Cianobacterias en diferentes estadíos fenológicos del cultivo de arroz en Entre Ríos (Argentina)

the aim of this study was to analyze the number and genera of cyanobacteria of rice crop fields of entre ríos at different phenological stages during two years. the microscopic cyanobacteria count in water and soil techniques were used and media comparison tests were perfomed to establish differences at tillering, booting and physiological maturity stages. the identification was conducted by morphological characteristics, dividing them them by unicellular, heterocystous filamentous and non-heterocystous filamentous groups. richness and simpson's reciprocal indexes were calculated. count distribution patterns in water were similar in both years. the lowest counts were registered at the tillering stageshowing significant differences between the first and second year. the maximum counts were observed at the booting stage in both years (3,6x104 and 4,0x104 cells ml-1 respectively). in the soil, the population exhibited a different evolution in the two years of analysis and was significantly different in booting and tillering. in the first year, 11 genera were registered, while 10 genera were registered in the second year. the genera lyngbya, oscillatoria, anabaena, nostoc, aphanocapsa, chroococcus, and gloeocapsa were observed in both years. nostoc and anabaena were present in most of the samplings. the unicellular cyanobacteria aphanocapsa, chroococcus and gloeocapsa were dominant in the soil. simpson's reciprocal index increased along the cycle of rice in the second year of evaluation. richness increased at the booting stage due to a better adaptation to the environmental conditions. the proportion of heterocystous filamentous in water was different during both years of study (50% and 26% for the first and second year).