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

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. 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

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

Other Dangers to the Marine Environment Solid wastes Thermal pollution 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 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

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