Most of the ocean pollution is caused by the increase in population and the expansion of industries which have created and increase in sewage and industrial waste effluent that is dumped into the ocean off the coast of most countries. This toxic material has added sludge to large areas, blocking sunlight from developing plants, destroying kelp forests and the habitat of marine animals and fish. The natural filtering systems in estuaries and wetlands have been drained and developed for land reclamation. These alterations to the relationship between land and ocean life destorys habitats and fish stocks. Each of these damaging effects interferes with the ocean's natural ability to deal with the disposal of toxic and non-toxic materials.