Sensitivity variations on soil health indicators related to arbuscular mycorrhizae in a highly disturbed urban basin of Buenos Aires, Argentina.

The Matanza-Riachuelo river basin (MRB) is considered one of the most polluted sites in the world, with very high levels of heavy metal(loid)s (HMs). However, as in almost all urban basins, studies on biological indicators of soil health are limited. In this work, we sampled soil and roots of mycorrhizal plants in three regions of the MRB (upper, middle, and lower basins) with the aim of exploring the potential of arbuscular mycorrhizal fungi (AMF) richness, based on spore morphology, plant mycorrhizal status, and glomalin-related soil proteins (GRSP) concentration as bioindicators of soil health. The highest concentrations of HMs were detected in the lower basin (degree of contamination mean value: 44.55), because it is exposed to a high input of pollutants and anthropogenic impact. AMF community composition was compared across the different soil samples. The Glomeraceae family was the most represented in the MRB (54.55% of species), and Rhizoglomus intraradices was the only AMF species detected at every sampled site. This work constitutes the first report of 8 of the 16 AMF species described so far in the MRB. GRSP differences were related to the lower basin of the MRB and to HMs concentrations, particularly Cu and Cr. Regarding the potential use of the studied AMF-related variables as bioindicators of soil health, GRSP concentrations increased with soil toxicity while AMF richness decreased with soil disturbance. These results suggest that these variables could serve as reliable biological indicators of soil health in future studies.