Chemocline

A chemocline is a type of cline, a layer of fluid with different properties, characterized by a strong, vertical chemistry gradient within a body of water.

[4][5] Meromictic lakes are the result of meromixis, which is a circumstance where a body of water does not fully mix and circulate, causing stratification.

[8] Containing the largest chemical gradient, the chemocline is a thin boundary layer that separates a meromictic lake into two parts: the upper mixolimnion and the lower monimolimnion.

[6] As a result of the differences between the upper and lower layers, aerobic life is restricted to the region above the chemocline, while anaerobic species able to live in anoxic conditions reside below the cline.

[7][9] Due to the gradient of conditions, the chemocline layer may contain an abundance of phototrophic bacteria and high concentrations of thiosulfate and elemental sulfur.

Processes like carbon dioxide fixation, sulfur cycling, and exoenzyme activities occur at heightened rates in the cline compared to the surrounding body of water.

Euxinic deep water that upwells into the photic zone can introduce sulfides and cause a bloom of sulfur oxidizing bacteria in the upper mixolimnion.