Lake Succession - Trophic States

Oligotrophic Oligotrophic

Mesotrophic Mesotrophic

EutrophicEutrophic

ExtinctionExtinction

General Characteristics of LakesOligotrophic Eutrophic

1. Deep, steep-sided basin

2. Very low nutrients and org. matter

3. High hypolimnetic DO

4. High light penetration

5. Little or no rooted veg., periphyton in littoral

6. Low phytoplankton density

7. Low fertility

1. Shallow, sloping basin

2. Relatively high nutrients and org. matter

3. Low hypolimnetic DO

4. Low light penetration

5. Rooted and emergent veg.

6. High phytoplankton density

7. High fertility

The Eutrophication Process: Succession

1. Nutrient enrichment

2. Increased organic matter production• Increased growth transfers up the food chain

3. Gradual filling of basin• Sedimentation• Accumulation of slowly decomposing plants

(peat)

4. Terrestrial plant invasion

Lake Succession

Natural succession depends on:1. Original basin shape

• Mean depth

2. Nature of drainage basin• Erosion rates• Soil composition nutrient inputs• Hydrologic residence time

3. Climate• Rain and snowfall• Mean temperature

4. Geologic age

Succession and

Stratification

Cultural (Human Induced) Eutrophication

1. Sources of nutrient enrichmenta. Municipal sewage

b. Industrial wastes

c. Agricultural fertilizers

d. Detergents (phosphorous)

e. Sediment from land clearing, road building, land development

f. Poor forest practices

Cultural Eutrophication

Examples of Cultural Eutrophication

1. The Great Lakes• Large population increases and forest clearing• Point and non-point nutrient sources• Volumes and retention times influence response

- Lake Erie (shallow) – most rapid eutrophication and recovery

- Lake Ontario (deep) – slow recovery due to internal loading

- Lake Michigan (large and deep) – extreme local eutrophication

- Lake Superior (larger volume) – slow response to nutrient loading

Eutrophicationin the Great Lakes

as Reflected in Total Dissolved

Solids

Lake Erie

2. Lake Washington• Progressive eutrophication – highly populated

watershed• Then recovery ( Transparency, Coliform)

following sewage diversion- Relatively rapid response – short hydraulic

residence time (little internal loading)- Mostly a P issue, N levels remained high

Lake Washington Recovery

Lake Washington

25% of the lakes in the US have become Eutrophic within the last

100 years