Comparative sensitivity to the fungicide tebuconazole of biofilm and plankton microbial communities in freshwater ecosystems

Abstract

Stream and lake ecosystems in agricultural watersheds are exposed to fungicide inputs that can threaten the structure and functioning of aquatic microbial communities. This research analyzes the impact of the triazole fungicide tebuconazole (TBZ) on natural biofilm and plankton microbial communities from sites presenting different degrees of agricultural contamination. Biofilm and plankton communities from less-polluted (LP) and polluted (P) sites were exposed to nominal concentrations of 0 (control), 2 and 20 μg TBZ L(-1) in 3-week microcosm experiments. Descriptors of microbial community structure (bacterial density and chlorophyll-a concentration) and function (bacterial respiration and production and photosynthesis) were analyzed to chart the effects of TBZ and the kinetics of TBZ attenuation in water during the experiments. The results showed TBZ-induced effects on biofilm function (inhibition of substrate-induced respiration and photosynthetic activity), especially in LP-site communities, whereas plankton communities experienced a transitory stimulation of bacterial densities in communities from both LP and P sites. TBZ attenuation was stronger in biofilm (60-75%) than plankton (15-18%) experiments, probably due to greater adsorption on biofilms. The differences between biofilm and plankton responses to TBZ were likely explained by differences in community structure (presence of extracellular polymeric substances (EPS) matrix) and microbial composition. Biofilm communities also exhibited different sensitivity levels according to their in-field pre-exposure to fungicide, with P-site communities demonstrating adaptation capacities to TBZ. This study indicates that TBZ toxicity to non-targeted aquatic microbial communities essentially composed by microalgae and bacteria was moderate, and that its effects varied between stream and lake microbial communities.

A high-throughput sequencing ecotoxicology study of freshwater bacterial communities and their responses to tebuconazole

“…Our hypothesis was that TBZ could lead to the replacement of some dominant species in the bacterial communities by species that were less abundant or even rare before the exposure to the pollutant. found in only one treatment: control or 2 lg L À1 TBZ or 20 lg L À1 TBZ) for each environment after normalizing the number of reads (12 000 TBZ-induced functional changes previously described in Artigas et al (2014) were mainly due to effects on eukaryotic communities (i.e. Moreover, the NGS approach, which provides a detailed description of the BCC, did not reveal any specific selection of rare species in the samples exposed to TBZ during the experiment.…”

“…More details about the channels are given in Artigas et al (2014). The prepared bottles were incubated in a growth chamber at 20°C with a 12 h/12 h light/dark cycle and air circulated through the bottles (SECOH pump SLL 50).…”

“…Previous findings had highlighted some moderate structural and functional effects of TBZ on algal and bacterial communities (Artigas et al, 2014). We therefore carried out a 21-day microcosm experiment with two planktonic bacterial communities isolated from two subalpine lakes and two benthic bacterial communities isolated from two stations on a French river; these communities had all experienced different levels of previous exposure to pollutants.…”

Influence of streambed substratum composition on stream microbial communities exposed to the fungicide tebuconazole

“…The fungicide also reduced species richness of aquatic hyphomycetes at all concentrations tested and modified the kinetics of β‐glucosidase, β‐xylosidase and cellobiohydrolase, resulting in slow cellulose degradation by leaf‐associated microorganisms (Artigas et al ., ). TBZ effects on aquatic ecosystems have been also studied in biofilm and plankton microbial communities (Artigas et al ., ; Pascault et al ., ), where different functional indicators showed variable responses to TBZ, whereas bacterial community structure was unaffected. Bacteria associated with decomposing leaves are also inhibited by TBZ, although less than fungi (Bundschuh et al ., ; Artigas et al ., ).…”

Structural and functional responses of leaf‐associated fungal communities to chemical pollution in streams

“…More precisely, the type of the pesticide molecule as well as its mode of action would determine its potential impact on target and non-target leaf microorganisms (Maltby et al, 2009). This is the case of fungicides, being more toxic to aquatic fungi than other pesticides, due to their direct action on fungal physiology Fern andez et al, 2015;Zubrod et al, 2015) but also indirectly affecting bacteria co-existing with fungi (Artigas et al 2014). Up to now, however, the effects of multi-stressors, including pesticides and environmental stressors (e.g.…”