Water column (railroad)
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The (oceanic) water column is a concept used in oceanography to describe the physical (temperature, salinity, light penetration) and chemical (pH, dissolved oxygen, nutrient salts) characteristics of seawater at different depths for a defined geographical point. Generally, vertical profiles are made of temperature, salinity, chemical parameters at a defined point along the water column. The water column is the largest, yet one of the most under-explored, habitats on the planet; it is explored to better understand the ocean as a whole, including the huge biomass that lives there and its importance to the global carbon and other biogeochemical cycles. Studying the water column also provides understanding on the links between living organisms and environmental parameters, large-scale water circulation and the transfer of matter between water masses. Water columns are used chiefly for
environmental studies Environmental studies is a multidisciplinary academic field which systematically studies human interaction with the environment. Environmental studies connects principles from the physical sciences, commerce/economics, the humanities, and social ...
evaluating the
stratification Stratification may refer to: Mathematics * Stratification (mathematics), any consistent assignment of numbers to predicate symbols * Data stratification in statistics Earth sciences * Stable and unstable stratification * Stratification, or str ...
or mixing of thermal or chemically stratified layers in a lake, stream or ocean. Some of the common parameters analyzed in the water column are pH,
turbidity Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality. Fluids can ...
,
temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...
,
hydrostatic pressure Fluid statics or hydrostatics is the branch of fluid mechanics that studies the condition of the equilibrium of a floating body and submerged body "fluids at hydrostatic equilibrium and the pressure in a fluid, or exerted by a fluid, on an imme ...
,
salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...
,
total dissolved solids Total dissolved solids (TDS) is a measure of the dissolved combined content of all inorganic and organic substances present in a liquid in molecular, ionized, or micro-granular ( colloidal sol) suspended form. TDS concentrations are often repor ...
, various
pesticide Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, and lampri ...
s,
pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...
s and a wide variety of chemicals and biota. Descriptively, the deep sea water column is divided into five parts—''
pelagic zone The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or wa ...
s'' (from Greek πέλαγος (pélagos), 'open sea')—from the surface to below the floor. The term ''water column'' is also commonly used in
scuba diving Scuba diving is a mode of underwater diving whereby divers use breathing equipment that is completely independent of a surface air supply. The name "scuba", an acronym for "Self-Contained Underwater Breathing Apparatus", was coined by Chris ...
to describe the vertical space through which divers ascend and descend.


Pelagic zones

The
pelagic zone The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or wa ...
s are as follows:


Epipelagic

The ''
epipelagic The photic zone, euphotic zone, epipelagic zone, or sunlight zone is the uppermost layer of a body of water that receives sunlight, allowing phytoplankton to perform photosynthesis. It undergoes a series of physical, chemical, and biological proc ...
'' zone, otherwise known as the sunlit zone or the euphotic zone, goes to a depth of about 200 meters (656 feet). It is the depth of water to which sunlight is able to penetrate. Although it is only 2 to 3 percent of the entire ocean, the epipelagic zone is home to a massive number of organisms. Among other organisms, the photic zone is home to vital communities of phytoplankton, zooplankton, and algae. These primary producers become the food source for hundred of other organisms such as sharks, stingrays, tuna, and sea turtles. The epipelagic zone is incredibly important due to its productivity and ability to help remove carbon dioxide from the atmosphere.


Mesopelagic

The ''
mesopelagic The mesopelagic zone (Greek μέσον, middle), also known as the middle pelagic or twilight zone, is the part of the pelagic zone that lies between the photic epipelagic and the aphotic bathypelagic zones. It is defined by light, and begins ...
'' zone is a layer of the oceanic zone lying beneath the epipelagic zone and above the bathypelagic zone, at depths generally between 200 and 1,000 m (656 and 3,280 ft). The mesopelagic zone receives very little sunlight and is home to many bioluminescent organisms. Because food is scarce in this region, most mesopelagic organisms migrate to the surface to feed at night or live off the falling detritus from the epipelagic ecosystem.


Bathypelagic

The ''
bathypelagic The bathypelagic zone or bathyal zone (from Greek βαθύς (bathýs), deep) is the part of the open ocean that extends from a depth of below the ocean surface. It lies between the mesopelagic above, and the abyssopelagic below. The bathypelagic ...
'' zone extends from about 1000 to 4000 meters below the surface. The bathypelagic zone receives no sunlight and water pressure is considerable. The abundance and diversity of marine life decreases with depth through this and the lower zones.


Abyssopelagic

The ''
abyssopelagic The abyssal zone or abyssopelagic zone is a layer of the pelagic zone of the ocean. "Abyss" derives from the Greek word , meaning bottomless. At depths of , this zone remains in perpetual darkness. It covers 83% of the total area of the ocean an ...
'' zone is the portion of the ocean deeper than about 2,000 m (6,600 feet) and shallower than about 6,000 m (20,000 feet). The zone is defined mainly by its extremely uniform environmental conditions, as reflected in the distinct life forms inhabiting it. The abyss is largely unexplored, but it is known to contain animals found nowhere else on earth. It is also abundant in minerals frequently used in manufacturing. The bottom at these depths accounts for about one-third of the planet's seafloor. The sheer size of this area, coupled with the challenges of descending to depths where water pressure can reach 600 atmospheres, makes exploration difficult—but by no means impossible.


Hadopelagic

The ''
hadopelagic The hadal zone, also known as the hadopelagic zone, is the deepest region of the ocean, lying within oceanic trenches. The hadal zone ranges from around below sea level, and exists in long, narrow, topographic V-shaped depressions. The cumula ...
(''or ''hadal)'' zone, refers to depths below 6000 meters, which occur mostly in the deep ocean trenches. The term hadal is a reference to the Greek god of the underworld ''Hades''. In these trenches, the temperature is just above freezing, and the water pressure is enormous. For example, the hadopelagic zone extends into the ocean's deepest trench, the Mariana Trench, located in the western Pacific Ocean basin, with a maximum depth of nearly 11,000 meters. At that depth, the water column above is exerting a pressure of over one thousand atmospheres.


See also

*
Hydrological transport model An hydrological transport model is a mathematical model used to simulate the flow of rivers, streams, groundwater movement or drainage front displacement, and calculate water quality parameters. These models generally came into use in the 1960s a ...


References


External links


Water column ecology
{{fishery science topics Environmental science Hydrology Fisheries science