The document outlines the causes and effects of marine dead zones. It begins by defining marine dead zones as areas of ocean with low oxygen levels caused by nutrient pollution from human activities like agriculture and development near coasts. Specifically, excess nitrogen and phosphorus from fertilizer runoff leads to algal blooms that die off and deplete oxygen as they decompose. This process, called eutrophication, is exacerbated by poor water circulation. When oxygen levels fall below 2mg/l, hypoxia results, harming marine life. Currently there are over 400 dead zones worldwide, with the largest in the Gulf of Mexico and off China's coasts. The document goes on to discuss the environmental, economic, and social impacts of

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3. Outline
 What is Marine Dead Zone (MDZ) ?
 History of Ocean Dead Zones
 Dead zones around the world
 How this happens?
 What causes hypoxia?
 When does the hypoxia occur?
 Environmental, Social & Economic effects
 What can be done?
 HABHRCA
 QUIZ TIME
 Conclusion
 Acknowledgement
 References
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4. What is Marine Dead Zone (MDZ) ?
 NOAA
 Hypoxia = Reduced level of oxygen in the water
 Less oxygen dissolved in the water
 Occur naturally OR created or enhanced by human
activity.
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5. What is Marine Dead Zone (MDZ)? cnt.
 Many physical, chemical, and biological factors
combine to create dead zones
 Nutrient pollution is the primary cause – Human
encroachment
 East Coast, the Gulf of Mexico (U.S) & Great
lakes
 Second largest - Northern Gulf of Mexico
 A significant portion of the world's population -
nearly half of which lives within 40 miles of a coast
is vulnerable to harmfully over-enriched ecosystems,"
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6.  The technical term for low oxygen = hypoxia.
 When oxygen concentration falls below 2mg/l =
hypoxic area
 The term for no oxygen is = anoxia.
 Anoxia = 0 mg/l dissolved oxygen
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7. Outline
 What is Marine Dead Zone (MDZ) ?
 History of Ocean Dead Zones
 Dead zones around the world
 How this happens?
 What causes hypoxia?
 When does the hypoxia occur?
 Environmental, Social & Economic effects
 What can be done?
 HABHRCA
 QUIZ TIME
 Conclusion
 Acknowledgement
 References
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8.  Dead zones in the coastal oceans have spread
exponentially since the 1960s and have serious
consequences for ecosystem functioning.
 First recorded in the 1970s off the coasts of developed
countries.
 Dead zones were originally discovered in the,
 US,
 Chesapeake Bay
 Kattegat Strait in Scandinavia
 Mouth of the Baltic Sea
 Black Sea,
 Northern Adriatic Sea.
 Currently about 400 ocean DZs worldwide,
 Ranging in size from 1 square km to 20,000 square Km.
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9.  Dead zones are reversible.
 The Black Sea dead zone, previously the largest in
the world, largely disappeared between 1991 and
2001
 After fertilizers became too costly
 Fishing had again became a major economic
activity in the region
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10. From 1985 to 2000, theNitrogen in North Sea DZ had
reduced by 37%
BECAUSE,,,
 Policy efforts by countries on the Rhine River , they
reduced
 Sewage and
 Industrial emissions of Nitrogen into the water.
 Other cleanups have taken place in the US along
the
 Hudson River and
 San Francisco Bay
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11. Hood Canal
 Fjord forming the western lobe & one of the four
main basins in the state of Washington
 NATURAL WATER WAY
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12. Outline
 What is Marine Dead Zone (MDZ) ?
 History of Ocean Dead Zones
 Dead zones around the world
 How this happens?
 What causes hypoxia?
 When does the hypoxia occur?
 Environmental, Social & Economic effects
 What can be done?
 HABHRCA
 QUIZ TIME
 Conclusion
 Acknowledgement
 References
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13.  In 2008, 415 Dead Zones Were Identified
 NASA Releases New Map of Aquatic
Dead Zones
July 23, 2010
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14.  Red circles on this map show the location and size of
many of our planet’s dead zones.
 Black dots show where dead zones have been observed,
but their size is unknown.
 It’s no coincidence that dead zones occur downriver of
places where human population density is high (darkest
brown)
 Naturally occurring low-oxygen zones are regular
features in some parts of the ocean. (Coastal upwelling
areas)
 However, these zones may grow larger with the
additional nutrient inputs from agricultural runoff.
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15. Two famous hypoxic
regions are:
 The Gulf of Mexico, fed
by the overly-enriched
Mississippi River
 2. The Black Sea, which
is currently recovering
- Soviet area
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16. Outline
 What is Marine Dead Zone (MDZ) ?
 History of Ocean Dead Zones
 Dead zones around the world
 How this happens?
 What causes hypoxia?
 When does the hypoxia occur?
 Environmental, Social & Economic effects
 What can be done?
 HABHRCA
 QUIZ TIME
 Conclusion
 Acknowledgement
 References
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17. Step 1
 Eutrophication starts with farmers spreading
fertilizers rich in Nitrates and Phosphates on
their fields.
 When it rains much of the fertilizers are washed
into large bodies of water
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18. Step 2
 The added nutrients then cause an increase in plant
and algae growth
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19. Step 3:
 The algae begins to grows in such large quantities that
sunlight is blocked from the lower levels of ocean.
Less light means that species of plants and animals are
only able to live at certain depths in the water due to lack
of sunlight.
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20. Step 4
 Like all other organisms the algae eventually start to die
and the fall to the bottom of the ocean.
 There bacteria attempt to breakdown the decomposing
matter
 But in the process they consume large amounts of
oxygen and leave the water uninhabitable for many
species such as fish.
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21. Marine Dead Zones W.A.D.M.Wijethilake 21
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22. Outline
 What is Marine Dead Zone (MDZ) ?
 History of Ocean Dead Zones
 Dead zones around the world
 How this happens?
 What causes hypoxia?
 When does the hypoxia occur?
 Environmental, Social & Economic effects
 What can be done?
 HABHRCA
 QUIZ TIME
 Conclusion
 Acknowledgement
 References
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23. Marine Dead Zones W.A.D.M.Wijethilake 23
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24. Natural factors Human induced
Slow water circulation & mixing Altering the river flows,
landscapes
Changes in weather Altering the marine life
High growth of Algae Adding excess nutrients to the
waters that can fuel extra Algae
growth
Loading of Carbon & Nitrogen Adding extra carbon to the
ecosystem
Changes in the native marine life Influencing climate change
composition
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26. Sometimes Eutrophication is human –
induced
 The culprits are:
 Agricultural fertilizer
 Domesticated animal manure
 Industrial & urban runoff
 Sewage
 Atmospheric nitrogen
 These waste products have caused
nitrogen and phosphorus in to
coastal areas in the last fifty years
ago.
 In Europe and the U.S. fertilizer
and manure are the main sources,
because much of their sewage is
treated before entering the water
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28.  There are several causes of ocean pollution
including oil pollution, marine debris, toxic
materials, and ocean dumping and mining.
 Oil pollution is not only caused by large
devastating tanker spills, it is also caused through
runoff from land and industrial wastes & natural
seepage which find their way to the ocean through
drains.
 Other causes include intensive farming, septic tank,
pesticide, animal dung, household waste,waste water,
nuclear waste... etc
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29. Outline
 What is Marine Dead Zone (MDZ) ?
 History of Ocean Dead Zones
 Dead zones around the world
 How this happens?
 What causes hypoxia?
 When does the hypoxia occur?
 Environmental, Social & Economic effects
 What can be done?
 HABHRCA
 QUIZ TIME
 Conclusion
 Acknowledgement
 References
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30.  Hypoxic conditions were disrupted in the fall by
tropical storms or cold fronts
 Associated with increased wind and wave action,
which increases mixing in the entire water column.
 This mixing replenishes oxygen concentration from
the surface to the bottom of the water column.
 The dead zone usually forms in the spring and
summer
 When water and air temperatures begin to rise.
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31. Outline
 What is Marine Dead Zone (MDZ) ?
 History of Ocean Dead Zones
 Dead zones around the world
 How this happens?
 What causes hypoxia?
 When does the hypoxia occur?
 Environmental, Social & Economic effects
 What can be done?
 HABHRCA
 QUIZ TIME
 Conclusion
 Acknowledgement
 References
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32. Environmental Social Economic
This eventually sparks Humans are exposed to The fish industry takes
the eutrophication toxins through the greatest his in terms
process. contaminated fish or of economic effects
water. caused by eutrophication.
Marine life dies or
suffers serious health Eutrophication is greatly Dwindling (decline)
problems. caused by contaminated fish populations will
local water from force fishing companies.
Algal blooms create factories, farms, sewage,
toxins, such as mercury homes, etc., entering the
or PCBs (Polychlorinated ecosystem and disturbing
Biphenyls), that get its cycles.
absorbed by the sea life.
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33.  As well as marine animals, the problem greatly affects
human communities, which rely on the coast and its
resources for their livelihoods.
 For example, a massive algae bloom in 1998 coast Hong
Kong $40 million USD as it wiped out almost the
entirety of Hong Kong's fish farms.
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34.  Dead zones can also effect……
 Benthos,
1. Stressed or die
2. Decreased diversity
3. Degraded environment
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35. Outline
 What is Marine Dead Zone (MDZ) ?
 History of Ocean Dead Zones
 Dead zones around the world
 How this happens?
 What causes hypoxia?
 When does the hypoxia occur?
 Environmental, Social & Economic effects
 What can be done?
 HABHRCA
 QUIZ TIME
 Conclusion
 Acknowledgement
 References
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36.  Programs and initiatives are being implemented
by the UN Environment Program and the US
Environmental Protection Agency.
 The National Resources Defense Council created
a bill called OCEANS 21(the Oceans,
Conservation, Education, and National Strategy
for the 21st Century Act).
 In Georiga, GreenLaw works to challenge
industry and government actions that have
compromised the environment.
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37.  - The Black Sea was once the largest dead zone in the
world, but during 1991-2001, fertilizers stopped
entering the ecosystem resulting in a reversal. The sea
naturally restored its equilibrium.
 - Solutions for preventing eutrophication is removing
algae growth by means of filtration. This would be
effective but costly.
 Stop the use of fertilizers !
 - There other means of fertilizing crops,
e.g. compost
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38.  What Can be Done to Remediate the
Problem?
Solutions include:
 Using fewer fertilizers and adjusting the timing of
fertilizer applications
 Control of animal wastes
 Monitoring of septic systems and sewage treatment
facilities to reduce discharge of nutrients to surface
water and groundwater
 Careful industrial practices such as limiting the
discharge of nutrients, organic matter, and chemicals
from manufacturing facilities.
 Funding efforts to restore wetlands along the coast to
naturally filter the water before it enters the ocean.
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39.  These solutions are relatively simple
to implement and would significantly
reduce the input of nitrogen and
phosphorus.
 A similar approach has been used
successfully in the Great Lakes
recovery from eutrophication.
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40. Outline
 What is Marine Dead Zone (MDZ) ?
 History of Ocean Dead Zones
 Dead zones around the world
 How this happens?
 What causes hypoxia?
 When does the hypoxia occur?
 Environmental, Social & Economic effects
 What can be done?
 HABHRCA
 QUIZ TIME
 Conclusion
 Acknowledgement
 References
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41. Harmful Algal Bloom and
Hypoxia Research and Control
Act
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42.  In December 2004,
 US Congress recognized the severity of these
threats
 Reauthorized the Harmful Algal Bloom and
Hypoxia Research and Control Act of 1998
(HABHRCA 1998) with the Harmful Algal
Bloom and Hypoxia Amendments Act of 2004
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43.  Scientific understanding and ability to
detect, monitor, assess, and predict HAB
and hypoxia events.
 It authorized funding for existing and
new competitive research programs on
HABs and hypoxia, including a new
program to research methods of
prevention, control, and mitigation of
HABs.
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44.  Harmful Algal Bloom Management and Response
Assessment and Plan, 2008
 Scientific Assessment of Marine Harmful Algal
Blooms, 2008
 Scientific Assessment of Hypoxia in U.S. Coastal
Waters, 2010
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45. Outline
 What is Marine Dead Zone (MDZ) ?
 History of Ocean Dead Zones
 Dead zones around the world
 How this happens?
 What causes hypoxia?
 When does the hypoxia occur?
 Environmental, Social & Economic effects
 What can be done?
 HABHRCA
 QUIZ TIME
 Conclusion
 Acknowledgement
 References
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46. Conclusion
 Marine dead zone is low oxygen area called
hypoxic region
 Ocean dead zones were occurred till 1960’s
 There are about 400 MDZ’s in the world
 This is continuous process
 Hypoxia can form by both natural & human
induced factors
 In fall hypoxic regions can disrupt & create in
the spring & summer.
 There are impacts for Environmental, Social &
Economic areas.
 There are such plans for avoid MDZ’s
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47.  My heartiest thanks goes to
Dr.RRMKP Ranatunga for his vital
encouragement.
 Persons in Zoology & main library in
University of Sri Jayawardenepura.
 Mrs.Sunethra Kariyawasam in NARA.
 For all are who helped me
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48.  Web sites
 Goddard Earth Sciences, Data and Information
Services Center, NASA
 Bleachpedia
 NOAA
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