Lecture 3: Movement of Light, Heat and Chemicals in Water

Attenuation

The gradual loss of light intensity as it penetrates deeper into water, typically following a logarithmic pattern.

Eutrophic

Water bodies rich in nutrients and biological activity, leading to high rates of light attenuation due to increased particle presence.

Chlorophyll a

A green pigment in plants that absorbs red and blue wavelengths of light for photosynthesis, reflecting green light.

Surface Ripples impact

Small waves on the water's surface that can enhance light reflection and penetration, impacting photosynthesis efficiency.

Depth Penetration

The extent to which light can reach into the water column, which decreases with depth due to microorganism absorption

Fick's Law

A formula that describes the diffusion process. J is diffusion flux, D is the diffusion coefficient, and C is concentration.

Molecular Diffusion

Caused by Brownian motion. diffusion by thermal movement of molecules, leads to mixing. Typically slow and dominant near solid surfaces.

Transport Diffusion

Diffusion that occurs due to turbulent flow in liquids, making it a faster and more efficient means of mixing.

Heat Capacity

The amount of heat energy required to raise the temperature of a substance; water has high heat capacity.

Mesotrophic Lake

A lake with moderate nutrient levels and biological activity.

Oligotrophic Lake

A lake that is nutrient-poor and has low biological activity.

Thermal Gradient

A change in temperature within a body of water that can cause movement and stratification due to density differences.

Advection

The process of heat and substances being transferred through the movement of fluid.

Diffusion Boundary Layer

A region near a solid surface where concentration gradients differ significantly from the bulk solution, affecting diffusion rates.

Diffusion from the Atmosphere

The transfer of heat from faster-moving air particles to water through collision, which affects water temperature.

Heat Distribution

The process by which heat energy is spread throughout a water body through diffusion and advection.

Stratification

Layering of water in a water body caused by differences in temperature and density.

Low Productivity Lakes Color

Low productivity lakes are not green because they primarily appear blue, as they have maximum blue light transmission and absorb red wavelengths. The low presence of chlorophyll a, which reflects green light, keeps them from appearing green.

High Productivity Lake

A lake that is rich in nutrients, resulting in abundant biological activity. These lakes often appear green due to the presence of chlorophyll a, as plants absorb red and blue wavelengths of light for photosynthesis and reflect green light.