Estuary
Say it: ES-choo-air-ee
An estuary is a partly enclosed coastal body of water where river water meets and mixes with seawater, so that the water there is brackish.
Also: estuaries
Definition
What is an estuary?
An estuary forms where a river meets the sea, in places such as bays, lagoons, sounds and tidal river mouths. Fresh water flowing off the land mixes with salty seawater pushed in by the tides, creating brackish water whose saltiness changes with the tide, the season and the rainfall. Barrier islands, sandbars or headlands usually shield estuaries from the strongest ocean waves. Around them lie habitats such as salt marshes, mudflats, seagrass beds, oyster reefs and, in the tropics, mangrove forests.
Life in an estuary is demanding, because salinity can swing within hours. Many plants there are halophytes, adapted to salty soil, and animals such as clams and mussels close their shells and slow their metabolism when the water turns too fresh. Yet estuaries rank among the most productive ecosystems on Earth, because rivers deliver nutrients and the shallow, sunlit water lets plants and algae grow quickly. Their sheltered waters serve as nurseries for young fish, crabs and shrimp, including many species caught for food, and as resting places for migrating birds. Marshes also trap sediment and pollutants and soak up storm surges.
Because they collect runoff from whole watersheds, estuaries are vulnerable to nutrient pollution and eutrophication. Chesapeake Bay in the United States and the Thames Estuary in England are well-known examples.
Word parts
Where does the word “estuary” come from?
- estu-
- tide, surgeLatin aestus, via aestuarium, tidal marsh
Related
Terms that go with it
- EutrophicationEutrophication is the over-enrichment of a lake, river or coastal sea with nutrients, fueling algal blooms that later decay and use up the water's oxygen.
- EcosystemAn ecosystem is a community of living organisms together with the nonliving environment they interact with, linked by energy flow and nutrient cycling.
- HabitatIn ecology, a habitat is the natural place where an organism or population lives, which supplies the food, water, shelter and space it needs to survive.
- BiomeA biome is a large region of Earth defined by its climate and its typical plants and animals, such as tundra, desert or tropical rainforest.
- PhytoplanktonPhytoplankton are microscopic photosynthetic organisms that drift near the surface of oceans and lakes and form the base of most aquatic food webs.
- BiodiversityBiodiversity is the variety of life in a place or on Earth as a whole, from genetic differences within species to the range of species and ecosystems.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- NOAA National Ocean Service: What is an estuary?
- US EPA: Basic Information about Estuaries
- OpenStax Biology 2e, 44.4 Aquatic Biomes
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