The Impacts of Human on the Marine The Impacts of Human on the Marine EnvironmentEnvironment

Shipley Marine BiologyShipley Marine Biology

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

Modification and Destruction of

Habitats

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

Coral Reefs

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

Problems Caused by Trawling

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

Pollution

1. Fertilizers2. Sewage3. Oil4. 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

Sources of Pollution

Solid wastes Thermal pollution Saline brines from desalination plants

Other Dangers to the Marine Environment

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

Threatened and Endangered Species

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

Conservation Methods Used to Protect Marine Organisms and

Habitats