Coral reefs are unique structures. Created primarily by animals they have a higher biomass productivity and contain a greater number of species than any other marine ecosystem. Symbiosis between corals and unicellular algae living within the polyp tissue is the mechanism for growth of corals and the consequent production of calcium carbonate which leads to the formation of coral reefs.... The detrimental effects on coral reefs and their inhabitants that result from human manipulation of the environment are, for example, construction work in coral regions produces extensive erosion; dredging sand and dragging the ocean floor increase the suspension load and turbidity resulting in loss of light, which is essential for tropical reef-building corals; municipal sewage and agricultural fertilizers cause eutrophication; pesticides and herbicides used in agriculture are transported to the sea by rain and wind and cause mortality in reef organisms; industrial effluent and mineral oils are toxic to coral reef environments; radioactive contamination due to the testing of nuclear weapons is affecting all marine organisms; and trade in marine animals is helping to denude coastal areas and coral reefs.
