Nutrient turnover by freshwater bacterivorous flagellates: differences between a heterotrophic and a mixotrophic chrysophyte

Rothhaupt, Karl O.

doi:10.3354/ame012065

Cited by 55 publications

(52 citation statements)

References 20 publications

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“…The prevailing nutritional mode of a mixotrophic species strongly de termines its influence on trophic dynamics, regarding grazing control, nutrient uptake and regeneration (e.g. Rothhaupt 1997, Fi scher et al 2016, and very likely also intracellular stoichiometry.…”

Section: Discussionmentioning

confidence: 99%

The functional role of planktonic mixotrophs in altering seston stoichiometry

Moorthi¹,

Ptáčník²,

Sanders³

et al. 2017

Aquat. Microb. Ecol.

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Mixotrophic protists are widespread and relevant primary producers and consumers in planktonic food webs. Given their dual mode of nutrition, mixotrophs face different constraints in allocating resources to cellular structures compared to strict photoautotrophs. However, little is known about their stoichiometric requirements and their flexibility in nutrient content and thus food quality, or how this affects consumer performance and nutrient recycling. In the present study, we tested for systematic differences in elemental composition between photoautotrophic and mixotrophic protists. We compiled intracellular nutrient ratios of mixotrophic and phototrophic species from culture experiments and from 2 lake surveys. Overall, both laboratory and field data indicated that mixotrophy has a stabilizing effect on the nutrient stoichiometry of primary producers under changing nutrient supply. In laboratory experiments, mixotrophs showed a lower variability in intracellular N:P ratios compared to strict phototrophs and were more stable in their elemental composition in response to a gradient of dissolved N:P availability. With increasing contributions of mixotrophic phytoplankton taxa to total lake phytoplankton, both the mean and variance in seston C:P ratios decreased, i.e. communities with higher proportion of mixotrophs overall exhibited more constrained seston stoichiometry. Our results show that mixotrophy may have direct implications for nutrient cycling and secondary production through regulation of seston stoichiometry, buffering stoichiometric constraints for herbivores and enabling a more stable secondary production compared to systems dominated by phototrophic specialists.

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Section: Discussionmentioning

confidence: 99%

The functional role of planktonic mixotrophs in altering seston stoichiometry

Moorthi¹,

Ptáčník²,

Sanders³

et al. 2017

Aquat. Microb. Ecol.

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“…Jürgens & Güde (1990) found that on average ~62% of the particulate P was incorporated into the bacterial size fraction in Lake Constance (Germany/Switzerland) during summer. In our experiment, the extremely high fraction of P bound in the bacterial fraction at the lowest L P might, in part, also reflect the lack of P transfer to primary producers by bacterivorous flagellates (Rothhaupt 1997).…”

Section: Phytoplankton-bacteria Paradoxmentioning

confidence: 99%

Effects of phosphorus loading on interactions of algae and bacteria: reinvestigation of the phytoplankton-bacteria paradox in a continuous cultivation system

Mindl¹,

Sonntag

Pernthaler

et al. 2005

Aquat. Microb. Ecol.

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The effect of different phosphorus loads (L P ) on the phosphorus (P) and carbon (C) content (biomass) of algae and bacteria was assessed in continuous culture. We tested if a mixed freshwater microbial assemblage co-cultured with a phytoflagellate (Cryptomonas phaseolus) would comply with the 'phytoplankton-bacteria paradox ' (sensu Bratbak & Thingstad 1985). This hypothesis states that the ratio of bacterial to algal abundance changes to the benefit of bacteria with decreasing L P . However, the phenomenon was originally investigated by simultaneously altering L P and microbial growth rates, and it is unclear to which extent it can be assigned to either parameter. Therefore, we set up 3 chemostat systems in triplicate at equal dilution rates, but with daily L P of 21, 41 or 62 µg l -1 d -1 (corresponding to 50, 100 and 150 µg P l -1 ). Higher L P led to a 5-fold increase in total algal abundance and biomass but to less than a doubling of these parameters in the bacterial assemblage. Total biomass ratios of bacteria to algae changed from 0.18 to 0.06 with increasing L P , while the bacteria-algae total phosphorus ratios decreased from 0.80 to 0.17. The cellular C:P ratio of algae remained similar at all P concentrations, whereas the molar C:P ratios of bacterial cells significantly increased at higher L P (from 44 to 73). An enrichment experiment with the 50 µg P l -1 treatment demonstrated that bacteria at the lowest L P were co-limited by P and C, and that increased P stimulated mainly the algal fraction. The phytoplankton-bacteria paradox at the level of a mixed microbial assemblage is thus characterised by the following aspects: (1) bacteria profit from their high affinity to P and are better competitors at lower L P ; (2) although algae compete with bacteria for P, P-limited algae release extracellular C that stimulates growth of their bacterial competitors; (3) when bacteria depend on algae as their sole source of organic C, this provides a feedback mechanism by which algae limit the abundance of their competitors at higher L P ; (4) large oscillations in the bacteria-algae ratios at the lowest L P point to a greater instability of this interaction with stronger P competition. However, bacteria were not able to outcompete C. phaseolus, as algae were their only C source.KEY WORDS: Algae-bacteria interaction · Chemostat · Continuous cultivation system · Cryptomonas phaseolus · Eutrophication · Phosphorus · Phytoplankton-bacteria paradox Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 38: [203][204][205][206][207][208][209][210][211][212][213] 2005 nutrients, such as nitrogen or phosphorus, the relationship between bacteria and algae is not considered mutualistic, but competitive (Currie & Kalff 1984b, Elser et al. 1995, Vadstein 2000.The competition for P between bacteria and algae cannot easily be studied in situ, i.e. in a planktonic food web of high complexity. Continuous cultivation systems have the advantage that algae and bacteria experience...

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“…strain 26.80 (formerly Rhodomonas sp.). This algae-bacteria community has already been used in many studies on the feeding behavior of protists [20,23,[26][27][28][29]36]. The scuticociliate was chosen for our experiments because several authors have already studied the size selectivity of the genus Cyclidium [5,19,23,30,35].…”

Section: Introductionmentioning

confidence: 99%

Size Selective Feeding in Cyclidium glaucoma (Ciliophora, Scuticociliatida) and Its Effects on Bacterial Community Structure: A Study from a Continuous Cultivation System

et al. 2001

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A B S T R A C TThree aspects of size selective feeding by the scuticociliate Cyclidium glaucoma were studied in continuous cultivation systems. Firstly, grazing-induced changes in abundance, biomass, and size structure of a bacterial community were investigated. Secondly, we studied possible grazingprotection mechanisms of bacteria as a response to permanent presence of the predator. And finally, we were looking for potential feedback mechanisms within this predator-prey relationship, i.e., how the ciliate population reacted to a changed, more grazing-protected bacterial community. The first stage of the cultivation system consisted of the alga Cryptomonas sp. and the accompanying mixed bacterial community. These organisms were transferred to two second stage vessels, a control stage without ciliates and a second one inoculated with C. glaucoma. After the first week, the abundance of bacteria in the latter decreased by 60% and remained stable until the end of the experiment (65 d), whereas bacterial biomass was less affected (393 µg C L −1 during days 0-7, 281 µg C L −1 afterwards). The mean bacterial cell volume doubled from 0.089 µm 3 to 0.167 µm 3 , which was mainly due to increasing cell widths. During the whole investigation period formation of colonies or filaments was not observed, but we found a clear feedback of ciliates on bacterial size. An increase in bacterial cell volume was always followed by a decline of the predator population, resulting in a yet undescribed type of microbial predator-prey relation. Literature and our own data on the optimal food size range grazed by C. glaucoma showed that bacterial cell width rather than length was responsible for that observed phenomenon. Finally, we suggest that uptake rates of spherical latex beads give only limited information on truly ingestible prey volumes and that prey geometry should be considered in future studies on size selective feeding of protists.

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Nutrient turnover by freshwater bacterivorous flagellates: differences between a heterotrophic and a mixotrophic chrysophyte

Cited by 55 publications

References 20 publications

The functional role of planktonic mixotrophs in altering seston stoichiometry

The functional role of planktonic mixotrophs in altering seston stoichiometry

Effects of phosphorus loading on interactions of algae and bacteria: reinvestigation of the phytoplankton-bacteria paradox in a continuous cultivation system

Size Selective Feeding in Cyclidium glaucoma (Ciliophora, Scuticociliatida) and Its Effects on Bacterial Community Structure: A Study from a Continuous Cultivation System

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Nutrient turnover by freshwater bacterivorous flagellates: differences between a heterotrophic and a mixotrophic chrysophyte

Cited by 55 publications

References 20 publications

The functional role of planktonic mixotrophs in altering seston stoichiometry

The functional role of planktonic mixotrophs in altering seston stoichiometry

Effects of phosphorus loading on interactions of algae and bacteria: reinvestigation of the phytoplankton-bacteria paradox in a continuous cultivation system

Size Selective Feeding in Cyclidium glaucoma (Ciliophora, Scuticociliatida) and Its Effects on Bacterial Community Structure: A Study from a Continuous Cultivation System

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Effects of phosphorus loading on interactions of algae and bacteria: reinvestigation of the phytoplankton-bacteria paradox in a continuous cultivation system