Large‐scale patterns of biofilm‐dwelling ciliate communities in a river network: Only small effects of stream order

Ritz, Stephanie; Eßer, Markus; Arndt, Hartmut; Weitere, Markus

doi:10.1002/iroh.201601880

Cited by 5 publications

(3 citation statements)

References 54 publications

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“…With their considerable sizes, conspicuous morphologies and movements, ciliates are among the most easily identifiable protozoan grazers in biofilms. Densities of ciliates can range from a few hundred to several thousand cells/cm 2 , reported for both marine (Gong et al 2005, Zhang andXu 2015) and freshwater biofilms (Ackermann et al 2011, Ritz et al 2017. Ciliates are conventionally assigned to taxonomic units based on their morphology.…”

Section: Density and Functional Diversity Of Biofilm-dwelling Consumersmentioning

confidence: 99%

The food web perspective on aquatic biofilms

Weitere

Erken

Majdi

et al. 2018

Ecological Monographs

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Biofilms, the complex communities of microbiota that live in association with aquatic interfaces, are considered to be hotspots of microbial life in many aquatic ecosystems. Although the importance of attached algae and bacteria is widely recognized, the role of the highly abundant biofilm‐dwelling micrograzers (i.e., heterotrophic protists and small metazoans) is poorly understood. Studies often highlight the resistance of bacterial biofilms to grazing within the microbial food web and therefore argue that the micrograzers have a modulating role (i.e., have effects on biofilm phenotype) rather than a direct trophic role within biofilms. In the present review, we show that this view comes too short, and we establish a conceptual framework of biofilm food webs consisting of three major elements. (1) Energy pathways and subsidization from plankton. As inhabitants of interfaces, biofilm‐dwelling grazers potentially access both planktonic organisms and surface‐associated organisms. They can play an important role in importing planktonic production into the biofilm food web and thus in the coupling of the planktonic and benthic food webs. Nevertheless, specialized grazers are also able to utilize significant amounts of autochthonous biofilm production. (2) Horizontal complexity of the basal food web. While bacteria and algae within biofilms are edible in general, food quality and accessibility of both bacteria and algae can differ considerably between different prey phenotypes occurring during biofilm formation with respect to morphology, chemical defense, and nutrient stoichiometry. Instead of considering bacteria and algae within biofilms to be generally resistant to feeding by micrograzers, we suggest considering a horizontal food‐quality axis to be at the base of biofilm food webs. This food quality gradient is probably associated with increasing costs for the micrograzers. (3) Vertical food web complexity and food chain length. In addition to the consumption of bacteria and algae, many predatory micrograzers exist within biofilm food webs. With the help of video microscopy, we were able to demonstrate the existence of a complex food web with several trophic levels within biofilms. Our conceptual framework should assist in integrating food web concepts and processes into whole‐biofilm budgets and in understanding food‐web‐related interactions within biofilms.

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Section: Density and Functional Diversity Of Biofilm-dwelling Consumersmentioning

confidence: 99%

The food web perspective on aquatic biofilms

Weitere

Erken

Majdi

et al. 2018

Ecological Monographs

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“…In such multitrophic systems, complex interactions including indirect effects can occur in response to external drivers (Wey et al 2008). So far, the multitrophic communities of fluvial biofilms as a whole has rarely been assessed (but see Romaní et al 2014;Ritz et al 2017;Bengtsson et al 2018) and hence effects of near bed flow within as well as across microbial guilds are poorly understood. Knowledge on single guilds indicates that near bed flow causes a guild-specific trait dependent shift of microbial communities (growth form of autotrophs, e.g., unicellular vs. filamentous morphotypes, and function, e.g., food preference of heterotrophic protists), resulting in effects on the overall trophic structure of biofilms.…”

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confidence: 99%

Near streambed flow shapes microbial guilds within and across trophic levels in fluvial biofilms

Risse‐Buhl

Anlanger

Chatzinotas

et al. 2020

Limnology & Oceanography

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Flow is an important physical driver of biofilm communities. Here, we tested the effects of the near bed flows in two mountainous stream reaches on the structure of biofilm microbial guilds (autotrophs, heterotrophic bacteria, and heterotrophic protists) within and across trophic levels. Near bed flow velocity and turbulent kinetic energy were important physical drivers for structuring the communities within and across guilds of the multitrophic fluvial biofilms. The effects of flow were nested in a seasonal and spatial (across-streams) context. Changes in physicochemical factors (temperature, light, dissolved carbon, and nutrients) along the reaches were alike in both streams suggesting that environmental boundary conditions at larger temporal scales were responsible for the seasonal differences of biofilm communities, whereas locally microbial diversity was shaped by near bed flow. Typically, the abundance of autotrophs increased with flow, indicating that biofilms shifted toward increasing autotrophy with increasing shear forces. Filamentous autotrophs seemed to provide protected habitats from the shear forces for smaller sized bacteria. Heterotrophic protist abundance decreased with flow leading to decreasing grazer to prey ratio. Bacteria thus benefitted from a reduction in grazing pressure at faster flowing, more turbulent sites. Our results suggest that near bed flow can impact the magnitude and direction of matter fluxes through the microbial food web and possibly affect ecosystem functioning of fluvial biofilms.

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“…A custom made biofilm brush sampler adapted from Ritz et al (2017) based on a toothbrush head within a sample chamber was used to sample the 34-day-old biofilms. Under a constant flow of sterile filtered stream water (0.2 μm) through the sample chamber realized by a peristaltic pump (Watson Marlow) at 2 mL s -1 , the toothbrush head was placed on the biofilm patch, rotated and pushed three times.…”

Section: Methodsmentioning

confidence: 99%

Hydrodynamics Alter the Tolerance of Autotrophic Biofilm Communities Toward Herbicides

et al. 2018

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Multiple stressors pose potential risk to aquatic ecosystems and are the main reasons for failing ecological quality standards. However, mechanisms how multiple stressors act on aquatic community structure and functioning are poorly understood. This is especially true for two important stressors types, hydrodynamic alterations and toxicants. Here we perform a mesocosm experiment in hydraulic flumes connected as a bypass to a natural stream to test the interactive effects of both factors on natural (inoculated from streams water) biofilms. Biofilms, i.e., the community of autotrophic and heterotrophic microorganisms and their extracellular polymeric substances (EPS) in association with substratum, are key players in stream functioning. We hypothesized (i) that the tolerance of biofilms toward toxicants (the herbicide Prometryn) decreases with increasing hydraulic stress. As EPS is known as an absorber of chemicals, we hypothesize (ii) that the EPS to cell ratio correlates with both hydraulic stress and herbicide tolerance. Tolerance values were derived from concentration-response assays. Both, the herbicide tolerance and the biovolume of the EPS significantly correlated with the turbulent kinetic energy (TKE), while the diversity of diatoms (the dominant group within the stream biofilms) increased with flow velocity. This indicates that the positive effect of TKE on community tolerance was mediated by turbulence-induced changes in the EPS biovolume. This conclusion was supported by a second experiment, showing decreasing effects of the herbicide to a diatom biofilm (Nitzschia palea) with increasing content of artificial EPS. We conclude that increasing hydrodynamic forces in streams result in an increasing tolerance of microbial communities toward chemical pollution by changes in EPS-mediated bioavailability of toxicants.

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Large‐scale patterns of biofilm‐dwelling ciliate communities in a river network: Only small effects of stream order

Cited by 5 publications

References 54 publications

The food web perspective on aquatic biofilms

The food web perspective on aquatic biofilms

Near streambed flow shapes microbial guilds within and across trophic levels in fluvial biofilms

Hydrodynamics Alter the Tolerance of Autotrophic Biofilm Communities Toward Herbicides

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