Growth and cytometric diversity of bacterial assemblages under different top-down control regimes by using a size-fractionation approach

LANSAC-TOHA, F. M.; VELHO, L. F. M.; SEGOVIA, B. T.; AMADEO, F. E.; SARMENTO, H.; MEIRA, B. R.; UNREIN, F.

JOURNAL OF PLANKTON RESEARCH

OXFORD UNIV PRESS

Lugar: Oxford; Año: 2018 vol. 40 p. 129 - 141

0142-7873

Zooplankton communitiesin tropical inland waters are generally characterized by small bodiedindividuals and the absence of large daphnids. However, the effects of thispeculiar food web configuration on microbial compartments have not been testedexperimentally. To establish which predator could be responsible for mostbacterial loss in a tropical shallow lake, we performed a predation experimentmanipulating consumer size fractions. We found that protists had an effect morethan four times greater (−86%) than the one exerted by microcrustaceans (−20%),whereas rotifers and nauplii had a minimum effect (−8%). Thus, our resultsindicate that predation was a crucial factor controlling bacterial abundance andthat protists (mainly ciliates) were responsible for most of this loss.Moreover, bacterial community structure was also affected by predation, with achange in the relative proportion of cytometric subpopulations (high-nucleicacid and low-nucleic acid) as a function of different degrees of predationpressure and a decrease in community evenness (assessed by cytometricdiversity) with the removal of predators. Therefore, protists play an importantrole in controlling the abundance and maintaining prokaryotic diversity in warmregions, where zooplankton is present and controlled by juvenile fishthroughout the year.