Our previous publication in “Life on the Earth” [7] was concerned with neuroactive substances in the capacity of new-generation pollutants exemplified by neurotransmitters such as acetylcholine and biogenic amines. At low concentrations, these substances exert a growth-promoting effect on microalgae. The present work deals with the mode of action of extremely low concentrations (“trace amounts”) of neurotransmitters that comprises their antioxidant effects and the influence on the dynamics and rhythms of microalgal cultures’ development, i.e. on the succession of their age-related stages. Such neurotransmitters that can enter natural ecosystems with the wastewater of food, drug, and cosmetic industry, can be grouped into (1) substances that increase the unsaturated fatty acid (UFA) content in microalgal membranes, elevate the photosynthetic pigment concentration in the cells, and prolong the “youth” of microalgal cultures; and (2) substances that decrease the UFA content, reduce the photosynthetic pigment concentration, and, accordingly, accelerate the “aging” of microalgal cultures.

The constantly extending list of humankind-produced environmentally toxic compounds currently includes pharmacological preparations. Among them, of potential relevance are neurotransmitters including such biogenic amines as norepinephrine, dopamine, serotonin, and histamine, as well as acetylcholine. These neurotransmitters were tested in the present work using such model organisms as the green microalgae Chlorella vulgaris Beijer, Scenedesmus quadricauda (Turp.) Breb. К-1149, and Haematococcus lacustris (= pluvialis) strains IPPAS H-239 and BM-1, as well as the cyanobacterium Limnospira platensis IPPAS B-256. It was established that all tested neurotransmitters significantly stimulate the growth of the cultures of microalgae at sufficiently low (micromolar) concentrations. In light of the results of this work, uncontrollable microalgal growth seems to be possible under the influence of trace amounts of neurotransmitters in natural and artificial water bodies, which might cause their eutrophication. All tested substances influenced the photosynthetic pigment content at micromolar (or submicromolar) concentrations, acetylcholine being a quasi-universal promoter of their biosynthesis that presumably stimulates the photosynthetic activity of the microalgae. The effects of the other tested substances varied depending on the microalgal species involved but predominantly resulted in promoting photosynthetic pigment biosynthesis. A biotechnological project aimed at stimulating the microalgal biomass yield by supplementing microalgal cultures with neurotransmitters seems to hold promise for producing drugs, food additives, or biofuel.