Some pollutants are transported through the atmosphere to the ocean. Some wastes enter the ocean from ships. Spills of petroleum and hazardous wastes occur when ships run aground or are damaged by storms. Before the 1980's, factories and power plants commonly discarded industrial and radioactive wastes into the ocean. Ships also incinerated hazardous wastes at sea.
Phytoplankton thrives on certain nutrients produced by the decay of organic matter.
Thus, organic pollution can lead to a huge increase in the population of phytoplankton off the continental shelf. The phytoplankton eventually decomposes, consuming more oxygen than normal in the process. The increase in the loss of oxygen can make the waters unfit for marine animals. Under some conditions, the populations of certain phytoplankton species can increase rapidly within a few days. They reach such high concentrations that they affect the color of the water.