In the provision of drinking water, the color strongly associated with aesthetics. The color of the water can be used as the appropriate type of processing instructions. Based on the cause substances, water color can be distinguished:
a) True Color (true color)
True colors due to the organic substances in the form of colloids. This color will not change even though experienced filtration and centrifugation. Examples of true color, ie the color of tea water, waste water the color of the textile industry, as well as the color due to humus acid, plankton, or due to the death of aquatic plants.
b) Pseudo Color (apparent color)
False color caused by particles suspended in the water. This color will change after filtered or centrifuged and can undergo precipitation. False color will be more concentrated when water turbidity increases.
Sunlight is the energy source for all life aquatic organisms. Biologically light is very important, without sunlight all life processes will not take place and there will be found the forms of life on this earth. While the terms of physics, the sun is the energy source for the currents, waves, warm waters and others. Sinar has an important meaning in conjunction with a variety of symptoms, including vision, photosynthesis, and heating.
Eyes sensitive to light strengths are different. Easy prey animals know their predators in the light than in the dark. In conjunction with photosynthesis, intensity and wavelength of light is very important. Solar radiation determines the intensity of light at a specific depth and also greatly affect the temperature of the water. Daily or annual variation in temperature of a body of water is the result of (a) beam, (b) vaporization (evaporation) and (c) heat conduction.
The sunlight that falls on the surface of the water, will be partly reflected and partly penetrate into the water. The reflected light depends on:
a. When in the waters falling angle (angle of inclination)
Angle of fall is the angle calculated from a line perpendicular to the surface of the water. In the fall 60o angle of light reflected by 6%; at 70o and 80o by 13.4% amounting to 34.8%.
c. The state of the surface of the water
To calm surface reflected light is greater than the wavy surface of the water.
d. The duration of irradiation
During the day the sun height changes, causing major changes in the part of the reflected light. It can be seen from the intensity of radiation in the afternoon decreases faster under water than above it, so that at night time the reflected light of the moon will be greater.
e. The nature of the water itself
there are many particles, either in the form of very fine clay, mud granules, phytoplankton and zooplankton will affect the sunlight through the water.
In terms of the productivity of the waters, the light that penetrates the surface of the water is very important. This light undergo assimilation (disperse) and absorbed (absorption) and that is absorbed will be converted into heat energy.
The sunlight that goes into the waters is meaningful for the life of the organism. Without sunlight, photosynthesis will not take place. The relationship between light intensity with the possibility of photosynthesis in the water vertically divided into three parts, namely:
photic zone (euphotic zone).
In this zone the light intensity is so high that phytoplankton actually acts as a producer. The lower limit of the euphotic zone is where the sun is no longer effective as producers or where marine plants can no longer effectively serve as an energy source for a variety of physiological processes. The physiological process dikenalsebagai respiration process, so it can be said that the lower limit of the euphotic zone is the depth at which the production of organic material (P) by marine plants is equal to the amount required for the ongoing respiration (R). So P = R or commonly referred to as the depth of compensation. This zone has a depth of up to ± 200 m.
Zone Twiligth (disfotic zone).
In this zone the light intensity so low that phytoplankton is not an effective producer. Producers in this area is not only alive and able to grow and multiply. If the state compensation P = R, then this dimintakat production of organic material (P) is smaller than the amount of organic material needed for respiration (R). Thus it is clear that there is a producer who is just dimintakat live alone and less likely to grow well. These waters have a depth of up to ± 1000 m.
Zone afotik (aphotic zone).
This Dimintakat tidakadacahaya sun so that the organism is obtained only heterotrophic organisms and saprofit. In this zone is also called the sea zone in which this zone also has a large hydrostatic pressures, temperatures were cold, very weak water circulation and supply of foodstuffs bit.
Sunlight in addition to a role in the process of photosynthesis also plays a role in heating water or fluctuations in water temperature, vision for the animals that live in these waters, vertical migration, and may also cause damage to the organism.