Deposition

All kinds of substances, particles and gases, including environmental pollutants, can be transported with the winds from one place to another. Through physical or chemical reaction, the airborne substances, particles or gases will sooner or later fall down on a surface of land or water. Some of the main gases deposited as atmospheric deposition of concern for the marine environment are nitrogen oxides emitted from combustion (traffic and industry), or ammonia from manure. Rivers have, until recently, been thought to be the most important source of reactive nitrogen to the coastal seas but scientists now know that inputs from the atmosphere are large and can equal, or exceed, those from the rivers.

In coastal areas the vast majority of waste seen shall be directly caused by recreational activities, usually from boats or effluent from sewers and disposal pipelines. Plastic bags can be mistaken for jellyfish and eaten by turtles, fishing wire can entangle seabirds and get ingested by whales, dolphins, and other marine mammals. Fisherman and boater safety is jeopardised by marine debris that clogs up water intake ports and snags on propellers.

Children in littered Manila Bay, Philippines. Photo: Hartmut Schwartzbach, UNEP.

Due to it's long life and durability plastic is the most commonly seen piece of marine debris, and the deadliest. A 1988 survey found 89% of the waste observed floating in the North Pacific Ocean to be plastic. Annex V of the International Convention for the Prevention of Pollution From Ships (known as MARPOL V) prohibits any vessel from discarding plastic at sea but it is still common practice because catching violators is near to impossible. Radioactive waste is created by many industries and, unfortunately, this waste is also being dumped at many sites in the planet's oceans. The U.N. International Atomic Agency (IAEA) monitors the levels of radioactivity at these sites and the 'global fallout' or level of activity due to nuclear testing that occurs in the marine environment, specifically the Pacific. In the vast majority of areas global fallout is still the dominant source of radioactivity. There are areas where activity is higher than residual global fallout. For instance releases from nuclear reprocessing plants in the Irish and North Seas and the Chernobyl accident (Baltic and Black Seas

Heavy metal poisoning (such as lead and mercury) from industrial fallout collect in the tissues of top predators such as whales and sharks. Sometimes this type of poisoning can cause birth defects and nervous system damage. Dioxins from pulp and paper bleaching processes, polychlorinated biphenyls (PCB's), and poly- aromatic hydrocarbons (PAH's), typically from oil pollution and the burning of wood and coal, are all marine pollutants that can have serious effects such as reduced fecundity and genetic chromosomal aberrations in many marine animals. The IAEA also investigates the effects of heavy metal contaminants on marine life. They trace radioactive material and heavy metals to see where in marine organism's tissues the contaminants lie, and have found that different contaminants become localised in different tissues of different marine organisms.