Efeito da salinidade no biovolume, crescimento e morfologia de cianobactérias formadoras de florações

Abstract

The current scenarios of increasing temperature and decreasing precipitation, together with human activities, are causing the increase of salinity in continental aquatic ecosystems. Salinization, a process that for years was typically associated with semi-arid and arid regions, promotes various problems to the economy, human health, and especially to the biological communities in rivers, lakes, and reservoirs. However, in comparison to other environmental problems, the salinization of continental aquatic ecosystems is little researched. There are few studies indicating the effects of salinization on the biovolume, growth and morphology of cyanobacteria. Thus, this work was developed to investigate the response of two cyanobacteria, Microcystis aeruginosa and Raphidiopsis raciborskii, to sudden increases in salinity. To do this, biovolume concentrations, growth rate, and morphology were analyzed. Both cyanobacterial species were exposed to treatments with 2.5, 5 and 10 g L-1 NaCl and a control (0 g L-1) for 12 days. In this study, all parameters for both cyanobacteria were negatively affected by increasing salinity relative to the control. In morphology, the increase in salt concentration promoted a decrease in cell size for M. aeruginosa and filament size for R. raciborskii. The results indicated that M. aeruginosa was able to grow in salinities between 0 and 10 g L-1, while R. raciborskii tolerated between 0 and 5 g L-1. Salinity exerted a decrease in biovolume concentrations and growth rate of M. aeruginosa and R. raciborskii. In addition, M. aeruginosa proved to be more tolerant.