Terrestrial isopoda as Model Organisms in Soil Ecotoxicology

Abstract

To better understand how terrestrial isopods impact agricultural soil enzymatic activity, methane absorption, and their role in decomposition by consuming and digesting leaf litter, this study examines the function of isopods in nutrient cycling, organic matter breakdown, and the safe disposal of diverse wastes. Five locations in the Al-Jadriya region were chosen. Sites 1, 2, and 3 had isopods, but sites 4 and 5 were devoid of isopods and exclusively populated by earthworms, ground insects, and snails, and their overall density was 2400 ind/m². This study was conducted in five agricultural fields in Baghdad from October 2023 to June 2024.

The results of the current study showed that the presence of isopods in sites 1, 2, and 3 had a clear effect in changing the environment, accelerating the processes of recycling nutrients, analyzing organic materials, and getting rid of many cellulosic wastes, as an increase in the effectiveness of soil enzymatic activities was observed: alkaline phosphatase, dehydrogenase, and urease, compared to the sites where the appearance of isopods was not recorded.

It also had a clear effect on the numbers of bacteria and fungi, as the numbers of bacteria decreased in the sites inhabited by isopods (sites 1, 2, and 3). It also had an impact on the abundance of bacteria and fungi, while only Bacillus and Pseudomonas species were recorded in sites 1, 2, and 3 (where isopods were present). In contrast, high numbers of bacteria were recorded in the soil of sites 4 and 5, where the isopods did not appear, represented by the species Rhizobium, Bradyrhizobium, Microbacterium, Serratia, Azotobacter, Actinomyces, Bacillus, Propionibacterium, Acetobacter, and Methanococcus.

As for fungi, high numbers were recorded in the sites inhabited by isopods, represented by the species Aspergillus niger, while the numbers of fungi were moderate in sites not inhabited by isopods and included different species such as Mucor, Aspergillus, Penicillium, Fusarium, and Rhizopus.

The results of the current study also showed a clear effect of the presence of isopods on the abundance of nutrient forms in the soil of the sites they inhabit. High values were recorded for potassium (K) and phosphorus (P), and the sites inhabited by isopods also recorded high values of methane (CH₄), ammonium (N-NH₄), nitrate (N-NO₃), and carbon dioxide (CO₂).