An investigation of the toxin of Microcystis aeruginosa: effects of varying the concentration of selected salts upon toxicity and the effects of the toxin on some physiological parameters

Abstract

Microcystis aeruginosa, a blue-green alga, is the agent responsible for fatal poisonings of a variety of animals following ingestion of water containing large numbers of this species. The waterblooms were of varying toxicity ranging from nontoxic to those having a mouse LD₁₀₀ of 40 mg/kg. Studies have shown that some of the factors controlling toxicity are aeration rate, temperature, and light intensity. The formation of waterblooms is dependent, to a certain extent, upon the influx of mineral nutrients from the surrounding environment. In this study an attempt was made to determine whether one or more of the mineral nutrients acted as stimulants to or depressants of toxin production. Allen's medium was selected as the standard medium in which the concentration of selected salts was altered. Those selected included NaNO₃, K₂HPO₄, MgSO₄, CaCl₂, ferric citrate, and the microelements. The results of the study indicate that toxin production by M. aeruginosa is stimulated both by increases and decreases in the concentration of the various salts. In addition to studying the effects of nutrient alterations on toxin production, the effects of crude extracts of M. aeruginosa on the cardiovascular system were studied. Intravenous administration of the extract to anesthetized dogs caused a precipitous fall in both the systemic and pulmonary blood pressures with no significant change occurring in the heart rate.