Lake Succession - Trophic States
Oligotrophic
Mesotrophic
Eutrophic
Extinction
General Characteristics of Lakes
Oligotrophic
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 enrichment
a.
b.
c.
d.
e.
Municipal sewage
Industrial wastes
Agricultural fertilizers
Detergents (phosphorous)
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
Eutrophication
in 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