Chapter 15 The Human Presence in the Ocean by 94CR64A8

VIEWS: 4 PAGES: 77

									The Human Presence
    in the Ocean
   15-1   Pollution: What is it?

Pollution is the introduction by man,
directly or indirectly, of substances or
energy into the environment resulting
in deleterious effects such as harm to
living resources, hazards to human
health, hindrance of marine activities,
including fishing, impairing quality
for use of sea water and reduction of
amenities.
• In studying pollution it is important to have
  a baseline from which to measure man’s
  impact upon the environment because some
  of what is considered to be pollution may be
  occurring naturally and not caused by man.
   15-1   Pollution: What is it?

• Pollution tends to be concentrated in three
  parts of the ocean environment: the sea
  floor, the pycnocline, and the neuston layer.
• Pollutants are eventually broken down by
  various oceanographic and biological
  processes.
   15-2    Hydrocarbons in the Sea


Petroleum is a complex mixture of
hydrocarbons, combinations of
hydrogen and carbon with various
amounts of nitrogen and metals.
• Oil as it comes from the ground is called
  crude oil or petroleum.
• Only a small fraction of the oil in the sea
  comes from major oil tanker accidents.
• Once in the environment, an oil spill begins
  to be altered.
• The rate at which the oil is dispersed and
  dissipated depends upon the weather,
  composition of the crude and the waves and
  currents.
   15-2    Hydrocarbons in the Sea

• All oil is toxic at all levels of the food chain,
  but degree of damage depends upon the type
  of petroleum and upon the specific habitat
  and ecosystem.
• There are several methods employed in
  attempting to clean a spill: Floating booms,
  Chemical dispersants, burning the oil at the
  surface, skimming, and bioremediation
   15-3    Municipal and Industrial
           Effluent

Each year humans produce over 20
billion tons of wastes, much of which
is disposed of in the ocean.
• Most of the wastes come from farmland,
  cities and industrial areas and enter the sea
  by way of rivers.
• Wastes tend to be concentrated in harbors,
  bays and estuaries.
• All bodies of water have a natural capacity to
  clean themselves of a certain amount of
  pollution, but dense populations can produce
  so much pollution that the self-cleaning
  capacity is exceeded.
• As pollution enters the sea, it can be greatly
  diluted depending upon the waves and
  currents.
   15-3   Municipal and Industrial
          Effluent
• Various pollutants behave differently
  depending upon their temperature, density
  and solubility.
• As effluents are released, they form a
  contaminant plume which increases in size
  with distance as the pollutant is diluted by
  surrounding water.
   15-3   Municipal and Industrial
          Effluent

Municipal and industrial wastes in
the ocean can be divided into three
general categories: sewage, metals
and artificial biocides.
• Sewage consists of mostly human waste
  sludge or organic and inorganic chemicals.
• Heavy metal is a term loosely applied to a
  collection of elements such as lead, mercury,
  cadmium, arsenic and copper that normally
  occur in trace amounts in the ocean, but
  become toxic in larger dosages.
• Artificial biocides are man-made toxic
  chemical compounds that do not occur
  naturally.
                  Hypoxia on Louisiana Shelf
1. Areal extent: Largest oxygen-depleted waters in west Atlantic
Ocean (up to 16,000 km2 to 18,000 km2 of hypoxic water
recorded, Rabalais, 1998)

2. Seasonality: From late Feb. to early Oct., and peaks in middle
Summer when stratification is most severe

3. Severity and duration of hypoxia depends on the amplitude
and phasing of discharge from the Mississippi/Atchafalaya
rivers (Justic et al, 1993; Rabalais, 1996, 1998)
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Epidemiologic Notes and Reports Toxigenic Vibrio
 cholerae 01 Infections -- Louisiana and Florida
• What is cholera?
• Cholera is an acute, diarrheal illness caused
  by infection of the intestine with the
  bacterium Vibrio cholerae. The infection is
  often mild or without symptoms, but
  sometimes it can be severe. Approximately
  one in 20 infected persons has severe
  disease characterized by profuse watery
  diarrhea, vomiting, and leg cramps. In these
  persons, rapid loss of body fluids leads to
  dehydration and shock. Without treatment,
  death can occur within hours.
• How does a person get cholera?
• A person may get cholera by drinking water or eating food
  contaminated with the cholera bacterium. In an epidemic,
  the source of the contamination is usually the feces of an
  infected person. The disease can spread rapidly in areas
  with inadequate treatment of sewage and drinking water.
  The cholera bacterium may also live in the environment in
  brackish rivers and coastal waters.
• Shellfish eaten raw have been a source of cholera, and a
  few persons in the United States have contracted cholera
  after eating raw or undercooked shellfish from the Gulf of
  Mexico.
• The disease is not likely to spread directly from one
  person to another; therefore, casual contact with an
  infected person is not a risk for becoming ill.
Gymnodinium
Noctiluca
Pseudo-nitzschia sp.
Pfiesteria
   15-3    Municipal and Industrial
           Effluent
• Bioaccumulation is the process whereby
  organisms retain and concentrate a toxic
  material within their body.
• Biomagnification is the process whereby a
  toxic material increases in concentration
  with each trophic level of a food chain.
      • It results from bioaccumulation at each trophic level.
   15-4   Ocean Dredging and Mining



Dredging accounts for 80 to 90% of
the material dumped at sea each
year.

• If the dredged material is clean, dumped
  slowly enough, and is the same material as
  the original substrate, it presents no long-
  term environmental problem.
• Contaminated sediment represents an initial
  and long-term source of pollution.
   15-4   Ocean Dredging and Mining


Mining of deep ocean deposits will
most likely be accomplished with a
hydraulic pumping system that will
vacuum water, sediment and
organisms from the sea floor and
bring them to the surface.
• The majority of the organisms drawn into the
  system will be killed.
• Large areas of the sea floor each day will be
  disrupted and stripped of life.
• Sediment released at the surface will create
  a massive sediment plume as it sinks to the
  bottom.
   15-6    Climate Change


All Earth systems, geologic,
atmospheric and hydrospheric, are
interconnected and alteration of one
will impact the others.
• Oceans store heat and transfer it poleward in
  the ocean gyres.
       • Currents and upwelling can have a direct impact on
         local and regional climate.
• Carbon dioxide (CO2) in the atmosphere
  allows light to pass, but traps heat.
• Burning fossil fuel is increasing the amount
  of CO2 in the atmosphere and together with
  deforestation is causing the greenhouse
  effect or global warming.
   15-6     Climate Change

• Possible consequences of global warming
  include:
  – Melting of glaciers in Greenland and Antarctica.
  – Rising sea level and flooding of most coastal cities.
  – Smaller temperature differences between the
    equatorial and polar regions resulting in changes in
    wind and rain patterns.
   15-7   The Ocean’s Future


Based upon a study by the U.N., the
current state of the marine
environment is:
• Most of the water of the open ocean is clean,
  except for heavily traveled shipping lanes.
• Coastal waters and shelf waters are
  contaminated to varying degrees everywhere
  and the amount of contamination depends
  upon population density, degree of
  urbanization, agricultural practices and
  shipping activity.
• Coastal habitats are being severely affected
  and destroyed at an increasing rate.
• Major pollutants in the ocean should be the
  immediate concern, but the long-term
  presence of minor pollutants is uncertain.
   15-7   The Ocean’s Future

• Too little is being done to reduce human
  activity on land that impacts the ocean.

								
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