Applicability of the Caenorhabditis elegans survival, growth and reproduction test to assess the effects of biosolids used in agriculture

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Huguier, Pierre | Manier, Nicolas | Meline, Camille | Pandard, Pascal | Bauda, Pascale

Edité par CCSD -

Modern high productivity agriculture has led to an impoverishment of nutrients and organic carbon in field soils, and as a consequence plants nutrition complements like fertilisers or wastes have to be used to keep high yield. These complex materials can also be a source of toxicants, depending on their origin, so there is a necessity to assess their environmental effects before field use. In this study, biosolids used in agriculture were tested as a mix with standard soil at different field dose through ecotoxicity test on the nematode Caenorhabditis elegans, endpoints for this organism being survival, growth and reproduction. In order to run these tests we first followed the standardized protocol for sediment and soil testing with C. elegans (ISO 10872, 2010). These results showed that the mixtures could be significantly different according to the type of soil (e.g. two phases system with overlaying water). Indeed, soil moistening in the standardized protocol is based on soil dry weight which means that the same amount of water is added for every soil, regardless of the water holding capacity (WHC) of the samples. Moreover, some biosolids can have a high WHC what increase humidity's differences among soil and soil mixed with biosolids when moistened as recommended by this protocol. To prevent this, improvements of the standardized protocol were developed, in which water addition is based on soil WHC instead of soil dry weight. Moreover, food volume added to the samples was lowered in order to be able to include it in the volume for soil moistening. In this context and in order to validate this new method, comparisons between standardized and optimized protocols were carried out for endpoints responses in five soils with different textures. This optimized protocol was used to assess the effect of different biosolids (limed sludge, manure ...) mixed with standard soil at different field rates and an example for a limed sludge is given. Regarding these results, improvements of the standardized protocol are adapted to assess the effects of these materials on C. elegans.

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