2. WHAT IS EUTROPHICATION??
Eutrophication or more
precisely hypertrophication, is the ecosystem
response to the addition of artificial or natural
substances, such as nitrates and phosphates,
through fertilizers or sewage, to an aquatic
system. One example is the "bloom" or great
increase of phytoplankton in a water body as a
response to increased levels of nutrients.
Negative environmental effects include hypoxia,
the depletion of oxygen in the water, which
induces reductions in specific fish and other
animal populations. Other species (such
as Nomura's jellyfish in Japanese waters) may
3. causes
Eutrophication can be human-caused or
natural. Untreated sewage effluent and
agricultural run-off carrying fertilizers are
examples of human-caused
eutrophication. However, it also occurs
naturally in situations where nutrients
accumulate (e.g. depositional
environments), or where they flow into
systems on an ephemeral basis. The three
main causes are:-
=> LAKES AND RIVERS
=> OCEAN WATERS
=> TERRESTRIAL ECOSYSTEMS
4. LAKES AND RIVERS
Eutrophication generally promotes excessive plant growth and decay,
favouring simple algae and plankton over other more complicated
plants, and causes a severe reduction in water quality. The addition of
phosphorus increases algal growth, but not all phosphates actually feed
algae.These algae assimilate the other necessary nutrients needed for
plants and animals. When algae die they sink to the bottom where they
are decomposed and the nutrients contained in organic matter are
converted into inorganic form by bacteria. The decomposition process
uses oxygen and deprives the deeper waters of oxygen which can kill
fish and other organisms. Enhanced growth of aquatic vegetation
or PHYTOPLANKTON and ALGAL BOOMS disrupts normal
functioning of the ecosystem, causing a variety of problems such as a
lack of OXYGEN needed for fish and SHELL FISH to survive. The water
becomes cloudy, typically coloured a shade of green, yellow, brown, or
red. Eutrophication also decreases the value of rivers, lakes, and
estuaries for recreation, fishing, hunting, and aesthetic enjoyment.
9. ECOLOGICAL EFFECTS
Many ecological effects can arise from stimulating PRIMARY
PRODUCTION, but there are three particularly troubling
ecological impacts: decreased biodiversity, changes in species
composition and dominance, and toxicity effects.
Increased biomass of PHYTOPLANKTON
Toxic or inedible phytoplankton species
Increases in blooms of gelatinous ZOOPLANKTON
Increased BIOMASS of BENTHIC and EPIPHYTIC ALGAE
Changes in MACROPHYTE species composition and biomass
Decreases in water transparency (increased TURBIDITY)
Colour, smell, and water treatment problems
DISSOLVED OXYGEN depletion.
11. PREVENTION AND REVERSAL
While eutrophication does pose problems, humans should be aware that
natural runoff (which causes algal blooms in the wild) is common in
ecosystems and should thus not reverse nutrient concentrations beyond
normal levels.
EFFECTIVENESS - Cleanup measures have been mostly, but not
completely, successful. Finnish phosphorus removal measures started in
the mid-1970s and have targeted rivers and lakes polluted by industrial and
municipal discharges. These efforts have had a 90% removal
efficiency.Still, some targeted point sources did not show a decrease in
runoff despite reduction efforts.
MINIMISING NONPOINT POLLUTION- Nonpoint pollution is the most
difficult source of nutrients to manage. The literature suggests, though,
that when these sources are controlled, eutrophication decreases. The
following steps are recommended to minimize the amount of pollution
that can enter aquatic ecosystems from ambiguous sources.
12. Riparian buffer zones- Studies show that intercepting non-point pollution
between the source and the water is a successful means of prevention.
RIPARIAN BUFFER ZONES are interfaces between a flowing body of water
and land, and have been created near waterways in an attempt to filter
pollutants; SEDIMENT and nutrients are deposited here instead of in water.
Creating buffer zones near farms and roads is another possible way to
prevent nutrients from traveling too far. Still, studies have shown that the
effects of atmospheric nitrogen pollution can reach far past the buffer zone.
This suggests that the most effective means of prevention is from the
primary source.
Prevention policy- Laws regulating the discharge and TREATMENT OF
SEWAGE have led to dramatic nutrient reductions to surrounding
ecosystems,[but it is generally agreed that a policy regulating agricultural use
of FERTILIZERS and animal waste must be imposed. In Japan the amount of
nitrogen produced by livestock is adequate to serve the fertilizer needs for
the agriculture industry. Thus, it is not unreasonable to command livestock
owners to clean up animal waste—which when left stagnant will LEACH into
ground water. Policy concerning the prevention and reduction of
eutrophication can be broken down into four sectors: Technologies, public
participation, economic instruments, and cooperation.