Disturbance alters the response of consumer communities towards warming: a mesocosm study with biofilm‐dwelling ciliates

Abstract

Citation: Marcus, H., J. K. Wey, H. Norf, and M. Weitere. 2013. Disturbance alters the response of consumer communities towards warming: A mesocosm study with biofilm-dwelling ciliates. Ecosphere 5(1):10. http://dx.Abstract. Environmental warming can have negative effects on the carrying capacity of communities because metabolic rates increase at the expense of biomass. Here, we tested the hypothesis that such warming effects are reversed in communities experiencing disturbance, as temperature-driven growth processes gain relevance and can compensate for negative disturbance effects. Model communities of seminatural, biofilm-dwelling ciliates were cultivated in mesocosms (river bypass systems) under two temperature regimes (ambient temperature and increased by 48C). The interactive effects between these different temperatures and seven disturbance intensities were tested in a nested design. Disturbance generally reduced total ciliate abundances, whereas only small effects on the prevalence of functional diversity were detected. Temperature effects differed between different disturbance intensities and seasons: Whereas warming reduced the carrying capacity of undisturbed communities irrespective of the season, pronounced positive warming effects were detected under disturbance in winter and, to a lesser extent, in spring. Neither significant temperature nor disturbance effects were recorded in summer, probably because ciliate growth rates were not temperature limited due to high summer background temperatures. Our results show that disturbance can markedly alter warming effects on temperature limited communities. Since natural communities commonly face disturbance, it should therefore be considered in models of future environmental warming responses.

Disturbance and distributions: avoiding exclusion in a warming world

“…Disturbance and distributions -page 6 also increase and modify competitive interactions consistent with H1 Totland 2005, Olsen and. Looking to other systems I note one experimental study of biofilm-dwelling ciliates that found that disturbance reduced some effects of artificial warming on community change, again consistent with H1 (Marcus et al 2014). Microcosm studies with single species and species combinations have highlighted that competitive hierarchies determine speciestemperature distributions for fruit flies indicating that similar dynamics operate in these taxa under these conditions ).…”

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

“…Sandy substrates may retain more nutrients than rock surfaces do because of more interstitial space (Hossain et al 2014), and the two substrate types may be exposed to different regimes of mechanical disturbance due to water flow. Both resource availability and disturbance can change the direction and magnitude of temperature effects on assemblages (Norf & Weitere 2010;Marcus et al 2014). Moreover, sand can be a different substrate depending on its grain size or composition, and retain fine organic material differently.…”

“…These factors affect the structure of the ciliate assemblages (e.g. Foissner & Berger, 1996) and could influence how ciliate assemblages respond to temperature differences (Norf & Weitere, 2010;Marcus et al, 2014). We expected ciliate assemblages on submerged rock surfaces to be more resource limited than on sandy substratum and thus predict a stronger reduction in biomass and alpha diversity with increasing temperature on rock compared with sandy substratum.…”

“…Furthermore, the direction and mangnitude of temperature effects can change depending on environmental factors such as seasonality (Norf et al 2007), nutrient availability (Norf & Weitere 2010), and mechanical disturbance (Marcus et al 2014). The nature of the bottom substrate is also known to affect the abundance and the species composition of ciliate assemblages (Gucker & Fischer 2003).…”

“…Previous studies have shown that temperature can increase the total biomass and species richness of ciliate assemblages and induce changes in their beta diversity (Norf & Weitere, 2010;Vidussi et al, 2011;Domaizon et al, 2012). Furthermore, the direction and magnitude of temperature effects can change depending on environmental factors such as seasonality (Norf et al, 2007), nutrient availability (Norf & Weitere, 2010) and mechanical disturbance (Marcus et al, 2014). The nature of the bottom substratum is also known to affect the abundance and species composition of ciliate assemblages (Gucker & Fischer, 2003).…”