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Lakes contain a balance of positive and negative ions. Each lake
has three major negative ions that balance four major positive ions
when their amounts are summed together:
- Negative ions (anions) Positive ions (cations)
- Bicarbonate (HCO3-) Calcium (Ca+2)
- Sulfate (SO4-2) Magnesium (Mg+2)
- Chlorine (Cl-) Sodium (Na+)
- Potassium (K+)
Other compounds make up less than 1% of the
ion balance for freshwater lakes:
- phosphate
- nitrate (NO3-)
- ammonium
All of these ions and compounds must balance each
other out for the lake to be considered "healthy."
Problems occur when one or more nutrients exceeds
their natural levels. Nutrient loading usually occurs when people
disturb one of the elements in the watershed. Lakes are subject
to two dangers that increase nutrient loading:
- Soil erosion caused by disturbing the landscape (i.e., filling
in a stream or river)
- Nonpoint source pollution
Of all of these compounds, phosphates are the most
critical ones to keep in balance because the element phosphorus
controls the amount of algae in the water, and as a result, the
amount of oxygen available for fish to survive.
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