The combined stress of increased soil salinity and zinc concentrations on earthworms

Abstract

In large areas of the world, e.g. in Australia and the Middel-Eastern countries, high or increasing soil salinity is a major problem in agricultural and native land. The salinity may either be due to naturally high levels of various salts or caused by poor irrigation practices. This knowledge lead to the reflection on whether soil salinity is a major determinant for distribution of earthworms in saline areas, such as South Australia. Plant studies have shown that increasing soil salinity may seriously reduce growth. Whether this is the case for earthworms and how high levels are needed has not previously been studied. In the present study the effect of increased salinity was studied on E. andrei. As in non-saline regions, saline soil can also receive an input of, or naturally contain, high levels of metals. The effect on E. andrei of increased levels of Zinc was also studied in a sandy soil. As both increased salinity and raised metals levels may occur, the combined effect of salinity and zinc exposure was studied. This was done by a surface-response-area study employing combination exposures of the two stressors. Finally, the results are related to the salinity stress obtained when performing regular metal exposure studies using metals salts.