In situ spatio-temporal changes in pollution-induced community tolerance to zinc in autotrophic and heterotrophic biofilm communities

Abstract

Pollution-induced community tolerance (PICT) uses increased tolerance in populations at contaminated sites as an indicator of contaminant effects. However, given the broad structural and functional complexity that characterizes biological communities, the acquisition of PICT could vary with (i) target community, (ii) intensity of toxicant exposure, (iii) the species succession stage, and (iv) the physicochemical characteristics of the studied site. To assess the spatio-temporal changes of zinc-induced tolerance in fluvial biofilm communities, we conducted an in situ study in Osor River (North-East Catalonia, Spain), which has zinc contamination. Biofilms were developed for 5 weeks in a non-metal-polluted site, and were then transferred to different sites in Osor River with different levels of zinc contamination. The spatio-temporal changes of biofilm PICT to zinc was determined using photosynthetic activity bioassays and respiration-induced aerobic bioassays at T(0), and at 1, 3 and 5 weeks of exposure. We also performed physicochemical characterization of the sites, taxonomic analysis of diatoms, bacterial and fungal diversity and profiled pigments of phototrophic communities. We used multivariate ordination to analyze results. In addition to natural species succession, the intensity of metal pollution exerted structural pressure by selecting the most metal-tolerant species, but differently depending on the type of biofilm. Zn-tolerance values indicated that exposure to high levels of zinc had effects that were similar to a longer exposure to lower levels of zinc.

Structural and functional recovery of microbial biofilms after a decrease in copper exposure: Influence of the presence of pristine communities

“…Heterotrophic communities: Bacterial community structure was analyzed using automated ribosomal intergenic spacer analysis (ARISA) following Tlili et al (2011) with slight modifications. Briefly, biofilm DNA was extracted using the FAST DNA kit (QBIOgene) according to the manufacturer's instructions.…”

“…Briefly, biofilm DNA was extracted using the FAST DNA kit (QBIOgene) according to the manufacturer's instructions. The 16S-23S bacterial intergenic spacer region was amplified using the primers S-D-Bact-1522-b-S-20 (eubacterial rRNA small subunit, 50-TGCGGCTGGATCCCCTCCTT-30) and L-DBact-132-a-A-18 (eubacterial rRNA large subunit, 50-CCGGGTTTCCCCATTCGG-30) (Ranjard et al, 2001) as described by Tlili et al (2011). ARISA analyses were performed using an Agilent 2100 Bioanalyzer (Agilent Technology) following the manufacturer's instructions, and ARISA profiles were analyzed using GelCompar II software (Applied Math NV) to output a matrix based on the quantification of relative band intensities.…”

Diatom responses to zinc contamination along a Mediterranean river

“…Briefly, glass slides were immersed as artificial substrates for periphyton colonisation upstream the Riera d'Osor (colonisation site, CS). This river exhibits a gradient of zinc contamination (Tlili et al 2011, Bonet et al 2014 downstream CS. After five weeks of colonisation, one series of substrates was kept at CS, and the others were transferred to five downstream sites (called Up, M1, M2, M3, plus one additional site at the mining source, MS) in comparable light and water flow conditions to CS.…”

“…The presence of a dam between M2 and M3 caused very low metal concentrations in the water downstream (retention and/or dilution) but sporadic transport of contaminated matter may explain some accumulation in M3 periphyton. Tlili et al (2011 and Bonet et al (2014) demonstrated that metals, zinc in particular, were the main driving factor of periphytic responses in the Riera d'Osor. Zinc…”

“…This second-order river drains a metal-polluted area due to former mining activities. In this river, photosynthetic processes ) and biomarkers (antioxidant enzymatic activities, Bonet et al 2014) were early warnings of metal contamination, whereas algal composition or tolerance of both heterotrophic and autotrophic compartments (Tlili et al 2011) were more powerful in detecting chronic exposure or extremely high stress on the short term. In complement to their work, we explored the temporal trajectories of the specific response of diatom features to the metal gradient of Riera d'Osor, using communities with the same exposure history (i.e.…”