# Tissue-Specific Accumulation of Heavy Metals and Oxidative Stress in Atlantic Bonito (Sarda sarda, Bloch 1793) Marketed in Kütahya

## TL;DR

This study found that heavy metals accumulate more in the gills than the edible muscle tissue of Atlantic bonito, causing oxidative stress in the fish but not posing a significant risk to human health.

## Contribution

The study identifies gill tissues as a primary site of heavy metal-induced oxidative stress in Atlantic bonito and validates MDA and OSI as reliable biomarkers for aquatic pollution.

## Key findings

- Cadmium and copper levels in gills were significantly higher than in muscle tissue.
- Oxidative stress markers like MDA and OSI were elevated in gill tissues.
- Human health risk metrics (HI and CR) remained within safe limits for edible muscle tissue.

## Abstract

Heavy metal pollution in oceans and seas is a growing concern because these toxic substances can accumulate in fish, which are a major part of the human diet. In this study, we investigated the Atlantic bonito (Sarda sarda, Bloch 1793) sold in local markets in Kütahya, Türkiye, to see how much heavy metals and arsenic they contain and how these metals affect the fish’s health. We specifically looked at two parts of the fish: the muscle (the part we eat) and the gills (which the fish uses to breathe). Our results showed that the gills had much higher levels of metals like cadmium and copper compared to the muscle. These metals caused “oxidative stress” in the fish, which is a type of internal cell damage that weakens their natural defense systems. However, when we calculated the potential risk for humans, we found that the metal levels in the edible parts were within safe limits.

Heavy metal pollution in aquatic environments presents a considerable risk to fish populations, primarily through the induction of oxidative damage. This study aimed to investigate the relationship between heavy metals (Cu, Cd, Hg, and Pb) and As accumulation and oxidative stress biomarkers, including malondialdehyde (MDA), total oxidant status (TOS), and oxidative stress index (OSI), together with antioxidant defenses such as reduced glutathione (GSH) and total antioxidant status (TAS), in the muscle and gill tissues of Atlantic bonito (Sarda sarda, Bloch 1793). Furthermore, human health risks were evaluated using the target hazard quotient (THQ), hazard index (HI), and carcinogenic risk (CR) metrics. Our findings indicate that heavy metals such as cadmium (Cd) and copper (Cu) accumulate significantly more in the gills than in the muscle tissue (p < 0.05). This accumulation seems to cause an unusual biological response, evidenced by a notable increase in oxidative stress markers—namely MDA, TOS, and OSI—within the gill tissues (p < 0.01). Specifically, gill MDA concentrations (5.43 ± 1.86 nmol/mg) were significantly higher than those observed in the muscle tissue (4.07 ± 1.63 nmol/mg). Concerning human safety, both the HI (0.8393) and CR values remained within established safety thresholds. These observations suggest that the gills are the primary site of metal-induced oxidative damage, and the robust correlation between metal accumulation and OSI/MDA levels implies that these parameters are reliable indicators for evaluating aquatic metal pollution.