Influence of low soil moisture on enchytraeids

Abstract

Former sewage irrigation sites in Berlin and Brandenburg are contaminated with heavy metals as well as PAH and PCB. At most of these sites enchytraeids have been found in low abundances and low species numbers only. The most obvious explanation for the low enchytraeid densities is the high concentration of heavy metals in the soil, often in combination with acidic conditions (pH 4.0 - 5.4). Furthermore, the soils were also exposed to extended periods of drought during the years of investigation. The objective of the present study therefore was to show in which way adverse soil moisture conditions contribute to the low numbers of enchytraeids found in the irrigation field soils. Field studies included determination of enchytraeid abundance and species composition as well as measurement of soil water contents. In addition, laboratory experiments were performed concerning the reproduction and growth of Enchytraeus buchholzi, one of the dominant species of the studied sites. In the field, water contents below 5 % (DW) coincided with very low enchytraeid densities. In the laboratory, reproduction was reduced at water contents of 15 % (DW) and lower. Body length of the adults was higher at 20 % water content than at 5 % water content. It was concluded that enchytraeid densities as well as species composition are influenced by low soil moisture at the studied site.