Growth rate and environmental conditions are recorded in daily and annual growth bands, elemental ratios, and isotopic signatures, offering high resolution historical records. These records can be used to infer past sea levels, growing conditions, the effects of environmental management, and other important phenomena. Some reef organisms transform biologically unavailable atmospheric nitrogen gas into a form useful for coral and plant growth. Reefs capture nutrients from the sea and from groundwater, storing them in the myriad organisms living on reefs and sediments and recycling them tightly within and between these organisms. The health of coral reefs is affected by the quality of surface waters, groundwater, and air for miles around.
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.