Microbial community and heavy metals content in soils along the Curu River in Ceara, Brazil

Authors: ANJOS, DAVID - Federal University - Brazil; HERNANDEZ, FERNANDO - Federal University - Brazil; Banuelos, Gary; Rana Dangi, Sadikshya; TIRADO-CORBALA, REBECCA - University Of Puerto Rico; DA SILVA, FRANCISCO - Brazilian Department Of Agriculture; FILHO, PAUL - Federal University - Brazil

Submitted to: Geoderma Regional
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/2018
Publication Date: 6/15/2018
Citation: Anjos, D.C., Hernandez, F.F., Banuelos, G.S., Rana Dangi, S., Tirado-Corbala, R., Da Silva, F.N., Filho, P.F. 2018. Microbial community and heavy metals content in soils along the Curu River in Ceara, Brazil. Geoderma Regional. 14:e00173. https://doi.org/10.1016/j.geodrs.2018.e00173.
DOI: https://doi.org/10.1016/j.geodrs.2018.e00173

Interpretive Summary: The drainage systems of the Curu River watershed in Brazil contain many contaminated soil sites. Irrigation with waters originating from this area are a significant source of further soil contamination. This study was aimed to evaluate the effects of the contaminants, e.g., heavy metals, on microbial biomass and community structure at 22 soil sites that were close to urban, industrial, and agricultural areas within the watershed. Chemical analysis confirmed that many of the soil sampling sites were contaminated with heavy metals. In these soils, resistant microbial species and different microbial communities were, however, found. They were able to survive by changing the structure of their metabolic activity. Our survey indicates that although heavy metals can exert harmful effects on both soil and crop quality, beneficial soil microorganisms have the ability to adapt and survive in the Curu River watershed region.

Technical Abstract: The drainage systems of the Curu River watershed in the North center of Ceará – Brazil permeates many contaminated sites that are used for intense farming. Surface waters from this region used for irrigation are harmful for crop production and soil quality, however, little information is available on the effects of these poor quality waters on microbial activities within the watershed. This study aimed to survey heavy metal content and examine its potential effect on microbial communities in soils surrounding the Curu River. In this regard, soil samples were collected from 0-5 cm and 5-30 cm depths at 22 different sites that, presumably, were contaminated by heavy metals (HM). The samples were analyzed for pH, electrical conductivity, organic matter (OM), arsenic, cadmium, cobalt, chromium, copper, molybdenum, nickel, lead, and selenium. In addition, the responses of microbial communities (MC) to heavy metals were also evaluated using phospholipid fatty acid (PLFA) analysis. Canonical correlations were used to identify possible relationships between groups of variables (e.g., soil physical-chemical characteristics, heavy metals, and soil microbiological communities). Our results showed that the coefficients of the first canonical pair indicated that there was no significant difference between soil microbiological characteristics and the content of heavy metals (Group II). These results suggest that these two factors are independent at these soil sites. The relationship between the attributes of Group I (total of microorganisms, Gram+, and Gram - bacteria) with Group II (HM) was inversely proportional to the increase in the content of heavy metals. However, there were no significant relationships between heavy metal content and the occurrence of different microbiological communities. Those sites supporting secondary vegetation created more favorable conditions for the development of microorganisms due to an increase in soil moisture and OM in the soil. In conclusion, soils and plants presently surrounding the Curu River need to be monitored for heavy metal content, however, resistant beneficial soil microorganisms have developed and do survive in such contaminated conditions.