1. The Impacts of Human on the Marine Environment
Unit 7
The Impacts of Human on the Marine Environment

2. 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

3. 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

4. Coral Reefs
One-third of reef-building corals currently face extinction

7. 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

8. 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

9. Sources of Pollution 1. Fertilizers 2. Sewage 3. Oil
4. Persistent toxic substances

10. 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

11. 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

12. Sources of Pollution

13. 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

14. Sources of Pollution

15. 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

16. Sources of Pollution

17. 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)

18. 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

19. Other Dangers to the Marine Environment
Solid wastes
Thermal pollution
Saline brines from desalination plants

20. 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

21. 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

22. Threatened and Endangered Species

23. 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

24. 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

25. 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