Human Impact on The Oceans

The Ocean  One of the most valuable and untapped resources.  Yet, seriously threatened by what humans have done to it.  The problem of controlling human impacts on the ocean boils down to short term costs.  These short term costs ($$$) often prevent effective controls.

Problem #1: Habitat Alteration Dredging –  Removing sediment from the bottom of the ocean with mechanical force to dislodge and excavate material.  Dredging is used to clear obstructions so larger ships can enter ports.  Used to keep harbors, rivers and other waterways from silting up.

 Dredging is also a method used to collect scallops.  Dredging dramatically affects marine ecosystems, causing severe seabed habitat destruction.  Sea creatures living on the bottom are crushed, buried or exposed to predators, and clouds of sediments rise, altering seabed biochemistry.

Natural healthy undisturbed cobble-shell bottom, habitat for scallops. After just one pass of a scallop dredge this is the result!

 By leveling the ocean floor, the food chain is disturbed, the hiding places have been removed and conditions favorable to faster growing species take over.  Seafloor recovery could take centuries.  Some species of sponges can reach 50 years old.  Some clams can live for more than 200 years.  Some individual corals have been estimated to live 500 years or more.

Problem #2: Offshore Drilling (Oil) Problems with it:  Noise from Seismic Testing  Water and air pollution  Visual impacts  Coastal Development

Sonic blasts damage the brain and ears of marine mammals and other species, disorienting them and causing them to beach themselves.

Problem # 3: By Catch  This refers to fish and other marine life caught "incidentally" while harvesting another species.  These are fish that are the wrong type, size, sex, or quality as well as marine mammals, sea turtles, and seabirds.  These are fish that are the wrong type, size, sex, or quality as well as marine mammals, sea turtles, and seabirds.

Facts about Bycatch  Commercial fishing worldwide wastes approximately 44 billion pounds of ocean life annually.  Roughly 25 percent of the entire global catch.  In the United States, all sea turtles are listed as endangered or threatened under the Endangered Species Act, as a result of fishing bycatch.

Whale Entanglement More whales, dolphins and porpoises die every year by getting entangled in fishing gear than from any other cause.

Problem #4 Toxic Ocean Pollutants  Our waste, even in small quantities, have huge effects on ocean communities and species.  Toxic pollutants in the ocean ecosystem have massive impacts on the plants and animals.

Some major types of pollutants:  garbage  sewage  chemicals  radioactive waste  eutrophication  heavy metals  oil

Oil Spills (1)  The effects of an oil spill of marine life depend on a number of physical and biological factors.  The distribution of the oil spill will be affected by currents and wind  In addition, the amount of oil spilled will determine the eventual geographic boundaries of the impact area.  The physical and chemical properties of the oil will determine the behaviour of the slick, in terms of its thickness and rate of spreading.

Oil Spills (2)  Environmental conditions such as salinity, water temperature, and type and slope of shoreline will determine habitat effects and clean-up procedures  Some example habitats include sandy beach, mud, cliffs, estuaries and open water. In terms of difficulty of clean-up and relative vulnerability, a salt marsh ranks the highest, followed by eelgrass, mud, mixed-fine sediment, mixed- coarse sediment, rock, sand, algae (kelp) and open water.

Oil Spills (3)  Biological characteristics of the organisms affected will determine the severity of impact.  These characteristics include the type of species, life stage (larval, juvenile or adult) and size.

Cleaning-up oil spills:  1. Dispersants: Oil can be broken down more quickly by spraying dispersants (chemicals) on the oil slick from boats or planes. This method only works on fresh, small oil spills.  2. Booms: A boom has a floating skirt suspended down in the water and a sail holding it above the water line. The floating skirt stops the oil from passing. These are used to prevent oil from entering delicate and protected areas.  3. Slick-lickers: This method uses a belt of oil absorbing material that sucks up the oil from the ocean water. The oil is then squeezed out of the absorbing material into a collecting bin.