biocoenosis

Biocoenosis is a term used in ecology to denote the complex of living organisms that constitute a biological community within a defined habitat, together with their interactions and ecological processes. The term was introduced by Karl Möbius in 1877 to distinguish the living system from the physical environment, the biotope. A biocoenosis includes plants, animals, microorganisms, and their combined network of relationships—predation, herbivory, competition, symbiosis, parasitism—and the energy flow and matter cycling that sustain it.

The structure of a biocoenosis is characterized by species composition, relative abundances, stratification, trophic organization, and seasonal dynamics. It may display functional groups, such as producers, consumers, decomposers, and mutualists, and show emergent properties such as stability and resilience that arise from interactions among members.

Examples include pond or lake biocoenosis with phytoplankton, aquatic macrophytes, zooplankton, fish, and microbes; a forest biocoenosis with trees, understory plants, invertebrates, birds, and soil fauna; a coral reef biocoenosis with corals, algae, fish, and invertebrates.

The concept is used to emphasize the integrated nature of living communities and their dependence on the abiotic environment. In modern ecology, the term is often replaced by or used interchangeably with "ecological community" or "ecosystem," but it remains a traditional concept in some texts and emphasizes the organismal interactions that define a habitat's living component.