POLLUTION
AND AQUATIC BIODIVERSITY
Pollution alters the
natural habitat. Water pollution especially injurious to the biotic components
of freshwaters, estuary and coastal ecosystem. Toxic wastes entering the water
bodies disturb the food chain, and so to the aquatic ecosystems. Insecticides,
pesticides, sulfur and nitrogen oxides, acid rain, ozone depletion and global
warming too, affect adversely the aquatic plant and animal species.
The word “Pollution”
is derived from a Latin word “Pullure” which means 'to soil' or 'to defile’
Pollution means an undesirable change in physical, chemical or biological
characteristics of air, land and water that may or will harmfully affect the
human, animal and plant life
Contamination of
environment with impurities making it unfit for its intend use is known as
pollution
Pollution may be defined as contamination of air, water or soil with undesirable
amounts of material
water pollution defined as " the introduction (into a body of water) of substances
of such character and in such quantity that its natural quality is so altered
as to impair its usefulness or render it offensive to the sense of sight, taste
or smell"
Marine pollution
The introduction by man,
directly or indirectly, of substances or energy (e.g. heat) into the marine
environment (Including estuaries) resulting in such deleterious effects as harm
to living resources, hazards to human health, hindrance to marine activities
including fishing, impairment of quality for use of seawater and reduction of amenities.
Coastal pollution
· The impact of coastal pollution is also very
important
· It is seen that coral reefs are being threatened by
pollution from industrialization along the coast, oil transport and offshore
mining
· Noise pollution is also the cause of wildlife
extinction
· According to a study Arctic Whales are seen on the
verge of extinction as a result of increasing noise of ships, particularly ice
breakers and tankers
Pollutant
A substance the presence
of which causes pollution is known as pollutant. At least seven kinds of
potential environmental pollutants are found in the oceans
(1) Toxic chemical
substances,
(2) Fertilizers,
(3) Organic matter,
(4) Bacterial
contamination,
(5) Radioactive
contamination,
(6) Thermal
contamination, and
(7) Inert solid matter
Some of the sources and types of wastes causing
pollution in coastal and marine environment
|
Sources
|
Waster discharged
|
|
Municipal sewers
|
Waste oil; street
washing; raw sewage; suspended sediments
|
|
Municipal sewage plants
|
Nutrient (phosphate and
nitrate); sewage sludges (solids from treatment)
|
|
Industrial wastes
|
Waste chemicals; e.g.,
acids, petrochemicals; waste oil
|
|
Runoff from
agricultural lands
|
Nutrient from
fertilizers; pesticides and herbicides; animal wastes
|
|
Electrical power plants
|
Waste heat; ash (from
coal); chemicals (corrosion inhibiting, foam (suppressing)
|
|
Dredging operations and
construction activities
|
Suspended sediments
|
|
Petroleum production
and exploration
|
Suspended sediments
(drilling, mud); crude oil
|
|
Ships (commercial and
recreational)
|
Untreated sewage;
garbage; waste oil
|
Sewage pollution and
eutrophication
This involves untreated
sewage or sewage which has undergone some level of treatment either to remove
organic material, reduce the coliform bacterial count and, very occasionally,
to remove nutrients and heavy metals
In general the forms of
pollution from sewage entering the aquatic environment are:
(1) Pathogenic organisms
(2) Eutrophication from
nutrients
(3) BOD to decompose
organic matter
(4) Heavy metal
contamination from industrial outfalls, and
(5) Chlorinated organic
compounds may occur which are potentially carcinogenic
Petroleum hydrocarbon
· Hydrocarbons are natural constituents of water since
they are produced by both phytoplankton and zooplankton.
· The non -volatile hydrocarbons dissolved in ocean waters
are reported to be 1 to 10 ppb, but may be much higher in areas of tanker
traffic, natural oil seeps or oil spills.
· Petroleum oils entering the oceans probably, amount
to are 6 X 106 tons per year of which a large fraction comes from
uncontrollable sources such as river runoff, atmosphere, and natural seeps.
· Less than half of the petroleum oils entering the
oceans come from the transportation and exploration of oil by the industry.
· During the last 30 years over 400 oil spills
(>200 tons) from tankers have occurred.
· The largest of these were the Amoco Cadiz (22,000
tons) and Torrey Canyon (117,000 tons) while many others were considerably
smaller (i.e. < 10,000 tons). In addition, large blow outs have occurred
such as in the Gulf of
Mexico in 1979 when 430,000
tons of crude oil entered the marine environment.
The general effects of an oil spill on the marine
biota
· Vary
with location, weather conditions, the amount spilled, and the type of oil
· Generally
the more volatile, low molecular weight oils are the more toxic in terms of
narcotic and carcinogenic activity towards higher organisms
· However
in coastal areas the presence of oil on littoral organisms can result in the
total annihilation of most populations of fauna and flora
· The
number of marine birds is decreasing day by day due to their slow rate of
recovery
· Small
amounts of petroleum hydrocarbons on the feathers can cause penetration of
water to the bird's body and eventually death from exposure
· Larger
quantities of oil prevent feeding and flying of aquatic organisms and birds
· Fish
eggs and larvae under experimental conditions may also be killed or undergo
abnormal development
· Pelagic
bacteria have been reported to be enhanced by low concentrations of be
hydrocarbons (ca. 10 µg/l) but inhibited at concentrations >300 u.g/1
Chlorinated hydrocarbons
· Chlorinated
hydrocarbons are used both in agriculture (e.g. dichlorodiphenyltrichloro-ethane,
DDT) and in industry (e.g. polychlorinated biphenyl, PCBs).
· These
substances are generally toxic and in some case lethal at quite low
concentrations.
· In
addition the use of DDT type compounds for spraying gives rise to appreciable
quantities in the atmosphere which can then be transported globally and
eventually deposited very widely in the oceans.
· Chlorinated
hydrocarbons inhibit photosynthetic activity. Chlorinated hydrocarbons are
toxic to aquatic environment.
· Some
marine birds are affected, including eggshell thinning; reduced breeding success
etc.
Effect of chemicals on biodiversity of aquatic
animals
· Annually
4,000-5,000 tones of 242 types of pesticides and 1.6 million tones of
fertilizer are used in Bangladesh.
· The
indiscriminate use of hazardous chemicals for crop production is detrimental to
resident and other aquatic fauna.
· Killing
of fish by pesticides mainly occurs due to the use of pesticides in improper
doses, use of banned chemicals and the aerial spraying of chemicals.
· Use
of harmful pesticides especially the organochlorine (popular to crop farmers)
has a detrimental effect on biodiversity of small indigenous species of fish in
the floodplains.
Among others the notable pollutants are
1. Heavy metals
2. Thermal contamination
3. Radioactive materials
4. Aquaculture nutrient
5. Chemicals and medication
6. Hatchery pollution
Pesticide and chemical
pollution in Bangladesh
· Bangladesh is an agricultural as well as highly populated
country and total area used for agriculture is very small compared to her
population.
· It is, therefore, needed to produce enough crops per
unit area to supply food for increased population.
· Farmers use different types of fertilizer, pesticide
and other chemicals to increase crop production.
· Use of pesticides in crop fields begins in 1940s
with the introduction of DDT.
· Since then many types of pesticides have been used
to remove insect, herb, fungus and pest.
· Generally higher than recommended rates of
pesticides and other chemicals are used in field.
· Pesticides have a high residual effect on wildlife
and its effect can be intact for many years.
· These chemicals used in crop fields finally find
their way to water bodies river, canal, ocean etc. though rainfall, flood and
water used for irrigation.
· Many pesticides also used directly for aquaculture
some of the chemicals used in crop fields.
Some of the chemicals used in crop fields
1. monocrotophos
2. Phosphamidon
3. Diazinon
4. Fenthoate
5. Malathion
6. Dimethoate
7. Diclorovos
8. Zinc phosphide
9. Amitrol
10. Simazine
Chemical
used in fish pond
|
Chemical/Drug
|
Purposes
|
|
Chemical/Drug
|
Disinfections of pond water & soil Prevention
of common fish disease
|
|
Bleaching powder
|
Disinfections of pond water & soil Prevention
of common fish disease
|
|
Dipterex
|
Eradication of external parasites of fish
|
|
Melathion/sumithion
|
Remove of copepods/crustacean parasites
|
|
Formalin
|
Eradication of external parasites of fish
|
|
Melachite green
|
Remove of fungus, cyst of parasites of fish
|
|
Methylene blue
|
Eradication of bacteria & fungus
|
|
KMnO4
|
Remove of external parasites and fungus
|
|
Sodium chlorite
|
For eradication of external parasites of fish
|
|
Cupper sulphate
|
Remove bacteria, fungus and ectoparasites
|
Fertilizers
used in crop fields and fish ponds
1.
MnO4
2. Urea
3. TSP
4. MP
5. Gypsum
6. ZnO
Conclusion
· Many of the pollutants entering aquatic ecosystems
(e.g., mercury lead, pesticides, and herbicides) are very toxic to living
organisms.
· They can lower reproductive success, prevent proper
growth and development, and even cause death.
· The organisms that are most directly and adversely
affected by toxic pollutants consist of larvae, eggs, and other organisms that
live at the surface or near the bottom of aquatic habitats where pollutants
tend to settle.
· Filter feeders (e.g., clams, and mussels) and other
organisms higher up in the food chain (e.g., swordfish, tuna) are also affected
by the presence of toxicants.
· Pesticides affect aquatic plants and animals by
impeding their growth and altering the composition of the mix of species.
