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Dr. Ong Meng Chuan
Department of Marine Science
Faculty of Maritime Studies and Marine ScienceUniversiti Malaysia Terengganu
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CHAPTER 4
NUTRIENT POLLUTION
Pollution is discharged either directly into the sea, or enters the coastal watersthrough rivers and by atmospheric decomposition
To control the impact of pollution on marine environment, it is essential that thetype and load of pollutants be identified
It involves determination of the sources and their location, the volume andconcentration of the pollutants
The discharge of nutrients into coastal waters is a major cause of eutrophicationespecially in areas of limited water circulation
Nutrient pollution is the common thread that links an array of problems along thecoastline, including
o eutrophicationo harmful algal bloomso dead zoneso fish killso some shellfish poisonings
o loss of seagrass and kelp bedso some coral reef destructiono marine mammal and seabird
deaths
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FACT
More than 60 percent of our coastal rivers and bays in every coastal state of the
continental are moderately to severely degraded by nutrient pollution
Many of the wastes entering the aquatic environment are plant nutrients The main nutrients are nitrogen and phosphorus compounds and they enter coastal
waters from point and nonpoint sources
Fertilizers used in agriculture are one source of nutrients reaching the coastal zone
Inputs of plant nutrients enhance the growth of phytoplankton EXAMPLE
o Seto Sea is the largest enclosed body of coastal water in Japan and provides 5%of the countrys commercial catch of fish.
o As Japanese economy grew after World War 2, increasing development resultedin elevated inputs of plant nutrients, boosting primary production in the sea
o The consequence, fishery catches increased
Continued economic growth and development drastically changed the traditionalland use patterns
Although moderate input of organic material may be beneficial, overfertilizationresults in extravagant growth of plants and the bacterial decay of dead plant
material may result in oxygen depletion
Sewage from coastal settlements is also a major source of nutrients in coastal waters
EUTROPHICATION
Simple definition : Increase in chemical nutrient compounds containing nitrogen orphosphorus in an ecosystem, and may occur on land or in water
However, the term is often used to mean the resultant increase in the ecosystem'sprimary productivity (excessive plant growth and decay), and further effects
including lack of oxygen and severe reductions in water quality, fish, and other
animal populations
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Eutrophication was recognized as a water pollution problem in European and NorthAmerican lakes and reservoirs in the mid 20th century
Since then, it has become more widespread Surveys showed that 54% of lakes in Asia are eutrophic; in Europe 53%; in North
America 48%; in South America 41%; and in Africa 28%
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CULTURAL EUTROPHICATION
Cultural eutrophication is the process that speeds up natural eutrophication becauseof human activity
Due to clearing of land and building of towns and cities, land runoff is acceleratedand more nutrients such as phosphates and nitrate are supplied to lakes and rivers,
and then to coastal estuaries and bays
Extra nutrients are also supplied by treatment plants, golf courses, fertilizers, andfarms
Eutrophication is an common phenomenon in marine, coastal waters In contrast to freshwater systems, nitrogen is more commonly the key limiting
nutrient of marine waters; thus, nutrient levels have greater importance to
understanding eutrophication problems in seawater
Estuary tend to be naturally eutrophic because landderived nutrients areconcentrated where runoff enters the marine environment in a confined channel
Upwelling in coastal systems also promotes increased productivity by conveyingdeep, nutrientrich waters to the surface, where the nutrients can be assimilated by
algae
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When an ecosystem experiences an increase in nutrients, primary producers reapthe benefits first.
In aquatic ecosystems, species such as algae experience a population increase (calledan algal bloom)
Algal blooms limit the sunlight available to bottomdwelling organisms and causewide swings in the amount of dissolved oxygen in the water.
Oxygen is required by all respiring plants and animals and it is replenished indaylight by photosynthesizing plants and algae
In addition, runoff from land and atmospheric anthropogenic fixed nitrogen canenter the open ocean
Some scientist found that this could account for around one third of the ocean sexternal (nonrecycled) nitrogen supply
It has been suggested that accumulating reactive nitrogen in the environment mayprove as serious as putting carbon dioxide in the atmosphere
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SOURCES OF HIGH NUTRIENT RUNOFF
Point source Nonpoint source
Soil retention Runoff to surface water and leaching to groundwater Atmospheric deposition
ETC
ECOLOGICAL EFFECT
Many ecological effects can arise fromstimulating primary production, but there arethree particularly troubling ecological
impacts:
o decreased biodiversity,o changes in species composition and
dominance
o toxicity effects
ECOLOGICAL EFFECT
Increased biomass of phytoplankton Toxic or inedible phytoplankton species Increases in blooms of gelatinous zooplankton Decreased biomass of benthic and epiphytic algae Color, smell, and water treatment problems Dissolved oxygen depletion Increased incidences of fish kills Loss of desirable fish species Reductions in harvestable fish and shellfish Decreases in perceived aesthetic value of the water body
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DECREASED BIODIVERSITY
Under eutrophic conditions, dissolved oxygen greatly increases during the day, butis greatly reduced after dark by the respiring algae and by microorganisms that feed
on the increasing mass of dead algae When dissolved oxygen levels decline to hypoxic levels, fish and other marine
animals suffocate
As a result, creatures such as fish, shrimp, and especially immobile bottom dwellersdie off
Zones where this occurs are known as dead zones
NEW SPECIES INVASION
Eutrophication may cause competitive release by making abundant a normallylimiting nutrient
This process causes shifts in the species composition of ecosystems For instance, an increase in nitrogen might allow new, competitive species to invade
and outcompete original inhabitant species
TOXICITY
Algal bloom
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