The Impacts of Human on the Marine Environment Shipley 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

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  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. Fertilizers 2. Sewage 3. Oil 4. 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

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  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

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  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

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  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

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  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

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