We usually can’t point to one discreet location of nonpoint source pollution like we can with a discharge pipe from a factory. Nonpoint source pollutants come from many areas and multiple land uses. When rain moves over and through the ground, the water carries sediments and absorbs any pollutants it comes into contact with. Following a heavy rainstorm, for example, water will flow across a parking lot and pick up oil left by cars driving and parking on the asphalt. This runoff then runs over the edge of the parking lot into a storm drain, and eventually empties into a stream. The water flows downstream into a larger stream, and then to a lake, river, or ocean. Nonpoint source pollution can smother corals directly (via sediment runoff), or lead to competition by algae which are better suited to extract the high levels of nutrients in the water. Toxins in this type of runoff, can contaminate corals with toxins, leading to lowered growth and reproduction. Photo credit: NOAA
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