Earthworms represent a great part of the soil biomass, and due to this fact they are suitable bioindicators of the chemical contamination, expressing the soil health and quality. The effect of the chemicals on earthworms depends on the used substance, but regardless the substance nature, it must be considered in the ecological risk assessment both the direct and the indirect effects of it on soil life. This paper shows the results of a laboratory study through which was tested the acute toxicity of two types of pesticides (herbicides), homologated in Romania, on adult earthworms: GARDOPRIM PLUS GOLD 500 SC ( classified in the risk category R50/53 - very toxic for aquatic organisms, able to cause long term adverse effects on environment, and belonging to the IV th group of toxicity ) and HELMSTAR 75 WG ( classified as N - dangerous for environment and belonging as well to the IV th group of toxicity ),. The active substances of these herbicides are S-metolachlor and terbuthylazine and respectively tribenuron-methyl. The tested earthworm species was Eisenia foetida (Savigny, 1826). The research aimed to establish the effect of these two herbicides on earthworm mortality using the methodology in force enounced by OECD guidelines (Organisation for Economic Co-operation and Development). There were tested five concentration levels of each herbicide in laboratory conditions. The mortality assessment was realized at intervals by 24 and respectively 72 hours from exposure. Results showed that the herbicide GARDOPRIM PLUS GOLD 500 SC exerts an extremely toxic action on earthworms, and the second tested herbicide, HELMSTAR 75 WG was tolerated by earthworms. These findings demonstrated once again the sensitivity of these organisms such important for the soil health and fertility and highlight the necessity of precaution in using chemical substances that can get into the soil, under aspects of pedofauna abundance and activity, in order to maintain the biological equilibrium of soils.

earthworms, Eisenia foetida, toxicity, S-metolachlor, terbuthylazine, tribenuron-methyl

Presentation: oral