The process of restoration and formation of new communities in habitats where they existed previously, but disappeared as a result of climatic and geological phenomena or as a result of human activity.

Succession (from Lat. succesio — succession, inheritance) — a consistent regular change of one biological community by another on a certain part of the reservoir over time as a result of the influence of natural factors (including internal forces) or human exposure.

There are many classifications of successions, according to indicators that can change during the succession or for reasons of shifts:

by time scale (fast, medium, slow, very slow),

by reversibility (reversible and irreversible),

by the degree of constancy of the process (permanent and non-permanent),

by origin (primary and secondary),

by trends productivity changes (progressive and regressive),

trends in species richness (progressive and regressive),

anthropogenic (anthropogenic and natural),

by the nature of the changes occurring during the succession (autotrophic and heterotrophic).

Secondary regenerative successions include changes in the aquatic ecosystem as a result of de-eutrophication after the flow of biogens into the ecosystem with wastewater has ceased. Such successions have been studied in Lake Washington. According to the description of the succession, abundant cyanobacteria are gradually replaced by green algae and diatoms, and in parallel the biodiversity of zooplankton and necton (fish) increases. Excess biogenic material absorbed by planktonic organisms settles to the bottom of the reservoir after they die and is buried in sapropel.