Grazing on Microcystis (Cyanophyceae) by testate amoebae with special reference to cyanobacterial abundance and physiological state

Abstract

We examined the growth of testate amoebae preying on Microcystis whose physiological states were different in laboratory experiments and a hypertrophic pond. We prepared three experimental systems using water samples dominated by Microcystis aeruginosa: light incubation (control), dark incubation (dark), and light incubation with addition of nitrogen and phosphorus (?NP). In all the systems, the colony density of M. aeruginosa decreased slightly during incubation. Physiological activity of phytoplankton as determined by chlorophyll fluorescence was high and almost constant in the control and ?NP systems, whereas it decreased in the dark system. Cell densities of testate amoebae increased in the control and ?NP systems, whereas in the dark system they remained low. Thus, growth of the amoebae was low in the systems where physiological activity of Microcystis was low. In a hypertrophic pond, cell density of testate amoebae increased and remained high when M. aeruginosa predominated. Cell density of testate amoebae increased remarkably, simultaneously with the increases in M. aeruginosa colony density and phytoplankton physiological activity. We also found a significant correlation between densities of M. aeruginosa colonies and testate amoebae. We suggested that the physiological activity of Microcystis is one important factor affecting the growth of testate amoebae grazing on Microcystis.

Checklist de tecamebas (Testacea) do estado de Mato Grosso do Sul, Brasil

“…Protozoários têm grande importância ecológica em ambientes aquáticos, devido à variedade de nichos trófi cos ocupados, são algívoros, bacterívoros, carnívoros, onívoros, osmotrófi cos ou mixotrófi cos (Godinho & Regali-Seleghim, 1999), constituem elos alimentares para níveis trófi cos superiores, transferindo a biomassa bacteriana para níveis trófi cos superiores (Sanders & Wickham, 1993;Bozelli & Huszar, 2003), são estudados como opção no controle biológico de cianobactérias (Mizuta et al, 2011), atuam como remineralizadores de nutrientes no meio aquático (Sherr & Sherr, 1994) e podem ser utilizados como bioindicadores de contaminação ou poluição pois estão associados à presença de matéria orgânica em decomposição (Dabés & Velho, 2001).…”

Microbial players involved in the decline of filamentous and colonial cyanobacterial blooms with a focus on fungal parasitism

“…Zooplankton communities able to graze on cyanobacteria encompass four major groups: rhizopods, ciliates, rotifers and crustaceans. For several decades, studies have investigated trophic interactions between cyanobacteria and diverse zooplankton communities such as testate amoebae (Nishibe et al ., ; Mizuta et al ., ), rotifers (Starkweather and Kellar, ; Van Wichelen et al ., ; Kâ et al ., ), ciliates (Canter et al ., ; Audrey et al ., ), cladocerans (Lampert, ; Boon et al ., ; Gustafsson and Hansson, ; Oberhaus et al ., ) (Fig. A) and copepods (Haney, ; DeMott et al ., ; Rollwagen‐Bollens et al ., ) (http://onlinelibrary.wiley.com/doi/10.1111/1462-2920.12860/suppinfo).…”