Diferentes respostas de espécies fitoplanctônicas aos efeitos da interação com Ceratophyllum demersum L. e herbivoria por Moina micrura Kurz, 1875

Abstract

The present work aims to understand the indirect allelopathic effects of Ceratophyllum demersum and the herbivory of Moina micrura on Microcystis aeruginosa and Raphidocelis subcapitata. To carry out the study, the algae strains were grown in 1000 mL erlenmeyers, filled with 800 mL of ASM1 medium, and under controlled temperature and light conditions. Two parallel experiments, lasting six days, were carried out in an aseptic room. The first experiment consisted of four treatments with triples, which evaluated the interaction of C. demersum + strains, M. micrura + strains, C. demersum and M. micrura + strains, and the control (strains in proportions equal 1:1). The second experiment had five treatments with triples, where the algae were coexisted under different concentrations: 1:0, 3:1, 1:1, 1:3 and 0:1. 2 mL aliquots were collected every two days (0, 2, 4 and 6) to determine density and subsequently obtain biomass. The data were treated statistically through ANOVA one-way with a significance level set at 5% (p> 0.05). Initially, the data were tested for normality predicted by the Kolmogorov-Smirnov test. In experiment 1, C. demersum and C. demersum + M. micrura significantly inhibited M. aeruginosa from the second day (p <0.01), whereas R. subcapitata did not show any differences during the whole experiment (p> 0.05). In treatments with only M. micrura, there was no change in the density of the strains (p> 0.05). Possibly C. demersum inhibited the growth of cyanobacteria through the release of allelochemicals, but chlorophyte was less affected by having greater physiological resistance. In experiment 2, M. aeruginosa did not inhibit the growth of R. subcapitata in equal (1:1) and dominant (3:1) proportions, but was inhibited by Raphidocelis in low concentrations (1:3). It is possible that chlorophyte is stimulated when competing algae are at lower densities. We conclude that the action of C. demersum is efficient in the control of M. aeruginosa, differently from M. micrura. At low concentrations, M. aeruginosa can be inhibited by R. subcapitata, while R. subcapitata is possibly to resist both the macrophyte allelochemicals and the cyanobacterial microcystins.