Sedimentation is the accumulation of sediments, or dirt, on the reef. Sedimentation is a natural event and results from erosion of the land and reef. Areas with high natural sedimentation rates, such as river mouths, generally do have coral reefs.

High sediment loads kill coral in two primary ways. First, sediments can settle directly on top of corals and smother them. Corals are not capable of moving, and most coral have very poor mechanisms with which to remove sediments from on top of them. Second, sediments in the water affect water clarity, making the water cloudy or turbid. High turbidity reduces the amount of light that gets through the water column to the corals, and reduces the ability of zooxanthelle to photosynthesize.

Under natural conditions, most areas around Guam should have low levels of sedimentation. However, human activity has significantly increased the rate of sedimentation along many areas of the coastline, including along the coast within War in the Pacific NHP. These human activities are primarily related to poor land management practices, including urban development, unregulated use off-road vehicles and wildfires.

Dwayne Minton