Estuaries are fragile ecosystems that provide a variety of ecosystem functions and services. Because of their protection by land, usually barrier islands, their calm water provides a stable environment for the young of a wide variety of species. Estuaries supply essential food, cover, migratory corridors, and breeding/nursery areas for coastal and marine wildlife.
However, because of the nature of the hydrology of the area, estuaries accumulate the brunt of runoff pollution. Eutrophication from fertilizer and pesticides often creates fish kills in estuaries. Because of the negligible currents, it is easy to quickly deplete dissolved oxygen levels. Increased erosion from urbanization also increases sedimentation in the estuary. Increased turbidity may be intolerable to certain species and may also lead to unwanted sediment buildup.
Alteration of natural hydrologic flows also poses a threat to estuarine ecosystems. With the increased development of beaches, barrier islands are degraded. The natural formations of inlets and point bars are often prevented due to existing buildings and developments. Disrupting the natural cycles of barrier islands disrupts the health of the ecosystem.