mesosaprobic organisms, plants and animals that inhabit water in which a moderate amount of organic material is present. Such waters (unlike heavily polluted ones inhabited by polysaprobes and slightly polluted ones inhabited by oligosaprobes) have free oxygen and oxidation products (nitrates and nitrites along with ammonia and such slightly oxidized nitrogenous compounds as amino acids and amines) but no undecomposed proteins. Mesosaprobes promote the biological self-purification of bodies of water. Some develop on a massive scale and serve as a biological indicator of water quality. Mesosaprobes are divided into two groups: alpha-mesosaprobes and beta-mesosaprobes. The former are capable of growing in more polluted waters with a substantial oxygen deficiency. They include many bacteria, some fungi and algae, protozoans, many rotifers, some oligochaetes, and the larvae of dipterous insects (for example, the larvae of nonbiting midges). Beta-mesosa-probes are inhabitants of less polluted waters with a slight oxygen deficiency. They include diatomaceous and green (Cladophora) algae and flowering plants, as well as a number of protozoans (flagellates, rhizopods, and ciliated infusorians) and some mollusks, crustaceans, insects, and fish.
V. I. ZHADIN