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Global map of low and declining oxygen levels in the open ocean and coastal waters, 2009. [1] The map indicates coastal sites where anthropogenic nutrients have exacerbated or caused oxygen declines to <2 mg/L (<63 μmol/L) (red dots), as well as ocean oxygen minimum zones at 300 m (blue shaded regions).
A fish's hypoxia tolerance can be represented in different ways. A commonly used representation is the critical O 2 tension (P crit), which is the lowest water O 2 tension (P O 2) at which a fish can maintain a stable O 2 consumption rate (M O 2). [2]
The term ocean deoxygenation has been used increasingly by international scientific bodies because it captures the decreasing trend of the world ocean's oxygen inventory. [2] Oceanographers and others have discussed what phrase best describes the phenomenon to non-specialists.
Phosphorus forms parts of important life-sustaining molecules that are very common in the biosphere. Phosphorus does enter the atmosphere in very small amounts when the dust is dissolved in rainwater and seaspray but remains mostly on land and in rock and soil minerals. Eighty per cent of the mined phosphorus is used to make fertilizers.
Phosphorus is the limiting factor for plant growth in most freshwater ecosystems, [15] and because phosphate adheres tightly to soil particles and sinks in areas such as wetlands and lakes, [16] due to its prevalence nowadays more and more phosphorus is accumulating inside freshwater bodies.
Remineralisation is normally viewed as it relates to the cycling of the major biologically important elements such as carbon, nitrogen and phosphorus. While crucial to all ecosystems, the process receives special consideration in aquatic settings, where it forms a significant link in the biogeochemical dynamics and cycling of aquatic ecosystems.
Coccolithophores have both long and short term effects on the carbon cycle. The production of coccoliths requires the uptake of dissolved inorganic carbon and calcium. Calcium carbonate and carbon dioxide are produced from calcium and bicarbonate by the following chemical reaction: [100] Ca 2+ + 2HCO − 3 ⇌ CaCO 3 + CO 2 + H 2 O
Because of possible phosphorus deficiencies in farmed animals, phosphorus is supplied in the form of inorganic feed phosphates. Consequences of deficiencies are known and well documented. The initial effect is a fall in blood plasma levels, followed by withdrawal of calcium and phosphorus from the skeleton. Loss of appetite and reduced ...