stratification in lakes

1. STRATIFICATION IN LAKES
CENTER FOR BIOTECHNOLOGY AND
MICROBIOLOGY
PRESENTED BY
ADAM KHAN C# 3 4
7 TH SEMESTER
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2. INTRODUCTION OF LAKES
A lake is an area, filled with fresh or salt water of
considerable size,localized in a basin, that is
surrounded by land.
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3. TYPES OF LAKE
There are two types of lakes
 Eutrophic lakes
Those that are shallow, saucer-like ones called eutrophic lakes
 Oligotrophic lakes
usually, turbid water and deep, steep-sided ones called oligotrophic
lakes with clear water.
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4. EFFECTS OF EUTROPHICATION
Oligotrophic
Low biomass
High diversity
Complex food web
Oxic waters
Cold-water fish present
High aesthetic quality
No taste or odor problems
Eutrophic
High biomass
Low diversity
Simple food chain
Anoxic bottom waters
Cold-water fish absent
Low aesthetic quality
Taste and odor problems
Rough fish abundant
Toxic algae present
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5. DARAL LAKE VALLEY LALKOO
LAKE
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6. STABILITY OF LAKE STRATIFICATION
 Stable stratification results when waters of differing densities are
positioned vertically in order of their density
 In other words, more density (heavier) water lies below less dense
(lighter) water
 Energy is required to break down this density gradient
 Stability of stratification is the energy required to uniformly mix a
stratified lake.
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7. THERMAL ZONES IN A STRATIFIED
LAKE
6 8 10 12 14 16 18 20 22 24 26
Temperature oC
Depth (m)
0
1
2
3
4
5
6
7
8
9
10
11
12
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8. LAKE COLOR
Scattering and absorption of light
give lake part of its characteristic
color
Clean water - blue color
More and bigger particles scatter
longer wavelengths and absorb
shorter wavelengths
Blue-green, green, yellow
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9. STRATIFICATION OF LAKES
Lake divided vertically into 3 regions
Epilimnion
Metalimnion(thermocline)
Hypolimnion
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10.  Epilimnion –top of the lake
uniformly warm layer mixed by wind
 Metalimnion – middle layer
Intermediate zone where temperature drops rapidly with
increasing depth
 Also referred to as thermocline - plane between two depths
between which temperature change is greatest
.
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11. HYPOLIMNION
THE BOTTOM LAYER.
 uniformly cool lower layer unaffected by wind
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13. CHEMISTRY OF LAKES - OXYGEN
o Oxygen is the second most abundant element in the
atmosphere (20%)
But is only weakly soluble in water (10 ppm)
o Most aquatic organisms require 4-5 mg/L for survival
So… oxygen can be a limiting factor in aquatic systems
The absence of oxygen can allow other chemicals like H2S to
build up. 13

14. LAKE CHEMISTRY - OXYGEN
Sources
 Atmosphere
Photosynthesis
o 6CO2 + 6H20 + light C6H12O6 + O2
Sinks
Respiration
Chemical oxidation
Gas bubbles
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15. NUTRIENT LIMITATION
The growth of algae and higher aquatic plants in lakes is
regulated by conditions of light and temperature and the
availability of those inorganic nutrients required to
support growth. The element most often in limiting
supply is phosphorus, P.
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17. LAKE CLASSIFICATION BY
CIRCULATION
• Amixis refers to a lake that does not ever turnover; called an
amictic lake.
• Holomixis refers to lake turnover. The frequency of mixis over
annual to decadal time scales is used in classifying lakes.
• Dimictic lakes follow the pattern described for temperate lakes;
spring and fall turnovers.
• Oligomictic lakes turnover every few years.
– .
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18. • MONOMICTIC LAKES TURNOVER ONCE.
Cold monomixis:
colder lakes that
inverse stratify
only under
winter ice cover
and mix the
remainder of the
year.
Warm monomixis:
warmer lakes
that mix during
winter (never
freeze over) and
stratify in
summer.
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19. MICROBIAL FAUNA IN LAKES
 Microbes include bacteria, bacteria-like organisms called
archaea, viruses, protozoa, helminths, and protists.
Cyanobacteria are an important group of plants often appearing a dominant
part of the phytoplankton of lakes and reservoirs. They tend to form a
dense surface bloom rising to the surface
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20. THANKS
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