Uptake of heavy metals (arsenic and lead) by earthworms in a Literature review

Uptake of heavy metals (arsenic and lead) by earthworms in a contaminated soils - Literature review Example Despite healthy soil formed in the absence of earthworms, their presence within the soil indicates the soil is productive. As a result of the tedious activities by earthworms their importance for the soil community includes enhancing mixing and aggregation of soil (Weeks et al 2004, p.820). While looking for food, Weeks et al. (2004, p.821) observe that, earthworms engage in a task of moving to the surface and back down, ingesting particles of soil and other organic substances in their way. Further, earthworms excrete the substances it takes in to the soil, and the excreted matter by the earthworms, are nutrient-dense casts. The result in this sense, involves a process that shift the top layer of soil down to the lower strata, and dragging the bottom soil to the upper surface. When earthworms burrow through the dust, this enhances the soil structure by loosening the soil that are compact and establish numerous tunnels under the surface. The importance of such tunnels includes enhancing soil porosity and creating pathways that allows the intake of water and air into the soil. The process further facilitates absorption and the retention of water, and minimizing run offs and soil erosion (Weeks et al 2004, p.822). ... the soil surface and in the process, mix the organic material as a result of tearing the organic materials and depositing these materials deep within the soil. Their cast also deposits on the soils surface thus, contributing to the soil content. In addition, they enhance bacteria and fungi activity in the soil that consumes organic materials and transforming these materials to humus. Earthworms largely, forms part of the food web within the soil, which presents a large community, composed of organism that plays a significant role in soil formation. In the same note, soil food web encompasses soil-inhabiting organisms that include algae, insects, plants, reptiles, fungi and small mammals. The organisms, impacts on soil formation through burrowing, breaking down materials (both animal and plant materials) that is significant in adding organic matter when they die. Earthworms often provide a food source to the soil community and their cast is important in facilitating the survival of ot her organisms within the soil community. They assist in terms of facilitation the provision of oxygen, water and nutrition for other organisms (Hobbelen et al 2006, p.644). The ecological groups of earthworms and their feeding behaviors According to ecology studies on soils by Nahmani, Hodson and Black (2007, p.402), that focuses on linkages between fauna and microbes, identifies earthworms, as a significant soil invertebrate within the ecosystem and contributes, to biomass and activity which operate as ecosystem engineers. Nahmani et al (2007, p.402) agree that, soil consists of various microorganisms and forms part of earthworm’s diet. In this regard, three ecological groups related to earthworms and their feeding behaviors, exists in literature. They include epigeic, which is