Biology Lecture

Lecture #1

• photons are absorbed in water & organic particles

o signal is degraded

• photos can also be scattered

o short wavelengths are scattered more easily, therefore the sky is blue because the light is scattered randomly

o long wavelengths (i.e., red & orange) reach the earth

o scattering of light from the objects removes information

o scattering of light from another object adds superfluous information

 scattering into path of view = veiling effect

• walking or swimming through fog

• different aquatic ecosystems have different spectral compositions due to organic matter, depth, etc.

o clear lakes or open oceans, coral reefs: very deep

 all colour visible at the surface

 red is absorbed very easily

 at approximately 200m deep there is nothing but blue spacelight (light around you), becoming increasingly dimmer until 1000m, where there is no light

o coastal areas, temperate lakes: typically shallow

 more organic particles/plant materials

 organic absorbs short wavelengths and water absorbs red wavelengths, causing the spacelight to look green-yellow

 colour does not transmit much information

o acidic tannins/lingins, peat bogs, black water river: very shallow

 water looks like tea

 decomposition of plant material, produces tannic acid (as in tea)

 burden of organic material that absorbs nearly all wavelengths except for orange/red spacelight

 below 3-4m, light does not reach

 Rio Negro in the Amazon contains endemic fish that have adapted to acidity and lack of light; a tributary from another river intersects it and contains completely different