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An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. [1] Estuaries form a transition zone between river environments and maritime environments and are an example of an ecotone.
Other types of estuaries also exist and have similar characteristics as traditional brackish estuaries. The Great Lakes are a prime example. There, river water mixes with lake water and creates freshwater estuaries. [16] Estuaries are extremely productive ecosystems that many humans and animal species rely on for various activities. [17]
Estuaries provide habitats for a large number of organisms and support very high productivity. Estuaries provide habitats for salmon and sea trout nurseries, [43] as well as migratory bird populations. [44] Two of the main characteristics of estuarine life are the variability in salinity and sedimentation.
Other types of estuaries also exist and have similar characteristics as traditional brackish estuaries. The Great Lakes are a prime example. There, river water mixes with lake water and creates freshwater estuaries. [20] Estuaries are extremely productive ecosystems that many humans and animal species rely on for various activities. [21]
The predominant human activities that have historically altered the estuary are jetty construction, diking and dredging. The direct results of these (among less pertinent natural changes) are huge losses of marshes and other shoreline habitats, reduced tidal prism and reduced tidal mixing.
For example, terrestrial habitat types include forest, steppe, grassland, semi-arid or desert. Fresh-water habitat types include marshes, streams, rivers, lakes, and ponds; marine habitat types include salt marshes, the coast, the intertidal zone, estuaries, reefs, bays, the open sea, the sea bed, deep water and submarine vents.
Model of Estuary. The residence time of water is a key variable determining the health of an estuary, particularly from human-induced stresses.Rapid flushing ensures that there is insufficient time for sediment accumulation or dissolved oxygen depletion in the estuary; thus a well flushed estuary is intrinsically more robust than a poorly flushed estuary. [1]
The biotic characteristics are mainly determined by the organisms that occur. For example, wetland plants may produce dense canopies that cover large areas of sediment—or snails or geese may graze the vegetation leaving large mud flats. Aquatic environments have relatively low oxygen levels, forcing adaptation by the organisms found there.