A influência do ambiente e do espaço na composição de microrganismos aquáticos presentes em bromélias-tanque (Portea petropolitana)

Abstract

Tank bromeliads are models of aquatic microcosms that, in addition to providing shelter, water and nutrients for the fauna, are considered critical points of biodiversity. The wide variation in biological diversity between bromeliad tanks and the surrounding area highlights the importance of this ecosystem in maintaining biodiversity at different scales. To understand the processes that regulate the structure of aquatic communities in tank bromeliads, two studies were carried out. The first aimed to evaluate the influence of environmental variables and dry and rainy seasons on the structure and composition of the community of heterotrophic bacteria, ciliate and macroinvertebrates of tank bromeliads from the UFJF Botanical Garden, MG, Brazil. Samples of water and microorganisms were collected from 12 bromeliads of the species Portea petropolitana located in the Botanical Garden (JB) of UFJF in two periods (March and July 2019). In the field, the height of bromeliad, canopy opening above the plant, temperature in the water of the tanks, color, volume and diameter of the central cup, and the concentration of dissolved carbon, nitrogen and phosphorus were measured. In the second study, the influence of space on the distribution of species of microorganisms in the tanks of bromeliads was evaluated. For this, in addition to the environmental variables and the aquatic communities of twenty tank bromeliads, the values of the distance of each bromeliad to the JB lake (potential source of dispersing organisms) were obtained. Bacterial community was investigated by the cytometric diversity approach. Ciliates and macroinvertebrates were identified and quantified at the family level. To analyze the influence of deterministic and stochastic processes on the distribution of organisms, alpha (Shannon) and beta (Whittaker and Bray Curtis) indices were used, in the Simple Linear Regression Analysis, Student's t Test, and Analysis of covariance (ANCOVA ). In the second study, for each community, a multiple linear regression analysis and selection of the most parsimonious models were used by the Akaike Information Criterion (AIC). The analyzes were performed using the GraphPad Prism 8.2.1, PAST 326 and R 3.6.0 software. Associations of macroinvertebrates with the volume of water in the tanks and dissolved organic carbon were found while the ciliate were regulated by dissolved nitrogen. The dry and rainy did not directly affect the ciliate and invertebrates communities, only the bacterial community, at the same time that it modified the structure of the organic matter that regulates the communities, indicating that it functioned as a filter for macro and microorganisms. The distribution of groups of bacteria was little explained by environmental factors, suggesting the predominance of stochastic processes in the structuring of this group. We conclude that the strength of random and deterministic events in biological communities depends on the plasticity of organisms as a function of the periods of drought and rain.