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Water Quality

APES Exam Review

Water Quality Testing & Monitoring



I. Temperature

Temperature preferences vary between species

Thermal stress and shock can occur when temperatures change more than 1-2 degrees in 24 hrs

II. Turbidity/Cloudiness

High turbidity levels may damage gills and interfere with food gathering by fish

Depth at which you can no longer see through the water is called the secci depth

When the secci depth is more than 1 meter, submerged aquatic vegetation can survive easily


A range of 6.5 to 8.2 is optimal for most organisms

Extreme acid and extreme alkaline conditions are hazardous

IV. Dissolved Oxygen (DO)

A dissolved oxygen level below 3ppm is stressful to most aquatic organisms

DO of 8-9 is very good, below 4 is gravely polluted

V. Nitrate/Nitrogen

Levels above 10ppm considered unsafe for drinking water

Unpolluted water has level below 1 ppm

VI. Phosphate

Total phosphorus levels higher than 0.03 ppm contribute to increased plant growth

Levels above 0.1 ppm can cause plant growth beyond normal eutrophication

VII. Hardness

Defined as the amount of calcium and magnesium (primarily), both of which enter the water mainly by leaching from rocks

Hard water = high amounts of Ca and Mg

Soft water = low amounts of Ca and Mg

VIII. Coliform Bacteria

Permissible fecal coliform levels are lowest for drinking water/well water, a little higher for swimming, and the highest for boating and fishing

IX. Salinity

Defined as the total of all salts dissolved in the water

Seawater = 35 ppt (parts per thousand), freshwater = 0 ppt

X. Carbon Dioxide

Above 25 ppm is harmful to most gill breathers