Interaction Between a Bacterivorous Ciliate Aspidisca cicada and a Rotifer Lecane inermis: Doozers and Fraggles in Aquatic Flocs

Abstract

Activated sludge is a semi-natural habitat composed of macroaggregates made by flocculating bacteria and inhabited by numerous protozoans and metazoans, creating a complicated interactome. The activated sludge resembles the biological formation of naturally occurring floc habitats, such as Bmarine snow.^So far, these two types of habitat have been analyzed separately, despite their similarities. We examined the effect of a bacterivorous ciliate, Aspidisca cicada, on the quality of the macroaggregate ecosystem by estimating (i) the floc characteristics, (ii) the proliferation of other bacterivores (rotifers), and (iii) the chemical processes. We found that A. cicada (i) positively affected floc quality by creating flocs of larger size; (ii) promoted the population growth of the rotifer Lecane inermis, an important biological agent in activated sludge systems; and (iii) increased the efficiency of ammonia removal while at the same time improving the oxygen conditions. The effect of A. cicada was detectable long after its disappearance from the system. We therefore claim that A. cicada is a very specialized scavenger of flocs with a key role in floc ecosystem functioning. These results may be relevant to the ecology of any natural and engineered aggregates.

The influence of Aspidisca cicada on nitrifying bacteria and the morphology of flocs in activated sludge

“…Such a setup allowed simulation of wastewater treatment process (SBR) with all phases involved. Activated sludge originating from WWTP created the habitat much more complicated than that of experiments described by Walczyńska and coauthors (2018), where only A. cicada and Lecane rotifers were used. In this research, the clear differences in floc area between control and experimental vessels probably resulted from the fact that control was maintained Aspidisca‐free throughout the experiment.…”

“…The role of ciliates in processes of the bacterial macroaggregates formation in natural water habitats and wastewater treatment plants was the subject of several research (Curds, 1963;Arregui et al, 2007Arregui et al, , 2008. Recent studies by Walczyńska et al (2018) showed that A. cicada significantly influences the size and structure of freshly created flocs. These results remain in contradiction to our current results showing that addition of dense culture of A. cicada did not have a statistically significant effect on the area and compactness of flocs.…”

“…In addition, Pajdak-Stós et al (2010) observed that during municipal treatment plant start-up changes in the sizes of ammonia and nitrite oxidisers colonies corresponded with increasing number of crawling bacterivorous ciliates dominated by the genus Aspidisca. Research conducted by Walczyńska et al (2018) showed that in a simple experimental set A. cicada promotes flocculation and ammonia removal.…”

Aerobic scope does matter in temperature-size rule, but only under optimal conditions

“…The initial densities of rotifers (which were same for each clone) planted at the beginning of experimental parts were 110, 120 and 250 indiv/mL for MH, SHT and SHO2 stages, respectively. This number was far below the population carrying capacity because L. inermis rotifers may reach densities as high as tens of thousands per mL (45 000 indiv/mL was reported by Walczyńska et al, 2017). The rotifers in each cage were fed 200 µL of commercial bioproduct Bio-Trakt®, which has been successfully used in L. inermis mass culture previously (Fialkowska et al, 2019).…”

Application of DNA barcoding for identifying potential biotechnological candidate organisms from the River Nile, Egypt.

“…They have been elucidated as biomarkers for improved environmental quality, such as in the soil (Abraham et al, 2019). Moreover, some species actively reduce bacterial flocs and increase ammonia removal from activated sludge, leading to a long-term enhancement of sewage-treatment through activated sludge (Walczyńska et al, 2018). Also, they are key aquatic biosensors towards heavy metals due to the absence of a rigid cell wall, exhibiting in many cases the loss in cells´ morphological integrity; roundness, intracellular vacuolization, morphological deformities and cellular rupture (Pudpong andChantangsi, 2015 andMadoni andRomeo, 2006;Somasundaram et al, 2018).…”