Stratification (water)

Aquatic layers
	Pelagic
	Photic
	Epipelagic
	Aphotic
	Mesopelagic
	Bathypelagic
	Abyssopelagic
	Hadopelagic
	Demersal
	Benthic
Stratification
	Pycnocline
	Isopycnal
	Chemocline
	Halocline
	Thermocline
	Thermohaline
Marine habitats
Lake stratification
Aquatic ecosystems
Wild fisheries

Water stratification occurs when water masses with different properties - salinity (halocline), oxygenation (chemocline), density (pycnocline), temperature (thermocline) - form layers that act as barriers to water mixing which could lead to anoxia or euxinia. These layers are normally arranged according to density, with the least dense water masses sitting above the more dense layers.

Water stratification also creates barriers to nutrient mixing between layers. This can affect the primary production in an area by limiting photosynthetic processes. When nutrients from the benthos cannot travel up into the photic zone, phytoplankton may be limited by nutrient availability. Lower primary production also leads to lower net productivity in waters.

Stratification may be upset by turbulence. This creates mixed layers of water. Forms of turbulence may include wind-sea surface friction, upwelling and downwelling.

Marshall et al. (2002) suggest that baroclinic eddies (baroclinity) may be an important factor in maintaining stratification.

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Wikipedia