B.  Dissolved Gases
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B. Dissolved Gases 1. Oxygen – Dissolved Oxygen (DO) vital to aquatic life Sources that ↑ DO PowerPoint PPT Presentation


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B. Dissolved Gases 1. Oxygen – Dissolved Oxygen (DO) vital to aquatic life Sources that ↑ DO atmosphere or aeration fromriffles (water over rocks) Photosynthesis (peaks during afternoon). Temperature affects DO: ↑ temp means ↓ DO ↓ temp means ↑ DO

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B. Dissolved Gases 1. Oxygen – Dissolved Oxygen (DO) vital to aquatic life Sources that ↑ DO

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B. Dissolved Gases

1. Oxygen – Dissolved Oxygen (DO)

vital to aquatic life

Sources that ↑ DO

atmosphere or aeration fromriffles (water over rocks)

Photosynthesis (peaks during afternoon)


Temperature affects DO:

↑ temp means ↓ DO

↓ temp means ↑ DO

(decomposition of organic matter

wastes with ↑ temps)

Other DO effects include pollutants such as acid mine drainage, sewage or agricultural runoff


Recommended DO level for aquatic life is above 5ppm


Mayfly nymph


Caddisflies


2. Carbon Dioxide- vital to plants

sources to ↑ CO2:

atmosphere

groundwater

decomposition

sources to remove CO2

photosynthesis

organisms absorb in form of

carbonates in shells


C. pH

Measure of the hydrogen ion concentration (H+)

PA streams are slightly acidic due to

1. acid rain

2. rocks in PA contain minerals

3. coal mines (AMD)

Fortunately, many PA streams have good buffering capabilities


Is a pH of 5 more or less acidic than a pH of 6?

More acidic

How much more acidic?

10 x


D. Alkalinity – measure of water’s ability to neutralize acids

Helps maintain pH at optimum level

Determined by types of soil and bedrock through which the water passes

Streams with limestone have ↑ alkalinity


E. Nitrates – in streams occurs as nitrate (NO3 ) nitrite (NO2 ) and ammonia (NH3 )

Nitrate enters stream from fertilizer runoff, septic systems or manure runoff

Excess nitrates will cause rapid plant growth

When excess plants die, decomposition uses large amount of DO


F. Iron

Excess iron from acid mine drainage ( remember: pyrite is iron sulfide, yellow boy is ferric hydroxide)

Iron precipitates (solids) clog gills and suffocate bottom dwelling invertebrates


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