Chapter 18
The Impacts of Humans 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
• Goal is to protect reef and other
ecosystem’s biodiversity
Coral mining for souvenirs, marine aquaria, and construction material
Bleached coral have lost zooanthellae and may die. Stressors like hot water,
pollution, and disease can cause bleaching.
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 “______”)
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
Sewage in a marsh and sources of oil.
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
• Oil
– Organisms can accumulate components, many of
which are toxic
– These components can affect reproduction, growth,
development and behavior
– Organisms may also die if their feathers or fur is
coated with oil
– Estuarine organisms, seagrasses and corals are also
at risk if coated with oil
Sources of Pollution
Oil-coated coot during Exxon Valdez spill. New text has a loggerhead
turtle being cleaned after Deepwater Horizon spill by British Petroleum
Sources of Pollution
• Persistent Toxic Substances
– Examples are chlorinated hydrocarbons (pesticides)
and polychlorinated biphenyls (PCB’s; used in
transformers and products like plastic and paint ) and
heavy metals (from many industrial sources)
– They enter as runoff and are passed from prey to
predator. As predators eat more prey, they continue
to accumulate in their tissues (known as biological
___). Some fish may not be safe to eat due to
magnified levels.
– Chlorinated hydrocarbons affect seabird reproduction,
PCBs cause cancer and birth defects, heavy metals
cause brain, kidney and liver damage, and birth
defects
Other Dangers to the Marine
Environment
• Solid wastes = trash you see washed up
on beach that can entangle animals or be
ingested by mammals
• Thermal pollution due to using seawater
as a coolant in power plants
• 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 Extinction by overhunting
• Stellar’s sea cow
• The species became known to science in
1741; the last known live individual was
taken in 1768
Overhunting the stellar sea cow
Threatened and Endangered
Species
• Examples of other species imperiled
today:
– Whales – due to overfishing
– Giant clams – for food and shells by collectors
– Cone shells – for shells by collectors
– Sharks – due to overfishing
– Sea turtles – for food, jewelry, and shells
Conservation Methods Used to
Protect Marine Organisms and
Habitats
• Efforts to keep development at sustainable
•
•
•
•
•
levels
These are local, national and international
efforts
Fisheries management
Marine protected areas
Habitat restoration
Artificial reefs
Restoration– Transplanting giant kelp plants
Building artificial reefs of concrete blocks
Gulf Coast
• Read Eye on Science, Pg 411 and discuss
• TPWD Power Point presentation
• http://www.youtube.com/watch?v=7c6Fn
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