Toxicity Fluctuations and Factors Determining Them

Abstract

More than 100 samples of waterblooms and of populations concentrated by plankton net of Microcystis aeruginosa and Aphanizomenon flos-aquae from the Dnieper reservoirs, uni-algal cultures of Microcystis aeruginosa and extracts made from these sources were tested for toxicity during a 3-year period. Using the cholinesterase blocking method of Kirpenko et al and bioassays with mice and rats, the quantities of toxin were found to fluctuate from 3.96 to 11×10⁻⁷mg/g dry wt (10⁻³ to 10⁻⁷mg/l.). It is concluded that the factors that cause toxicity fluctuations are: (1) major changes in the physical, chemical and biological environment associated with eutrophication that affect the growth of blue-green algae and their attendant microflora, (2) changes in species composition of waterblooms, especially those dominated by M. aeruginosa, during the stage of rapid growth and in the presence of exogenous metabolites from algal antagonists to the dominant species, and (3) initial stages of decomposition of dead cells of the blue-green algae which produce toxic amines and phenolic compounds in the water, especially when temperatures are high. Algal toxicity is an important factor in water quality which needs more study.