Editing Ecology (section)

==== Water ====
{{Main|Aquatic ecosystem}}
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| quote = Wetland conditions such as shallow water, high plant productivity, and anaerobic substrates provide a suitable environment for important physical, biological, and chemical processes. Because of these processes, wetlands play a vital role in global nutrient and element cycles.
| source = Cronk & Fennessy (2001)<ref name="Cronk01" />{{Rp|29}}
| width = 25%
| align = right}}
Diffusion of carbon dioxide and oxygen is approximately 10,000 times slower in water than in air. When soils are flooded, they quickly lose oxygen, becoming [[Hypoxia (environmental)|hypoxic]] (an environment with O<sub>2</sub> concentration below 2&nbsp;mg/liter) and eventually completely [[Anoxic waters|anoxic]] where [[anaerobic bacteria]] thrive among the roots. Water also influences the intensity and [[Electromagnetic spectrum|spectral composition]] of light as it reflects off the water surface and submerged particles.<ref name="Cronk01"/> Aquatic plants exhibit a wide variety of morphological and physiological adaptations that allow them to survive, compete, and diversify in these environments. For example, their roots and stems contain large air spaces ([[aerenchyma]]) that regulate the efficient transportation of gases (for example, CO<sub>2</sub> and O<sub>2</sub>) used in respiration and photosynthesis. 

Salt water plants ([[halophyte]]s) have additional specialized adaptations, such as the development of special organs for shedding salt and [[osmoregulation|osmoregulating]] their internal salt (NaCl) concentrations, to live in [[Estuary|estuarine]], [[brackish]], or [[ocean]]ic environments. Anaerobic soil [[microorganism]]s in aquatic environments use [[nitrate]], [[Manganese|manganese ions]], [[ferric|ferric ions]], [[sulfate]], [[carbon dioxide]], and some [[organic compounds]]; other microorganisms are [[facultative anaerobes]] and use oxygen during respiration when the soil becomes drier. The activity of soil microorganisms and the chemistry of the water reduces the [[Reduction potential|oxidation-reduction]] potentials of the water. Carbon dioxide, for example, is reduced to methane (CH<sub>4</sub>) by methanogenic bacteria.<ref name="Cronk01"/> The physiology of fish is also specially adapted to compensate for environmental salt levels through osmoregulation. Their gills form [[electrochemical gradient]]s that mediate salt excretion in salt water and uptake in fresh water.<ref name="Evans99"/>