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Water Quality Indicators. A Fish Story. How did we alter the quality of the water for the fish? What physical changes did you see happening to the water? What chemical changes do you think were happening?. Water Quality.
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A Fish Story • How did we alter the quality of the water for the fish? • What physical changes did you see happening to the water? • What chemical changes do you think were happening?
Water Quality • The health of a water system is determined by the balance between physical, chemical, and biological variables. Physical variables include temperature, turbidity, and water movement. Chemical variables include dissolved oxygen and other gases, pH, nitrates, and salinity. Both natural and man-made forces are constantly changing these variables.
Our indicators of water quality.. • Turbidity • pH • Dissolved oxygen • Temperature • Nitrates • Bioindicators
Turbidity • Measure of the degree to which water loses its transparency due to the presence of suspended particulates. • Basically how cloudy or clear water is! • What would cause an increase in turbidity? When erosion occurs, when an increase in algae occurs, etc.
What happens to water when turbidity increases? • The cloudy water is able to absorb more sunlight than clear water. • This means the water heats up faster. • Warm water doesn’t hold as much dissolved oxygen (remember, when atoms warm up, they move faster). • This makes it difficult for fish to live!
How do we measure turbidity? • We measure turbidity with a SECCHI DISK!
pH • This should be a review! • Remember, there are acids, bases, and neutral! • Acids would be like lemon juice (it burns your eyes) pH is 0-6.9 • Bases would be like detergents (they feel oily) pH is 7.1-14 • Pure water is neutral, it has a pH of 7.
pH • Pollutants usually cause a change in pH. • Examples: battery acid runoff would LOWER THE pH (make it more acidic); farm runoff of fertilizers would RAISE the pH (make it more basic). • Either of these conditions would harm fish.
Dissolved Oxygen • The oxygen dissolved in the water. • If the DO drops too low, fish will die! • Things that decrease DO: high turbidity, high temperature! • A healthy amount of algae will keep the DO levels healthy (remember they make oxygen via photosynthesis). But TOO MUCH ALGAE will actually increase the turbidity, causing the DO LEVELS TO DECREASE.
Temperature • Remember, cold water holds DO better because the molecules are moving SLOWER. • Warmer water has less DO. • Causes of change in temperature: source of water, time of year, suspended sediment, depth of water, and shade from shoreline vegetation
Nitrates • Nitrates: compound that contains the nitrogen based polyatomic ion NO3 • (Ex: Sodium Nitrate) • Causes of nitrates: fertilizer runoff (both farm and home), manure pits, leaks in septic systems, animal waste, and rain trapping car exhaust
Nitrates • 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)
Bioindicators • macroinvertibrates found living in water (they tend to remain in one place) that are sensitive to pollution • Causes of changes in bio-indicators: pollution that results in changes in pH, temperature, dissolved oxygen, or nitrate levels • Results of few varieties of bio-indicators present: the lack of a large number of different varieties of bio-indicators is indicative of pollution
Question: • Which of these six indicators do you think we altered by adding things to the tank during “A Fish Story”?
