TEMPERATURE

Water temperature is an important factor for survival of aquatic life. Very high and very low water temperature can kill many aquatic plants and animals. The temperature can affect how an organism’s internal mechanisms (metabolism) work. For example salmon and trout prefer temperatures between (4.5E C) 40E and 20E C (65E F). Different stages of the growth of fish are susceptible ranges of fish. In the summer when temperatures are high, juvenile fish actively look for the cooler pools of water. A fish must pump water across its gills to meet its need for oxygen. If the dissolved oxygen in water is low, the gills must move faster to get enough oxygen for the fish to survive.

Thermal pollution can occur when heated water is discharged into cooler streams or rivers. This heated water generally is from power plants or industrial processes. If the water is not cooled down before entering into a stream or pond, it can cause organisms to die of increased temperature. 

pH

A simple test to determine chemicals dissolved in water that might be harmful to organisms is pH. The percentage of free hydrogen (H% ) and a hydroxy ion (OH-) determines the pH of the liquid. Pure water (HOH) is made up one part hydrogen and one part hydroxy and given a neutral standing or a "7." If you have more hydrogen than hydroxy it is an acidic solution. If the hydroxy ions, are greater than the hydrogen ions you have a basic or alkaline solution. The concentration of the hydrogen ions [H+] in a solution determines the pH.

A pH of 6.0 to 9.0 is the range that fishes and invertebrates can successfully survive. Each species has its own tolerance level. The table below gives some special effects of pH on fish and aquatic life.

 

Minimum	Maximum	Effects
3.8	10.0	Fish eggs could be hatched, but deformed young are often produced
4.0	10.1	Limits for the most resistant fish species
4.1	9.5	Range tolerated by trout
	4.3	Carp die in five days
4.5	9.0	Trout eggs and larvae develop normally
4.6	9.5	Limits for perch
	5.0	Limits for stickleback fish
5.0	9.0	Tolerable range for most fish
	8.7	Upper limit for good fishing waters
5.4	11.4	Fish avoid waters beyond these limits
6.0	7.2	Optimum (best) range for fish eggs
	1.0	Mosquito larvae are destroyed at this pH value
3.3	4.7	Mosquito larvae live within this range

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