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Environmental Gradients

Part of the Encyclopedia of Earth Sciences Series book series (EESS)


Environmental gradients in estuaries refer to gradual changes in abiotic factors and, consequently, in biotic factors, through space and time.

Ecotone is a transition area between two different habitats, ecosystems, or biomes.

Ecocline is a gradation from one ecosystem to another when there is no sharp boundary between the two.


Estuarine ecosystems are characterized by a constantly changing mixture of saltwater and freshwater (McLusky, 1989). The flux of saltwater and freshwater presents physiological challenges to estuarine organisms. Gradients of salinity, for example, restrict many animal species in the adjacent sea or rivers from entering estuaries. In highly stratified estuaries, denser marine water entering an estuary along the bottom gradually mixes vertically with the outgoing surface flow of freshwater. Environmental gradients in estuaries depend on seasonal and daily fluctuations of abiotic factors.

Environmental gradients

Abiotic factors

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Correspondence to Mario Barletta .

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© 2016 Springer Science+Business Media Dordrecht

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Barletta, M., Dantas, D.V. (2016). Environmental Gradients. In: Kennish, M.J. (eds) Encyclopedia of Estuaries. Encyclopedia of Earth Sciences Series. Springer, Dordrecht.

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