Water Resources, Lake Processes, Ecology, and Limnology

Vocabulary flashcards covering key definitions, principles, and concepts from Lectures 1 through 8 on aquatic ecology, limnology, water physics, lake mixing, optics, plankton biology, and biogeochemical cycles.

Limnology

The study of inland aquatic systems, including organisms, water chemistry, physics, resources, and human interactions.

Hydrogen Bond (in Water)

An attraction between a hydrogen atom of one water molecule and the oxygen atom of another.

Calorie

The energy required to raise $1\,\text{mL}$ of water by $1\,^\circ\text{C}$.

Thermal Inertia

Resistance to rapid changes in temperature.

Mining an Aquifer

Removing groundwater faster than it is naturally replaced.

Cirque Lake

An amphitheater-shaped glacial lake formed by scouring at the head of a valley.

Paternoster Lakes

A chain of glacial lakes resembling beads on a string.

Fjord

A deep, steep-sided glacial lake or inlet along a coastline.

Kettle Lake

A lake formed when a buried block of glacial ice melts and leaves a depression that fills with water.

Graben

A block of Earth's crust that drops between faults.

Rifting

Land sinking between approximately parallel faults.

Caldera

A large volcanic depression caused when magma removal causes the ground to collapse.

Oxbow Lake

A lake formed when a river meander becomes separated from the main river channel.

Lake Mixing

The vertical circulation of lake water.

Lake Stratification

The development of water layers that resist vertical mixing.

Epilimnion

The warm upper layer of a stratified lake.

Hypolimnion

The cold deep layer of a stratified lake.

Metalimnion

The transition layer between the epilimnion and hypolimnion in a stratified lake.

Thermocline

The zone within a lake where temperature changes rapidly with depth.

Isothermal

Having approximately the same temperature from top to bottom.

Dimictic Lake

A lake that undergoes vertical mixing twice each year.

Thermal Bar

A springtime vertical density gradient that restricts mixing between nearshore and offshore water.

Fetch

The distance wind travels across open water.

Seiche

A standing oscillation caused when water sloshes back and forth across a lake.

Seiche Period Equation

$T = \frac{2L}{n\sqrt{gh}}$, where $L$ is lake length, $n$ is number of nodes, $g$ is acceleration due to gravity, and $h$ is lake depth.

Internal Wave

A wave occurring between distinct water layers in a stratified lake.

Upwelling

The movement of deep or bottom water toward the surface.

Laminar Flow

Smooth fluid flow where adjacent layers of water mix very little, common at low speeds and small scales.

Turbulent Flow

Chaotic fluid flow characterized by strong mixing, occurring at higher speeds and larger scales.

PAR (Photosynthetically Available Radiation)

Electromagnetic radiation in the range of approximately $400\text{--}700\,\text{nm}$ used by organisms for photosynthesis.

Light Attenuation Equation

$I_z = I_0 e^{-kz}$, where $I_0$ is subsurface irradiance, $I_z$ is irradiance at depth $z$, and $k$ is the attenuation coefficient.

Compensation Depth

The depth receiving about $1\%$ of subsurface light, where net photosynthetic production equals zero.

CDOM (Colored Dissolved Organic Matter)

Dissolved organic matter that strongly absorbs ultraviolet and blue wavelengths of light in water.

Secchi Disk

An instrument used to estimate water clarity without a light meter.

Seston

All particulate matter suspended in water, including both living and nonliving components.

Bioseston

Living particulate matter suspended in water.

Tripton

Nonliving particulate matter or detritus suspended in water.

Nekton

Larger aquatic organisms capable of swimming independently and overcoming water turbulence, such as fish.

Plankton

Small aquatic organisms whose movement is strongly influenced by water turbulence.

Meroplankton

Organisms that spend only part of their life cycle as plankton.

Benthos

Organisms living on or in the bottom substrate of an aquatic ecosystem.

Photoautotroph

An organism that uses light for energy and $\text{CO}_2$ as its carbon source.

Photoheterotroph

An organism that uses light for energy but relies on organic compounds for its carbon source.

Chemoautotroph

An organism that obtains energy from inorganic chemical reactions and carbon from $\text{CO}_2$.

Chemoheterotroph

An organism that obtains both its energy and carbon from organic compounds.

Autochthonous Organic Matter

Organic matter produced inside a body of water.

Allochthonous Organic Matter

Organic matter entering a lake or stream from outside sources, such as the watershed.

Microbial Loop

A food-web pathway where microorganisms assimilate dissolved organic matter and transfer that energy up to higher trophic levels.

Periphyton

A complex community of algae and other microorganisms attached to submerged plants, rocks, or other surfaces.

Parthenogenesis

A form of reproduction where females produce offspring without fertilization.

Ephippium

A protective saddle-like structure containing resting eggs produced by certain branchiopods.

Diapause

A dormant developmental period in an organism's life cycle.

Cyclomorphosis

Seasonal or predator-induced development of altered defensive body structures across generations.

Eutrophication

Nutrient enrichment of an aquatic ecosystem leading to excessive plant and algal growth.

Cultural Eutrophication

Human-accelerated nutrient enrichment of water bodies occurring over years or decades.

DRP (Dissolved Reactive Phosphorus)

Soluble phosphorus operationally defined by passing through a $0.45\,\mu\text{m}$ filter.

Liebig's Law of the Minimum

The principle stating that organism growth is controlled by the essential nutrient in shortest supply relative to demand.

Redfield Ratio

The atomic stoichiometry ratio of carbon, nitrogen, and phosphorus ($\text{C}:\text{N}:\text{P}$) in plankton, defined as $106:16:1$.

Point Source Pollution

A discrete, single measurable source of pollution discharge, such as a pipe.

Nonpoint Source Pollution

A diffuse, unlocalized source of pollution, such as agricultural runoff.

Internal Phosphorus Loading

The recycling or release of phosphorus into the water column from lake sediments.

Bioturbation

The physical disturbance and resuspension of aquatic sediment caused by living organisms.

Nitrification

A two-step aerobic bacterial process converting ammonium ($\text{NH}_4^+$) into nitrite ($\text{NO}_2^-$) and subsequently nitrate ($\text{NO}_3^-$).

Denitrification

An anoxic biological process that converts nitrate ($\text{NO}_3^-$) to nitrogen gas ($\text{N}_2$).

Nitrogen Fixation

The energetic conversion of atmospheric nitrogen gas ($\text{N}_2$) into biologically usable forms like organic nitrogen or ammonia ($\text{NH}_3$).

Heterocyst

A specialized cyanobacterial cell designed for anaerobic nitrogen fixation.