Water Quality

Water Quality

• How are physical and biological factors used to determine water quality?–How do we know if water is safe to drink?

–How do we know if water is safe for aquatic organisms?

Water Quality Indicators

• Temperature• Dissolved Oxygen• pH• Nitrates and Phosphates• Turbidity• Bio-Indicators

TemperatureCauses of Temperature Change:• Color of water:

– Dark colored water or dark muddy bottoms absorb more heat.

• Water depth: – Deep waters usually are colder than shallow waters

simply because they require more time to warm up.

• Shade: – Shoreline vegetation and trees that cover the water

prevent water from heating to fast.

• Location and time of year

TemperatureEffects of Temperature Change:• Rapid temperature change and temperature

extremes can stress aquatic organisms.• Fish and most aquatic organisms are cold-

blooded. – Their metabolism increases as the water warms

and decreases as it cools.

• Each species has its own optimum water temperature. – If the water temperature shifts too far from the

optimum, the organism suffers.

TemperatureEffects of Temperature Change:• Temperature affects the oxygen-

carrying capacity of water.–As the water warms, the amount of

dissolved oxygen decreases.– If high water temperatures are

combined with low dissolved oxygen levels, the toxicity is increased.

Dissolved Oxygen• Dissolved Oxygen is oxygen that is

dissolved in water. It gets there by –diffusion from the surrounding air–aeration of water that has tumbled over

falls and rapids–a waste product of photosynthesis.

• Fish and aquatic animals cannot split oxygen from water (H2O) or other oxygen-containing compounds.

Dissolved OxygenCauses for Lack of Dissolved Oxygen:• Warm water holds less oxygen• Overpopulation—too many

organisms using Dissolved Oxygen• Over-fertilization of water plants by

run-off from farm fields containing phosphates and nitrates (the ingredients in fertilizers).

Dissolved OxygenEffects of Dissolved Oxygen• Dissolved Oxygen below 3.0 parts

per million, can cause the most versatile fish to die.

• High Dissolved Oxygen in a community water supply makes drinking water taste better. –But speeds up corrosion in water pipes.

pH• pH is the measure of the hydrogen ion

(H+) concentration. • The pH scale is zero to 14.

– Pure water has a equal number of H+ and OH- ions, which makes it neutral 7.

• Most aquatic organisms exist within a pH range of 5.5 to 9.5.

Acidic BasicNormal Levels

pHCauses of change in pH:• Lakes or ponds

–age and the chemicals discharged by communities and industries.

Effects of pH:• More acidic water can kill certain

aquatic organisms.–A change of .3 units a day can put a fish

into shock

Phosphates

• The element phosphorus is necessary for plant and animal growth. –Phosphate concentrations in clean water is generally low.

Phosphates

• Causes of high Phosphorus–Fertilizer from runoff–Detergents–Natural mineral deposits.

PhosphatesEffects of high amounts of Phosphates:

• Can over stimulate the growth of aquatic plants and algae.

–This will cause high Dissolved Oxygen consumption and death to fish and many aquatic organisms.

Nitrates

• Nitrates are a form of nitrogen and is a primary plant nutrient.

• Excess nitrate causes algal blooms that reduce water quality.

Nitrates

Causes of increased Nitrates:• Waste water• Fertilizer from runoff• Discharge from car exhaust

NitratesEffects of increased Nitrogen:• Stimulate the growth of plankton and water

weeds that provide food for fish. – May increase the fish population. – If algae grow too wildly, oxygen levels will be

reduced and fish will die.

• Nitrates can be reduced to toxic nitrites in the human intestine, and many babies have been seriously poisoned by well water containing high levels of nitrate-nitrogen.

Turbidity

• Turbidity refers to water clarity.• Sediments suspended and/or

dissolved in the water decrease the amount of light that is able to pass through.

Turbidity

Causes• Soil erosion of agricultural

lands, forest soils exposed by logging, degraded stream banks, overgrazed rangelands, strip mines, and construction.

• Plankton

TurbidityEffects:• Interference with sunlight penetration. • Large amounts of suspended matter may clog

the gills of fish and shellfish and kill them directly.

• Suspended particles may provide a place for harmful microorganisms to lodge and reproduce.

• Difficulty finding food. – May make it easier for fish to hide from

predators.

Turbidity• Turbidity is the clarity of water or how much dirt is in

the water.• Low Turbidity water is clear, less dirt• High Turbidity water is polluted, more dirt• Dirt• #1 cause of pollution• Decreases oxygen• Contents blocks sunlight from reaching plants• Rises temperatures causing Thermal Pollution, this

causes water to expand and lose oxygen• Gets in gills of fish • Crushes fish eggs

Bioindicators• Bioindicators are living organisms

that provide information about the health of an ecosystem. – Lichens, which are plants that live on trees

rocks and soil, are very sensitive to toxins in the air.

– Algae blooms are often used to indicate large increases of nitrates and phosphates in lakes and rivers.