1. LAKES

2. WHAT ARE LAKES?
Lakes are inland depressions containing
standing water.

3. WHERE ARE LAKES FOUND?
 All over the world
 Lakes are not evenly distributed on the
earth's surface; most are located in high
latitudes and mountainous regions.
Canada alone contains 50% of the world’s
lakes

4. HOW ARE LAKES FORMED?
 Glacial erosion and deposition
 Shifts in earth’s crust
 Craters of some extinct volcano
 Land slides

5.  Glaciers formed lake basins by gouging holes in loose soil or
soft bedrock, depositing material across stream beds, or leaving
buried chunks of ice that later melted to leave lake basins. When
these natural depressions or impoundments filled with
water, they became lakes.

6. EXAMPLE: GREAT LAKES
Glaciers are responsible for the large basin that holds most of the Great
Lakes. The Great Lakes consist of Lake Superior, Lake Huron, Lake
Michigan, Lake Erie, and Lake Ontario.

7.  Shifts in earth’s crust
EXAMPLE: LAKE TITICACA IN SOUTH AMERICA
The highest large lake in the world is Lake Titicaca in South America. It was formed by
melted ice and snow. The melted ice and snow filled a basin in the Andes Mountains that
was formed by the folding of the mountains that caused cracks or faults in the earth’s
crust.

8.  Craters of some extinct volcano
EXAMPLE: TAAL LAKE

9.  Landslides
EXAMPLE: ALABAD LAKE
lake in the Hunza valley of northern Pakistan created in January 2010 by
a massive landslide.

10. PHYSICAL CHARACTERISTICS OF LAKES
 Light
influenced by silt and
other materials carried
into the lake and by the
growth of phytoplankton.
 Temperature
temperature varies
seasonally and with
depth.

11.  Density
Water is most dense at
4°C and becomes less
dense at both higher and
lower temperatures.
Because of this density-
temperature
relationship, many lakes
in temperate climates
tend to stratify, that
is, they separate into
distinct layers.

12. 3 LAYERS IN LAKE STRATIFICATION
Intense heating of the surface waters of the lake
help create a strong stratification of lake waters.
Epilimnion- an upper layer of circulating warm
water, usually no more than 6 m (20 ft) deep, where
dissolved oxygen concentrations are moderate to
high.
Metalimnion or thermocline- a layer of rapid
temperature and oxygen decrease with depth, often
quite thin, separating the upper and lower layers.
Hypolimnion – a cold, deep-water, non-circulating
layer in which oxygen is low or absent.

14. WHAT IS AN OVERTURN?
 Overturn is a circulation which recharges
oxygen and nutrients through the basin.

15. LAKE OVERTURN
 In temperate lakes, the changing of the
seasons help move water in the lake.
 Tropical lakes often stay stratified because
warm water always stays on the top.
 In temperate lakes the winter months chill
the surface water so that it gets colder
than the water underneath, causing it to
sink. This happens in the spring and fall

16. LAKE OVERTURN IN A TEMPERATE LAKE

18. 1. LITTORAL ZONE
 Shallow-water zone
 Light reaches the bottom
 Stimulates the growth of rooted plants
 the area near the shore at the top of the
lake that receives sunlight

19. 2. LIMNETIC ZONE
 is the sunlight part at the top of the lake,
similar to the littoral zone.
 However, the limnetic zone is the open area
away from the shore.
 Most photosynthesis occurs in this part of the
lake.

20. 3. PROFUNDAL ZONE
 is the deep open water, where it is too
dark for photosynthesis to occur.
 Its beginning is marked by the
compensation level of light, the point at
which respiration balances photosynthesis
 For the profundal and benthic zones, low
levels of photosynthesis result in low
levels of dissolved oxygen.

21. 4. BENTHIC ZONE
 the very bottom of the lake
 Organisms here tend to tolerate cooler
temperatures well.
 Place where decomposition takes place.
 For the profundal and benthic zones, low
levels of photosynthesis result in low levels
of dissolved oxygen.

22. NUTRIENT STATUS
 Eutrophic Systems
 Oligotrophic Systems
 Dystrophic Systems

23. EUTROPHIC SYSTEMS
 Lakes type with high production
 associated with high nitrogen and
phosphorus
 increase in growth of algae and other
aquatic plants.
 May experience oxygen depletion

24. OLIGOTROPHIC SYSTEM
 Water is clear and appears blue to blue green in
the sunlight
 The nutrient content in the water is low; and
although nitrogen is abundant, phosphorus is
highly limited
 Low production of organic mater, particularly
phytoplankton
 Oxygen concentration remains high

25. DYSTOTROPHIC SYSTEMS
 Lakes that receive large amounts of organic
matter from surrounding lands particularly in the
form of humic materials that stain the water brown
 Low only in planktonic vegetation but have
generally high productive littoral zones
 Littoral vegetation dominates the metabolism of
the lake, providing a source of both dissolved and
particulate organic matter.

27. DISSOLVED OXYGEN

28. LAKE ORGANISMS
THOSE THAT GO WHERE THEY CHOOSE
FISH AMPHIBIANS LARGER
TURTLES ZOOPLANKTON
INSECTS
THOSE THAT GO WHERE THE WATER TAKES THEM
LIVING THINGS = PLANKTON DEAD MATERIAL = DETRITUS
animals - zooplankton internal - produced within lake
algae - phytoplankton external - washed in from watershed
bacteria - bacterioplankton
THOSE THAT LIVE ON THE LAKE BOTTOM
BENTHOS = ANIMALS PLANTS BACTERIA & FUNGI
aquatic insects higher plants - sewage sludge
molluscs - clams, snails macrophytes aufwuchs - mixture
other invertebrates - attached algae - of algae, fungi
worms, crayfish periphyton and bacteria

29. PLANT ADAPTATIONS
 Zonation of emergent, floating, and submerged
vegetation at the edge of a lake or a pond as a
response of water depth

30. SHALLOW WATER
Spike rushes and
small sedges
ADAPTATION:
Roots are anchored
in the bottom bud.

31. DEEPER WATER
Bulrushes, reeds, and
cattails
ADAPTATION:
Narrow, tubular, linear
leaves and have
broad leaves

32. FLOATING PLANTS
 Pond lily (Nuphar
spp.) and Pond
weed (Potamegaton)
ADAPTATION:
Poorly developed
root system but
highly developed
aerating system

33. SUBMERGED PLANTS
Certain pond weed
species (Chara
muskgrass)
ADAPTATION:
Lacks cuticles. These
plants absorb
nutrients and gases
directly from the water
through thin and finely
dissected or ribbon
like leaves,

34. ANIMAL ADAPTATION
Fishes lack strong
lateral muscles
characteristics of fish
living in swift water
such as sunfish.
ADAPTATION:
Have compressed
bodies that permit
them to move with
ease through the
masses of acquatic
plants.

35. ANIMAL ADAPTATIONS
 Diving insects such
as water boatman
and Diving beetles
ADAPTATION:
Carry a bubble of air
with them when they
go under water in
search of prey.

36. HUMAN IMPACT
The shore line is parceled into lots, residences spring up, nutrient seep in
the septic tanks and pesticides find their way into the lake. Before long
the structure of the lake changes.

37.  Motorboats discharge an oily mixture that can lower oxygen levels
and adversely affect the growth and longetivity of fish.
 Wake created by motor boating disturbs littoral vegetation.

38. HUMAN IMPACT
 Overfishing, pollution and introduction of
exotic species accidentally or on purpose
 Human activities like road construction,
logging, mining, agriculture add another
heavy loads of silts and nutrients, especially
nitrogen, phosphorus and organic matter.

39. END OF REPORT