Planktonic rotifer feeding in hypertrophic conditions

Abstract

We studied the role of rotifers as grazers in hypertrophic waters, dominated by poorly edible filamentous and colonial cyanobacteria. Population growth of Anuraeopsis fissa and Brachionus angularis, from hypertrophic lake Albufera in Valencia, was followed for 15 days in three treatments of different food size fractions: (a) 0-15 mm (lake water filtered through 15 mm nytal sieve), (b) 0-3 mm (15 mm lake water filtrate filtered through 3 mm nuclepore filter), and (c) 3-15 mm (re-suspension, in absolute filtered lake water, of the seston collected on the 3 mm filter, after passing lake water previously filtered through 15 mm). None of the species grew when fed the food size fraction of 3-15 mm that contained a large proportion of filamentous and colonial cyanobacteria. A. fissa showed highest growth parameters when fed the <3 mm food size fraction, which was mainly composed of bacterioplankton, but much reduced growth on the whole <15 mm seston fraction. On the other hand, B. angularis showed highest growth on the whole <15 mm seston fraction and a moderate growth when fed only on the <3 mm seston fraction. Clearance, ingestion, and assimilation rates were measured with 3 H-thymidine plus 3 H-leucine-labeled lake bacteria community, suspended in the 15 and

Phenotypic plasticity in freshwater picocyanobacteria

“…the formation of spines, colonies and thicker cell walls) have been also observed in many nano‐ and microphytoplanktonic species of Cyanobacteria, Chlorophyte and diatoms (van Donk et al ., ). However, the effect of zooplankton on picoplankton phenotypic composition has usually been neglected, despite the fact that direct consumption of Pcy by zooplankton has been well documented (Callieri et al ., , and cites therein; Motwani and Gorokhova, ; Miracle et al ., ). Work and Havens () observed that all zooplankton taxa from a eutrophic lake grazed on bacteria, eukaryotic algae and Cyanobacteria, yet colonial Cyanobacteria were negatively selected as compared with other food sources.…”

Elevated Magnesium Concentrations Altered Freshwater Assemblage Structures in a Mesocosm Experiment

“…appeared to be unaffected by the addition of Mg, with minor fluctuations in abundance across all treatments including the controls, whereas A. fissa was only present in high abundances in the controls, albeit with high variability. A previous study examining the feeding habits of A. fissa reported that this species grew best when fed the <3‐µm filtered fraction of lake water that was comprised of bacterioplankton and smaller algal species (Miracle et al 2014); these small‐sized food items may have declined in abundance with the addition of Mg, potentially exacerbating the response of A. fissa to Mg due to indirect effects. Overall, zooplankton species displayed a high level of sensitivity compared with responses of zooplankton species in other Mg and salinity sensitivity studies (Nielsen et al 2003; Waterkeyn et al 2010; Bielańska‐Grajner and Cudak 2014).…”

Predators and nutrient availability favor protozoa-resisting bacteria in aquatic systems

“…Rotifers and protozoa are both potential predators of bacteria. Omnivory is very common among both ciliates and rotifers 34 – 36 , so it is likely that they fed on both bacteria and HNF in the in situ and enriched treatments. In the present study, it is not clear whether the Mycobacterium were growing intracellularly in the protozoa or saprozoically (extracellularly), as shown for Mycobacterium avium in co-culture with amoeba 37 .…”