The luminescent microscopy (LM) is especially convenient for express analysis of the toxicity of various substances or for detecting the degree of inhibition of the physiological state of cyanobacteria populations as a result of the action of certain chemical compounds on them. In natural water bodies, the suppression of the development of the phytoplankton occurs, in particular, under the influence of low-molecular-weight organic compounds (LMWOCs), metabolites-allelochemicals, of aquatic macrophytes. LM, which allows observing the primary or secondary luminescence of microorganisms, was used by us to study changes in the physiological state of the cyanobacteria cultures of Synechocystis aquatilis and Aphanizomenon flos-aquae under the influence of allelochemicals of water macrophytes in laboratory experiments. We have shown (including using LM) that selected LMWOCs (linoleic, heptanoic, octanoic, tetradecanoic, hexadecanoic, and gallic acids) possess inhibitory allelopathic activity against cyanobacteria. However, their inhibitory effect was different. The highest values of the suppression index (SI > 10) were recorded (in ascending order) for hexadecanoic, linoleic, tetradecanoic, and gallic acids and a mixture of four allelochemicals (heptanoic, octanoic, tetradecanoic, and gallic acids). The creation of a new generation of algaecides/cyanocides based on LMWOCs of aquatic plants is a very promising strategy for combating “algal blooms.”
Harmful algal “blooms”, or HABs, is a hazardous natural phenomenon that often occurs under the influence of anthropogenic factors, for example, during the anthropogenic eutrophication of water bodies. An increase in the frequency and duration of cyanobacterial “blooms” carries a number of serious threats, including local and global degradation of water resources and the impact of cyanotoxins. There are various methods of fighting cyanobacterial “blooms” - physical, chemical, the use of bacterial preparations, etc. However, these methods are not effective enough and, most importantly, do not allow effectively solving the problem of suppressing HABs in water bodies without damage to other components of the aquatic ecosystem. Allelopathy is a natural phenomenon for both stimulatory and inhibitory effects of one plant upon another including microorganisms that resolves this problem. Allelochemicals of macrophytes can be considered as natural algaecides and become the basis of a nature-like convergent technology to suppress the development of plankton cyanobacteria and prevent HABs in water bodies. In our work, we used some allelochemicals of aquatic macrophytes to create a combined algicide of the new generation for suppressing the development of cyanobacteria. The effectiveness of suppressing cyanobacterial “blooms” is demonstrated by the example of field experiments with mesocosms and natural phytoplankton.
Part of the book: Plankton Communities