Lake Ecology Vocabulary

Vocabulary terms and definitions covering limnology, basin origins, physical water properties, mixing patterns, light attenuation, dissolved oxygen dynamics, and metabolic balances from the lecture notes.

Limnology

The science of the physical, chemical, biological, and meteorological study of inland waters.

Reservoir

A man-made lake or pond.

Inland Waters

Bodies of water located within land boundaries, including reservoirs, swamps, rivers, streams, wetlands, ponds, bogs, and fens.

Ecosystem

A unit where living organisms collectively interact with physical and chemical factors.

Epilimnion

The top thermal layer of a stratified lake.

Thermocline

The middle thermal layer of a stratified lake where temperature changes rapidly with depth.

Hypolimnion

The bottom thermal layer of a stratified lake.

Lake Nyos Disaster

A $1986$ limnological event in which cooling and rainfall disrupted lake stratification, entraining hypolimnetic water and releasing a lethal amount of carbon dioxide ($\text{CO}_2$).

Covalent Bond (in Water)

The chemical bond that holds a single water molecule together by sharing electrons between oxygen and hydrogen.

Hydrogen Bond

An intermolecular bond that links separate water molecules together.

Specific Heat

The amount of heat energy needed to change the temperature of $1\text{ g}$ of a substance by $1^\text{o}\text{C}$.

Viscosity

A measure of a liquid's resistance to flow, which is inversely proportional to water temperature.

Hydrological Balance

The ecological balance expressed by the formula $\text{Precipitation} = \text{runoff} + \text{evaporation} + \text{transpiration}$, or $P = Q + E + T$.

Water Balance Equation

The balance equation represented by $Q_o = Q_i + P - E$.

Cirques

Glacial lake basins formed by the carving and damming of mountain valleys.

Moraine Lakes

Lakes formed when accumulated glacial material acts as a dam.

Mean Depth

A morphometric index calculated as $\text{Mean depth} = \frac{\text{volume}}{\text{surface area}}$.

Water Residence Time

The average time required to refill a lake basin with new water if emptied, calculated as $\text{Water residence time} = \frac{\text{reservoir volume}}{\text{average annual inflow}}$.

Flushing Rate

The reciprocal of water residence time, expressed in units of $\text{year}^{-1}$.

Paleoclimate Research

The study of ancient climates and environments prior to the existence of widespread modern instrumentation.

Photic Zone

The upper layer of a body of water that approximately corresponds to the $1\text{\%}$ light depth for Photosynthetically Active Radiation (PAR).

Amictic Lake

A lake that does not mix.

Cold Monomictic Lake

A mainly frozen lake that undergoes mixing once per year.

Cold Polymictic Lake

A lake that undergoes constant mixing.

Warm Polymictic Lake

A shallow tropical or subtropical lake without ice cover that experiences frequent turnover with weak, short-lived stratification.

Dimictic Lake

A lake that undergoes mixing twice a year, during spring and fall.

Meromictic Lake

A lake with persistent stratification that never undergoes complete mixing to the bottom.

Vertical Attenuation Coefficient ($K_D$)

The light extinction coefficient measured in units of inverse length.

Winter Kill

A phenomenon where low dissolved oxygen under snow and ice kills aquatic organisms as photosynthesis decreases while respiration continues.

Biological Oxygen Demand (BOD)

A measure of oxygen consumption used as a proxy for the organic matter consumed by microbes.

Hypoxia

Low dissolved oxygen conditions defined as concentrations below $2\text{ mg}\text{ dm}^{-3}$.

Anoxia

The complete absence of oxygen, defined as $0\text{ mg}\text{ dm}^{-3}$ dissolved oxygen.

Diurnal Oxygen Variation

The daily fluctuation in dissolved oxygen caused by changing balances of photosynthesis and respiration.

Clinograde Oxygen Profile

A dissolved oxygen profile where oxygen concentration decreases with depth due to elevated hypolimnetic respiration.

Orthograde Oxygen Profile

A dissolved oxygen profile where oxygen concentration is higher in the hypolimnion than in upper waters.

Positive Heterograde DO Profile

A vertical dissolved oxygen profile characterized by a metalimnetic oxygen maximum.

Negative Heterograde DO Profile

A vertical dissolved oxygen profile characterized by a metalimnetic oxygen minimum.

Volumetric Hypolimnetic Oxygen Depletion Rate (VHOD)

The rate at which hypolimnetic oxygen is consumed per unit volume.

Redox Potential

A measure of the balance and intensity of oxidizing versus reducing conditions, expressing an environment's tendency to receive or supply electrons.

Internal Loading

The return of nutrients that have settled to the lake bottom back into the water column.

Autotrophic

Describing an organism or system capable of primary production and using $\text{CO}_2$ as a carbon source using light energy.

Heterotrophic

Describing an organism or system that obtains metabolic energy and growth from the degradation of organic molecules.

$P:R$ Ratio

The ratio calculated by dividing gross primary production ($P$) by community respiration ($R$).

Gross Primary Production (GPP)

The total rate of photosynthesis in an ecosystem before accounting for losses to respiration.

Respiration (R)

The total respiratory demand or oxygen consumption of all living organisms in a system.

Net Ecosystem Production (NEP)

The net organic production calculated as $\text{NEP} = \text{GPP} - \text{R}$.

Autochthonous

Originating from within the system, such as organic carbon produced by internal primary producers.

Allochthonous

Originating from outside the system, such as organic carbon supplied to a lake from its surrounding watershed.