Chapter 4 - Nutrient Pollution.pdf

7/29/2019 Chapter 4 - Nutrient Pollution.pdf

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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

Aquatic Pollution | MMS 3202 2

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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