Comparative assessment of the quantitative and qualitative composition of zooperiphyton on the surface of duckweed (<i>Lemna minor</i>) grown in a recirculating water supply system

Abstract

Relevance. The quantitative and qualitative composition of organisms settling on floating macrophytes depends on the presence in the water of nutrients necessary for their life, such as fish waste products, food residues and excrement.Methods. The roots and leaves of duckweed (Lemna minor) act as a substrate for the attachment and development of aquatic organisms. And they, in turn, consume organic substances as food sources, thereby reducing the amount of pollutants in the water. In this regard, it seems relevant to study the faunal composition, frequency of occurrence and density of various taxonomic groups of organisms settling on duckweed leaves during the integrated cultivation of aquatic plants and aquaculture objects.Results. The results of the study showed that the zooperiphyton of duckweed is characterized by a high diversity of the faunal complex. On the surface of aquatic macrophytes (Lemna minor), grown by the integrated method together with carps, the number of hydrobionts is twice as large as on duckweed grown in a control installation of a closed water supply, in which there were no fish. Fish excrement and washed-out food residues created a nutrient substrate for the development of aquatic organisms.A total of 22 species of organisms were found inhabiting duckweed in the experimental variant, among which barnacle crustaceans dominated, rotifers were subdominants, and chironomids, copepods, and nematodes were also found. The zooperiphyton of duckweed in the control version consisted of 12 taxa of hydrobionts, most often there were protozoa and barnacles, there were protists, paddlefoot crayfish and oligochaetes. The greatest faunal diversity was recorded on duckweed in the experimental version.