Gulf Islands National Seashore protects seven barrier islands. These dynamic bars of sand parallel to the mainland are treasures at the edge of the Gulf of Mexico. The name “barrier” describes how these islands protect natural and human communities against ocean storms. Waves expend their energy as they break on the islands’ beaches. Because they buffer the Gulf’s wave action, barrier islands also protect salt marshes and seagrass beds, which are nurseries for valuable marine species.
Change is constant on these islands. Over time barrier islands move, erode, and grow again as ocean currents and wind gradually shape the seashore. Along the Gulf of Mexico the barrier islands move north and west. Wave action and onshore breezes transfer sand from the south side of the island to the north side of the island. While prevailing south easterly winds set up longshore currents that gradually move sand from east to west. This combination of wind and waves result in the barrier islands moving towards the mainland while also marching steadily westward.
Sand is always moving either by wind, currents, or storms. Sand usually moves from the east to the west, but sometimes change comes suddenly during fierce storms. Extreme weather like hurricanes can profoundly affect barrier islands. Wind, waves, and flooding constantly reshape these islands and frequently damage structures and vegetation. These major storms also cause islands to roll over themselves and migrate to the north.
There’s life on the beach, but it is tough to live here. This border between land and sea offers a place to live for animals that have adapted to these challenges. In the swash zone, where waves break and retreat, there’s a surprising diversity of life hidden under the sand and seaweed. As waves break and the sand heats up, animals hide in materials washed up on the shore, called wrack, or burrow in the sand to survive. Burrowing in the sand protects animals from waves, predators, and extreme temperatures.
Some of these animals are microscopic and live between the individual grains of sand. These animals are known collectively as meiofauna. These small but vital organisms make up the base of the ecological food chain by providing food for larger animals, like crabs living in the swash zone. The crabs are then preyed upon by the fish and birds you see when you go to the beach.