movement of water, light, heat, and chemicals

brownian motion

• the random, jittery movement of tiny particles suspended in a fluid

• takes place at the finest scales

• higher temps= more motion

movement of water

• brownian motion

• laminar flow

• turbulent flow

laminar flow

unidirectional flow

turbulent flow

eddies, flow vectors in many direction

flow boundary layer

the thin layer of fluid next to a solid surface where viscous forces & friction significantly slow down the fluid motion

stokes law

• sinking rate of small spheres

  • denser, larger spheres, sink more quickly

  • as viscous force increase, sinking slows

if you wanted to design an object that sank the fastest, what would it look like?

big, dense, streamline

forces that move water

• hydrologic cycle

• wind

• coriolis effect

• organisms (bioturbation)

hydrologic cycle

• the movement of water due to solar heating and evaporation of water

• potential energy is gained against gravity when evaporated by the sun

• potential energy is released when water flows downhill and gravity is involved

wind

• important for surface mixing

• importance decreases with depth

coriolis effect

affects large lakes (>100 km²) and the ocean

fick’s law

used to describe chemical diffusion

diffusion in water

• molecular diffusion is due to brownian motion

• advective transport (eddy/ transport diffusion) occurs due to water movement

diffusion boundary layer

• region where molecular diffusion dominates

• similar to the flow boundary layer

• depressions in solid surfaces lead to thicker boundary layers

• thinner layer occur where a solid surface protrudes

SA: V ratio alter diffusion

• smaller the size, greater the ratio (good thing)

• larger SA/V means more area for materials to move across and lower volume means less distance to travel to the surface

why does light matter?

• photosynthesis is driven by light

• organisms with eyes or light sensors use light as a cue

• water is heated by light leading to stratification in lakes

attenuation

light intensity decreases logarithmically with depth

eutrophic

very productive

mesotrophic

moderately productive

oligotropic

nutrient poor, with limited primary production

specific wavelengths of light can be attenuated selectively

• pure water transmits blue light most efficiently

• chlorophyll absorbs red and blue light most efficiently

• cyanobacteria have pigments that can use green light