatic resource.
Biological assemblages
a group of phylogenetically or ecologically related organisms that are part of an aquatic community.
Biological criteria
under the Clean Water Act, numerical values or narrative statements that define a desired biological condition for a waterbody and are part of the water quality standards.
Biological diversity
the variety and variability among living organisms and the ecosystems in which they occur. Biodiversity includes the numbers of different items and their relative frequencies; these items are organized at many levels, ranging from complete ecosystems to the biochemical structures that are the molecular basis of heredity. Thus, biodiversity encompasses expressions of the relative abundances of different ecosystems, species, and genes.
all of the living material in a given area
homogeneous areas defined by similarity of climate, landforms, soil, potential natural vegetation, hydrology, or other relevant physical, chemical, or biological variables.
Colonization stability
Ability to reside in a semi-permanent status; not transient.
aggregate of more than one sampling effort.
the measure of the ionic strength or concentration in water/
Dissolved oxygen
oxygen dissolved in water and available for living organisms to use for respiration.
Ecological integrity
the condition of the biotic (aquatic community) and abiotic (water chemistry and habitat) components of unimpaired waterbodies as measured by assemblage (an association of interacting populations of organisms in a given waterbody, e.g., fish assemblage) structure and function, water chemistry, and habitat measures of a site.
a taxonomic level of organization containing several genera and multiple species.
an associated group of species.
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.
Habitat assessment
the evaluation of the structure of the surrounding habitat that influences the quality of the water resource and the condition of the aquatic community.
High gradient streams
streams in moderately to highly sloping landscapes having substrate primarily composed of course sediment particles or frequent course particulate aggregations along stream reaches.
Hyporheic – referring to groundwater flow and connections to stream features.
a usually dimensionless, numeric combination of scores derived from biological measures called metrics.
Low gradient streams
streams in low to moderately sloping landscapes having substrates of fine sediment or infrequent aggregations of coarse particulate aggregations along stream reaches.
a measurable characteristic of the biota that changes in some predictable way with increased human influence.
multimeric approach
analysis techniques using several measurable characteristics of a biological assemblage.
Multimeric index
A dimensionless numeric combination of scores derived from biological measures called metrics. A metric is a characteristic of the biota that changes in some predictable way with increased human influence and can therefore be scored according to conditions.
Multivariate approach
statistical methods (e.g., ordination or discriminant analysis) for analyzing physical and biological community data using multiple variables.
Niche space
the position of a particular species or population in an ecological community.
a determining characteristic or factor.
a broad organismal assemblage composed of attached algae, bacteria, their secretions, associated detritus, and various species of microinvertebrates.
a numerical measure of the hydrogen ion concentration use to indicate the alkalinity or acidity of a substance.
a pleasant smell that frequently accompanies the first rain after a long period of warm, dry weather; the earthy scent produced when rain falls on dry soil
Primary producers
organisms capable of producing their own food, e.g., algae.
Reference conditions
expectations on the state of aquatic biological communities in the absence of human disturbance and pollution.
Reference sites
real sites that are used for characterizing reference conditions. These sites should be minimally impaired by human disturbance and pollution.
referring to flowing conditions of the stream feature.
shallow areas in a stream where water flows swiftly over gravel and rock.
deep areas in a stream where water flows fast with little or no turbulence.
fundamental category of classification consisting of organisms capable of interbreeding.
Species diversity
the variance of distinct species that are found in an assemblage community, or sample.
Structural heterogeneity
composed of parts of different kinds, or having widely dissimilar elements.
the hieratical identification of a particular organism using dichotomous keys. A glossary of taxonomic terms is not included here, but is discussed during taxonomic workshops.
Taxonomic composition
the number and arrangement of distinct species that are found in an assemblage.
murkiness or cloudiness of water, indicating the presence of some suspended sediments, dissolved solids, natural orman-made chemicals, algae, etc.
statistical tests for comparing two or more groups; techniques include t-test, analysis of variance, sign test, Wilcoxan rank test, and the Mann-Whitney U-test.
a measure of the variability or precision of a set of observations.
Water Quality Standard
A law or regulation that consists of the beneficial designated use or uses of a water body, the numerical and narrative water-quality criteria that are necessary to protect the use or uses of that particular water body, and an antidegradation statement. Water quality standards are set by States, Territories, and Tribes. They identify the uses for each waterbody, for example, drinking water supply,contact recreation (swimming), and aquatic life support (fishing), and the scientific criteria to support that use. (From federal Clean Water Act).
concerning geographic distribution of animal populations and assemblages

*Most of these terms and definitions were obtained from the Glossary in the Rapid Bioassessment Protocol and from the USEPA Watershed Academy