# Bioaccumulation of Metals in Brain, Eye, Skeleton, and Skin Tissues of Wastewater-Fed Fish: A Case Study in Turkey

## TL;DR

This study examines metal accumulation in fish tissues from wastewater-fed aquaculture in Turkey, finding elevated levels of toxic metals like Cd and Pb.

## Contribution

The study provides new insights into metal bioaccumulation in specific fish tissues under wastewater-fed conditions.

## Key findings

- Cd and Pb concentrations exceeded standards in all tissues, indicating potential toxicity.
- Fe and Zn were the most prevalent metals in all tissues, with seasonal variations observed.
- Bioaccumulation was confirmed for all metals, but only Pb showed a carcinogenic hazard.

## Abstract

In this study, the metal accumulation (Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) and toxicity status in the brain, eye, skeleton, and skin tissues of Carassius gibelio species of fish fed with wastewater treated with secondary treatment were investigated, and the usability of wastewater and fish for human food against climate change and food crisis was investigated. Treated wastewater (TWW) complied with Turkish aquaculture standards, but was not found to comply with drinking and irrigation water standards. The national and international food standards for metal concentrations varied. Cd and Pb were found to be high in all tissues according to all standards, but Cu, Cr, Mn, Ni, Fe, and Zn were found to vary according to tissues. It was determined that Fe and Zn concentrations were generally higher than those of the other metals in all tissues. The orders of the metals according to their annual mean concentrations were: Zn > Fe > Mn > Pb > Ni > Cr > Cu > Cd in skeletons; Zn > Fe > Pb > Ni > Cr > Cu > Mn > Cd in skins; Zn > Fe > Cu > Pb > Mn > Ni > Cr > Cd in eyes; and Fe > Zn > Pb > Cu > Cr > Ni > Mn > Cd in brains. Concentrations in tissues were higher in the summer months, but seasonal changes were statistically insignificant (p ≥ 0.05). According to Principal Component Analysis (PCA), ANOVA, and Pearson correlation analysis, it was statistically determined that Cd, Cr, Cu, Mn, Ni, and Pb, and the other two elements (Fe and Zn), showed similar accumulation characteristics among themselves. According to transfer factor (TF) calculations, it was determined that there was bioaccumulation (TF > 1) in all tissues for all metals throughout the year, but according to hazard coefficient (HQ) values, only Pb was determined to be >1 and carcinogenic. As a result, after the wastewater is treated with different advanced treatment methods and brought to potable water standards, the accumulation of metals and other micropollutants in the tissues of different species of fish should be monitored for many years.