Eutrophication
Introduction
• The word eutrophication is derived from the greek
words where eu means well and trophe means
nourishment.
• Naturally occuring biological process of the
enrichment of water with nutrients.
• Alters the dynamics of a number of plant, animal
and bacterial populations. thus, bringing about
changes in community structure.
• In absence of control measures, cultural or manmade
eutrophication proceeds at an accelerated rate
compared to the natural one.
• Algal blooms, algal mats , heavy infestation of rooted
macrophytes are main features resulting to
deoxygenation and unpleasant odour.
• Lake become unattractive , commercial as well as
recreational fisheries reduced.
• Ageing of lakes : Prolonged eutrophic conditions lead to
dystrophic state and further extinction of the lakes.
• Limiting nutrient : The one in shortest supply
relative to demand. If you add more of that
nutrient the plants/algae will grow.
Phosphorus freshwater
Nitrogen salt & brackish
• Lakes are generally categorized by limnologists
according to the degree of nutrient enrichment.
• A young lake formed will be of mainly sandy
bottomed, transparent lake with little plant life.
It has low in nutrient input or loading –
oligotrophic lake.
• As the lake becomes older, it receives nutrients
and sediments from the surrounding drainage
basin – mesotrophic lake.
• The lake then eventually becomes nutrient
rich and plant growth in the form of
phytoplankton and rooted aquatic plants, can
occur to a level in which the water becomes
undesirable for various uses – Eutrophication
lake.
STEPS OF
EUTROPHICATION
1. Fertilizer flows into water 2. Increased plant growth on the surface of
causing…. water, causing…..
3. Decreased light in lower levels of water,
causing…
4. Plants in lower levels of water
to die, causing…. 6. Death of fish and other animals.
5. Decay using up O2 and increasing
CO2,causing…...
• The nutrient enrichment of an aquatic
ecosystem.
• Natural Eutrophication – A process that
occurs as a lake or river ages over a period of
hundreds or thousands of years.
• Cultural Eutrophication – A process that
occurs when humans release excessive
amounts of nutrients, it shortens the rate of
aging.
Natural Eutrophication
Lake classification based on
nutrient content and production
of organic matter.
Oligo- nutrient poor
meso- middle nutrient
eu- nutrient rich.
Cultural Eutrophication
• The addition of excess
nutrients from a variety of
sources results in the
rapid aging of aquatic
ecosystems.
• During this process the
species composition of
the aquatic community
changes.
• During the process, many nutrients are locked
into the benthic sediments , so that even if the
major inputs of nutrients are cut off, remains
eutrophic condition.
• A particular genera or even a specific species
alone is not considered to be a good indicator of
pollution or as a warning sign.
• With in any genera, there may be some species
that are good indicators and others that are not.
• In general, this approach is not reliable
because most species are tolerant to wide
range of condition specific to each species.
• However, when algae are studied as a
community, certain group of interrelated
types may be reliable index.
• The most frequent groups are the blue green
algae and the dinoflagellates.
Sources of nutrients
• Point sources
• Sewage treatment plant discharges
• Industrial discharges
• Non-point sources
• Atmospheric deposition
• Agricultural runoff (fertilizer, soil erosion)
Control of algae and eutrophication
• Almost impossible to resolve natural
eutrophication, but it is quite possible to address
the problem of cultural eutrophication.
• Diversion of nutrients.
• Increased flushing or dilution technique.
• The most effective but probably least desired from
an ecologic stand point is the use of chemicals.
• Copper sulfate, kills more than just algae.
Fishes are more susceptible to it , and a build
up in the sediments also possible.
• Herbicides can be used but can have
undesirable long term effects.
• Other chemical strategies include the addition
of aluminium, iron and calcium based
coagulants /precipitants to directly remove
phosphate.
• Temporary and costly, locks the nutrients into
the sediments.
• Chemicals also have been used to shift the pH
to a range more favorable to less offensive
algae or herbivores.
• In a very few cases, species have been used to
eat excess algae or other plant life.
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