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PLHS Environmental Science

D. Blanck, MS

Lake Successionand Eutrophication

Trophic StatesOligotrophic

Mesotrophic

Eutrophic

Extinction

Characteristics of Trophic States

1. Shallow, sloping basin2. Relatively high

nutrients and org. matter3. Low hypolimnetic DO4. Low light penetration5. Rooted and emergent

veg.6. High phytoplankton

density7. High fertility

1. Deep, steep-sided basin2. Very low nutrients and

org. matter3. High hypolimnetic DO4. High light penetration5. Little or no rooted veg.,

periphyton in littoral6. Low phytoplankton

density7. Low fertility

EutrophicOligotrophic

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Oligotrophic diagram

Mesotrophic Diagram

Eutrophic Diagram

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The Eutrophication Process:Succession

1. Nutrient enrichment2. Increased organic matter production

• Increased growth transfers up the food chain3. Gradual filling of basin

• Sedimentation• Accumulation of slowly decomposing plants

(peat)4. Terrestrial plant invasion

NaturalLake

Succession

Natural succession depends on:1. Original basin shape

• Mean depth2. Nature of drainage basin

• Erosion rates• Soil composition → nutrient inputs• Hydrologic residence time

3. Climate• Rain and snowfall• Mean temperature

4. Geologic age

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Cultural (Human Induced)Eutrophication

1. Sources of nutrient enrichmenta. Municipal sewageb. Industrial wastesc. Agricultural fertilizersd. Detergents (phosphorous)e. Sediment from land clearing, road building,

land developmentf. Poor forest practices

CulturalEutrophication

A Lake Erie dock

Eutrophicationin the Great Lakes(Total Dissolved

Solids)

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It doesn’t just “go away”

Septic Tank Cutaway

Septic System