The Effects of marine pollution are very diverse. This is because the forms of marine pollution are very diverse. Organic matter (organisms that were alive but are not anymore), when in the sea/ocean, causes a drop in dissolved oxygen this can lead to the death of marine animals. These algal blooms can also release toxins that can kill fish and poison people. Human waste from sewage works etcetera because of its fertilizing properties in plants can cause algal blooms. Not only do these blooms cause discoloration of water which looks horrible it also can clog fish gills, or even be toxic. The breakdown of the algae also causes the drop of oxygen talked about in the above paragraph.

When human waste gets into water, for whatever reason, it can cause a higher concentration of Pathogenic microorganisms (germs) in that part of the sea. Filter feeding bicuspid marine animals like mussels, clams and oysters concentrate pathogens in their gut so eating these animals from polluted external image 438_1050592619053_pollut.jpg?filename=1050592619053_pollution_degradation.jpg&refID=438waters has a health risk.

Oil causes lots of dammage to marine life. it gets into the water not only from spills but also through land based sources such as cars and industry. With low level contamination it can kill larvae and cause disease in marine life. Spills cause some of the most devastating effects out of all the types of marine pollution. Marine animals get suffocated by the thick oil and therefore die. Also sea birds wings get covered in it and because of this they cannot get food and therefore die. In seabirds and mammals it can cause a breakdown in their thermal insulation and they can die of hyperthermia because of it. The toxic chemicals in the oil can cause physiological damage which can include changes of behavior. It can also damage the reproductive systems which has an effect on the population of a species. It is also an eyesore and tar balls created on beaches and are very difficult to clean up.

Sediments from mining, forestry and farming when in the can cause the water to become cloudy this can harm photosynthesis under water. It can also burry marine habitats which can kill fish and other marine species such as coral.

Pesticides like DDT and other chemicals run into rivers and, through the food chain, build up in large quantities in marine mammals and birds and cause them to have reproductive failure which causes a decline in the number of these marine mammals and birds.

Chemicals which are painted onto the side of boats, to prevent growth of marine organisms, often seep into the sea these pollutants can affect animal life especially in places of high traffic like harbors and marinas.

Alien species (animals that are not native to the place they are in) compete with native species for food resources ect. can kill off native species and reduce biological diversity. To add to all this these species can intoduce new marine diseases

One of the most dangerous pollutants to marine life is plastics. Items like plastic bottles and bags kill marine animals due to choking and suffocation as they eat them thinking that they are food. Other animals are also killed by getting tangled in plastic items.

Other items littered into the sea also can harm marine life. For instance discarded fishing nets continue to catch fish and so kill fish that are not even going to be consumed. The plastic debris on beaches can last up to 400 years.

Radioactive substances also pollute underwater. these substances can enter food chain and cause disease in marine life.

Another type of marine pollution is thermal pollution or the changeing of the temperature of seas or oceans this can be caused by cooling water from power plants and industrial sites this can kill temperature sensitive marine species such as coral it can also confuse and displace marine animals.
An example from UK
An incident of marine pollution in the UK recently happened at the firth of forth in Scotland. Equipment used for pumping sewage at the Seafield Wastewater Treatment Plant in Leith failed. this resulted in three days worth, or millions of litres, of partialy treated sewage pouring into the firth of forth. As of yet no major environmental effects have happened because of this although the water and beaches that are included in the firth of forth have been mildly contaminated as well as the marine life in the area, although it is not meant to have caused any long term damage.
An example from Canada
Recently, in Nova Scotia, Canada, the Rowan Gorilla VI, a USA-registered self-elevating drilling unit spilled between 5,000 and 6,000 litres of marine diesel fuel in Canadian ocean, which result in marine pollution. This was the violation of Canada Shipping Act this resulted A Nova Scotia provincial court judge to order the Rowan Gorilla VI to pay a $70,000 penalty. A fine of $70,000 would not be enough to bring the ocean into previous condition. The pollution of diesel fuel had resulted in devestation of marine habitats.