The Co-Evolution Aspects of the Biogeochemical Role of Phytoplankton in Aquatic Ecosystems: A Review.

In freshwater and marine ecosystems, the phytoplankton community is based on microalgae and cyanobacteria, which include phylogenetically very diverse groups of oxygenic photoautotrophs. In the process of evolution, they developed a wide range of bio(geo)chemical adaptations that allow them to effectively use solar radiation, CO2, and nutrients, as well as major and trace elements, to form O2 and organic compounds with a high chemical bond energy. The inclusion of chemical elements in the key processes of energy and plastic metabolism in the cell is determined by redox conditions and the abundance and metabolic availability of elements in the paleoenvironment. Geochemical evolution, which proceeded simultaneously with the evolution of biosystems, contributed to an increase in the number of metals and trace elements acting as cofactors of enzymes involved in metabolism and maintaining homeostasis in the first photoautotrophs. The diversity of metal-containing enzymes and the adaptive ability to replace one element with another without losing the functional properties of enzymes ensured the high ecological plasticity of species and allowed microalgae and cyanobacteria to successfully colonize a wide variety of habitats. In this review, we consider the main aspects of the modern concepts of the biogeochemical evolution of aquatic ecosystems and the role of some metals in the main bioenergetic processes in photosynthetic prokaryotes and eukaryotes. We present generalized data on the efficiency of the assimilation of key nutrients by phytoplankton and their importance in the cycle of carbon, silicon, nitrogen, phosphorus, sulfur, and iron. This article presents modern views on the evolutionary prerequisites for the formation of elemental signatures in different systematic groups of microalgae, as well as the possibility of using the stoichiometric ratio in the study of biological and geochemical processes in aquatic ecosystems.