The indirect effects of development are the most damaging. Reef-building corals specifically the algae within their coral polyps, which generate energy for photosynthesis require sunlight waters to survive. Algal blooms resulting from excess nutrients that come from sewage releases and other sources block sunlight, reducing coral growth. Shoreline construction and modification disturbs sediments, which smother corals. Other threats include hot-water discharges from power plants, and mine runoff and industrial toxic waste effluents, which poison reef communities.
Tourism can also pose a threat, where it is unregulated.
Careless boating, diving, fishing, and other recreational uses of coral reef areas can cause damage to coral reefs. Dropping anchors onto reefs can crush or break coral. When people grab, kick, w alk on, or collect coral, they also contribute to coral reef destruction. Marine-Based Pollution Petroleum products and other chemicals dumped near coastal waters by passing ships eventually find their way to reefs. Oil and gas leaked or spilled near a coral reef poison coral polyps and other marine life.