Pollutants migrate in coastal currents, air flow patterns, rivers, and underground aquifers. Activities throughout the airshed and watershed, including those which destroy or degrade mangrove forests and seagrass meadows, further threaten the integrity of reefs. These forests also regulate fresh water flows into coastal waters, reducing their volume through evapotranspiration and discharging freshwater over long time periods, moderating sudden changes in salinity that are harmful to coral reefs and perhaps seagrasses. Closer to the coast, mangrove forests retain sediments, transform nutrients into organic matter, and harbor diverse and productive forms of life. Seagrasses and mangroves also export dissolved organic materials and provide shelter and nursery grounds for myriad organisms that move between the three marine habitats, enriching coral reef productivity.
Coral reefs dissipate wave energy, allowing mangroves and seagrass meadows to flourish.
Reefs also produce calcareous sediment which provides substrate for seagrasses and mangroves to grow. The relatively narrow physiological limits of reef-building corals and other reef organisms make coral reefs sensitive to changes in environmental conditions induced by climate change, disturbance of watersheds, pollution, and other factors. Temperature is affected by water circulation, light levels, and regional temperature trends. While coral reefs are sensitive to environmental changes, they appear to be able to recover effectively from physical disturbance or temporary pollution events provided that water quality is generally high. For example, the corals in Kaneohe Bay, Hawaii, for the most part recovered from severe overgrowth by algae after sewage inputs were diverted away from the Bay.