The health status of an urban riparian soil using soil nematodes and various microorganisms as biological indicators

Abstract

Riparian zones are vital interfaces which connect rivers and terrestrial ecosystems while playing a key role in basin and river functioning. The properties of the riparian soil are highly susceptible to anthropogenic activities and biological properties can provide us with a short-term reference of the health of the soil. This is because soil inhabiting organisms are extremely sensitive to changes in the soil and can serve as biological indicators of ecosystem health. This study focuses on the state of the riparian zone of the Chiquito river in Morelia, Mexico, using soil bioindicators. This river originates in a forest and has become a dump for waste and wastewater as it crosses the city. This transformation in the riparian soil use led us to investigate these effects on the soil biological properties, especially its nematofauna (bacterivorous, predators, plant parasitic, fungivorous) and other soil microorganisms (fungi, actinobacteria, bacteria, mycorrhiza). The total concentration of potentially toxic elements was determined, shedding light on the ramifications of anthropogenic contamination. We found that fungivorous nematodes were more abundant in the soil at the origin of the river. Bacterivorous nematodes and Gram-negative bacteria were more abundant at the end of the river where the highest concentration of Pb and Zn was found. We determined that there was a significant positive correlation between these microorganisms and the concentration of these toxic elements. This research shows that certain soil bioindicators can serve as cues to identify potential contamination hotspots from anthropogenic activity in the riparian areas of urban rivers.