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A

abiotic

Those non-living factors which make up our environment and which can affect the biotic (living) environment.  They can include such things as climate (wind, moisture, temperature,...), geology (rocks, minerals), and atmosphere (oxygen, carbon dioxide,...).

 

activated sewage sludge

Activated sewage sludge is a product of a secondary sewage treatment process.  The process utilizes aerobic microorganisms for to break down organic matter.

 

aerate

The introduction of oxygen into a system.

 

aerobes

Microorganisms which require free oxygen or air in order to grow and survive.

 

aerobic

An environment which has the presence of oxygen.

 

aerobic respiration

Respiration (utilization of food, i.e. carbohydrates) which occurs in the presence of oxygen and in which the food has been completely oxidized to carbon dioxide and water.  There is a release of chemical energy during the process.

 

agitator

An agitator is a device which stirs or shakes.  Its purpose is to create irregular, rapid, or violent movement.

 

algae

Algae is a heterogenous group of eukaryotic (see eukaryote) plants.  They photosynthesize, they can be unicellular (one-celled) or multicellular (many celled), and their tissues are not differentiated into roots, stem, and leaves.  Algae are found in many habitats on the earth including both land and water, however they are primarily found in fresh or marine waters.  Note:  blue-green algae are actually Cyanobacteria (see cyanobacteria).

 

algal bloom

Algae blooms are a sudden growth of algae in fresh or marine waters (aquatic ecosystem).  Algae blooms generally occur under two conditions.  The first type of algae bloom occurs naturally during spring or early summer after "turn-over" in the aquatic system leaves the surface water rich in nutrients.  At this time the primary production (see primary production) exceeds the consumption by aquatic herbivores such as daphnia, fresh water shrimp, and water fowl resulting in excessive growth of algae.  The second type of algae bloom occurs as a result of human induced water pollution.  Nutrient enrichment of the surface water, as a result of nutrient rich runoff from fields, sewage being accidentally or purposely dumped or leaked into surface waters, and non-point source nutrient rich runoff, can all induce algal blooms.  Both of these blooms are characteristic symptoms of eutrophication (see eutrophication).

 

alkane (paraffins)

Fairly unreactive, saturated hydrocarbons with the general formula C_nH_2n+2.  They are found in natural gas and petroleum and form a homologous series which includes methane (CH₄), and ethane (C₂H₆).  The lower molecular weight members of the series are gases, i.e. methane, whereas the higher molecular weight members are waxy solids.

 

ambient

A term used to indicate the immediate surroundings or environment.  Ambient pressure and ambient temperature is the pressure and the temperature of the surrounding atmosphere and is generally used as a reference in relation to a specific object or system.

 

amines

Amines are an organic compound produced when one or more hydrogen atoms are replaced by an organic group in ammonia.  This occurs during the decomposition of organic matter.

 

ammonia: NH₃

Ammonia is a colourless gas with a strong odour.  It is an important component of the nitrogen cycle and is produced by the decomposition of organic nitrogen compounds, i.e. when nitrogen gas is reduced to form ammonia. Nitrification occurs when ammonia is oxidized to form nitrite, and nitrite is oxidized to form nitrate.

 

anaerobe

Anaerobes are organisms which can live or grow in an environment that does not contain free oxygen.  Facultative anaerobes are normally aerobic but can respire anaerobically during periods of oxygen shortage, whereas obligate anaerobes cannot exist in an aerobic (free oxygen) environment.

 

anaerobic

An anaerobic environment is one in which free oxygen is absent.

 

anaerobic respiration

A type of respiration in which food, i.e. carbohydrates, is partially oxidized and occurs under anaerobic conditions.  There is a release of chemical energy during the process, however, because the substrate is never completely oxidized the energy yield is lower than that during aerobic respiration.

 

anoxic

Anoxic conditions exist where their is an absence or deficiency of oxygen.  Anoxic sediments and bottom waters are commonly produced when there is a deficiency of oxygen due to high organic productivity and a lack of oxygen replenishment to the water or sediment.  Examples of this would be in stagnant and/or stratified surface waters.

 

antibiotics

Substances that destroy or inhibit the growth of microorganisms, particularly disease-producing bacteria.  Antibiotics are obtained from microorganisms or synthesized.  Overuse of antibiotics can lead to the development of resistant strains of microorganisms.

 

aquatic environment

An aquatic environment is a habitat that is composed primarily of water.

 

archaebacteria or Archaea

The domain name Archaebacteria, now known as Archaea, is split into two kingdoms of organisms: Crenarchaeota and Euryarchaeota.  The domain Archaea contains methanogens (responsible for the production of methane), sulfur-reducing organisms (responsible for the production of hydrogen sulfide), and extremophiles.

 

autotroph

An autotroph is an organism that uses carbon dioxide as its main or sole source of carbon.

B

benthic zone

The benthic zone is the lowest region in surface and marine waters.  It is where the benthos (collection of benthic organisms) exists. 

The benthic abyssal region is a region of low productivity because little light is able to penetrate to this depth.

The benthic littoral region is a shallower benthic region which is well lit and therefore supports very productive ecosystems.

 

benthos

In both surface and marine waters, the benthos is the collective term for the organisms, flora and fauna, which live at the bottom.  Those benthos which attach to or rest on the bottom are referred to as epifauna, and those which bore or burrow into the sediment are referred to a infauna.

 

biochemical or biological oxygen demand (BOD)

BOD is the amount of dissolved oxygen used by aerobic and facultative microorganisms to stabilize organic matter (decompose) in an aquatic environment (includes sewage).  It is used as an indicator of the polluting capacity of effluent or to measure the amount of organic pollution in water.  It is measured as the weight (mg) of oxygen used (by microorganisms), in a one litre sample of effluent/water, over a five day period at 20 °C in the dark.

 

biodegradable

Biodegradable is a  term used to indicate that a substance is capable of being broken down by microorganisms into smaller products.

 

biodiversity

(biological diversity).  Biodiversity, or biological diversity, is the existence of a wide variety of species (species diversity), or other taxa of plants, animals, and microorganisms within a natural community or habitat.

 

Species within a particular environment are referred to as ecological diversity.

 

Maintaining a high level of biodiversity is important for maintaining a stable ecosystem.  Biodiversity includes the aspects of species richness, ecosystem complexity, and genetic variation.

 

biofilm

A biofilm is a microbial community which resides or lives on a surface, e.g. rock in a stream, as a microlayer.

 

biogas

Biogas is a mixture of methane (primarily) and carbon dioxide which is the result of anaerobic decomposition by methanogenic bacteria of waste materials such as domestic, industrial, and agricultural sewage.

 

biogeochemical (cycle) - (nutrient cycle).

A biogeochemical cycle is the cyclical movement of elements between living organisms (the biotic phase) and their nonliving (abiotic) surroundings (e.g. rocks, water, air).  Examples of biogeochemical cycles are the carbon cycle, nitrogen cycle, oxygen cycle, phosphorus cycle, and sulfur cycle.  It is the movement of chemical elements from organisms to physical environment to organisms in more or less circular pathways. 

 

A perfect cycle, i.e. the nitrogen cycle, has a readily accessible abiotic, usually gaseous, reservoir and many negative-feedback controls.  In contrast the phosphorus cycle, which has a sedimentary reservoir accessed only by slow-moving physical processes, has few biological-feedback mechanisms.

 

Human activities can disrupt these cycles, leading to pollution.  Theoretically, perfect cycles are more resilient than imperfect cycles.

 

biological conservation

Biological conservation is active management to ensure the survival of the maximum diversity of species and the maintenance of genetic variety within species.  The term also implies the maintenance of biosphere functions, e.g. biogeochemical cycling, without which the basic resources for life would be lost.

 

biological productivity

Biological productivity is the productivity of organisms and ecosystems, as defined by primary, secondary, and community productivities.

 

biomass

Biomass is the total mass of all living organisms (producers, consumers, and decomposers) present in an ecosystem or at a particular trophic level in a food-chain, and usually expressed as dry weight or as the carbon, nitrogen, or calorific content per unit area.

 

bioreactor (industrial fermenter)

A bioreactor is a large stainless steel tank used to grow producer microorganisms in the industrial production of enzymes and other chemicals.  An agitator mixes the medium, which is constantly aerated.

 

bioremediation

Bioremediation is the use of biological agents or organisms to reclaim soils and waters polluted by substances hazardous to human health and /or the environment; it is an extension of biological treatment processes that have traditionally been used to treat wastes in which microorganisms typically are used to biodegrade environmental pollutants.

 

biosphere

Biosphere is the part of the Earth's environment in which living organisms are found, and with which they interact to produce a steady-state system; the part of the earth in which life can exist; it is the whole of the region of the earth's surfaces, the sea, and the air that is inhabited by living organisms.

 

biotic

Biotic is any of the factors of an organism's environment that consist of other living organisms.

 

biotic indices

Biotic indices are indicator species. For example, the presence of certain invertebrate groups in fresh water can be awarded a score that indicates the quality of the water.  A scheme employing biotic indices has a scale ranging from 10 (clean water with diverse fauna) to 0 (grossly polluted water with no fauna or with only a few anaerobic organisms).

 

bloom

A bloom is a visible abundance of microorganisms, generally referring to the excessive growth of algae or cyanobacteria at the surface of a body of water.

C

carbon cycle

The carbon cycle is one of the major cycles of chemical elements in the environment and involves the movement of carbon through the surface, interior, and atmosphere of the Earth.

 

Carbon exists in atmospheric gases, in dissolved ions in the hydrosphere, and in solids as a major component of organic matter and sedimentary rocks.

 

Inorganic carbon exchange is mainly between the atmosphere and hydrosphere.

 

The major movement of carbon results from photosynthesis and respiration (in plants, algae and cyanobacteria), with exchange between the biosphere, atmosphere, and hydrosphere.

 

carbon dioxide: CO₂

Carbon dioxide is a colourless, odourless gas that is soluble in water.  It is the product of the complete oxidation of carbon and the compound most involved in the transport of carbon through the carbon cycle.  Carbon dioxide is utilized by autotrophs (plants, algae and cyanobacteria) in the process of photosynthesis.  The process of respiration, organic matter decomposition and respiration all produce CO₂.

 

catchment

A catchment is a drainage basin, or watershed and is the area from which a surface watercourse derives its water.

 

chemical oxygen demand

Chemical oxygen demand, or COD, indicates how much oxidizable material there is in a sample and is used an an indicator of water or effluent quality. Potassium dichromate is used as the oxidizing agent.

 

chemoautotroph

Chemoautotrophs are organisms that use carbon dioxide as their main or sole source of carbon/energy. These microorganisms obtain energy from the oxidation of inorganic carbon and carbon compounds.

 

chemoheterotroph

Chemoheterotrophs are organisms that obtain their carbon for energy chiefly from organic compounds.

 

chemoorganotroph

Chemoorganotrophs are organisms that obtain their energy from the metabolism/oxidation of organic compounds.

 

chemotroph

A chemotroph is an organism that obtains its energy from chemical reactions.

 

chlorophyll

Chlorophyll is the green pigment in plants, algae and cyanobacteria that functions in photosynthesis by absorbing radiant energy from the sun.

 

chlorophyta

Chlorophyta are a large phylum of green algae in which its members possess chlorophylls a and b, store food reserves as starch, and have cellulose cell walls.

 

coliforms

Coliforms or coliform bacteria are gram-negative, lactose-fermenting, enteric rods, e.g. Escherichia coli (E.coli).

 

coliform count

Coliform count is a count made of the numbers of coliform bacteria present as part of most standard analyses of water.  The number of organisms present is normally expressed per 100 ml of water, e.g. 10 CFU/100 mL.

 

community

A general term applied to any grouping of populations of different organisms found living together in a particular environment. The organisms interact by competition, predation, mutualism,..., and give the community a structure.

 

compensation level or compensation depth

The depth at which light penetration in aquatic ecosystems is so reduced that oxygen production by photosynthesis just balances oxygen consumption by respiration; in lakes, the depth of effective light penetration, separating the limnetic and profundal zones.

 

competition

Competition is the interaction between individuals of the same species (intraspecific competition), or between different species (interspecific competition) at the same trophic level, in which the growth and survival of one or all species or individuals is affected adversely. Competition favors the separation of closely related or otherwise similar species.

 

competitor

A competitor is an organism that lives in competition with another organism.

 

compost

Compost is a mixture of decaying organic matter, such as vegetation and manure, that is used as a fertilizer.  The organic material is decomposed by aerobic organisms, mostly fungi and bacteria.  Some decomposition if also carried out by detritivores.

 

consumer

A consumer in the widest sense is a heterotrophic organism that feeds on living or dead organic material.  The two main consumer types are the macroconsumers that include mainly animals (herbivores, carnivores, and detritivores), that wholly or partly ingest other living organisms or organic particulate matter; and the microconsumers such as bacteria and fungi that feed by breaking down complex organic compounds.

 

coprophagous

Coprophagous is the ability to grow or feed on fecal matter, dung or excrement.

 

cyanobacteria

Cyanobacteria is a large and varied group of bacteria that possess chlorophyll a and carry out photosynthesis in the presence of light and air, and produce oxygen. They are a phylum of photosynthetic bacteria comprising the blue-green bacteria - thus the reason for formerly being classified as blue-green algae.  Cyanobacteria occur in all aquatic habitats and a few species fix atmospheric nitrogen in the soil

 

D

daphnia

A genus of crustaceans belonging to the class Branchiopoda and order Cladocera (water fleas).

decomposer

A term that is generally synonymous with microconsumers.  In an ecosystem, decomposer organisms, mainly bacteria and fungi, enable nutrient recycling by breaking down the complex organic molecules of dead protoplasm and cell walls into simpler organic and (more importantly) inorganic molecules which may be used again by primary producers.  Some macroconsumers may play a role in decomposition in that detritivores, in breaking down litter, speed its bacterial breakdown.  In this sense decomposer has a wider meaning than that traditionally implied.

An organism that obtains energy from the chemical breakdown of dead organisms or animal or plant wastes.  Decomposers, most of which are bacteria and fungi, secrete enzymes onto dead matter and then absorb the breakdown products.  Many decomposers are specialized to break down organic materials that are difficult for other organisms to digest.  Decomposers fulfill a vital role in the ecosystem, returning the constituents of organic matter to the environment in inorganic form so that they can again be assimilated by plants.

organisms, often bacteria or fungi, in a community that convert dead organic matter into inorganic nutrients.

decomposition

decay.  The chemical breakdown of organic matter into its constituents by the action of decomposers.

degradation

A type of organic chemical reaction in which a compound is converted into a simpler compound in stages.

degradative succession - heterotrophic succession.  A succession that occurs on dead organic matter over a relatively short time-scale (months to years).  Detrivores feed in sequence, each group releasing nutrients that are utilized by the next group in the sequence until the resources are exhausted.

denitrification

The conversion of nitrate or nitrite to gaseous products, chiefly nitrogen (N₂) and/or nitrous oxide (N₂O), by certain types of bacteria (denitrifying bacteria).  denitrification occurs mainly under anaerobic or micro-aerobic conditions.

A chemical process in which nitrates in the soil are reduced to molecular nitrogen, which is released into the atmosphere.  This process is effected by denitrifying bacteria (e.g. Pseudomonas denitificans), which use nitrates as a source of energy for other chemical reactions in a manner similar to respiration in other organisms.

the formation of gaseous nitrogen or gaseous nitrogen oxides from nitrate or nitrite by microorganisms.

denitrifying bacteria

Bacteria which can carry out denitrification; they occur, for example, in soil and in freshwater and marine environments, and include, for example, certain species of Bacillus, Hyphomicrobium, Paracoccus, Pseudomonas, and Thiobacillus.

desmids

Unicellular mainly freshwater green algae that belong to the class Desmidioideae.  Like Spirogyra, they have an elabourate chloroplast.

detritivore

detritus feeder.  A heterotrophic animal that feeds on dead material

detritus.

the dead material is most typically of plant origin, but it may include the dead remains of small animals.  Since this material may also be digested by decomposer organisms (fungi and bacteria) and forms the habitat for other organisms (e.g. nematode worms and small insects), these too will form part of the typical detritivore diet.

An animal that feeds on detritus.  Detritivores play an important role in the breakdown of organic matter from decomposing animals and plants.

an organism that feeds on detritus; an organisms that feeds on organic wastes and dead organisms.

detritus

Litter formed from fragments of dead material (e.g. leaf litter, dung, molted feathers, and corpses).  In aquatic habitats, detritus provides habitats equivalent to those which occur in soil humus.

Particles of organic material derived from dead and decomposing organisms, resulting from the activities of the decomposers.

waste matter and biomass produced from decompositional processes

diatom

A microscopic alga, belonging to the division Bacillariophyta, in which the cell wall is composed of silica and consists of two halves, one of which overlaps the other like the lid of a box.  Most diatoms are unicellular, but some are colonial or filamentous.  Most are photosynthetic, but some species live heterotrophically among decaying algae.
unicellular algae having a cell wall composed of silica, the skeleton of which persists after the death of the organism.

diazotroph

An organism capable of utilizing (fixing) atmospheric nitrogen.

differential resource utilization

resource partitioning.  The situation in which ecologically similar species sharing the same habitat exploit different resources, or the same resources but in different ways, thereby avoiding competition.

diffusion

The movement of molecules or ions from a region of higher to one of lower solute concentration as a result of their random thermal movement.
The process by which different substances mix as a result of the random motions of their component atoms, molecules, and ions.  In gases, all the components are perfectly miscible with each other and mixing ultimately becomes nearly uniform, though slightly affected by gravity.

dimictic

Applied to a lake in which two seasonal periods of free circulation occur, as is typical of lakes in mid-latitude climates.  In summer, thermal stratification occurs as surface waters are warmed and cease to mix with the denser, colder, deep waters.  In winter, when they cool to below 4 °C, surface waters expand, so becoming less dense than warmer waters beneath them, giving a reverse stratification.  Free circulation through the depth of the lake is possible only in spring, when the surface temperature rises to above 4 °C, and the water becomes heavier than that beneath and so sinks and mixes, and in autumn, when the surface (epilimnion) waters cool to the temperature of the deep (hypolimnion) waters.
A lake that is stratified by a thermocline that is not permanent but is turned over twice during one year.  The thermocline is disrupted due to seasonal changes in the climate.  A meromictic lake is one in which there is a permanent stratification.

dinoflagellates

An order of protozoans that are heterotrophs but closely allied to brown algae and diatoms.  Moist are planktonic, some in fresh water but most in marine environments, and some live in symbiosis with animals with which they exchange nutrients.  Some are colonial.

algae of the class Pyrrhophyta, primarily unicellular marine organisms, possessing two unequal flagella.

discharge

A measure of the water flow, expressed as volume per unit time, at a particular point (e.g. a river gauging station, sewage works, or groundwater abstraction well).

dissolved oxygen level - DO.

the concentration of oxygen held in solution in water Usually it is measured in mg/L (sometimes in mg/m³) or expressed as a percentage of the saturation value for a given water temperature.  The solubility of oxygen varies inversely with temperature; this is important, because the warmer the water the larger the proportion of dissolved oxygen that is used by poikilotherms.  The dissolved oxygen level is an important first indicator of water quality.  In general, oxygen levels decline as pollution increases.

diversity

Most simply, the species richness of a community or area, though it provides a more useful measure of community characteristics when it is combined with an assessment of the relative abundance of species present.  Diversity in ecosystems has been equated classically with stability and climax communities.

the heterogeneity of a system

the variety of different types of organisms occurring together in a biological community.

diversity index

The mathematical expression of the species diversity of a given community or area, which includes due allowance for the relative abundance of different species present.  Such indices are generally considered an important means for comparisons of community structure and stability.  A different and specialized case of a diversity index is the biotic index used in water-pollution studies.

a mathematical measure which describes the species richness and apportionment of species within the community.

dystrophic

Applied to a lake that is usually shallow, rich in humus giving its water a brown colour, with variable amounts of nutrients, and with the deeper water often depleted of oxygen.  A dystrophic lake was proposed as one of three categories of standing water, the others being described as oligotrophic and eutrophic, with mesotrophic water comprising an intermediate category.

E

ecosystem

Ecological system.

A term used to describe a discrete unit that consists of living and non-living parts, interacting to form a stable system.  Fundamental concepts include the flow of energy via food-chains and food-webs, and the cycling of nutrients biogeochemically.
a functional self-supporting system that includes the organisms in a natural community and their environment.

effluent

the liquid discharge from sewage treatment and industrial plants.

endorheic lake

a lake that loses water only by evaporation, i.e. no stream flows from it.

environment

The complete range of external conditions, physical and biological, in which an organism lives.  Environment includes social, cultural, and, for humans, economical and political considerations, as well as the more usually understood features such as soil, climate, and food supply.

environmental impact assessment

EIA, environmental impact statement

An attempt to identify and predict the impact on the biogeophysical environment and on human health and well-being of proposed industrial developments, projects, or legislation.  EIA also aims to devise early comprehended, universally applicable  schemes for communicating the results of the assessment.

environmental resistance

The sum total of the environmental limiting factors, both biotic and abiotic, which together act to prevent the biotic potential of an organism from being realized.  Such factors include the availability of essential resources (e.g. food, oxygen, and water), predation, disease, the accumulation of toxic metabolic wastes, and, in some species, behavioral changes due to stress caused by overcrowding.

epifauna

Benthic organisms that live on the surface of the seabed, either attached to objects on the bottom or free-moving.  They are characteristic of the intertidal zone.

epilimnion

The upper, warm, circulating water in a thermally stratified lake in summer.  Usually it forms a layer that is thin compared to the hypolimnion.

the warm layer of an aquatic environment above the thermocline.

epineuston

The organisms (zooneuston) living in the upper part of the surface film of water.

estuarine waters

estuary.  A coastal body of water which has a free connection with the open sea and where fresh water, derived from land drainage, is mixed with sea water.

eubacteria

domain archaea.  The single kingdom of the domain bacteria, which contains the true bacteria.

prokaryotes other than archaebacteria.

eukaryote

An organism whose cells have a distinct nucleus enveloped by a double membrane, and other features including double-membraned mitochondria and 80S ribosomes in the fluid of the cytoplasm (i.e. all protists, fungi, plants, and animals).

cellular organisms having a membrane-bound nucleus within which the genome of the cell is stored as chromosomes composed of DNA; eukaryotic organisms include algae, fungi, protozoa, plants, and animals.

eulittoral zone

The habitat formed on the lower shore of an aquatic ecosystem, below the littoral zone.

euphotic depth  or euphotic zone

the top layer of water, through which sufficient light penetrates to support the growth of photosynthetic organisms.

In a lake, the depth at which net photosynthesis (i.e. carbon dioxide uptake by photosynthesis minus carbon dioxide release by respiration occurs in a light intensity about 1 % of that at the surface.

The upper, illuminated zone of aquatic ecosystems; it is above the compensation level and therefore the zone of effective photosynthesis.  In freshwater ecosystems it is subdivided into littoral (shallow edge) and limnetic zones.

euryarchaeota

domain archaea.  The more derived of the two kingdoms of Archaea, comprising a broad range of phenotypes including methanogens, halophiles, and sulfur-reducing organisms. 

euryoxic

Able to tolerate a wide range of concentrations of oxygen.

eutrophic

Originally applied to nutrient rich waters with high primary productivity but now also applied to soils.  Typically, eutrophic lakes are shallow, with a dense plankton population and well-developed littoral vegetation.  The high organic content may mean that in summer, when there is stagnation caused by thermal stratification, oxygen supplies in the hypolimnion become limiting for some fish species (e.g. trout).

containing high-nutrient concentrations, such as a eutrophic lake with high phosphate concentration that will support excessive algal blooms

eutrophication

Defined as an increase in the nutrient status of natural waters that causes accelerated growth of algae or water plants, depletion of dissolved oxygen, increased turbidity, and general degradation of water quality.  The levels of N required to induce eutrophication in fresh and estuarine waters are much lower than the values associated with drinking water contamination.  Although estimates vary and depend considerably on the N:P ratio in the water, concentrations of 0.5-1.0 mg N/L are commonly used as threshold values for eutrophication.  Waters are considered to be eutrophic when:  nutrient status is high, i.e. Total P = > 30 µg/L, Total N = > 500 µg/L, algal blooms and biomass are common to high, i.e. chlorophyll = >8 mg/L, aquatic diversity is low, dissolved oxygen is low, i.e. < 10 saturation %, and turbidity is < 2 m (Secchi disk transparency). (Soils and Environmental Quality. Pierzynski, Sims, and Vance  1994)

The process of nutrient enrichment (usually by nitrates and phosphates) in aquatic ecosystems, such that the productivity of the system ceases to be limited by the availability of nutrients.  It occurs naturally over geological time, but may be accelerated by human activities (e.g. sewage disposal or land drainage); such activities are sometimes termed cultural eutrophication.  The rapid increase in nutrient levels stimulates algal blooms.  On death, bacterial decomposition of the excess algae may deplete oxygen levels seriously.  this is especially critical in thermally stratified lakes, since the decaying algal material typically sinks to the hypolimnion where, in the short term, oxygen replenishment is impossible.  The extremely low oxygen concentrations that result may lead to the death of fish, creating a further oxygen demand, and so leading to further deaths.

the enrichment of natural waters with inorganic materials, especially nitrogen and phosphorus compounds, that support the excessive growth of photosynthetic organisms.

euxinic

Applied to an environment in which the circulation of water is restricted, leading to reduced oxygen levels or anaerobic conditions in the water.  Such conditions may develop in swamps, barred basins, stratified lakes, and fiords.  Euxinic sediments are those deposited in such conditions, and are usually black and organic rich.

exorheic lake

A lake that has one or more outflow streams.

extracellular compound

F

facilitator

Something which promotes an action.

facultative

Applied to organisms that are able to adopt an alternative mode of living.  for example, a facultative anaerobe is an aerobic organism that can also grow under anaerobic conditions.

fauna

The animal life of a region or geological period.

feedback loop

feedback mechanism.  A control device in a system.  Homeostatic systems have numerous negative-feedback mechanisms which tend to counterbalance positive changes and so maintain stability.  For example, denitrifying bacteria counteract the effects of nitrogen-fixing bacteria.  Positive feedback reinforces change and in natural systems may result in radical environmental alteration.

fertigation

irrigating with a nutrient solution, e.g. the water may contain nitrogen, phosphorus, and potassium, and micronutrients

floc

a mass of microorganisms cemented together in a slime produced by certain bacteria, usually found in waste treatment plants.

flora

All the plant species that make up the vegetation of a given area.

fresh water

Water containing little or no chlorine.  According to the Venice system, which classifies brackish waters by their percentage chlorine content, fresh water contains 0.03 per cent or less of chlorine. - lakes, ponds, swamps, springs, streams, and rivers.

G

gaining stream

influent stream.  A stream that receives water emerging from a submerged spring or other groundwater seepage which adds to its overall flow.

gas vacuole

A small, gas-filled vesicle, numbers of which are found in certain aquatic bacteria and cyanobacteria.  Their function appears to be that of giving buoyancy to the cells.

grazers

organisms that prey upon primary producers; protozoan predators that consume bacteria indiscriminately; filter-feeding zooplankton.

gross primary production

total amount of organic matter produced in an ecosystem.

gyttja

nekron mud.  a rapidly accumulating, organic, muddy deposit, characteristic of eutrophic lakes.  The precise nature of gyttja varies with the producer organisms involved, which include small algae or macrophytes.

H

habitat

a location where living organisms occur.

hardness

A measure of the ability of water to form a carbonic scale when boiled, or to prevent the sudsing of soap.  Permanent hardness is due mainly to dissolved calcium and magnesium sulfate or chloride; the bicarbonate ion causes temporary hardness.  Dissolved carbon dioxide and the weathering of carbonate rocks are the main sources of hardness in water.

helophyte

A plant typical of marshy or lake-edge environments, in which the perennating organ lies in soil or mud below the water level, but the arial shoots protrude above the water, e.g. the common reed.

herbivore

A heterotroph that obtains energy by feeding on primary producers, usually green plants.

heterotroph

An organisms that is unable to manufacture its own food from simple chemical compounds and therefore consumes other organisms, living or dead, as its main or sole source of carbon.

organisms requiring organic compounds for growth and reproduction, the organic compounds serve as sources of carbon and energy.

holomictic

Applied to lakes in which the water turns over at least once a year.

hydration

A chemical reaction in which water combines with another substance.

hydrocarbon

A naturally occurring compound that contains carbon and hydrogen.  Hydrocarbon may be gaseous, solid, or liquid, and include natural gas, bitumens, and petroleum.

hydrology

The study of the hydrologic cycle; this involves aspects of geology, oceanography, and meteorology, but emphasizes the study of bodies of surface water on land and how they change with time.

hydrophyte

A plant that is adapted morphologically and/or physiologically to grow in water or very wet environments.  Adaptations include the development of finely divided submerged leaves, large floating leaves, the presence of aerenchyma, and the reduction of root systems.  The perennating bud lies at the bottom of fairly open water.  With the leaves submerged or floating, only the inflorescence protrudes above the water surface.

hydrosphere

The total body of water which exists on or close to the surface of the Earth.

the aqueous envelope of the earth, including bodies of water and aqueous vapor in the atmosphere.

hypolimnion

The lower, cooler, non-circulating water in a thermally stratified lake in summer.  If, as often occurs, the thermocline is below the compensation level, the dissolved oxygen supply of the hypolimnion depletes gradually; replenishment by photosynthesis and by contact with the atmosphere is prevented.  Re-oxygenation is possible only when the thermal stratification breaks down in autumn.

the deeper, colder layer of an aquatic environment; the water layer below the thermocline.

hyponeuston

The organisms living in the lower part of the surface film of water.

I

infauna

Benthic organisms that dig into the sea bed or construct tubes or burrows.  They are most common in the subtidal and deeper zones.

intracellular product

indicator organism

an organism used to identify a particular condition, such as Escherichia coli as an indicator of fecal contamination.

Indigenous

native to a particular habitat

J

K

kettle hole, kettle lake

A depression in the surface of glacial drift (especially ablation or kettle moraine), which results from the melting of an included stagnant ice mass.  It may be filled with water to form a small lake

L

labyrinth fish

Fish that have accessory respiratory organs in the gill chambers, enabling them to utilize atmospheric oxygen when necessary.

leachate

The solution formed when water percolates through a permeable medium.  When derived from solid waste, in some cases the leachate may be toxic or carry bacteria.

lentic

Applied to a freshwater habitat characterized by calm or standing water (e.g. lakes, ponds, swamps, and bogs).

Liebig's law of the minimum

The concept first stated by J. von Liebig in 1840, that the rate of growth of a plant, the size to which it grows, and its overall health depend on the amount of the scarcest of its essential nutrients that is available to it.  This concept is now broadened into a general model of limiting factors for all organisms, including the limiting effects of excesses of chemical nutrients and other environmental factors.

limiting factor

ecological factor.  Defined originally as whichever essential material is available in an amount most closely approaching the critical minimum needed, but now used more generally to describe any environmental condition or set of conditions that approaches most nearly the limits (maximum and minimum) of tolerance for a given organism.

limnetic zone

sublittoral zone.  The area in more extensive and deeper fresh water ecosystems which lies above the compensation level and beyond the littoral (lake-edge) zone.  This zone is mainly inhabited by plankton and nekton with occasional neuston species.  The limnetic and littoral zones together comprise the euphotic or well-illuminated zone.  In very small and shallow lakes or ponds the limnetic zone may be absent.

in lakes, the portion of the water column excluding the littoral zone where primary productivity exceeds respiration.

limnology

The study of freshwater ecosystems.

limnophilous

Applied to organisms that thrive in ponds or lakes.

lithotroph

An organism that obtains energy from the oxidation of inorganic compounds or elements.

microorganisms that live in and obtain energy from the oxidation of inorganic matter; chemoautotrophs.

littoral

Pertaining to the shore.

littoral fish

Those fish that are found along the shores of a lake from the edge of the water down to the limits of rooted vegetation.

littoral zone

The area in shallow fresh water and around lake shores, where light penetration extends to the bottom sediments, giving a zone colonized by rooted plants.

situated or growing on or near the shore; the region between the high and low tide marks

logistic equation

A mathematical description of growth rates for a simple population in a confined space with limited resources.  The equation summarizes the interaction of biotic potential with environmental resources, as seen in populations showing the S-shaped growth curve, as: dN/dt = rN(N-K)/K where N is the number of individuals in the population, t is time, r is the biotic potential of the organism concerned, and K is the saturation value or carrying capacity for that organism in that environment.  The resulting growth rate or logistic curve is a parabola, while the graph for organism numbers over time is sigmoidal.

lotic

Applied to a freshwater habitat characterized by running water (e.g. springs, rivers, and streams).

M

man-induced turnover

The additional flow of an element through the active part of a biogeochemical cycle, which results from human activity.  For example, by burning fossil fuels human add an extra 5 billion tonnes per year of carbon to the turnover of the carbon cycle, which is naturally about 75 billion tonnes per year.

marsh

A more or less permanently wet area of mineral soil, as opposed to a peaty area, e.g. around the edge of a lake or on a flood-plain of a river.  Colloquially, marsh is often used interchangeably with swamp and bog.

meromictic

A meromictic lake is one in which there is a permanent stratification, i.e. no seasonal turnover as in a dimictic lake.

meroplankton

Temporary zooplankton, i.e. the larval stages of other organisms.

mesotrophic

Applied to waters having levels of plant nutrients intermediate between those of oligotrophic and eutrophic waters.

metalimnion

That part of a water column where the thermocline and pycnocline are steepest.

methane

A colourless odourless gas, CH₄.  Methane is the simplest hydrocarbon, being the first member of the "alkane series.  It is the main constituent of natural gas and as such is an important raw material for producing other organic compounds.  It can be converted into methanol by catalytic oxidation.

The simplest hydrocarbon compound, which is released as a gaseous by-product of the metabolic activity of certain bacteria.  The principal sources of atmospheric methane are swamps, marshes, and natural wetlands , and paddy-rice fields.  Methane is an important greenhouse gas.

methanogen

Any of various archaebacteria that produce methane.  They include such genera as Methanobacillus and Methanothrix.  Methanogens are obligate anaerobes found in oxygen deficient environments, such as marshes, swamps, sludge (formed during "sewage treatment), and the digestive system of ruminants.  They mostly obtain their energy by reducing carbon dioxide and oxidizing hydrogen, with the production of methane.  Formate, methanol, or acetate may also be used as substrates by certain methanogens.  Methanogenic bacteria are important in the production of "biogas".

A single-celled organism, belonging to domain Archaea, that produces methane gas as a product of its metabolism.

methane-producing prokaryotes; a group of archaebacteria capable of reducing carbon dioxide or low-molecular-weight fatty acids to produce methane.

methanotroph

A bacterium that can use methane as a nutrient.

methylotroph

An organism that can use (as its sole source of carbon and energy) organic compounds that contain only one carbon atom (i.e. compounds such as methane and methanol).

micro-aerobic

applied to an environment in which the concentration of oxygen is less than that in air.

micro-aerophilic

Applied to an organism that grows best under micro-aerobic conditions.

microbial

Of or pertaining to microorganisms.

microbivore

An animal which feeds on microorganisms.

microorganisms

Literally, a microscopic organism.  The term is usually taken to include only those organisms studied in microbiology (i.e. bacteria, fungi, microscopic algae, protozoa, and viruses), thus excluding other microscopic organisms such as eelworms and rotifers.

microscopic organisms, including algae, bacteria, fungi, protozoa, and viruses.

mineralization

The conversion of organic tissues to an inorganic state as a result of decomposition by microorganisms.

the microbial breakdown of organic materials into inorganic materials brought about mainly by microorganisms.

mixotroph

An organism in whose mode of nutrition both organic and inorganic compounds are used as sources of carbon and/or energy.

organisms capable of utilizing both autotrophic and heterotrophic metabolic processes, e.g. the concomitant use of organic compounds as sources of carbon and light as a source of energy.

mollusc

A member of a phylum (Mollusca) of invertebrate animals, most of them aquatic, comprising classes which are morphologically quite diverse.

monomictic

Applied to lakes in which only one seasonal period of free circulation occurs.  In cold monomictic lakes, typical of polar latitudes, the seasonal overturn occurs briefly in summer and the water temperature never rises above 4 °C, so inducing density stratification.  In warm monomictic lakes, typical of warm temperate or subtropical regions, the seasonal overturn occurs in winter.  At other times thermal stratification, with the formation of a distinct epilimnion, prevents free circulation through the depth of the lake.

muck

Highly decomposed organic matter in which original plant material cannot be recognized. 

Farmyard manure composed of animal feces and urine mixed with straw and highly decomposed.

mutualism

a stable condition in which two organisms of different species live in close physical association, each organisms deriving some benefit from the association; symbiosis.

N

natural gas

neutralism

the relationship between two different microbial populations characterized by the lack of any recognizable interaction.

net primary production

amount of organic carbon in the form of biomass and soluble metabolites available for heterotrophic consumers in terrestrial and aquatic habitats.

nitrification

the process in which ammonia is oxidized to nitrite and nitrite to nitrate; a process primarily carried out by the strictly aerobic, chemolithotrophic bacteria of the family Nitrobacteraceae.

nitrifying bacteria

Nitrobacteraceae; gram-negative, obligately aerobic, chemolithotrophic bacteria occurring in aquatic environments and in soil that oxidize ammonia to nitrite or nitrite to nitrate.

nitrogen cycle

nitrogen fixation

the reduction of gaseous nitrogen to ammonia, carried out by certain prokaryotes.

 nitrous oxide

dinitrogen oxide.  A colourless gas, N₂O.  It is soluble is water.

 nutrients -

O

obligate aerobes

organisms that grow only under aerobic conditions, i.e. in the presence of air or oxygen.

obligate anaerobes

organisms that cannot use molecular oxygen; organisms that grow only under anaerobic conditions, i.e. in the absence of air or oxygen; organisms that cannot carry out respiratory metabolism.

oligotrophic

lakes and other bodies of water that are poor in those nutrients that support the growth of aerobic, photosynthetic organisms,; microorganisms that grow at very low nutrient concentrations.

organic matter

oxidation

oxidation pond

a method of aerobic waste disposal employing biodegradation by aerobic and facultative microorganisms growing in a standing water body.

oxygen cycle

P

P/R ratio

the relationship between gross photosynthesis and rate of community respiration.

parasites

organisms that live on or in the tissues of another living organism, the host, from which they derive their nutrients.

parasitism

an interactive relationship between two organisms or populations in which one is harmed and the other benefits; generally, the population that benefits, the parasite, is smaller than the population that is harmed.

pathogens

organisms capable of causing disease in animals, plants, or microorganisms

pollution

phosphorus cycle

photoautotrophs

organisms whose source of energy is light and whose source of carbon is carbon dioxide; characteristic of plants, algae and some prokaryotes.

photoheterotrophs

organisms that obtain energy from light but require exogenous organic compounds for growth.

photosynthesis

the process in which radiant (light) energy is absorbed by specialized pigments of a cell and is subsequently converted to chemical energy; the ATP formed in the light reaction is used to drive the fixation of carbon dioxide, with the production of organic matter.

phototrophs

organisms whose sole or principal primary source of energy is light; organisms capable of photophosphorylation.

phytoplankton

passively floating or weakly motile photosynthetic aquatic organisms, primarily cyanobacteria and algae.

plankton

collectively, all microorganisms and invertebrates that passively drift in lakes and oceans.

poikilotherms

predation

a mode of life in which food is primarily obtained by killing and consuming animals; an interaction between organisms in which one benefits and one is harmed, based on the ingestion of the smaller organisms, the prey, by the larger organisms, the predator.

predators

organisms that practice predation.

prey

an animal taken by a predator for food.

primary productivity

primary producer

organisms capable of converting carbon dioxide to organic carbon, including photoautotrophs and chemoautotrophs.

profundal zone

in lakes, the portion of the water column where respiration exceeds primary productivity.

proto-cooperation

synergism; a nonobligatory relationship between two microbial populations in which both populations benefit.

Q

R

recalcitrant

a chemical that is totally resistant to microbial attack.

reduction

remediation

the act of reclaiming or improving an undesirable state.

S

saprotrophic

Secchi disk transparency test

secondary sewage treatment

the treatment of the liquid portion of sewage containing dissolved organic matter, using microorganisms to degrade the organic matter , using microorganisms to degrade the organic matter that is mineralized or converted to removable solids.

self-purification

inherent capability of natural waters to cleanse themselves of pollutants based on biogeochemical cycling activities and interpopulation relationships of indigenous microbial populations.

sulfur cycle

biogeochemical cycle mediated by microorganisms that changes the oxidation state of sulfur within various compounds.

symbionts

symbiosis

an obligatory interactive association between members of two populations, producing a stable condition in which the two organisms live together in close physical proximity to their mutual advantage.

T

tertiary sewage treatment

a sewage treatment process that follows a secondary process, aimed at removing nonbiodegradable organic pollutants and mineral nutrients.

thermal stratification

division of temperate lakes into an epilimnion, thermocline, and hypolimnion, subject to seasonal change; zonation of lakes based on temperature where warm and cold water masses do not mix.

thermocline

zone of water characterized by a rapid decrease in temperature, with little mixing of water across it.

total suspended solids

trickling filter system

a simple, film-flow aerobic sewage treatment system; the sewage is distributed over a porous bed coated with bacterial growth that mineralizes the dissolved organic nutrients.

trophic

turbidity

cloudiness or opacity of a suspension.

U

ultraviolet light (UV)

short wavelength electromagnetic radiation in the range of 100 - 400 nm.

upwelling

V

volatile organic chemical (VOC)

organic compound that vaporizes into the atmosphere.

W

X

xenobiotic

a synthetic product not formed by natural biosynthetic processes; a foreign substance or poison.

Y

Z