Recharge through till : developing a methodology for estimating groundwater recharge with examples from two case studies in East Anglia

This report describes the results of a desk study to investigate recharge in an area of discontinuous low permeability till in the Waveney catchment. Within the study area the till is absent in the valley of the River Waveney and also in the lower parts of some of the tributary valleys. The study develops a methodology to identify the main recharge areas and make initial estimates of recharge in such hydrogeologically complex areas. Following earlier work on Chalk recharge through till this combined study area was selected to include both the Chalk and the Crag aquifers. It was thought that the difference between these two aquifers may shed further light on the recharge mechanisms through the overlying till. The main outcomes of the study have been: 1. A recharge estimate methodology is devised based on the effective rainfall, the till thickness, estimates of runoff from the till sheet and delimiting the main recharge areas where the till is thin or absent. 2. The infiltration through thick till (>10 m) is low and as a consequence, runoff from the till sheet is large and is potentially a significant component of recharge at the margins of the till sheet. Estimating the quantity of water that may runoff the till sheet is essential when attempting to assess the amount and distribution of groundwater recharge. 3. An important issue, when considering catchment water balances, is the relative proportion of runoff that infiltrates to groundwater at the margins of the till sheet, compared with that which flows directly into the river. It has not been possible in this study to devise a methodology to split these two components. More catchment scale studies are required to evaluate how catchment characteristics influence the infiltration rates. 4. The time-lag between rain falling at the soil surface and recharge arriving at the water table will be relatively short at the margins of the till sheet where the water table is generally shallow. This has important implications for water quality, as widespread changes in land-use are likely to be observed more rapidly in groundwaters at the edge of the sheet than in areas of extensive Chalk-Crag outcrop

Toolbox for the sampling and monitoring of benthic cyanobacteria

Benthic cyanobacteria are a nuisance because they produce highly potent toxins and taste and odour compounds. Despite this, benthic cyanobacteria remain far less studied than their planktonic counterparts. For example, little is known about their growth or the seasonality of their secondary metabolite production. Moreover, sampling and monitoring techniques commonly used for the survey of planktonic species are not necessarily applicable to benthic forms. This study aimed to develop and validate a new sampling device for the routine monitoring of benthic mats. Molecular monitoring techniques were established and validated on environmental samples collected in a South Australian reservoir (SA-L2). A total of eight qPCR assays were applied to samples in order to track seasonal variations in cyanobacteria concentrations and associated secondary metabolite production. Next Generation Sequencing was utilised to conduct a microbial community composition analysis and to select the most appropriate substrate material for the sampling of benthic cyanobacteria. The concentration of the secondary metabolites geosmin and 2-methyl-isoborneol were quantified using High-Performance Liquid Chromatography, and concentrations of key nutrients (N, P) were quantified in water samples. The sampling device designed proved efficient and easy to use in the field. The qPCR assay designed for the amplification of the cyanobacterial MIB synthase had a high efficiency with a minimum limit of quantification of 4 cell-equivalents per reaction and identified a potential source of MIB in SA-L2 Reservoir. The peak season for benthic growth and secondary metabolite production was observed in spring. Proportionally, 35% of the variability in water geosmin concentrations can be explained by benthic actinobacterial and cyanobacterial activity, showing that freshwater benthic mats represent a significant source of taste and odour compounds.Virginie Gaget, Peter Hobson, Angela Keulen, Kelly Newton, Paul Monis, Andrew R. Humpage, Laura S. Weyrich, Justin D. Brooke

Problems associated with the presence of cyanobacteria in recreational and drinking waters

Eutrophication of waters can lead to the development of blooms of cyanobacteria (blue-green algae) and consequent health and environmental problems. The presence of these organisms in recreational and drinking waters is generally undesirable or even hazardous, although nitrogen fixing blue-green algae can be beneficially used as biofertilisers for plantation crops. This paper reviews the characteristics of cyanobacteria and particularly their toxins. The mechanisms of toxic algal blooms are discussed, as are the factors influencing toxin production. The nuisance and health hazards associated with freshwater bluegreen algae are discussed and the options for public health control are evaluated. The problems associated with statutory control of toxic algae problems is also considered

Effect of microcystin-LR on protein phosphatase 2A and its function in human amniotic epithelial cells*

Due to their toxicity, the increased distribution of microcystins (MCs) has become an important worldwide problem. MCs have been recognized as inhibitors of protein phosphatase 2A (PP2A) through their binding to the PP2A catalytic subunit. However, the exact mechanism of MC toxicity has not been elucidated, especially concerning the cellular response and its autoregulation. To further dissect the role of PP2A in MC-induced toxicity, the present study was undertaken to determine the response of PP2A in human amniotic epithelial (FL) cells treated with microcystin-LR (MCLR), one of the MC congeners. The results show that a low-dose treatment of MCLR in FL cells for 6 h induced an increase in PP2A activity, and a high-dose treatment of MCLR for 24 h decreased the activity of PP2A, as expected. The increased mRNA and protein levels of the PP2A C subunit may explain the increased activity of PP2A. Furthermore, MCLR altered microtubule post-translational modifications through PP2A. These results further clarify the underlying mechanism how MCLR affects PP2A and may be helpful for elucidating the complex toxicity of MCLR