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| DO HIGH VOLTAGE POWERLINES AFFECT VICINAL EARTHWORM POPULATIONS? | ||
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Introduction Earthworms are an important concomitant of topsoil health, responsible for soil aeration, decomposition of organic debris, decreasing soil acidity, and the conversion of minerals to bioavailable form, and they also act as natural antibiotic agents, encouraging the growth of benign microflora whilst inhibiting potential pathogens. In providing plants with assimilable nitrogen, phosphorus and potassium earthworms thus occupy a vital and pivotal position in the food chain. Many earthworms demonstrably avoid electric and magnetic fields and currents. Should this aversion lower earthworm populations beneath powerlines it would create an environment in which malign bacterial species can flourish, and from there enter the human food chain via herbivores. Against this background we conducted an investigation to see if earthworm populations under a 132kV high voltage transmission line varied significantly from populations in the same pasture but distant from the line, and whether there were any significant differences in pH values of the topsoil. Method and Materials Six 500gm samples taken from the topsoil to a depth of 7.5cm beneath the midspan and six other samples 70m perpendicularly distant from the line were simultaneously collected in moist weather during December 1995 (under-line samples 2 metres apart from each other). These were bagged and coded by a third party not involved in the analysis. All samples were then analysed blind for pH value (Jenway 3030) and the size, mass and number of worms and related biota counted for each sample. Abbreviated Results Worm populations beneath the line as measured by biomass (77gm/m2) appeared to be similar to other samples reported from pastureland studies (52-120gm/m2). If anything the control samples at 70m appeared to be more sparsely populated (26gm/m2). There were no significant differences in population numbers, even so the average length of the largest worms (L. terrestris) at less than 100mm suggested that few mature worms were present in the under-line sample. The mean pH values did not differ significantly between exposed and control samples, but it was observed that the SD of mean pH was more widely spread in the under-line samples. Discussion and Conclusions The study was limited in that hand sorting was used, and the populations comparatively small due to season. Moreover it might have been more informative to take samples to a deeper level than 7.5cm. However one cannot draw any positive conclusions from these figures. The broader spread of pH values needs following up especially since some pathogenic strains of bacteria flourish in over-acid environments. A more detailed version of this study is available from our laboratory. |
