Spatial Variability of Heavy Metals in Native Oysters From an Anthropogenically Impacted Estuary in Northeastern Brazil

Thaise Machado Senez-Mello,Carlos Augusto Ramos E Silva,Mírian Araújo Carlos Crapez,Estefan Monteiro Da Fonseca,Eduardo Teixeira Da Silva

doi:10.3389/fmars.2020.00412

Thaise Machado Senez-Mello, Carlos Augusto Ramos E Silva + Show 3 more

Open Access

https://doi.org/10.3389/fmars.2020.00412

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Abstract

This brief research compares the bioconcentration of heavy metals (Cd, Cr, Cu, Pb, Ni, and Zn) in the soft tissues of native oysters Crassostrea rhizophorae (Guilding, 1828) from two areas in the Potengi estuary, northeastern coast of Brazil. The purpose was to test the hypotheses of relevant differences in bioaccumulation while the environmental conditions change upstream. The downstream station showed higher concentrations for cadmium and nickel, while the upstream one, revealed increased values for body weight, condition index, chromium, lead, and zinc (p < 0.05). The cooper variation between sites was negligible, but, as for zinc and chromium, the metal content observed was above guidance levels. Results revealed two aspects that were mainly influencing the bioavailability and bioaccumulation of metals in oysters. Firstly, the predominance of marine or riverine characteristics of each site, and secondly, the relative proximity to the point of introduction of the pollutant, even though stations were not quite far apart. Crassostrea rhizophorae accumulated heavy metals in significant concentrations, endorsing its efficiency as a biomonitor.

Highlights

Heavy metals have been considered potentially toxic elements by a considerable part of the literature (Mendoza-Carranza et al, 2016; Griboff et al, 2018; Kulkarni et al, 2018)
Analysis of the water column demonstrated that, at Qt, the salinity, turbidity, pH, and dissolved oxygen (DO) were higher than those measured at Naval Base (NB) the water temperature, biochemical oxygen demand (BOD), and total organic carbon (TOC) were higher on the NB (Supplementary Table S2)
With the exception of the BOD, all other parameters cited above were within the standards for water quality proposed by the Brazilian legislation for saltwater where recreational and Variables N Mean C.L. ± 95% SE N Mean C.L. ± 95% SE

Summary

Introduction

Heavy metals have been considered potentially toxic elements by a considerable part of the literature (Mendoza-Carranza et al, 2016; Griboff et al, 2018; Kulkarni et al, 2018). They are natural constituents of the earth’s crust, occurring in several compartments, such as the atmosphere, water bodies, sediments, and the biosphere (Garrett, 2000). Mangrove ecosystems are transitional areas between marine and continental environments located in the intertidal zone (Odum, 2004) and, characterized by significant fluctuations of salinity, temperature, and conditions of oxidation (Lewis et al, 2011). The vegetation, with its euryhaline characteristic, plays great importance in the maintenance of other species offering shelter, refuge, and food sources for both marine organisms and riverine communities (Usman et al, 2013).

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