GLOSSARY
Abiotic:
Not alive, non-biological. For eg., temperature
is an abiotic factor that influences O2 concentration whereas photosynthesis and respiration are biotic factors
that influence O2 concentration.
Acid:
A solution that is a proton donor and has a pH less than 7
on a scale of 0-14. Lower the pH, higher is the acidity of the solution.
Acidity:
A measure of how acidic a solution is. Solutions with pH
less than 4.5 contain mineral acidity (due to strong inorganic acids) while a
solution having a pH greater than 8.3 contains no acidity.
Algae:
Simple, single-celled, colonial or multi-celled aquatic
plants. Aquatic algae are mostly microscopic plants that contain chlorophyll and
grow by photosynthesis, and lack roots and stems (non-vascular), and leaves.
They absorb nutrients (carbon–di-oxide, nitrate, ammonium, phosphate and
micronutrients) from water or sediments, release oxygen to water and are the
major sources of organic matter at the base of the food web in lakes. Freely
suspended forms are called as phytoplankton; while
forms that are attached to rocks, stems, twigs etc. are called as
periphyton.
Alkalinity:
Acid neutralising or buffering capacity of water; a
measure of ability of water to resist changes in pH caused by the addition of
acids or bases. In natural waters, it is mainly due to the presence of
carbonates, bicarbonates and to a lesser extent borates, silicates and
phosphates. A solution having pH below 5 contains no alkalinity.
Alkaloid:
Nitrogenous organic bases found in plants having specific
physiological function.
Allochthonous:
The organic matter synthesised within the drainage basin
and brought to the lakes or streams in various forms.
Amictic:
The lakes that never mix as they are permanently frozen.
Anaerobic:
Lacking in oxygen.
Anions:
Negatively charged ions.
Anisogamy:
The conjugation of
two gametes of unequal size and form.
Anoxia or anoxic:
Conditions of being without
dissolved oxygen.
Anthropogenic:
Human caused.
Aquatic respiration:
Refers to the use of
oxygen in an aquatic system, including the decomposition of organic matter and
the use of oxygen by fish, algae, zooplankton, aquatic macrophytes and
microorganisms for metabolism.
Autochthonous:
The energy stored in photosynthetically formed organic matter that is
synthesised in the lake or stream.
Base:
A substance which accepts protons (or
donates electrons) and has a pH greater than 7 on a scale of 0-14.
Basin:
Geographic land area draining into a lake or
river; also referred as drainage basin or watershed.
Bathymetry:
The analysis of the depth profile of the
lake.
Benthic
zone: Refers to the bottom of a lake; lake
bottom sediment.
Biliproteins:
The biliproteins are water-soluble, pigment-protein complexes in the
cyanobacteria.
Bioaccumulation:
The increase in concentration of a
chemical in organisms that reside in environments contaminated with low
concentrations of various organic compounds. Also used to describe the
progressive increase in the amount of a chemical in an organism resulting from
rates of absorption of a substance in excess of its metabolism and excretion.
Certain chemicals such as PCB’s, mercury and some pesticides can be
concentrated from very low levels in the water to toxic levels in animals
through this process.
Biomanipulation:
Reducing algal blooms by altering
the fish community to reduce predation on certain zooplankton, that can most
efficiently graze on algae.
Biomass:
The weight of a living organism or
assemblages of organisms.
Biotic:
Referring to a living organism.
BOD:
The biochemical oxygen demand (BOD) is an
approximate measure of the amount of biochemically degradable organic matter
present in the water sample.
Bog:
A wetland community
dominated by moss, sedges, shrubs or evergreen trees rooted in deep peat. Bogs
are found in boreal and temperate regions.
Buffer:
A substance which tends to keep pH levels
constant.
Carbon cycle:
The circulation of carbon atoms
through the ecosystem.
Carbon dioxide: A colourless and odourless gas which
becomes carbonic acid when dissolved in water; CO2 is assimilated by
plants in the “dark” cycles of photosynthesis.
Carnivores: “Meat
eaters”; organisms that eat other organisms.
Carotenoids:
The photosynthetic pigment present in plankton.
Cations: Negative ions.
Chelators:
Substances that combine chemically with the toxic substances and render them
harmless.
Chemical equilibrium:
Concentrations of reactants
and products in a reaction that is in balance; there is no net exchange as the
rate of the forward reaction is equal to the backward reaction.
Chlorophyll:
The green pigment in leaves that
transforms light energy into kinetic energy.
Clinograde:
In productive lakes
where oxygen levels drop to zero in the hypolimnion, the oxygen curve is called
as clinograde curve.
COD:
The Chemical Oxygen Demand
(COD) is a measure of the oxygen equivalent of the organic matter in a water
sample that is susceptible to oxidation by a strong chemical oxidant, such as
dichromate.
Conductivity:
Measures the ability of water to
conduct electric current and is directly related to the total dissolved solids
(ions) in water. It is also called as electric conductivity (EC).
Consumers:
Organisms that must eat other organisms
for their energy; organisms that cannot produce new organic matter by
photosynthesis.
Cyanobacteria:
Blue-green algae; organisms that are
biochemically bacterial in nature but perform photosynthesis.
Decomposition:
The breakdown of organic matter by
bacteria and fungi.
Denitrification:
Anaerobic
(bacterial) process of metabolism in which nitrogen is used instead of oxygen
during the oxidation of organic compounds to yield energy. The process converts
nitrate to nitrous oxide and molecular nitrogen under anoxic conditions.
Density stratification:
.Creation of layers in the
water body due to density differences; controlled by temperature and
concentration of dissolved solids
Density:
The mass of a substance per unit volume
(grams/liter).
Detritivory:
Organisms that feed on detritus
Detritus:
Dead or decaying organic matter.
Diatom: Group of algae characterised by cell wall
made up of silica; usually found attached to rock surfaces.
Dimictic: Having two mixing periods; one in summer
and one in fall.
Dipteran:
True flies.
Dissolved oxygen (DO):
The concentration of
molecular oxygen (gas) dissolved in water; usually expressed in milligrams/litre
or parts per million. Adequate concentration of dissolved oxygen is essential
for fish and other aquatic organisms. DO levels are considered the most
important and commonly employed measurement of water quality and indicator of a
water body’s ability to support desirable aquatic life.
Diurnal: A 24-hour period of time characterised by
one period of rest and one period of activity.
DNA:
Deoxyribonucleic acid.
Drainage lakes:
Lakes having defined surface inlet
and outlet.
Dystrophic:
Organically rich lakes.
Ecological pyramid:
Conceptual scheme whereby the
amount of biomass or energy at each level of the food “chain” decreases as
one moves from the primary producers through the different levels of the
consumers.
Ecosystem:
All of the interacting organisms in a
defined space in association with their interrelated physical and chemical
environment.
Epilimnion:
The upper wind-mixed layer of a
thermally stratified lake. The water is mixed thoroughly, at least during a
portion of the day and because of its exposure can freely exchange gases (such
as O2 and CO2) with the atmosphere.
Erodibility:
The ability to erode (disintegrate).
Euphotic zone:
Layer of water where sunlight is
sufficient for photosynthesis to occur.
Eutrophic lake:
A very biologically productive lake due to relatively high rates of
nutrient input.
Eutrophication:
The process by which lakes and
streams are enriched by nutrients (usually phosphorous and nitrogen) which leads
to excessive plant growth – algae in the open water, periphyton (attached
algae) along the shoreline and the higher plants in the near shore.
Flagella:
Whip like structure that enables motility
in certain groups of algae.
Floodplain:
The flat floor of a wide valley, which is periodically flooded by the river.
Fluorescence:
The property of
some compounds of emitting rays of greater wavelength than those received, when
subjected to radiation.
Food chain:
The transfer of food energy from plants
through herbivores to carnivores. Example, sequence of algae being eaten by
zooplankton (grazers; herbivores) which in turn is eaten by small fish (planktivores,
plankton) which are then eaten by larger fish (piscivores; fish eating
predators) and eventually by other predators (fish eating birds, mammals and
reptiles).
Food web:
Food chains hooked together in a complex
interconnected web.
Frustule:
The
outer cast of diatoms made up of silica.
Grazers:
Herbivores; zooplankton in the open water
zone.
Hepatotoxin:
A substance poisonous to the liver.
Herbivores:
Plant eaters.
Heterocysts:
They are differentiated cells and are major sites of nitrogen fixation found in
cyanobacteria.
Holomictic:
Typically mixes completely throughout
the water column at least once a year.
Hydrosere:
The zone of
succession where the gradation of plants from land into water takes place,
representing a transition from one environment to another.
Hypolimnion:
The bottom and most dense layer of a
stratified lake. It is typically the coldest layer in summer and warmest in
winter. It is isolated from wind mixing and typically too dark for much plant
photosynthesis to occur.
Inflow: Water flowing into a lake.
Inorganic: Substances
of mineral origin.
Ion:
An electrically charged particle.
Isogamy: The
conjugation of two gametes of similar size and form.
Isotopes:
Chemically identical
species of an atom, which have the same atomic, number but different mass
numbers.
Leach:
To remove soluble or other constituents from
a medium by the action of a percolating liquid, as in leaching salts from the
soil by the application of water.
Lentic:
Aquatic ecosystems characterised by standing water such as ponds, lakes etc.
Limnetic zone:
Open water zone.
Littoral zone: Near shore area.
Lotic:
Aquatic ecosystems characterised by running water like rivers.
Macrophytes:
Higher aquatic plants. They have roots
and differentiated tissues and maybe emergent (cattails, bulrushes, reeds, wild
rice), submergent (water milfoil, bladderwort) or floating plants (duckweed,
lily pads).
Mean depth:
The average depth of a water body.
Meromictic:
Lakes that do not mix completely.
Mesotrophic:
Moderately productive; moderate
fertility of a lake in terms of its algal biomass.
Metalimnion:
The middle or transitional zone between
the well mixed epilimnion and the colder hypolimnion layers in a stratified
lake.
Micronutrient:
Trace nutrients required by
microorganisms or zooplankton such as molybdenum and cobalt; nitrogen and
phosphorous are considered as macronutrients.
Monomictic:
Lakes that mix once each year, either in winter or summer.
Moraine:
The
debris of glaciers.
Morphometry:
Relating to the shape of lake basin;
includes parameters needed to describe the shape of the lake such as volume,
surface area, mean depth, maximum depth, maximum length and width, depth versus
volume etc.
Motile:
Ability to move at will.
Nekton:
Nektons are microscopic plants present in open waters and characterised by the
ability to swim.
Neurotoxin:
A
substance poisonous to the nerve tissue.
Neuston:
The collection of minute or microscopic
organisms that inhabit the surface layer of a body of water. Organisms resting
or swimming on the surface of still bodies of water.
Nitrification:
Bacterial metabolism in which
ammonium ion is oxidised to nitrite and then to nitrate in order to yield
chemical energy that is used to fix carbon-di-oxide into organic carbon. These
bacteria are aerobic and so require dissolved oxygen to survive.
Non-point source:
Diffuse source of pollutant(s);
associated with land use such as agriculture or contaminated groundwater flow.
Nutrient loading:
Discharging of nutrients from the
watershed (basin) into a receiving water body (lake, stream, wetland); expressed
usually as mass per unit area per unit time.
Oligomictic:
Lakes do not mix
every year as they are large and have higher heat storing capacity, the mixing
depending on specific climatic conditions.
Oligotrophic:
Very unproductive; lakes low in
nutrients and algae, usually very transparent with abundant hypolimnetic oxygen
if stratified.
Omnivorous:
Capable of eating plants, fungi and
animals.
Oogamy:
Union
of unlike gametes.
Organic:
Substances, which contain carbon atoms and
carbon-carbon bonds.
Orthograde:
The oxygen profiles
in holomictic lakes where water is saturated with oxygen from top to bottom is
called as orthrograde.
Outflow:
Water flowing out of a lake.
Oxic:
Presence of oxygen.
Parthenogenesis:
Reproduction by means of unfertilised ovum.
Pelagic:
The
open waters of a lake.
Periphyton:
Algae attached to substrate like rocks.
pH:
Measure of concentration of hydrogen ions.
Phagotrophy:
Feeding directly on living or dead
particulate organic matter.
Photosynthesis:
The process by which green plants
convert carbon-di-oxide dissolved in water to sugars and oxygen using sunlight
for energy. Photosynthesis is essential in producing a lake’s food base, and
is an important source of oxygen for many lakes.
Phycobilins: They are the
primary light absorbers in cyanobacteria and lack oxygen evolving photosystem
and show higher reducing activity
Phytoplankton:
Microscopic floating plants, mainly
algae, that live suspended in bodies of water and drift about as they cannot
move by themselves or are too small or weak to swim effectively against a
current.
Polymictic:
Lakes that mix intermittently.
Polypeptide:
Amino acids linked to form a peptide and peptides together form polypeptides.
Primary consumers:
First level of consumers,
according to the ecological pyramid concept; organisms that eat herbivorous
grazers.
Primary producers:
Organisms that convert carbon-di-oxide
to biomass. Usually refers to photosynthesisers, bacteria that use chemical
instead of light energy to fix carbon-di-oxide to biomass.
Primary productivity:
The productivity of the
photosynthesisers at the base of the food chain in ecosystems. This refers to
the yield of new biomass (plant) growth during a specified time period. The
entire year’s accumulation is termed annual production.
Profile:
A vertical, depth by depth characterisation
of a water column, usually at the deepest part of a lake.
Raphe:
A slit
present in the cell wall of diatoms.
Resilience:
The ability to regain original state.
Respiration:
The metabolic process by which organic
carbon molecules are oxidised to carbon-di-oxide and water with a net release of
energy. Aerobic respiration requires and therefore consumes molecular oxygen
(algae, weeds, zooplankton, benthic invertebrates, fish, many bacteria, people).
Certain bacteria (denitrifiers) or sulphate (sulphate reducers), but only under
anaerobic (anoxic) sediments or in the hypolimnion after prolonged oxygen
depletion has occurred.
RNA:
Ribonucleic acid.
Secondary consumers:
Consumers such as plankton
eating fish or predatory zooplankton that eat other zooplankton.
Seepage lakes:
Lakes having an inlet or an outlet
but not both; primary water inputs are precipitation and groundwater.
Sorption:
Absorption and/or adsorption
Stratification:
An effect where a substance or
material is broken down into distinct horizontal layers due to different
characteristics such as density and temperature.
Substrate:
Attachment surface or bottom material in
which organisms can attach; such as rock substrate, woody debris or living
macrophytes.
Tertiary consumers:
Larger consumers in the fourth
trophic level.
Thermal stratification:
Existence of turbulently
mixed layer of warm water (epilimnion) overlying a colder mass of relatively
stagnant water (hypolimnion) in a water body due to cold water being denser than
warm water.
Thermocline:
The depth at which the temperature
gradient is steepest during the summer; usually this gradient must be at least 1°C
per meter of depth.
Total dissolved solids (TDS):
The amount of
dissolved substances, such as salts or minerals, in water remaining after
evaporating the water and weighing the residue.
Trophogenic zone:
The lighted zone where organic
matter is synthesised and oxygen generated.
Tropholytic zone:
The dark zone where organic matter
is decomposed and oxygen consumed.
Turnover:
The cooling and warming of surface water
to make density uniform throughout the water column. This allows wind and wave
action to mix the entire lake. Mixing allows bottom waters to contact the
atmosphere, raising the waters oxygen content. However, warming may occur too
rapidly in summer for mixing to be effective.
Watershed:
All land and water areas that drain
toward a river or lake, also called drainage basin or water basin.
Xanthophyll:
Oxygenated derivatives of carotenes.
Zooplankton:
The animal portion of the living
particles in water that freely float in open water, eat bacteria, algae,
detritus and sometimes other zooplankton and are in turn eaten by planktivorous
fish.