Estuaries are narrow bodies of water that branch out from rivers and streams as they empty into larger bodies of water along coastal areas. Estuaries are generally surrounded by coastal wetlands, low areas of land that are saturated for all or much of the year. These areas are important environments for plants, animals and sea life.
Estuaries form the transition zone between rivers and oceans. As such, these bodies contain a mixture of fresh water from the river and salt water from the ocean. Estuaries are affected by tides, but are usually protected from sea storms and winds by barrier islands, peninsulas or other land areas. However, the salt that washes in on the tides creates an environment that is toxic to many land-based plants. As a result, only species that have made the adaptations to filter out the salt, or to utilize it in some fashion, can grow in these areas. Fish live in abundance in estuaires, and the plants that grow in estuaries provide help to filter impurities and pollutants from the water.
Where estuaries are semi-contained systems, wetlands are more open and amorphous. Four major types of wetlands exist—swamps, bogs, marches and fens. Not all watery land areas are wetlands. A wetland must have a water table that stands at or near the land surface for a long enough period to support aquatic type plants. They form the transition ecology between terrestrial systems and aquatic systems. Wetlands form an important water purification system for the moisture that accumulates from rainfall.
Mixed Salt and Fresh Waters
The mixed salt and fresh water environment of the estuaries and coastal wetlands create a unique environment where specialized plants and animal species are found. Wetlands are also the most biologically diverse of all the eco-systems, with a broad range of fish, reptiles, mammals, birds and plant species.
Plants For Brackish Waters
Wetlands grow plants that are adapted to frequently being underwater. Even the soil has a different composition in brackish water, with greater moisture-holding capability. Land-based plants would die from the excess salt in the water. The plants that can survive usually have an internal filtering systems that pulls in water, but keeps out the salt. Mangroves are one of the plants that has this ability to filter out salt. Rushes, salt grass, cattails, milkweed, cordgrass and nettle are just a few of the plants that thrive in the fresh-and-salt conditions of the estuaries and wetlands.
Phytoplankton are abundant in wetland areas and feed a wide range of aquatic creatures. Water fowl often make estuaries and coastal wetlands their stopping-off places for migrations at various times of the year. Herons, bitterns, coots, rails, wrens and gnatcatchers also make the wetlands their home. Turtles, salamanders, snakes, alligators all thrive in the brackish environment of the estuary. Muskrats, beaver, deer and otter are mammal species that live in wetland areas. Many kinds of fish live and breed in the brackish waters of estuaries and coastal wetlands.
Our estuaries and coastal wetlands are important ecologies that filter our water and provide habitats for many types of plants and animals. Protecting these areas is now a primary concern for environmentalists.