Dissolved oxygen and dissolved carbon dioxide are often discussed together due their coupled role in respiration and photosynthesis. Dissolved oxygen concentrations can be altered by physical, chemical, and biological processes and reaction. Physical processes including wind mixing can increase dissolved oxygen concentrations, particularly in surface waters of aquatic ecosystems. Because dissolved oxygen solubility is linked to water temperatures, changes in temperature affect dissolved oxygen concentrations as warmer water has a lower capacity to "hold" oxygen as colder water.[15] Biologically, both photosynthesis and aerobic respiration affect dissolved oxygen concentrations.[14] Photosynthesis by autotrophic organisms, such as phytoplankton and aquatic algae, increases dissolved oxygen concentrations while simultaneously reducing carbon dioxide concentrations, since carbon dioxide is taken up during photosynthesis.[15] All aerobic organisms in the aquatic environment take up dissolved oxygen during aerobic respiration, while carbon dioxide is released as a byproduct of this reaction. Because photosynthesis is light-limited, both photosynthesis and respiration occur during the daylight hours, while only respiration occurs during dark hours or in dark portions of an ecosystem. The balance between dissolved oxygen production and consumption is calculated as the aquatic metabolism rate.[16]
Grundlage dieser Betrachtung liefern die Verteilung und die Dynamik der chemischen Elemente, Isotope und Molekülen. Dies reicht von der grundlegenden physikalischen, thermodynamischen und kinetischen Chemie hin zu den Interaktionen der marinen Chemie mit biologischen, geologischen und physikalischen Prozessen. Dieses umfasst sowohl anorganische und organische Chemie sowie Studien der atmosphärischen und terrestrischen Prozesse. Darüber hinaus beinhaltet die Chemische Ozeanographie Prozesse, die auf einer Vielzahl von räumlichen und zeitlichen Skalen auftreten: Von global zu lokal, von mikroskopischen zu makroskopischen Dimensionen und von geologischen Epochen zu kurzzeitigen Phänomenen.
The chemical composition of water in aquatic ecosystems is influenced by natural characteristics and processes including precipitation, underlying soil and bedrock in the drainage basin, erosion, evaporation, and sedimentation.[12] All bodies of water have a certain composition of both organic and inorganic elements and compounds. Biological reactions also affect the chemical properties of water. In addition to natural processes, human activities strongly influence the chemical composition of aquatic systems and their water quality.
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