Heavy metals bioconcentration in Crassostrea rhizophorae: A site-to-site transplant experiment at the Potengi estuary, Rio Grande do Norte, Brazil

T M Senez-Mello,E M Fonseca,M A C Crapez,E T Silva,C A Ramos E Silva

doi:10.1038/s41598-019-57152-w

T M Senez-Mello, E M Fonseca + Show 3 more

Open Access

https://doi.org/10.1038/s41598-019-57152-w

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Abstract

In this study, we analyzed the bioconcentration of Cd, Cr, Cu, Pb, Ni, and Zn in the soft tissue of transplanted oysters in two sites in the Potengi estuary for six months. Native oysters collected before and after the transplantation experiment provided the background for statistical analyses. Cd, Cr, and Ni showed a strong inverse correlation with oyster weight in both sites. Transplantation upstream of the estuary presented increasing concentrations of Zn, Cu, and Pb and condition index (CI) and decreasing trends for Cd and Ni, whereas Cr oscillated significantly. In the downstream transplantation, Cu, Pb, and Zn and the CI tended to decrease, whereas for Ni, Cd, and Cr, the concentrations increased. Spatiotemporal principal component analysis correlated these results mainly with proximity to the polluting source, seasonality, and previous exposure to heavy metals. These results helped interpret the responses provided by these biomonitors to environmental changes, whether they are natural or anthropogenic.

Highlights

Metals widely available in estuarine environments tend to be trapped in sediments and incorporated into the local food chain
The Potengi estuary region is extremely impacted by pollution[13,14,15] and serves here as a study site to evaluate the bioconcentration of heavy metals (Cd, Cr, Cu, Pb, Ni, and Zn) in Crassostrea rhizophorae oysters
Analysis of the water column demonstrated that, at Qt, the salinity, turbidity, pH, and dissolved oxygen (DO) were higher compared to the upstream site (BN)

Summary

Introduction

Metals widely available in estuarine environments tend to be trapped in sediments and incorporated into the local food chain. Once discarded in an estuarine system, heavy metals can undergo various processes, such as dissolution, precipitation, adsorption, and complexation (with organic and inorganic dissolved ligands and particulate matter), and become deposited in bottom sediments[7]. These processes can create a potential source of pollution and adversely affect the environmental quality[8,9]. The second mechanism involves altering the structure of bivalve cell membranes when combined with some heavy metal This combination may interfere with the transport of ions, such as Na+, K+, and Ca−, and substances essential for maintaining vital processes[12]. The results obtained contribute both to the understanding of the mechanisms involved in the kinetics of heavy-metal uptake by C. rhizophorae oysters and to the creation of a knowledge base, enabling the use of this method in places where the sampling of native oysters is not possible, or in situations of true environmental changes

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