Light: Guided Reading Questions Flashcards
Describe how light in the ocean behaves differently than in air (on land). How do these differences change how organisms live or interact in the ocean?
The ocean absorbs light much more strongly than air
Blue wavelengths penetrate deepest into the water and this gives it its color
Red, orange and yellow wavelengths are absorbed in the first few meters
Waves on the surface can increase and decrease the brightness of light by factors of 100
Lots of the light is also UV and polarized
Many organisms can see UV and polarized light to make use of it, for detection
What is the difference between light being scattered and light being absorbed? Provide examples of where these two different processes are observed in the ocean. What are the impacts that these processes can have on biological processes?
When light hits molecules and bounces off in all sorts of different directions it is scattered
But it can also have all or part of its wavelength absorbed by a molecule making it disappear
In nearshore waters with lots of phytoplankton, they absorb much of the light and reflect the green light so the water appears much darker and greener
In open ocean with little particles very little light is scattered so it appears blue and bright with high visibility
Imagine you are a vertically migrating zooplankton (or fish, or diver, or….whale). Compare and contrast what you would observe (just thinking about light) as you move from the surface of the ocean to the bottom in an open ocean environment (depth 1000
m +) and in a coastal environment (depth ~ 300 m). What do you think causes the differences in light characteristics between these environments?
In an open ocean environment, I would notice that at the surface there is plenty of full spectrum light and is very bright. As I descend the light becomes less intense but still hold its blue color for quite a while. It would take much deeper for much of the light to be absorbed out and lose colors and light visibility.
In nearshore waters, the surface would appear bright and blue, but just a few meters below the colour would change to green as the blue and red wavelengths are absorbed by phytoplankton. It would also be considerably darker.
What are some adaptations of organisms to the different types and amounts of light that are present at different depths in the ocean?
Phytoplankton have evolved to use blue and green light for photosynthesis
To fight UV damage many have developed UV-absorbing pigments, repair DNA damage, and behaviours to avoid UV by going deeper
Many organisms have body colouration to match the background light for camouflage. Dark backs to match dark depths and light sides and belly to match bright sunlight surface
Compounds to absorb or scatter UV light to make them less visible and eyes to detect UV light to see transparent animals
Why are phytoplankton important? How do phytoplankton both depend on and change,
light in the ocean?
Phytoplankton are essential to producing half the oxygen on earth, providing base of food web for ocean systems and removing greenhouse gases from the atmosphere.
Phytoplankton are dependent on light penetration to photosynthesize but also play a huge role in altering it. Their mere presence can absorb and reflect sunlight to give the ocean an entirely different color and make it appear very dark at the surface.
