Metal contaminations impact archaeal community composition, abundance and function in remote alpine lakes.

Using the 16S rRNA and mcrA genes, we investigated the composition, abundance and activity of sediment archaeal communities within 18 high-mountain lakes under contrasted metal levels from different origins (bedrock erosion, past-mining activities and atmospheric depositions). Bathyarchaeota, Euryarchaeota and Woesearchaeota were the major phyla found at the meta-community scale, representing 48%, 18.3% and 15.2% of the archaeal community respectively. Metals were equally important as physicochemical variables in explaining the assemblage of archaeal communities and their abundance. Methanogenesis appeared as a process of central importance in the carbon cycle within sediments of alpine lakes as indicated by the absolute abundance of methanogen 16S rRNA and mcrA gene transcripts (105 to 109 copies g-1 ). We showed that methanogen abundance and activity were significantly reduced with increasing concentrations of Pb and Cd, two indicators of airborne metal contaminations. Considering the ecological importance of methanogenesis in sediment habitats, these metal contaminations may have system wide implications even in remote area such as alpine lakes. Overall, this work was pioneer in integrating the effect of long-range atmospheric depositions on archaeal communities and indicated that metal contamination might significantly compromise the contribution of Archaea to the carbon cycling of the mountain lake sediments.

Ecotoxicological assessment of soils polluted with chemical waste from lindane production: Use of bacterial communities and earthworms as bioremediation tools.

An ecotoxicological survey of soils that were polluted with wastes from lindane (γ-HCH) production assessed the effects of organochlorine compounds on the metabolism of microbial communities and the toxicity of these compounds to a native earthworm (Allolobophora chlorotica). Furthermore, the bioremediation role of earthworms as facilitators of soil washing and the microbial degradation of these organic pollutants were also studied. Soil samples that presented the highest concentrations of ε-HCH, 2,4,6-trichlorophenol, pentachlorobenzene and γ-HCH were extremely toxic to earthworms in the short term, causing the death of almost half of the population. In addition, these soils inhibited the heterotrophic metabolic activity of the microbial community. These highly polluted samples also presented substances that were able to activate cellular detoxification mechanisms (measured as EROD and BFCOD activities), as well as compounds that were able to cause endocrine disruption. A few days of earthworm activity increased the extractability of HCH isomers (e.g., γ-HCH), facilitating the biodegradation of organochlorine compounds and reducing the intensity of endocrine disruption in soils that had low or medium contamination levels.

Ecotoxicity studies of the levulinate ester series.

The increasing interest in the development of novel green solvents has led to the synthesis of benign alternative products with minimized environmental impacts. However, most of published studies on green solvents focus primarily on their physicochemical properties, with limited emphasis on absence of ecotoxicological assessment. In this study, we evaluated the acute ecotoxicity of four levulinates (levulinic acid, methyl levulinate, ethyl levulinate and butyl levulinate) on freshwater algae (Chlamydomonas reinhardtii), bacteria (Vibrio fischeri), daphnids (Daphnia magna) and earthworms (Eisenia foetida) using various dose-response tests. As a general trend, the toxicity of levulinate esters in aquatic exposure (assessed as the EC50) increased as a function of increasing alkyl chain length; accordingly, the most toxic compound for the aquatic organisms was butyl levulinate, followed by ethyl levulinate and methyl levulinate. The most toxic compound for E. foetida (terrestrial exposure) was methyl levulinate, followed by ethyl levulinate, butyl levulinate and levulinic acid; in this case, we observed an inverse relationship between toxicity and alkyl chain length. Based on both the lowest EC50 found in the aquatic media and the ratio between predicted environmental concentration and the predicted no-effect concentration, we have estimated the maximum allowable values in the environment for these chemicals to be 1.093 mg L(-1) for levulinic acid, 2.761 mg L(-1) for methyl levulinate, 0.982 mg L(-1) for ethyl levulinate and 0.151 mg L(-1) for butyl levulinate.

Effects of 18 pharmaceuticals on the physiological diversity of edaphic microorganisms.

Pharmaceutical residues can enter the terrestrial environment through the application of recycled water and contaminated biosolids to agricultural soils, were edaphic microfauna can would be threatened. This study thus assessed the effect of 18 widely consumed pharmaceuticals, belonging to four groups: antibiotics, non-steroidal anti-inflammatory drugs (NSAIDs), blood lipid-lowering agents (BLLA) and ß-blockers, on the physiology of soil microbial communities from a ecological crop field. Biolog EcoPlates, containing 31 of the most common carbon sources found in forest and crop soils, were used to calculate both the averaged well colour development (AWCD), as an indicator of the entire capacity of degrading carbon sources, and the diversity of carbon source utilization, as an indicator of the physiological diversity. The results show that pharmaceuticals impact microbial communities by changing the ability of microbes to metabolize different carbon sources, thus affecting the metabolic diversity of the soil community. The toxicity of the pharmaceuticals was inversely related to the log Kow; indeed, NSAIDs were the least toxic and antibiotics were the most toxic, while BLLA and ß-blockers presented intermediate toxicity. The antibiotic sulfamethoxazole imposed the greatest impact on microbial communities at concentrations from 100 mg/L, followed by the other two antibiotics (trimethoprim and tetracycline) and the ß-blocker nadolol. Other chemical parameters (i.e. melting point, molecular weight, pKa or solubility) had little influence on toxicity. Microbial communities exposed to pharmaceuticals having similar physicochemical characteristics presented similar physiological diversity patterns of carbon substrate utilization. These results suggest that the repeated amendment of agricultural soils with biosolids or sludges containing pharmaceutical residuals may result in soil concentrations of concern regarding key ecological functions (i.e. the carbon cycle).

Influence of global change-related impacts on the mercury toxicity of freshwater algal communities.

The climatic-change related increase of temperatures, are expected to alter the distribution and survival of freshwater species, ecosystem functions, and also the effects of toxicants to aquatic biota. This study has thus assessed, as a first time, the modulating effect of climate-change drivers on the mercury (Hg) toxicity of freshwater algal photosynthesis. Natural benthic algal communities (periphyton) have been exposed to Hg under present and future temperature scenarios (rise of 5 °C). The modulating effect of other factors (also altered by global change), as the quality and amount of suspended and dissolved materials in the rivers, has been also assessed, exposing algae to Hg in natural river water or a synthetic medium. The EC50 values ranged from the 0.15-0.74 ppm for the most sensitive communities, to the 24-40 ppm for the most tolerant. The higher tolerance shown by communities exposed to higher Hg concentrations, as Jabarrella was in agreement with the Pollution Induced Community Tolerance concept. In other cases, the dominance of the invasive diatom Didymosphenia geminata explained the tolerance or sensitivity of the community to the Hg toxicity. Results shown that while increases in the suspended solids reduced Hg bioavailability, changes in the dissolved materials - such as organic carbon - may increase it and thus its toxic effects on biota. The impacts of the increase of temperatures on the toxicological behaviour of periphyton (combining both changes at species composition and physiological acclimation) would be certainly modulated by other effects at the land level (i.e., alterations in the amount and quality of dissolved and particulate substances arriving to the rivers).

Phytotoxicity of 15 common pharmaceuticals on the germination of Lactuca sativa and photosynthesis of Chlamydomonas reinhardtii.

Pharmaceuticals reach terrestrial environments through the application of treated wastewaters and biosolids to agricultural soils. We have investigated the toxicity of 15 common pharmaceuticals, classified as nonsteroidal anti-inflammatory drugs (NSAIDs), blood lipid-lowering agents, ß-blockers and antibiotics, in two photosynthetic organisms. Twelve pharmaceuticals caused inhibitory effects on the radicle and hypocotyl elongation of Lactuca sativa seeds. The EC50 values obtained were in the range of 170-5656 mg L-1 in the case of the radicle and 188-4558 mg L-1 for the hypocotyl. Propranolol was the most toxic drug for both root and hypocotyl elongation, followed by the NSAIDs, then gemfibrozil and tetracycline. Other effects, such as root necrosis, inhibition of root growth and curly hairs, were detected. However, even at the highest concentrations tested (3000 mg L-1), seed germination was not affected. NSAIDs decreased the photosynthetic yield of Chlamydomonas reinhardtii, but only salicylic acid showed EC50 values below 1000 mg L-1. The first effects detected at low concentrations, together with the concentrations found in environmental samples, indicate that the use of biosolids and wastewaters containing pharmaceuticals should be regulated and their compositions assessed in order to prevent medium- and long-term impacts on agricultural soils and crops.

Impacts of agricultural irrigation on nearby freshwater ecosystems: the seasonal influence of triazine herbicides in benthic algal communities.

A small hydrological basin (Lerma, NE Spain), transformed from its natural state (steppe) to rain-fed agriculture and recently to irrigation agriculture, has been monitored across four seasons of an agricultural year. The goal of this study was to assess how and whether agricultural activities impacted the nearby freshwater ecosystems via runoff. Specifically, we assessed the toxicity of three triazine herbicides, terbuthylazine, atrazine and simazine on the photosynthetic efficiency and structure of algal benthic biofilms (i.e., phototropic periphyton) in the small creek draining the basin. It was expected that the seasonal runoff of the herbicides in the creek affected the sensitivity of the periphyton in accord with the rationale of the Pollution Induced Community Tolerance (PICT): the exposure of the community to pollutants result in the replacement of sensitive species by more tolerant ones. In this way, PICT can serve to establish causal linkages between pollutants and the observed biological impacts. The periphyton presented significantly different sensitivities against terbuthylazine through the year in accord with the seasonal application of this herbicide in the crops nowadays. The sensitivity of already banned herbicides, atrazine and simazine does not display a clear seasonality. The different sensitivities to herbicides were in agreement with the expected exposures scenarios, according to the agricultural calendar, but not with the concentrations measured in water, which altogether indicates that the use of PICT approach may serve for long-term monitoring purposes. That will provide not only causal links between the occurrence of chemicals and their impacts on natural communities, but also information about the occurrence of chemicals that may escape from traditional sampling methods (water analysis). In addition, the EC50 and EC10 of periphyton for terbuthylazine or simazine are the first to be published and can be used for impact assessments.

Ultraviolet radiation dose calculation for algal suspensions using UVA and UVB extinction coefficients.

Although the biological importance of ultraviolet light (UVR) attenuation has been recognised in marine and freshwater environments, it is not generally considered in in vitro ecotoxicological studies using algal cell suspensions. In this study, UVA and UVB extinction were determined for cultures of algae with varying cell densities, and the data were used to calculate the corresponding extinction coefficients for both UVA and UVB wavelength ranges. Integrating the Beer-Lambert equation to account for changes in the radiation intensity reaching each depth, from the surface until the bottom of the experimental vessel, we obtained the average UVA and UVB intensity to which the cultured algal cells were exposed. We found that UVR intensity measured at the surface of Chlamydomonas reinhardtii cultures lead to a overestimation of the UVR dose received by the algae by 2-40 times. The approach used in this study allowed for a more accurate estimation of UVA and UVB doses.

Analysis of the diversity of substrate utilisation of soil bacteria exposed to Cd and earthworm activity using generalised additive models.

Biolog EcoPlates™ can be used to measure the carbon substrate utilisation patterns of microbial communities. This method results in a community-level physiological profile (CLPP), which yields a very large amount of data that may be difficult to interpret. In this work, we explore a combination of statistical techniques (particularly the use of generalised additive models [GAMs]) to improve the exploitation of CLPP data. The strength of GAMs lies in their ability to address highly non-linear relationships between the response and the set of explanatory variables. We studied the impact of earthworms (Aporrectodea caliginosa Savigny 1826) and cadmium (Cd) on the CLPP of soil bacteria. The results indicated that both Cd and earthworms modified the CLPP. GAMs were used to assess time-course changes in the diversity of substrate utilisation (DSU) using the Shannon-Wiener index. GAMs revealed significant differences for all treatments (compared to control -S-). The Cd exposed microbial community presented very high metabolic capacities on a few substrata, resulting in an initial acute decrease of DSU (i.e. intense utilization of a few carbon substrata). After 54 h, and over the next 43 h the increase of the DSU suggest that other taxa, less dominant, reached high numbers in the wells containing sources that are less suitable for the Cd-tolerant taxa. Earthworms were a much more determining factor in explaining time course changes in DSU than Cd. Accordingly, Ew and EwCd soils presented similar trends, regardless the presence of Cd. Moreover, both treatments presented similar number of bacteria and higher than Cd-treated soils. This experimental approach, based on the use of DSU and GAMs allowed for a global and statistically relevant interpretation of the changes in carbon source utilisation, highlighting the key role of earthworms on the protection of microbial communities against the Cd.

Irrigation agriculture affects organic matter decomposition in semi-arid terrestrial and aquatic ecosystems.

Many dryland areas are being converted into intensively managed irrigation crops, what can disrupt the hydrological regime, degrade soil and water quality, enhance siltation, erosion and bank instability, and affect biological communities. Still, the impacts of irrigation schemes on the functioning of terrestrial and aquatic ecosystems are poorly understood. Here we assess the effects of irrigation agriculture on breakdown of coarse organic matter in soil and water. We measured breakdown rates of alder and holm oak leaves, and of poplar sticks in terrestrial and aquatic sites following a gradient of increasing irrigation agriculture in a semi-arid Mediterranean basin transformed into irrigation agriculture in 50% of its surface. Spatial patterns of stick breakdown paralleled those of leaf breakdown. In soil, stick breakdown rates were extremely low in non-irrigated sites (0.0001-0.0003 day(-1)), and increased with the intensity of agriculture (0.0018-0.0044 day(-1)). In water, stick breakdown rates ranged from 0.0005 to 0.001 day(-1), and increased with the area of the basin subject to irrigation agriculture. Results showed that irrigation agriculture affects functioning of both terrestrial and aquatic ecosystems, accelerating decomposition of organic matter, especially in soil. These changes can have important consequences for global carbon budgets.