The document discusses water pollution in lakes, focusing on limnology, lake stratification, and productivity as well as the classification of lakes into oligotrophic, mesotrophic, eutrophic, and senescent. It explains the processes of natural and cultural eutrophication, the nutrient requirements for algal growth, and the impact of acidification on lake ecosystems. Solutions to mitigate acidification include liming and reducing air pollution to prevent acid rain.

1. Water Pollution in
Lakes
Cañaveral | Eleccion | Gingoyon | Manto | Sarong | Ybarley

2. Limnology
the study of the biological,
chemical, and physical
features of lakes and other
bodies of fresh water.
2

3. Stratification
& turn over
Seasonal movement of water
from top (epilimnion) to bottom
(hypolimnion) in a lake.
3

4. Let’s start with the first set of slides
4
Turn over

5. Biological
Zones
Euphotic Zone
Littoral Zone
Benthic Zone

6. Euphotic Zone
✘ The upper layer of water through
which sunlight can penetrate
✘ Plant growth
✘ Depth is determined by the
amount of turbidity blocking
sunlight penetration
✘ Plants produce more oxygen by
photosynthesis than they
remove by respiration
✘ Profundal zone – lies
below the euphotic
zone
✘ Light compensation
level – the transition
between the two zones

7. Littoral Zone
✘ The shallow water near the shore in which
rooted water plants can grow
✘ The extent of the littoral zone depends on the
slope of the lake bottom and depth of the
euphotic zone
✘ Cannot extend deeper than the euphotic zone

8. Benthic Zone
✘ Bottom sediments
✘ Bacteria are always present
✘ Presence of worms, insects and other higher life
forms

9. LAKE
PRODUCTIVITY
 a measure of its ability to support a food
web and may be determined by
measuring the amount of the algal
growth that can be supported by the
available nutrients.
 The base of the food web is algae
 Increased productivity generally results
in reduced water quality because of
undesirable changes that occur as algal
growth increases.

10. Oligotrophic
Eutrophic
Mesotrophic
Senescent
10
Classification of
Lakes

11. Classification of Lakes
Oligotrophic Lakes
- have a low level of productivity due to
a severely limited supply of nutrients to
support algal growth.
- As a result, the water is clear enough
that the bottom can be seen at
considerable depths.
- Euphotic zone often extends into the
hypolimnion, which is aerobic.

12. Lake Tahoe
California-Nevada

13. Classification of Lakes
Eutrophic Lakes
- have a high productivity
because of an abundant supply of
algal nutrients.
- algae cause the water to be
highly turbid, so the euphotic
zone may extend only partially
into the epilimnion.

15. Classification of Lakes
Mesotrophic Lakes
- lakes which are intermediate
between oligotrophic and
eutrophic
- substantial depletion of
oxygen may have occurred in
the hypolimnion, it remains
aerobic.

16. Penland Lake
Oregon

17. Classification of Lakes
Senescent Lakes
- very old, shallow lakes which have thick organic
sediments and rooted water plants in great
abundance
- these lakes wil eventually become marshes

18. Dwarf Lake
Sky Lakes Wilderness

19. EUTROPHICATION
Is a natural process in which lakes gradually
become shallower and more productive
through the introduction and cycling of
nutrients
Thus, oligotrophic lakes gradually pass through
the mesotrophic, eutrophic, and senescent
stages, eventually filling completely

20. Cultural Eutrophication
- caused when human activity speeds the
processes naturally occurring by increasing the
rate at which sediments and nutrients are added
to the lake.
- lake pollution can be seen as the intensification
of a natural process

21. Algal growth
requirements
MACRONUTRIENTS
a. CARBON
b. NITROGEN
c. PHOSPHORUS
d. MICRONUTRIENTS
- TRACE ELEMENTS
NOTE!
For algae to grow,
ALL nutrients must be
available

22. C ARBON
✘ Obtained from carbon
dioxide in water
✘ When algae are either
consumed or die and
decompose, the organic
carbon is oxidized back to
carbon dioxide

23. N itrogen
✘ Usually in the form of nitrates [NO3
−
]
✘ Converting nitrogen gas to organic
nitrogen though nitrogen-fixing bacteria
such as cyanobacteria
✘ Comes from external sources by way of
inflowing streams or groundwater
✘ Aerobic
○ When taken for algal growth, forms
amino-nitrogen NO2
−
○ When algae dies, forms ammonia
[NH3 ]
✘ Anaerobic
○ Nitrate is reduced to [N2] through
denitrification

24. P hosphorus
✘ Originates from external
sources
✘ Taken up by algae in the
inorganic form [PO4
3−
] and
incorporated into organic
compounds
✘ When algae dies, returns to
its inorganic form

25. Trace elements
✘ a chemical element
required only in minute
amounts by living
organisms for normal
growth
✘ Most fresh waters have
sufficient amounts for a
substantial algal population

26. Acidification
of
lakes

27. Acidification of lakes
Change towards more acidic conditions in
lakes
A lake can be considered acid or slightly
acid when pH is below neutral (<6.5). More
evident biological consequences will
develop at pH < 5.5.
👉
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28. Causes
✘ Acid Rain
is caused by emissions of sulphur
dioxide and nitrogen oxide, which react
with the water molecules in the
atmosphere to produce acids.
✘ Buffer Solution
a solution that resists changes in pH
when acid or alkali is added to it.

29. Harmful Effects
✘ Fish and other aquatic animals will die in
water with low pH.
✘ Acidified water cannot be used for drinking.
First the water has to be neutralized (neutral
pH), as acidic water is damaging to your
health and could possibly cause kidney
problems.
✘ High aluminum concentrations are often the
trigger that kills fish

30. Solution
✘ Liming Method
de-acidification of the lakes by
adding a suspension of calcium
carbonate.
✘ Stop air pollution at its source and so
reduce acid rain.