Performance evaluation of phycocyanin probes for the monitoring of cyanobacteria

The performance of two field probes (YSI 6600 and TriOS), used for the measurement of in vivo phycocyanin fluorescence, was compared and validated in the laboratory in 2008 and 2009 with cultures of Microcystis aeruginosa and field samples. The background noise of the two probes was low and the detection limits were estimated at 1500 cells mL(-1) for the YSI and 0.69 μg PC L(-1) for the TriOS. The linearity and repeatability of both probes have been excellent. Strong relationships were observed between the in vivo fluorescence and the total cyanobacterial biovolume (R(2) = 0.82 YSI; 0.83 TriOS) or the abundance (R(2) = 0.71 YSI; 0.75 TriOS) of cyanobacteria. However, the difference between cell densities determined by microscopy and measured by the YSI can be very large and has been associated to the variability of cell volume among cyanobacteria. This last observation makes the YSI a qualitative tool if a post-calibration is not done. The analysis of filtrated samples showed that dissolved phycocyanin (extracellular) may represent a significant fluorescence signal. No relationship could be established between the abundance, the total cyanobacterial biovolume or the in vivo fluorescence of phycocyanin and the concentrations of cyanotoxins (R(2) ≤ 0.22).     

Impact of peri-urban landscape on the organic and mineral contamination of pond waters and related risk assessment

Environmental Science and Pollution Research - Ponds are important for their ecological value and for the ecosystem services they provide to human societies, but they are strongly affected by human...     

Congenital heart anomalies in the first trimester: From screening to diagnosis

Congenital heart defects occur in approximately 1% of liveborn children and represent the most common form of congenital malformation. Due to the small size and complexity of the heart structures, prenatal diagnosis is most often made in the second trimester of pregnancy. Early diagnosis however offers significant advantages regarding the timing of further investigations, prenatal counseling, and access to management options. In the last decade, advances in antenatal imaging have improved the detection of cardiac malformations with increasing emphasis on earlier pregnancy screening and diagnosis. We aim to summarize current “state of the art” imaging of the fetal heart in the first trimester.     

Effects of pesticides on soil enzymes: a review

The use of pesticides in agriculture has highly increased during the last 40 years to increase crop yields. However, today most pesticides are polluting water, soil, atmosphere and food. Pesticides are also impact soil enzymes, which are essential catalysts ruling the quality of soil life. In particular, the activity of soil enzymes control nutrient cycles, and, in turn, fertilization. Here, we review the effects of pesticides on the activity of soil enzymes in terrestrial ecosystems. Enzymes include dehydrogenase, fluorescein diacetate hydrolase, acid phosphatase, alkaline phosphatase, phosphatase, β-glucosidase, cellulase, urease and aryl-sulfatase. Those enzymes are involved in the cycles of carbon, nitrogen, sulfur and phosphorus. The main points of our analysis are (1) the common inhibition of dehydrogenase in 61 % of studies, stimulation of cellulase in 56 % of studies and no response of aryl-sulfatase in 67 % of studies. (2) Fungicides have mainly negative effects on enzymatic activities. (3) Insecticides can be classified into two groups, the first group represented by endosulfan having an overall positive impact while the second group having a negative effect. (4) Herbicides can be classified into two groups, one group with few positive effect and another group with negative effect.     

Combinatory chemical and biological approaches to investigate metal elements in agricultural runoff water

As part of a project studying the interactions between farming practices, soil erosion processes, and fate of agricultural pollutants into runoff waters, we conducted a pilot study to investigate the relationship between metal contents and metallothionein-2A (MT-2A) as a bioindicator of metal exposure. Runoff water samples were collected between May and November 1999 at the point of outlet of an elementary watershed located in the Paris basin. Selected metals (Al, As, Cd, Cr, Cu, Pb, Hg, Ni, and Zn) were analyzed using conventional techniques. In parallel, human T cells were exposed to water samples for 6 and 18 h and then cell viability and MT-2A gene expression were measured. Results show that among the 10 water samples tested, Al and Zn predominate (highest values = 4.9 and 2.6 microM, respectively), while other metals were below the microM level. Five out of 10 samples induced MT-2A gene expression (30-80% increase at 18 h) as compared with the control. When comparing MT-2A induction profile with metals contents, no obvious correlation was found, suggesting that additional components or parameters are involved. Finally, there was an apparent inverse relationship between Ca concentration and MT-2A gene induction. Although still preliminary, in the absence of longer monitoring, this study shows that MT-2A gene expression is a useful tool to complement chemical analysis in assessing metal elements in water. These combinatory approaches will be pursued and integrated in an ongoing watershed field research project.     

Spatial and temporal occurrence of N-nitrosamines in seven drinking water supply systems

The spatiotemporal presence of eight N-nitrosamines in the water of seven supply systems in Quebec considered to be susceptible to these emerging disinfection by-products was evaluated. This is the first study on the presence of N-nitrosamines in drinking water utilities in Quebec. Seven sampling campaigns were carried out at several sampling points in each of the systems over a period of 1 year. The results show that N-nitrosamines, primarily N-nitrosodimethylamine (NDMA), were not commonly detected in the water of the facilities under study (10 % of samples). The concentrations measured were lower than those reported in recent North American studies. None of the 195 samples taken exceeded the Ontario standard of 9 ng/L for NDMA (maximum value observed of 3.3 ng/L). N-nitrosomethylethylamine and N-nitrosopiperidine were detected once, with concentrations of 3.7 and 6.0 ng/L, respectively. Chloramination was identified as being the main risk factor regarding the presence of N-nitrosamines, but water quality and some operating parameters, in particular disinfectant residual, also seem to be related to their presence. NDMA concentrations at the end of the distribution systems were generally higher than water leaving the plant. No seasonal trends were observed for the formation of N-nitrosamines in the investigated supply systems. Finally, an association between the presence of N-nitrosamines and the levels of trihalomethanes and haloacetic acids was observed in some facilities.     

Internal distribution of uranium and associated genotoxic damages in the chronically exposed bivalve Corbicula fluminea

Uranium (U) internal distribution and involved effects in the bivalve Corbicula fluminea have been studied after direct chronic exposure (90 d, 10 μg.L-1). U distribution was assessed at the subcellular level (Metal Rich Granules -MRG-, pellets and cytosol fractions) in two main organs of the bivalve (gills and visceral mass). Micro-localisation was investigated by TEM-EDX analysis in the gills epithelium. DNA damage in gill and hemolymph samples was measured by the Comet assay. The 90-d exposure period led to a significant increase of U concentration in gills over time (×5) and a large U quantity in subcellular granules in gills. Finally, a significant increase (×2) in DNA damage was noted in exposed gills and haemocytes. This study shows that the accumulation levels and consequently the potential toxicity cannot be successfully predicted only on the basis of concentration in water or in tissues and subcellular fractions after chronic exposure.