redoxstratified

Redoxstratified refers to aquatic environments in which redox potential decreases with depth, creating vertically layered zones dominated by different electron acceptors. These redox gradients arise from limited vertical mixing and ongoing consumption of oxidants by microbial and chemical processes.

In such systems, the surface layer is typically oxygenated (oxic) due to photosynthesis, while deeper waters become suboxic or anoxic as oxygen is depleted and alternative electron acceptors are exhausted. A narrow transition zone, the redoxcline, marks where the dominant electron acceptor shifts from O2 to other species such as nitrate, manganese and iron oxides, sulfate, and finally carbon dioxide.

Microbial communities exploit the available electron acceptors in a sequence known as a redox ladder: aerobic respiration in the oxic zone; denitrification or anaerobic ammonium oxidation when nitrate is present; Mn(IV) and Fe(III) reduction in suboxic zones; sulfate reduction and methanogenesis in anoxic waters and sediments. The distribution of these processes shapes the chemical makeup of the water column and sediments, influencing gas production and consumption.

Redox stratification strongly affects biogeochemical cycles by controlling nutrient remineralization, inorganic carbon cycling, and the fate of trace metals. It can promote phosphorus release from sediments under reducing conditions and enhance production of greenhouse gases such as methane and nitrous oxide. The structure is dynamic, responding to temperature, wind, freshwater input, and overall stratification strength, and climate change can alter its extent and intensity.

Detection relies on profiling dissolved oxygen, sulfide, nitrate, methane, iron, and manganese, along with redox potential measurements (Eh). The term redoxstratified is widely used in limnology, oceanography, and sedimentology to describe lakes, estuaries, and basins exhibiting persistent vertical redox structure.