Effect of Nutrients and Temperature Conditions on the Production of Microcystins by Microcystis aeruginosa Isolated from a Wild Population

AMÉ, MARÍA VALERIA; WUNDERLIN, D.A

WATER AIR AND SOIL POLLUTION

Springer

Lugar: Holanda; Año: 2005 vol. 168 p. 235 - 248

0049-6979

We report results of a study conducted to evaluate effects of ammonium, iron and temperature on microcystins (MC) and proteins production in cultures of Microcystis aeruginosa isolated from San Roque reservoir (Córdoba - Argentina). Based on a previous field study, we tested two temperatures (20 and 28°C), two iron concentrations (1 µM and 10 µM) and two ammonium-nitrogen conditions (absence and 54 µM) in semi-continuous cultures. Total MC (TMC=MC-LR+MC-RR) and protein production per cyanobacteria cell increased when Fe concentration was enlarged. However, the ratio TMC: protein was almost the same for both iron concentrations. Thus, a high level of iron enhances both protein and MC production in the same proportion. TMC and protein production are significantly lowered in presence of 54µM-N-ammonium. However, the ratio TMC: protein is significantly lower for cultures having ammonium. Therefore, during the present study, could be considered that the presence of ammonium reduces the production of MC. Increasing the temperature does not affect the protein production or TMC per cell. However, cultures carried out at 28°C maintain the same MC-LR: MC-RR ratio during all the studied period, while cultures developed at 20°C show a progressive dominance of MC-LR over MC-RR. As a result, in our case, different temperatures produce a significant change in the pattern of MC production but not in the content of TMC per cell. Results reported here open questions related to the inhibitory role of ammonium on MC production as well as on the incidence of the temperature on the production of different variants of MC by Microcystis aeruginosa.