Biological filtering and ecological machinery for self-purification and bioremediation in aquatic ecosystems: towards a holistic view.

According to one of the approaches to the definition of criteria for the phenomenon of life, the key attribute is the ability of the system for some self-regulating and self-supporting. Part of such holistic functions of aquatic ecosystems as self-regulating and self-supporting is their cleaning the water via a multitude of various mechanisms. The goal of this paper is to present some fundamental elements of the theory of ecosystem self-purification which emphasizes the importance of the four functional biological filters that are instrumental in purification and upgrading the quality of water in aquatic ecosystems. These functional filters are: (1) direct water filtering by aquatic organisms that are filter-feeders; (2) the filter (represented mainly by communities of aquatic plants/periphyton) which prevents input of pollutants and biogenic elements (N, P) from land into water bodies; (3) the filter (represented by benthic organisms) which prevents re-entry of pollutants and biogenic elements from the bottom sediments into the water; (4) the filter (represented by microorganisms attached to particles which are suspended in the water) that provides microbiological treatment of water column. New experimental data by the author reveal the role of man-made effects on the ecological machinery which purifies water. The analysis and discussion lead to the holistic theory of the natural process of bioremediation of aquatic ecosystems.