Implicações limno-ecológicas derivadas da infecção viral no plâncton

Abstract

Virus are described as the most abundant and dynamic organisms in the aquatic environment, influencing communities composition and biogeochemical and ecological processes. These organisms are responsible for great part of the bacterial and phytoplanktonic mortality, for algal blooms decrease and for increasing the nutrients and carbon availability. Many previous works approach the viral ecology in temperate aquatic ecosystems, although there are only two references for the tropical area. The goal of this work was to determine the viral and bacterial abundances in Amazonian aquatic systems, as well as to evaluate the interactions between these groups. In order to achieve it, optical and electronic microscope techniques were applied. The number of viruses (VLP) varied both in temporal and in spatial scales, even though the virus/bacteria ratio was kept unaltered. In a spatial scale, VRB was correlated to the dissolved organic carbon (COD) concentration, suggesting that humic lakes present reduced rate of bacterial mortality caused by virus. In average, 20% of the bacteria were infected by 10 phagos per cell. The VLP was correlated to phosphorus availability, lake depth, light penetration, and mainly bacterial abundance. We suggest that most of the virus in Amazonian aquatic ecosystems are bacteriophages and, hence, that they play a fundamental role in controlling the bacterial community, in nutrient cycling and in energy flux.