What is pH?
pH is a measure from 0 to 14 of the acidity or alkalinity of a solution. In molecular terms, pH (parts Hydrogen) is a measure of the concentration of H+ ions in a substance; the more H+ ions are present, the lower the pH measurement will be. The strongest acids (substances with the most H+ ions) have a pH of 0, neutral solutions have a pH of 7, and the most basic substances have a pH of 14. Something with a pH above 7 is called basic, or alkaline, while something with a pH of less than 7 is called acidic. Lemon and lime juices both have pH values around 2 and are acids. Battery acid is an even stronger acid with a pH of only 0.5. Household bleach is a very strong base and has a pH of 12.5. Distilled water, which is pure H2O, has a pH of 7. Both strong bases and strong acids can be harmful to life.
Some organisms can survive in only a narrow range of pH, while others are more tolerant of changes in pH. Streams and lakes generally have pH values in a range from 6 to 9, but a single stream will have a narrower range of pH values.
Why is pH important to aquatic life? It is important because the concentration of free hydrogen ions (H+ ions) in water affects the concentration and form of other important molecules, such as nutrients and toxic metals, in water. When water is acidic, for example, more metal ions can be dissolved into the water from rocks and sediments it runs over. When water is too basic, even small amounts of ammonia, a nitrogen-based compound that is a product of the decomposition of plant and animal material, becomes poisonous to fish.
Why is Water Temperature Important? | What is Dissolved Oxygen (DO)? | What is pH?
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