Variability in Zinc Tolerance, Measured as Incorporation of Radio-Labeled Carbon Dioxide and Thymidine, in Periphyton Communities Sampled from 15 European River Stretches

Abstract

Fifteen European rivers and streams belonging to watersheds in Sweden, the Netherlands, and Spain respectively, were sampled by allowing periphyton to colonize submerged glass substrata. Their zinc tolerances were quantified in short-term laboratory tests, where inhibition of photosynthesis in microalgae and thymidine incorporation in bacterial DNA was measured, and expressed as EC50 values. The variability in zinc tolerances was high reaching 1.5-2.5 orders of magnitude, ranging from 25-8145 microM for photosynthesis and 15-467 microM for thymidine assays. Based on the observed variability, uncertainty factors were estimated for the extrapolation of zinc toxicity data from river to river, both regionally and interregionally. Under the assumption to protect 95% of the observed communities the regional uncertainty factors were 1.7-4.3 and the interregional 2.4-8.6. The sampling sites were characterized in terms of biotope physiography, water chemistry, periphyton biomass, trace element content, and species composition. Multivariate analysis of the data using PLS (Projection to Latent Structure), was used to generate hypotheses about the relation between periphyton zinc tolerance and the 123 so-called predictor variables. Zinc contamination, phosphate, nitrogen nutrients, pH, calcium, bicarbonate, dissolved organic carbon, and various diatom species are important predictors for zinc tolerance in the entire data set representing all 15 river stretches. Regional models suggested that very different factors determined the zinc tolerance in the Swedish and Dutch periphyton. The results are interpreted in terms of Pollution-Induced Community Tolerance (PICT) and the bioavailability of zinc.

Seasonal variations of metal concentrations in periphyton and taxonomic composition of the algal community at a Yenisei River littoral site

“…Concentrations of Mn, Ca, Cr, Fe, Ni in Yenisei periphyton were below median values for periphyton, primarily diatomic, of 15 European rivers, while contents of K, Zn, Cu, and Pb in periphyton of the Siberian river were close to lower levels of these elements in periphyton of the European rivers [6]. In periphyton of an unpolluted site of the Birs River (Switzerland), Cu and Zn ranges were practically equal to those in the Yenisei River [3].…”

“…The variability is likely caused by seasonal changes in the communities, but most of the surveys of metal contents in periphyton performed one to four samplings per year, and studies on periphyton based on monthly sampling frequencies are rare [5]. Although element content of periphyton is likely dependent on the species composition [6], the species composition of periphyton is routinely used as an indicator of heavy metal pollution only [5,7], and there are no data correlating metal concentrations in periphyton with taxonomic composition of algal community in the available literature.…”

pH Tolerance in Freshwater Bacterioplankton: Trait Variation of the Community as Measured by Leucine Incorporation

“…The response curves of a community can then be regarded as the trait distribution (community tolerance) of that community. In soil this approach has been commonly applied to study community tolerance to heavy metals (1-3), other toxicants (4, 5), temperature (6-8), and salinity (9, 10), but this method has been applied less often in aquatic habitats (11)(12)(13).pH has been shown to be a decisive environmental factor determining the bacterial community composition in both soil (14-16) and water (17-22), often being the most important one compared to factors such as temperature and moisture in soil (15) and temperature, water retention time, organic matter, and nutrient concentrations in freshwater systems (17,(19)(20)(21)(22). pH is also an environmental factor that can vary greatly in aquatic systems.…”

“…The response curves of a community can then be regarded as the trait distribution (community tolerance) of that community. In soil this approach has been commonly applied to study community tolerance to heavy metals (1-3), other toxicants (4,5), temperature (6)(7)(8), and salinity (9,10), but this method has been applied less often in aquatic habitats (11)(12)(13).…”

Analysis of Structural and Physiological Profiles To Assess the Effects of Cu on Biofilm Microbial Communities

“…These authors did not detect large differences between bacterial communities growing at Cu concentrations ranging from 3 to 87 M. Our results suggest that the complex and organized structure of the biofilm (10,18,30) would not protect the bacterial community in the same way that sediments do, even through the formation of extracellular polymeric substances was found to increase several resistance capacities of each encased organism (24) by reducing the bioavailability of heavy metals (33). Short-and long-term toxicity tests of heavy metals on aquatic biofilms have focused either on the response of the phototrophic compartment (1,2,5,17) or on that of the heterotrophic compartment (34), but toxic effect assessments based on physiological tests (3,19) or studies considering the biofilm as a whole have not investigated the effect of Cu (6,23). Possible interactions between phototrophic and heterotrophic compartments of a biofilm may be disturbed when one compartment is severely affected by a stress factor, e.g., an increase in toxicant concentration.…”