Herbivory effects on the periphytic algal functional diversity in lake ecosystems: an experimental approach

Abstract

Herbivory can determine the rates of ecosystem functions and is key factor to periphytic algae development. Here, we aimed to evaluate the effects of herbivory of zooplankton and omnivorous fish in periphytic algae of lake ecosystems. Based on prediction of grazer:prey size ratio, we tested that periphytic algal biomass and density will be lower in the fish treatments. Based on prediction of the size-selective predation, size-efficiency hypothesis, and general allometric equations, and that both herbivores will feed with distinct mode, we tested the hypothesis that periphytic algal functional diversity will be higher in the mixed treatment. There were four treatments (Control, T1-zooplankton, T2-fish, T3-zooplankton+fish). We evaluated algae biomass, density, functional traits, functional diversity, and the herbivory effect. Our results show that the presence of both herbivores were related to higher functional diversity, lower density values, and prostrate periphytic algae, and in T2 occurs higher periphytic algae biomass via nutrient facilitation. Fish was responsible for the higher consumer effect size, and was more important modifier than zooplankton of the periphytic algae community. The greater variation in producer species traits was directly related to mixed foraging patterns of herbivores together, which allow rare species to persist, decreasing the dominance of stronger competitive species.