Copper‐induced modifications of the trophic relations in riverine algal‐bacterial biofilms

Abstract

The effects of copper (Cu) on photosynthetic riverine biofilms were studied in artificial stream channels. Direct effects on the composition and functioning of the biofilms were investigated using plant pigments, community-level physiological profiles (CLPP), and pulse-amplitude-modulated (PAM) fluorescence. Copper caused a significant reduction of microalgal biomass and induced a shift in the population from diatoms to cyanobacteria. However, a decrease in biomass indicated that the replacement of species was not totally effective to counteract the toxic effects of Cu. A direct effect of Cu could also be shown in the bacterial community, and, furthermore, changes in the CLPP could be related to the Cu treatment. Copper-exposed biofilms lost the capacity to use between 11 and 15% of the substrates, but many of the remaining capacities became more robust, indicating an increased Cu tolerance due to the exposure. The change in the biofilm microbial composition points to the indirect effects of Cu on biofilms due to the close interdependence between biofilm autotrophic and heterotrophic compartments. Grazing by snails, which appeared to be an important factor structuring biofilms without any Cu addition, had a very minor effect on Cu-exposed biofilms. Although grazing changed the bacterial composition, its effects were not detected either on the algal community or on the biofilm community tolerance to Cu.

Effect of light and temperature on biomass, photosynthesis and capsular polysaccharides in cultured phototrophic biofilms

“…Both the effective quantum yield of PSII (ΔF/ F m ′) and the relETR max showed increasing values with increasing irradiance in the two experimental runs, indicating biofilm photoacclimation, which has also been observed in natural biofilm assemblages from different environments (Kromkamp et al 1998;Underwood 2002;Barranguet et al 2003;Rascher et al 2003;Serõdio 2003;Lugomela et al 2005). When comparing between the two runs at a specific light intensity the values of ΔF/F m ′ and relETR max were higher at 20°C than at 30°C.…”

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

“…Genter et al (1987) noted a shift in phototrophic community composition from diatoms to cyanobacteria and green algae after exposure to Zn. Other studies also reported biofilm community shifts towards a dominance of cyanobacteria after long-term exposure to metals, indicating that cyanobacteria may be more tolerant to metal contamination (Barranguet et al 2002(Barranguet et al , 2003Serra et al 2009). Cyanobacteria are known to lack a xanthophyll cycle, but still contain significant amounts of zeaxanthin and other xanthophylls (Jeffrey and Vesk 1997), which could help explain their high tolerance to metals.…”

The periphyton as a multimetric bioindicator for assessing the impact of land use on rivers: an overview of the Ardières-Morcille experimental watershed (France)

“…In such environments, living organisms, both prokaryotic (bacteria) and eukaryotic (mostly microalgae, but also fungi), interact strongly (Rier & Stevenson, 2002;Barranguet et al, 2003) and are responsible for most of the energy input through primary production and nutrient cycling (Battin et al, 2003a, b). They play a marked ecological role in biochemical processes such as organic matter degradation (Romani et al, 2004) or nitrogen biotransformation (Teissier & Torre, 2002).…”