Why predation is not a controlling factor of phytoplankton in a Neotropical shallow lake: a morpho-functional perspective

RODRIGO SINISTRO; YAMILA BATTAUZ; DIEGO FRAU

HYDROBIOLOGIA

SPRINGER

Lugar: Berlin; Año: 2017 vol. 788 p. 115 - 130

0018-8158

This work explores the reasons why predation plays a minor role in structuring phytoplankton composition in a Neotropical shallow lake. Phytoplankton, zooplankton, and fish were sampled from a shallow lake over the course of a year, and the stomach contents of 80 individuals of the dominant omnivorous?planktivorous fish species were analyzed. The field study was complemented with a 5-day microcosm experiment in which the predation effects of micro, meso, and macrozooplankton were measured. Stomach content analysis revealed that fishpredation was high, and primarily comprised by Cladocera (Ivlev?s index [0.75). Both meso and macrozooplankton fractions are able to feed on colonial cyanobacteria, silica cell-wall organisms ( lm), and mixotrophic flagellate ([35 lm). Macrozooplankton, however, can feed on single cells, mucilaginous colonies, non-mucilaginous colonies, and silica cell-wall organisms ([35 lm) (P�.05 in all cases). Our results support the idea that absence of predation on phytoplankton is mainly mediated by fish predation on zooplankton and morpho-functional characteristics of algae which prevent zooplankton predation; showing fish a lack of direct predation effect on phytoplankton.