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17.14: Phosphorus, Nitrogen, and Other Nutrient Pollution

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    Phosphorus, Nitrogen, and Other Nutrient Pollution

    The nutrients in fertilizer makes plants grow. Whereas using fertilizers may help crop yields (and profits) on land, their unintended release into waterway that lead to the ocean can have devastating impacts in the marine environment. Phosphorus and nitrogen compounds are essential nutrients for plant growth and is naturally occurring in upwelling ocean waters that support primary production. However, too much nitrogen and phosphorus from fertilizers used in agriculture and suburban lawn care can stimulate an overgrowth of phytoplankton resulting in a harmful algal bloom (HAB). When the phytoplankton sinks, dies, and decays, it can suck all the free oxygen out of the water, resulting in hypoxia (creating “dead zones” in regions that would otherwise be a marine environment teaming with life). Unwanted nutrients in runoff and groundwater seepage from agricultural and urban areas of the Midcontinent region of the United States is resulting in an ever-expanding dead zone in the coastal waters around the mouth of the Mississippi River in the Gulf of Mexico (Figure 17.28).

    Hypoxia in the Gulf of Mexico
    Figure 17.28. Map of the region near the mouth of the Mississippi River impacted by hypoxia caused by harmful algal blooms caused by nutrient pollution from farms and urban areas inland.

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