The intensity and quality of light that goes into the water and are absorbed produces heat. From the point of ecological, thermal energy and its relationship with the things that happen in the water, is a very important factor in maintaining water as a living environment for animals and plants. Temperature is an important physical factor everywhere in the world. The increase in temperature accelerates chemical reactions; The law according to van’t Hoff temperature rise of 10 ° C will double folding reaction speed, although this is not always applicable law.
For example, the process of metabolism will increase as the temperature rises to a peak and then declined again. Any changes in temperature are likely to affect many chemical processes that occur simultaneously on the network of plants and animals, thereby also affecting the overall biota. In the process of egg hatching temperature affects the length of time of incubation of eggs, for example in fish hatcheries higher the water temperature, the faster the incubation time. At a temperature of 29 ° C incubation period of 27-32 hours and at a temperature of 31.5 ° C incubation time from 20.5 to 22 hours.
Temperature is one of the parameters measured water often, because of their usefulness in studying the physics, chemistry and biology. The water temperature varies with the circumstances of space and time. Temperatures tropical waters are generally higher than the temperature of the main sub-tropical waters in winter. Deployment in open water temperatures mainly caused by the movement of water, such as currents and turbulence. Molecular hot deployment can be said to be very little or almost nothing (Romimohtarto, 1985).
The properties of this water heat affecting aquatic environments consist of:
a) Heat types
Water is one of the substances that have a high specific heat, which is very good for the environment. This type of heat is a capacity factor of heat energy to raise the temperature of a unit weight on a scale of 1ºC.
Temperature directly or indirectly greatly influenced by sunlight. Heat possessed by the water will experience a gradual change between day and night and from season to season. In addition, water has the properties where the maximum density occurs at a temperature of 4 ° C and not at the point of freezing. The water temperature affects the amount of oxygen dissolved in the water. If the temperature is high, the water will be quickly saturated with oxygen compared with a low temperature.
The water temperature in a body of water can be affected by season, latitude (latitude), elevation above sea level (altitude), time of day, cloud cover, the flow and depth of water. Increased water temperatures lead to increased viscosity, chemical reaction, evaporation and volatisasi as well as a decrease in gas solubility in water such as O2, CO2, N2, CH4, and so on. The range of water temperatures is necessary for the growth of fish in tropical waters may take place ranging between 25-32 ° C.
The temperature range is generally applicable in Indonesia as a tropical country so it is advantageous to carry out fish farming activities. The water temperature affects the process chemistry, physics and biology in the waters, so that the temperature changes in a body of water will result in changes in all the processes in the waters. It is seen from the increase in water temperature, the solubility of oxygen is reduced. Increased water temperature 10 ° C resulted in increased consumption of oxygen by aquatic organisms around 2-3 times, so that the oxygen demand by increasing aquatic organisms.