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Chapter 18
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Chapter 18
The Impacts of Human on the
Marine Environment
Modification and Destruction of
Habitats
• Most habitat destruction occurs close to
shore (due to the greater number of
humans nearby)
• Much of this destruction results from
unplanned or poorly planned development
• This destruction is more pronounced in
developing countries, but it is not
restricted to these areas
Coral Reefs
• Approximately one-fourth of all coral reefs
have already been lost or are at risk
• Pollution from sewage, sedimentation, and
rising temperatures have caused some of
this damage
• Corals are also lost due to collection for
the aquarium trade and for sale as
souvenirs
Coral Reefs
• One-third of reef-building corals currently
face extinction
Problems Caused by Trawling
• Trawl nets are a major threat to subtidal
habitats
• These nets, which drag along the bottom,
cause resuspension of sediments which
can kill suspension feeders
• The trawls can also break off attached
organisms
Pollution
• Pollution is described as the human
introduction of a substance that reduces
the quality of the environment
• Some pollutants are liberated by human
activities such as the release of heavy
metals from mining
• Most pollutants come from land-based
substances
Sources of Pollution
1.
2.
3.
4.
Fertilizers
Sewage
Oil
Persistent toxic substances
Sources of Pollution
• Fertilizers
– Land-based fertilizers wash into streams and
rivers and are carried into coastal waters
– This influx of nutrients causes phytoplankton
numbers to rise rapidly (called a “bloom”)
resulting in eutrophification
– These blooms can cause several problems
including reducing the amount of light
available to organisms attached to the bottom
such as seagrasses and corals
Sources of Pollution
• Fertilizers
– Other problems with these blooms occur after
the phytoplankton die
– As cells die and drop to the bottom, the influx
of massive amounts of organic matter means
decomposing bacteria begin to work
– As a result of this breakdown, oxygen is
consumed and anoxic conditions may occur
Sources of Pollution
Sources of Pollution
• Sewage
– Domestic sewage comes from homes and city
buildings as well as stormwater runoff
– Industrial sewage comes from factories, etc.
and may contain a variety of substances
– This sewage may contain disease-causing
organisms
– It may also contain heavy metals or other
toxic substances even if treated
Sources of Pollution
Sources of Pollution
• Oil
– Organisms can accumulate components, many of
which are toxic
– These components can affect reproduction, growth,
development and behavior
– Organisms may also die of their feathers or fur is
coated with oil (remember the Exxon Valdez and
other accidents)
– Estuarine organisms, seagrasses and corals are also
at risk if coated with oil
Sources of Pollution
Sources of Pollution
• Persistent Toxic Substances
– Examples are chlorinated hydrocarbons and
polychlorinated biphenyls (PCB’s) and heavy metals
– In the case of chlorinated hydrocarbons, these
substances are dissolved in the fats of organisms and
are passed from prey to predator
– As predators eat more prey, they continue to
accumulate in their tissues (known as biological
magnification)
Sources of Pollution
• Some fishes may not be safe to eat due to
these levels
• Fortunately, the levels of chlorinated
hydrocarbons is not as high as it once was
• The levels of PCBs and heavy metals in
the ocean continues to be a problem as
well
Other Dangers to the Marine
Environment
• Solid wastes
• Thermal pollution
• Saline brines from desalination plants
Threatened and Endangered
Species
• Organisms normally adapt to changing
conditions through a process known as
natural selection
• If they cannot adapt, they go extinct
• Human-induced extinctions can be called
exterminations
Threatened and Endangered
Species
• Threatened status – numbers of a species
are low and a species is in danger of
becoming endangered
• Endangered status – species is in
immediate danger of extinction
Threatened and Endangered
Species
Threatened and Endangered
Species
• Example of an Extermination
• Stellar’s sea cow
• Extermination by overfishing
• The species became known to science in
1741; the last known live individual was
taken in 1768
Threatened and Endangered
Species
• Examples of other species imperiled
today:
– Whales – due to overfishing
– Giant clams – for food and shells (collectors)
– Cowries and cone shells – for shells
(collectors)
– Sharks – due to overfishing
– Sea turtles – for food, jewelry, shells and
other purposes
Conservation Methods Used to
Protect Marine Organisms and
Habitats
• Efforts to keep development at sustainable
•
•
•
•
•
levels
These are on local, national and international
efforts
Fisheries management with EEZ’s
Marine protected areas
Habitat restoration
Artificial reefs