Tolerance Range

Just like species have geographic ranges, they also have a range of tolerance to abiotic environmental conditions. In other words, they can tolerate (or survive in) a certain distance of a particular factor, but it can not survive if there is too much or too little of a factor. Measuring temperature, for example. polar bears survive very well in low temperatures, but will die from overheating in the tropics. On the other hand, the giraffe is not very good in the heat of the African savanna, but will quickly die frozen in the Arctic. This example shows an important aspect of the tolerance range - different kinds of organisms have different tolerance ranges for the same factor. And in fact, the tolerance limits of the individual may change from time to time; individuals of certain species of salmon, for example, started life in the flow of fresh water, migrate to the open sea, and then return to their home streams to reproduce. salmon tolerate large changes in salinity (salt content) of various water passes during the journey, and also experienced a lot of changes in water temperature.

Most of the changes in water temperature as a result of the use of land activities generally upward trend. Exceptions are under cold water release from storied artificial impoundments that can alter the flora and fauna for many miles downstream from the dam. Most of the other activities that generally raise the temperature of receiving waters with the following effects:

(A) A higher temperature reduces the solubility of oxygen dissolved and thus lowers the availability of this important gas.

(B) Increased temperature increases metabolism, respiration and oxygen demand of fish and other aquatic life, roughly double the respiration for 10 ° C temperature rise. Therefore, increased oxygen demand in conditions where oxygen supply is derived.

(C) The solubility of many toxic substances increased and intensified with increasing temperature.

(D) A higher temperature fish life contradicts desired by supporting the growth of mold waste and putrification of sludge, and finally

(E) even with sufficient dissolved oxygen, there is a maximum temperature of each species of fish or other organisms can tolerate. higher temperatures resulted in death. The maximum temperature of adult fish can tolerate varies with the species of fish, acclimatization before, the availability of oxygen and the synergistic effects of other pollutants.