Indicators of Water Quality

TurbidityDefinition: •measure of the degree to which water looses its transparency due to the presence of suspended particulates

Acceptable Levels

Ideal level:• low•Measured using a

Secchi Disk

Causes of increased turbidity •increased levels of phytoplankton, •sediment from erosion, •re-suspended sediments from the bottom (stirred by bottom dwellers), •waste discharge, •algae growth, and •urban runoff

Results of high turbidity•high turbidity increases the absorption of sunlight thus making the water warmer•Warmer water has lower levels of dissolved oxygen causing fish and larvae to die

pH (potential hydrogen)

Definition: the acidity of the water which is the presence of hydrogen ions.• 0 to 7 is acidic • 7 is neutral• 7 to 14 is basic

Importance & Ideal Level• The pH of water determines the amount

of nutrients and heavy metals that can be utilized by aquatic life. Nutrients include phosphorus, nitrogen, and carbon. Heavy metals include lead, copper, cadmium, etc.• The ideal level is close to Neutral• Measured using pH paper or Litmus

paper

Causes of changes in pH

• natural conditions (especially in swamps) can lower pH• dumping of waste (batteries)

can lower pH• farm runoff (lime) can raise pH

Results of changes in pH• a change in pH by 2 units results

in a water system having 100 times a difference in acidity. Most aquatic life cannot withstand water outside of the optimum pH thus resulting in death.

Dissolved Oxygen• the oxygen

dissolved in the water• Abbreviated

DO

Acceptable LevelsIdeal level:• Aquatic life

thrives when DO levels are high

• DO levels are measured in parts per million (ppm)

Causes of DO and Level Changes• surrounding air - can increase or decrease DO

levels• turbulent actions (waves, rapids, falls) –

increases DO levels• water depth – water gets colder as it

deepens, colder water holds more DO than warm water

• plant growth or plant activities (like photosynthesis) - can increase or decrease DO levels

Results of changes in dissolved oxygen

• When DO drops too low fish die. In some cases large fish kills are a result of DO. • When DO is high, the water actually

tastes better but can corrode water pipes. Fish can also die from excess amounts of DO.

TemperatureDefinition• the property of matter that shows the

energy of motion. The faster the movement, the higher the temperature. There are several scales used to measure this value (e.g., Kelvin, Celsius, Fahrenheit)

Levels of Tolerance• Low: cannot be

tolerated below 320F

• High: few fish can tolerate temperatures above 850F

Causes of change in temperature

• source of water• time of year• suspended sediment• depth of water• shade from shoreline vegetation

Results of changes in temperature

• changes in temperature can make aquatic life susceptible to disease and at extreme levels can result in death

Nitrates• Nitrates are nitrogen-oxygen

chemical units which combine with various organic and inorganic compounds. • The greatest use of nitrates is as a

fertilizer.

Ideal Levels• Ideal level for human consumption is less than 20

ppm

Causes of Nitrates• fertilizer runoff

(both farm and home)

• manure pits• leaks in septic

systems• animal waste• rain trapping car

exhaust

Results of presence of Nitrates

• Nitrates can increase the plant production and fish population resulting in overcrowding. • If algae increases due to nitrates, the

DO levels can decrease, killing fish. • Nitrates are converted to nitrites in

humans (can kill children)

Bio-indicators• species that are found living in

water • they tend to stay in one place• can be used to monitor the

health of an environment or ecosystem• sensitive to pollution

Acceptable Levels

• High Level of Variety = healthy water source

• Small Level of Variety = poor water source (indicator of high levels of pollution)

Causes of changes in bio-indicators

• pollution that results in changes in pH• temperature• dissolved oxygen• nitrate levels

Results of few varieties of bio-indicators present

• the lack of a large, varied number of bio-indicators indicates pollution in the water system

• bio-indicators can tell us about the increasing effects of pollutants in the ecosystem and about how long a problem may have been present

References

• http://www.pbs.org/safarchive/5_cool/galapagos/g52a_water.html