What is pH?
It is a general measurement of the acidity or alkalinity of a water
sample. The symbol pH stands for the "potential for hydrogen".
What factors influence the pH of water?
1. Rainwater provides a significant amount of water to a watershed.
Acid rain is caused by increased amount of nitrogen oxides and sulfur
dioxides automobile and coal-fired power plant emissions. Nitrogen oxides
and sulfur dioxides are changed to nitric acid and sulfuric acid when
they interact with water in the atmosphere. These acids combine with
moisture in the air and fall to the earth as acid rain or snow. Consequently,
the pH of rain influences the overall pH of the watershed.
2. The kind of rocks or soil around a watershed over which runoff passes
can also affect the overall pH. If limestone is present, the alkaline
rocks may neutralize the acidic water.
3. Algal blooms may cause the waters pH to become more basic.
4. As aquatic plants decompose, they release carbonic acid into the
water.
What is the optimal pH for most aquatic plants and animals?
1. Most living organisms require a pH that is near neutral (pH=7). Pure
deionized water has a pH that is neutral because it has an equal number
of hydrogen (H+) and hydroxide (OH-) ions.
2. A pH level between 6.5-7.5 is considered to be excellent.
3. A pH level between 6.0-6.4 or 7.6-8.0 is considered to be good.
4. A pH level between 5.5-5.9 or 8.1-8.5 is considered to be fair.
5. When the water becomes too acidic (pH=0-7) or basic (pH=7-14), few
organisms survive. Serious problems occur when the pH is below 5 or
above 8.5.
What factors are affected by your watersheds pH?
1. Most aquatic organisms are adapted to a specific pH level. When the
pH increases or decreases rapidly, the diversity of a water ecosystem
can change dramatically.
2. Immature stages of aquatic insects and young fish are extremely sensitive
to low pH values, thus, pH can affect hatching and development of aquatic
animals. Fish larvae and eggs usually have a narrower pH requirement
than adult fish. Also, the optimal pH of Brine Shrimp embryos to leave
their shell is 7.5-8.5.
3. When acidic water comes in contact with certain chemicals and metals
that occur in soil and bedrock, these toxic sediments are often released
into the waters causing the water to be more toxic than normal. Very
acidic water can cause heavy metals, such as copper and aluminum, to
be released into the water. Heavy metals can collect on fish gills or
cause deformities in young fish, making it hard for them to survive.