Effects of temperature increase on the grazing of planktonic bacteria by biofilm-dwelling consumers

Abstract

Biofilms, the complex microbial communities associated with surfaces, can play an important role in the flux of matter in running waters. In addition to bacteria and algae, heterotrophic protists and small metazoans can also occur in high abundances in biofilms. By grazing on planktonic prey, biofilm-dwelling grazers can act as a trophic link between planktonic and benthic food webs, parallel to filter-feeding benthic macroinvertebrates. Here we introduce a flow cell method for the quantification of grazing rates of semi-natural biofilms on suspended bacteria, parallel to microscopic biofilm community analysis. This technique was used to measure the temperature response of the grazing rates of complex biofilm communities (established in a bypass system to the River Rhine, Germany) on planktonic bacteria. Results showed that 14 d old biofilms (dominated by ciliates) clear planktonic bacteria at rates between 29 (in winter) and 99 l m -2 biofilm d -1 (in summer) at ambient temperature. These rates increased with test temperature, even at temperatures (> 30°C) at which the grazing rates of filter-feeding macrofauna in moderate climates are negatively influenced. The acclimation temperatures under which the biofilm developed can have a significant effect on community clearance rates, largely due to a temperature effect on the abundance and structure of the grazer community, whereas no indication of an acclimation effect on individual grazing rates could be found. In the function of bentho-pelagic couplers, biofilm-dwelling consumer communities can react to temperature changes substantially faster than macrofaunal filter feeders.

Substratum‐dependent responses of ciliate assemblages to temperature: a natural experiment in Icelandic streams

“…Moreover, ciliates play significant roles in the microbial food web and the cycling of organic material. For example, by feeding on bacteria and increasing decomposition rate (Ribblett, Palmer & Coats 2005;Kathol et al 2009), contributing to the import of organic material from the water column into the benthos (Eisenmann et al 2001;Weitere, SchmidtDenter & Arndt 2003;Kathol et al 2009), and being consumed by invertebrate meiofauna (Norf, Arndt & Weitere 2007).…”

Influence of sampling sufficiency on biodiversity analysis of microperiphyton communities for marine bioassessment

“…As the primary components of periphyton communities, microperiphytons play a crucial role for energy flux and element cycling in many aquatic ecosystems (Fischer et al 2002;Debenest et al 2009;Kathol et al 2009). Autotrophic microalgae that are predominated by benthic diatoms are responsible for the bulk of primary production (Debenest et al 2009;Duong et al 2010), while protozoan consumers mediate the flow of both matter and energy from plankton to benthos in most aquatic ecosystems (Kathol et al 2009;Norf et al 2009;Xu et al 2011).…”

A simplified experimental model for clearance of some pathogenic bacteria using common bacterivorous ciliated spp. in Tigris river

“…Therefore, the understanding of the micro-ecosystem and the relationship between protozoa and disease-causing bacteria within contaminated water has become increasingly important in the context of freshwater purification and pollution control design. Among the most important factors controlling bacterial communities in polluted river water is the ciliates' ability to graze on a variety of bacterial species (Jennifer et al 2008;Kathol et al 2009;Ana et al 2010); they can partly control bacterial standing stock abundance by preferentially removing dividing cells (Simek et al 1997). Diverse ciliates exhibit different feeding types; some of them up taking suspended bacteria, while some preferably feed on surface-binding bacteria.…”