Effects of waste water irrigation on soil properties and soil fauna of spinach fields in a West African urban vegetable production system

Arthropod Communities in Urban Agricultural Production Systems under Different Irrigation Sources in the Northern Region of Ghana

Urban and peri-urban agricultural (UPA) production systems in West African countries do not only mitigate food and financial insecurity, they may also foster biodiversity of arthropods and partly compensate for structural losses of natural environments. However, management practices in UPA systems like irrigation may also contribute to disturbances in arthropod ecology. To fill knowledge gaps in the relationships between UPA management and arthropod populations, we compared arthropods species across different irrigation sources in Tamale. During a 72-h sampling period, 14,226 arthropods were caught with pitfall traps and pan traps from 36 fields. These specimens comprised 13 orders, 103 families, 264 genera, and 329 taxa (243 identified species, 86 unidentified species) and categorized into five feeding guilds (carnivores, decomposers, herbivores, omnivores, and pollinators). Species richness, species accumulation curves, and diversity functions (richness, evenness, and dispersion) were calculated to characterize the arthropod community. Non-metric multidimensional scaling was applied to examine structural similarity of arthropod communities among sites. To account for the effects of soil-related data, we furthermore applied a redundancy analysis. Arthropods grouped according to the irrigation water source, whereby the dipterans were most dominant under wastewater conditions. Here, particularly the eye gnat, Hippelates pusio, a disease-causing vector for humans, accounted for the dipterans. The occurrence of three alien ant species suggested community shifts through invasive species, while the occurrence of seven ant species (at least one ant species occurred under each water source) that form mutualistic relationships with aphids highlighted future risks of aphid pest outbreak. Future studies on these taxa should specifically target their ecological and economic effects and potential countermeasures.

Effect of treated wastewater irrigation in East Central region of Tunisia (Monastir governorate) on the biochemical and transcriptomic response of earthworms Eisenia andrei

Treated wastewater (TWW) reuse for irrigation has become an excellent way to palliate water scarcity in Mediterranean arid regions. However, the toxicological effects of these effluents on the soil's organisms, especially earthworms, have not been well studied as yet. In this paper, earthworms Eisenia andrei were exposed for 7 days and 14 days to five agricultural soils irrigated with TWW for different periods: 1 year, 8 years, and 20 years. In addition, they were also exposed to soil from one reference site sampled from the Ouardenin perimeter in the Monastir Governorate in Tunisia. The effect on earthworms was assessed at the biochemical level by evaluating for catalase (CAT), glutathione-S-transferase (GST), malondialdehyde accumulation (MDA) and acetylcholinesterase inhibition (AChE). On the other hand, genotoxicity and transcriptomic responses were evaluated using micronuclei test (MNT) and gene expression level of CAT and GST. Moreover, metals uptake by earthworms was analyzed. Results showed that CAT and GST activity in the earthworm increased significantly when they were exposed to soils irrigated with TWW for 1, 8 and 20 years. Furthermore, MDA concentration also increased significantly with the increase in exposure period. However, AChE activity decreased and MNi frequency increased in earthworms after 7 and 14 days of exposure to soils irrigated with TWW for more than a year. The gene expression level of CAT and GST showed a significant variability, thus data are discussed in relation to the studied biomarkers (CAT and GST). These data provide new insights into the effect of toxicity of TWW on the soil's macro fauna, which is strongly affected by the trace elements and other organic compounds accumulated in soils after 20 years of TWW irrigation.

Long-term ecological effects of the red mud disaster in Hungary: Regeneration of red mud flooded areas in a contaminated industrial region

As one of the most severe ecological disasters ever to take place in Europe, the 2010 red mud accident has left behind long-term environmental impact, prompting the need for monitoring of soil biodiversity. Red mud (wet storage solution) can be regarded as a complex mixture of contaminants due to its extreme alkalinity and the presence of potentially toxic trace elements. After-effect investigations on soil properties and soil microarthropods were carried out in three distinct habitat types (agricultural land, grassland, woodland) in the red mud affected area. Soils in the red mud affected area were moderately to strongly alkaline (pH 7.5 to 8.5). Total content of trace metals Cd, Ni, Cr exceeded threshold concentrations for soil. Acari and Collembola were by far the most abundant taxa, while important groups like Pauropoda, Protura and Symphyla were completely absent from the samples of red mud affected plots. These observations were also reflected by the low values of the soil biological quality (QBS-ar) index. Independently of habitat types, total collembolan abundance tended to be lower in the contaminated area when compared with nearby control samples. Typical species distribution of Collembola communities in the contaminated area generally included one or two very common and abundant species and more, relatively rare species of low abundance. In the red mud affected open habitats, a distinct eudominance of Brachystomella parvula and Parisotoma notabilis was observed; whereas in contaminated woodland Parisotoma notabilis formed the bulk of the community with Sphaeridia pumilis, Folsomia manolachei and F. quadrioculata being subdominant. Species sensitive to alkalinity and red mud components (e.g. Hypogastrura vernalis, Lepidocyrtus tomosvaryi) were completely absent or were present only in limited numbers in the contaminated samples.