Basic oceanography, Marine biology: Light weakens exponentially when reaching tr

Question

Basic oceanography, Marine biology:

Light weakens exponentially when reaching trough the ocean, as the formula below shows us:

Id = I0 e-Kd

Where ID og I0 are the intensity of light in the depth, (d) and the depth 0, (at the water’s surface).

K is an extinction coefficient, which tells us how fast the light weakens, and is affected by the closeness of particles in the ocean.

a) What makes K change from one place to another or one time to another?

b) What is PAR and how are PAR’s abilities to reach trough the ocean dependant of wavelength of light?

Explanation / Answer

a) The value of "K" changes from one place to another or one time to another because it depends on density of material in which it is moving, the turbidity that is present in the medium, the amount of microscopic bio-organisms that is present in the water i.e "K" is dependent on the amount of foreign material or the closeness of particle (density) of medium.

b) PAR stands for Photosynthetically Active Radiation which is light rays of 400 to 700 nanometer wavelength range they are important because they are needed by green plants for photosynthesis. The penetration of light wave in general or PAR in specific is dependent on wavelength with long wavelengths light rays like red, yellow, and orange can penetrate to approximately 15, 30, and 50 meters respectively and the short short wavelengths of the light spectrum violet, blue and green can penetrate further, to the lower limits.

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