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Beach


Beach

Most people are very familiar with beaches. Beaches are fun places where people enjoy the intersection of very different terrestrial and marine environments, and millions of tourists visit beaches every year. Even people who have never visited a beach have likely seen a photograph or video of one, making beaches one of the most recognizable marine ecosystems. Though they are often thought of simply as empty expanses of sand, beaches are actually lively ecosystems with most of the life hidden from the human eye.


Beaches occur in areas where fairly strong wave action deposits sand, and a lack of strong currents prevents it from being carried away. Sand can either be geological or biological in origin. Geological sand is a result of the weathering of rocks. Biological sand comes from the breakdown of coral skeletons, shells, and other hard body parts from marine plants and animals. Many beaches consist of a mix of these two types of sand. A beach’s slope is important in determining what sorts of organisms live there. Much of the marine life that lives on beaches is buried in the sand within the intertidal zone (the area that is underwater at high tide but exposed at low tide), so beaches with larger intertidal zones have larger areas for those organisms.


Clams and other shellfish, crustaceans, and numerous types of worms all live buried in the sand. These species are able to survive the low tide because small amounts of water is trapped between sand particles, even when the area is exposed. During the high tide, soft-bottom predators (like rays and some sharks, flatfishes, croakers, and other species) patrol beaches for small fishes and mobile invertebrates that come into the intertidal zone to feed on buried invertebrates. During the low tide, shorebirds pick through the sand to find their preferred invertebrate prey, a demonstration of the amphibious nature of this ecosyste