The importance of Protozoa in controlling the abundance of planktonic algae in lakes

ArticleinBiological Journal of the Linnean Society 179(2):203 - 219 · June 2008with15 Reads
DOI: 10.1111/j.1095-8312.1968.tb00978.x
Abstract
Apart from ciliates, there are other protozoans which can form an important element in the herbivorous zooplankton of lakes.The protozoans discussed in this paper feed on colonial algae. They can greatly reduce the numbers of certain Chlorophyta in Windermere, Esthwaite Water and Blelham Tarn, lakes in the English Lake District.A very short period, often 7–14 days, can suffice for the destruction of more than 99% of an algal population.Experiments with a species of Pseudospora showed that it would only ingest one out of six green algal species, although, in nature, Pseudosporae which are morphologically similar to this species have been observed in all these algae.The importance of such protozoans, and of parasitic fungi, has been underrated or neglected in studies of the quantitative relationships between primary and secondary production in the plankton.
    • "As no protozoa were observed in control flasks their presence may be connected to the exposure medium. Protozoa are well known to feed on algae565758 and their grazing effects on algal density cannot be excluded even in this case. As a consequence caution is requested in the evaluation of the toxic effects of zosteric acid on algal communities and in depth investigations should be performed to have more extended ecotoxicological data on algae and to evaluate if the growth inhibition is directly related to zosteric acid or to protozoa grazing activity. "
    [Show abstract] [Hide abstract] ABSTRACT: This study provides data to define an efficient biocide-free strategy based on zosteric acid to counteract biofilm formation on the membranes of submerged bioreactor system plants. 16S rRNA gene phylogenetic analysis showed that gammaproteobacteria was the prevalent taxa on fouled membranes of an Italian wastewater plant. Pseudomonas was the prevalent genus among the cultivable membrane-fouler bacteria and Pseudomonas putida was selected as the target microorganism to test the efficacy of the antifoulant. Zosteric acid was not a source of carbon and energy for P. putida cells and, at 200 mg/L, it caused a reduction of bacterial coverage by 80%. Biofilm experiments confirmed the compound caused a significant decrease in biomass (-97%) and thickness (-50%), and it induced a migration activity of the peritrichous flagellated P. putida over the polycarbonate surface not amenable to a biofilm phenotype. The low octanol-water partitioning coefficient and the high water solubility suggested a low bioaccumulation potential and the water compartment as its main environmental recipient and capacitor. Preliminary ecotoxicological tests did not highlight direct toxicity effects toward Daphnia magna. For green algae Pseudokirchneriella subcapitata an effect was observed at concentrations above 100 mg/L with a significant growth of protozoa that may be connected to a concurrent algal growth inhibition.
    Full-text · Article · Jun 2014
    • "A monthly or even biweekly sampling frequency is likely to miss an amoebae population peak, as herbivorous amoebae densities can change dramatically within a few days (this study, see also Canter and Lund, 1968). As a consequence, a strong influence of grazing amoebae on the dynamics of natural phytoplankton populations has only rarely been reported (e.g. Canter and Lund, 1968; Bailey-Watts and Lund, 1973; Cook and Ahearn, 1976; Van Wichelen et al., 2006). In the case of Microcystis, it was only shown thus far that laboratory cultures could be completely destroyed by Microcystisassociated amoebae (Reynolds et al., 1981). "
    [Show abstract] [Hide abstract] ABSTRACT: Despite its importance for bloom toxicity, the factors determining the population structure of cyanobacterial blooms are poorly understood. Here, we report the results of a two-year field survey of the population dynamics of Microcystis blooms in a small hypertrophic urban pond. Microscopic enumeration of Microcystis and its predators and parasites was combined with pigment and microcystin analysis and denaturing gradient gel electrophoresis of the ITS rDNA region to assess population dynamics and structure. Two main Microcystis morpho- and ITS types were revealed, corresponding to M. aeruginosa and M. viridis. In both years, high population densities of naked amoebae grazing on Microcystis coincided with rapid decreases in Microcystis biomass. In one year, there was a shift from heavily infested M. aeruginosa to the less-infested M. viridis, allowing the bloom to rapidly recover. The preference of amoebae for M. aeruginosa was confirmed by grazing experiments, in which several amoeba strains were capable of grazing down a strain of M. aeruginosa, but not of M. viridis. Zooplankton and chytrid parasites appeared to be of minor importance for these strong and fast reductions in Microcystis biomass. These findings demonstrate a strong impact of small protozoan grazers on the biomass and genetic structure of Microcystis blooms.
    Full-text · Article · Oct 2010
    • "grazing the green alga Paulshulzia sp. (Canter and Lund, 1968), suggest that phagotrophy of larger algal cells by HMF may be widespread. In addition, reports of larger protozoans grazing even larger algal cells (Canter, 1973; Popovsky, 1982; Gaines and Taylor, 1984) further emphasizes the potential importance of protozoan grazers, although the size of protozoan grazers may affect their ecological role. "
    [Show abstract] [Hide abstract] ABSTRACT: Colorless microflagellates (6–14 μm in diameter) were isolated from an oligotrophic lake in Western Canada, and shown to consume diatoms up to six times longer than the diameter of the flagellate. Observations were also made of morphologically similar flagellates attached to diatoms from the Great Lakes, indicating that this phenomenon may occur in nature. It is suggested that predation by microflagellates on much larger algal cells could potentially affect the pathway of nutrient and energy transfer in aquatic foodwebs.
    Full-text · Article · Jan 1986
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