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GLOSSARY AND MOST COMMONLY USED SYMBOLS AND ABBREVIATIONS

Aerobes - organisms, which can live only in aerobic conditions as they gain energy from the process of respiration.

Aggregation - the process of combining smaller spatial units in to larger sets.

Algae- microscopic, usually unicellar, plants.

Allochthonous - brought into a waterbody from outside.

Allochthonous organic matter -  organic matter transported into a lake or river from adjacent ecosystems.

Anaerobes - organisms living in anaerobic conditions and gaining energy from chemical reactions which are not based on oxygen transformations.

Analogue map - map printed on a paper using graphic symbols to represent features and values.

Arc - a line consisting of series of vertices.

Attribute - an alphanumeric characteristic of a geographic object (point, line, area) that can be stored in a relational data base and linked by an identifier to an object.

Autochthonous - produced within the waterbody

Biological survey (Biosurvey) - the process of collecting and processing representative portions of a resident aquatic community to determine the community membership, structure, and functions.

Biological assessment (Bioassessment) - an evaluation of the biological condition of a waterbody through the use of biosurveys and other direct measurements of resident biota in surface waters.

Biological monitoring (Biomonitoring) - the use of a biological entity as a detector, and its response as a measure, to determine environmental conditions. Biosurveys and toxicity tests are common biomonitoring methods.

Biological criteria (Biocriteria) - numeric values or narrative expressions that describe the reference biological conditions of aquatic communities inhabiting waters that have been given a designated aquatic life use.

Biomanipulation - an inclusive term for methods of changing the biological structure of an ecosystem in order to improve water quality.

Biomass - the quantity of living organisms expressed in units of volume or mass, generally related to a unit of volume or area within a waterbody.

Biotope - populations of all species living in particular space.

Blooms - high concentrations of phytoplankton biomass

Buffer - a zone of given radius around a geographical object (point, line, area).

Cartesian coordinate system - a system of two or three mutually perpendicular axes along which the location of any point can be precisely described by a set of (x,y,z) coordinates.

Carrying capacity - the dynamic equilibrium around which a population fluctuates; regulated by available space and the amount (and quality) of the available resources.

Cascade effect - the transmission of changes within a given trophic level to lower trophic levels.

Contour - a line connecting points of equal elevation (or other attribute).

Cyanobacteria [also Cyanophytes or blue-green algae] - a group of phytoplankton, some of which can produce toxins, regulate their depth using a gas-vacuole buoyancy mechanism, and/or fix atmospheric nitrogen for use in growth. They often occur in eutrophic waters as a bloom.

Data - the basic element of information that can be processed by a computer; may be alphanumeric or graphical.

Data model - a formal method of arranging data to represent the observed environment.

Database - a computer file containing data, organized, inter alia, as a set of tables or coordinates of the points and their attendant attributes.

Denitrification - the microbiologically-mediated reduction of oxygenated nitrogen compounds to gaseous nitrogen.

Denitrifying bacteria - the group of bacteria which utilise nitrate in one of three metabolic pathways: a) without accumulating nitrite, b) with transient accumulation of nitrite, and c) in a two-step denitrification process that transforms nitrate into gaseous nitrogen.

Diatoms [also Bacillariophytes]- a group of algae with siliceous walls.

Digital Terrain Model (DTM) -  data which depict the relief of given area of terrain using a grid or irregular triangular network and contour elevations.

Digitise - a means of entering geographical data into computerised data basesfrom analogue maps.

Dinoflagellates - a group of phytoplankton with flagella, or whip-like appendages, by which the organisms have limited movement.

Diversity of fish - the proportion of a given fish species within a sample population. Diversity may be calculated using the Shannon Index (H), where: H' = ∑p_i lnp_i . p_i is the ratio of each component (the % of a given species) to the total value (all species=100%). The index may be scaled from 0 to 1, where 0 is the lowest possible diversity and 1 is the maximum possible diversity by dividing H' by lnS, where S is the number of species having the indicated p_i value (after Odum 1980).

Ecological integrity - the condition of the biotic (aquatic community) and abiotic (water chemistry and habitat) components of unimpaired waterbodies, as measured by assemblage structure and function, water chemistry, and habitat measures.

Ecoregions - a relatively homogeneous area defined by the similarity of climate, landform, soil, potential natural vegetation, hydrology, or other ecologically relevant variable.

Ecotone - the transition zone between two different types of ecosystems, such as a river and a meadow, characterised by very high biodiversity; ecotones may play an important role as buffers, modifying and limiting flows of nutrients and pollutants between ecosystem components.

Entity - a discrete geographical object represented as a digital data structure.

Feature - a representation of a geographical object as a point, line, or polygon.

Filter - a small matrix (mask) containing coefficients used for modifying pixel values in a raster image on a map, using a variety of mathematical procedures.

Fluorescence - the process whereby light is absorbed at one wavelength and almost instantaneously emitted at new and longer wavelength by an organic molecule, as in the case of photosynthetic pigments.

Generalization - the reduction of the volume of geographical data; such reductions are usually used to construct a better graphical representation on a map or in image enhancement.

Geographic object - a user-defined part of the real world that can be represented using geographical features and attributes.

Georeference - the relationship between raster data and cartographic coordinates.

Grid data - the structure of data used to represent geographical objects, composed of square cells of equal area, arranged in rows and columns.

Green algae [ also Chlorophytes] - a group of algae which are usually a good food for zooplankton.

Image - a graphic representation of an object produced by an optical or electronic device. An image is stored as raster data in the form of pixel values.

Interpolation - making predictions based on measurements done only in a certain area.

In vivo - in living organisms.

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• International Year of Forests
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