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Water is the medium of the oceans, the medium which carries all the substances and elements involved in the marine biogeochemical cycles. Water as found in nature almost always includes dissolved substances, so water has been described as the "universal solvent" for its ability to dissolve so many substances.
Dissolved oxygen is a requirement for aerobic respiration, and while the surface ocean is usually oxygen-rich due to atmospheric gas exchange and photosynthesis, the mesopelagic zone is not in direct contact with the atmosphere, due to stratification at the base of the surface mixed layer.
Like inorganic carbon, there are two main forms of organic carbon found in the ocean (dissolved and particulate). Dissolved organic carbon (DOC) is defined operationally as any organic molecule that can pass through a 0.2 μm filter. DOC can be converted into particulate organic carbon through heterotrophy and it can also be converted back to ...
Ocean deoxygenation is the reduction of the oxygen content in different parts of the ocean due to human activities. [ 28 ] [ 29 ] There are two areas where this occurs. Firstly, it occurs in coastal zones where eutrophication has driven some quite rapid (in a few decades) declines in oxygen to very low levels. [ 28 ]
Dissolved gases, such as H 2, H 2 S, and CH 4, and metals, such as Fe and Mn, present at high concentrations in hydrothermal vent fluids relative to seawater may also be diagnostic of hydrothermal plumes and thus active venting; however, these components are reactive and are thus less suitable as tracers of hydrothermal activity.
Dissolved inorganic carbon is a key component of the biological pump, which is defined as the amount of biologically produced organic carbon flux from the upper ocean to the deep ocean. [6] Dissolved inorganic carbon in the form of carbon dioxide is fixed into organic carbon through photosynthesis.
In the ocean by volume, the most abundant gases dissolved in seawater are carbon dioxide (including bicarbonate and carbonate ions, 14 mL/L on average), nitrogen (9 mL/L), and oxygen (5 mL/L) at equilibrium at 24 °C (75 °F) [122] [123] [124] All gases are more soluble – more easily dissolved – in colder water than in warmer water. For ...
Ocean basin bathymetric features. The bathypelagic zone is characterized by a nearly constant temperature of approximately 4 °C (39 °F) and a salinity range of 33-35 g/kg. This region has little to no light because sunlight does not reach this deep in the ocean and bioluminescence is limited. [2]